LED wankery edition
http://pastebin.com/9UgLjyND
>>927390
How can I go about making a <10 mW power supply with a HUGE adjustable voltage range?
>>927391
Tesla coil
Who Peltier here?
>>927391
Do you really mean milliwatt or did you mean to write MW (megawatt)?
Where does /ohm/ get their components from?
dumpster diving?
Ebay?
sucking dick?
Also, can I harvest usable stepper motors from slot loading drives for a CNC hobby machine? Or will they have practically 0 torque?
I've seen like a job lot of 25 faulty drives for $25.
>>927457
>Or will they have practically 0 torque?
Their job is to move a lightweight sled. They do it pretty slowly. Why would anyone use big, heavy, expensive motors for that job?
Where do you get cheap LEDs? I'm interested in making a grow light to grow some lettuce or something indoors
>>927459
Riddle me this.
I anticipate that they will have the same torque as a regular tray based Optical drive, but with a slimmer form factor.
Would I be correct in that assumption?
>>927459
They don't use a sled at all.
They use rubber rollers on arms that follow the outside of the CD. It's the same principle as that chicken-gathering machine.
http://m.youtube.com/watch?v=qi3v7X6BpAA
>>927537
No no, he's talking about the steppers moving the laser diode in and out of the disc.
>>927434
>Do you have an actual question?
I was just wondering what projects other anons are doing with thermoelectric modules. I have a few and have been playing around with them, getting used to what they can and can't do. They are pretty fun to play around with.
Normally, the mere mention of something will spur someone to talk about it if they are doing a project or like the subject matter.
>>927457
>Where does /ohm/ get their components from?
From buyfag trash bins.
>>927583
what are those rainbow peanut things?
>>927577
I installed one in my right buttcheek, under the skin, and wired it up to an NFC tag in my pocket.
When I put my phone in my pocket, the nfc tag operates and my ass gets cooler.
I also hooked it up in parallel with a vibration motor. Slipped it up my bumhole so I get a prostate massage when my mom calls.
Can anyone give me an idea on how to create a 600W 24V 25A power supply without using any transformer. I am thinking of using an scr bridge but I am finding it hard to control the phase angle needed
I'm designing a (bass) guitar amplifier. This is what I've come up with as far as the power amp for driving the speaker. The input stage is an op amp.
This is the first time I've actually tried designing and simulating my own circuit rather than copying some shit someone else posed online, although it is heavily derived from other amps i've studied / built before. Is it retarded?
>>927666
>is it retarded
yep
Does anyone have a good list of stuff to buy to start a hobby in electrical tomfoolery.
>>927778
Like essential supplies?
>>927577
Well, I've used them to cool cold traps and small environmental test chambers (that was a fancy name for thing which was basically just a tiny fridge).
I've also seen a project which was a non-obscene version of anon's joke. Tiny peltier cooler was attached to skin and it was used to notify the user about ... something via temperature (hot/cool/neutral).
>>927666
Your schematic is very confusing
And please use something better than the tl072 that is just as retarded as all those lm386 amplifiers
>>927666
Build it and see! You might want to try the diyaudio forums.
I have an 8-bit A/D converter chip with four single-ended inputs connected to an AVR microcontroller. I'd like to attach some sensors to it and build a small weather station that I could place on a windowsill. It would measure temperature, relative humidity, illuminance and maybe wind speed.
What kind of temperature sensor would be good for this use? Would a simple NTC thermistor be sufficient for a temp. range of -30°C ... +40°C?
I'm planning to use the thermistor amplifier circuit shown on this Texas Instruments application note. It transforms the variable resistance into an analog voltage that can be fed into A/D converter. I just wonder if it would be possible to use cheap LM324 quad op-amp instead of expensive TLV2472. Pic related.
>>927906
NTCs are nonlinear and linearization and calibration can be annoying. Consider using IC temperature sensors, like LM335 (analog output, 10mV/K) or DS1631 (digital output via I2C).
>8b external ADC instead of an AVR with internal 10b ADC
>TLV2472 is too expensive
Dude, are you sure it makes sense to penny-pinch that much?
>>927666
Look up the book "Designing power amplifiers" by Bob Cordell (which may or may not be available in slightly illegal bodies of water where pirates reside).
It is great for amplifier design and learning the basics, and how to go further and improve THD etc
>>927806
Remote tactile temperature sensing. That sounds pretty neat actually.
I'm using mine for generating electric from body heat. It isn't much through, like 0.001mW since the temp differences are not that great..
>>927598
Wtf are you even doing here?
>Resistors.
>>927779
Yeah.
So /ohm/, I just bought myself some 555s and I'm having no trouble using them when following instructions but would like to learn more about them
Do you have any books/videos on 555s by chance? I'd very much appreciate that
>>928055
nope, there are no books, videos, or web pages dealing with the 555. it's just too obscure a part, even google returns 0 results.
I need to have 8 LEDs, each controlled by a switch, so that each LED can be turned on or off on separately. Would something like pic related be basically the only way to do this?
I've read that using LEDs in parallel can be tricky, and that one led can burn out, causing the rest to take even more power, causing them to burn out too, etc.
>>927457
The radio shack near me still sells this stuff. I guess most don't? It's all overpriced though.
>>928064
that problem disappears when each LED has it's own resistor. you have zero worries in that case.
>>928064
as long as each LED has its own resistor there is no risk of weird shit happening. The drawing you posted should work perfectly for what you describe.
>>928060
Didn't ask for a spoonfeed, was just wondering what /ohm/'s favourite material was
>>928104
the datasheet.
>>928104
we cant decide for you. some people are calculator-heads, they wanna see formulas. some people appreciate schematics, others think they're gibberish. some like cute flashing lights, others like timer applications, others want big-power stuff like Tesla coils.
>>928125
Thanks
I built the most basic stuff I could find (a monostable LED timer and an astable tone generator) and I'd like to move on to slightly more advanced stuff, I thought about putting two in series to have a tone for some time whenever you press a button but other than that I have no ideas
>>927916
>LM335
Thanks for your tip. This part has built-in linearization but still can be fine-tuned with a trimmer pot. I could make a simple op-amp circuit for scaling the output signal of LM335 to fit the full input range of the ADC. For example -30..+40°C -> 0..3 V or so.
>8b external ADC instead of an AVR with internal 10b ADC
Unfortunately the part that I have doesn't have any analog inputs.
>>928127
ok, well an Atari Punk console is quite a popular project. every noob makes one to show their geek friends. one step above that is the Atari Punk Organ, where you make like a piano thingy. also, popular is the 3-monostable traffic light. of course, there are real-world uses for 555s, as part of bigger projects, as timers, oscillators, PWM drivers, edge detectors, etc
I am interested in trying to wire up LEDs for lighting in my barn. I do not know much about electronics but I think I have some of the equipment picked out necessary to test on a small scale what I want to do.
http://www.ebay.com/itm/30-Watt-Waterproof-LED-Power-Supply-Driver-Transformer-120-to-12-Volt-Dc-Output-/171219085379?hash=item27dd73e843:g:3uQAAOxygPtS14Pl
http://www.ebay.com/itm/2-Pcs-20W-1800LM-LED-Chip-Cold-White-High-Power-LED-Panel-20-Watt-Lamp-Light-/111781134602?hash=item1a06acc10a:g:sf8AAOSwEetWBPpX
http://www.ebay.com/itm/LED-Heatsink-for-20-50W-High-Power-LEDs-073-062-/221562674742?hash=item33962a1e36:g:~gQAAOSwGvhUKZ4L
I am not sure If the 20 watt led will provide enough lighting but they are cheap enough that It wont bother me if I can't use them for the full project. I plan on going with a 50 watt driver but didn't have one picked out to go with this post. I figured if I went with 50 and found out that 20 watts was too little light that I could still have room to jump up to 30 watt higher lumens and not need a different driver as well. From what I understand the larger LED need heat sinks for cooling so planned on buying a few of them also but the link provided is the final pick. My general thinking was I could plug the driver into an outlet that has a on off switch and from there run wiring across exposed beams and place LED wherever I decided. I was thinking of making my own fixtures out of wood somehow or just screwing the heatsink right into a beam. Are my chosen supplies what is needed?
>>928157
That is really nice to hear and I'll be sure to check those out!
Thanks a lot for your help and advice and have a nice day
>>928191
You're missing an important piece of the project. You can't just stick 12v to an LED unless it's got circuits to limit the current/voltage to levels it can handle without being destroyed, and it doesn't look like those LEDs have anything like that built in. For a high power LED you need a switching current regulator; a series resistor won't work out.
>>928191
wouldn't it be easier to get these and use 120vac led bulbs. then all you need to do is run a bunch of ac outlets (or extenson cords) throughout the barn. also make it easier to change the wattage if you need more light.
So I was cleaning out my grandma's garage when u came across this. She had no idea what it was so I kept it. It has a microphone with a 10ft cable, Ethernet port (no it's not rj45), and power. When I opened it I found a speaker.
What is this device!?
What does it do and how do I use it?
>>928310
>Ethernet port (no it's not rj45)
Wut? Ethernet ports are RJ45 so if it's not RJ45 why do you think it's Ethernet?
It looks more like an RJ11 connector like you'd use for a piece of analog phone line equipment. That device is probably part of an intercom system.
>>928318
Sorry I meant to say its not RJ11 port. Got my ports mixed up.
I was thinking it was some sort of phone thing too but why does it have ethernet and why is the mic so long.
It's really old and it has no lables so I can't tell anything else about it except for the internals
I'm just starting to learn about circuity and electronics of my own vocation, but I'm having a little trouble conceptualizing the value of an ohm.
Would the value of one ohm indicate that there is absolutely no resistance of a conductor?
For example, if I were to have a 1 volt battery in a closed circuit, with 1 amp of current in that circuit, can I assume that there is no resistance, and that the ohm value of the circuit is 1?
My logic is that a 12V battery in a closed circuit with 4 ohms resistance would produce 3 amps in accordance with Ohm's law, thus, 1V with 1 ohm would produce 1 amp (no resistance).
>>928336
You're gonna kick yourself, but no resistance means 0 ohms.
Think about real wires. Real wires have resistance. In practice it's very small.
>>928325
Are you sure it's not RJ45s? That looks almost identical to RJ45, but it was used in old analog telecom equipment, not Ethernet.
>>928340
Maybe I'm misunderstanding voltage then. I understand in reality that real conductors have a little resistance, but for the purposes of my example, I'm just pretending my circuit is a superconductor.
If I have 0 ohms of resistance, will 1 volt produce 1 amp...? I can't divide by zero... but as resistance approaches zero, it takes very little voltage to produce one amp... Or one volt will produce an large amount of amps...
So an ohm is just defined as the impedance required to slow a current (amperage) to one coulomb per second from a 1 volt battery?
>>928336
>Would the value of one ohm indicate that there is absolutely no resistance of a conductor?
No, it would indicate that the conductor had a resistance of one ohm.
You seem to be looking at your problems backwards. The resistance of a simple circuit (containing only restive elements) never changes. A battery and almost every other power supply is a voltage source which means it gives a voltage that never changes (ideally). The current through the circuit is what changes to satisfy Ohm's law, not resistance or Voltage.
>>928346
even batteries have some internal resistance
that will limit the current during a short
>>928348
>>928350
I think I'm caught in a vicious cycle of conceptual theory.
Amps are easy; just a charge (coulombs) traversing a conductor per second (current).
Voltage is the amount of potential energy needed to overcome resistance to current, and ohms are a value of that resistance? So volts and ohms are purely arbitrary values that correlate to amps via Ohm's Law? One cannot exist without the other?
If this is right, I think it's starting to make sense. I guess I was trying to define them as something tangible.
>>928356
Yeah, speaking as an EE who's taught electronics lab for physics students, forget about potential energy and shit. Start from V = IR and the concepts will fill themselves in as you go.
>>928336
This may blow your mind, but there's such a thing as a milliohm.
An ideal 12v battery connected to a 100milliohm resistor would develop 120 amps.
I wanna get this amp board kit, but I can't find out if it's AC or DC input voltage. The description says
"Supply voltage: Recommended +/- 25V (maximum voltage can not exceed +/- 30V, 18V AC full bridge rectifier is 25V)"
Listing is
http://www.ebay.com/itm/HIFI-Mono-Channel-LM1875T-Stereo-Audio-Amplifier-Board-DIY-Kit-/261872771029?hash=item3cf8d55fd5:g:858AAOSwBahVQ40-
pls help
>>928432
DC, dual supply.
Chink is trying to say that you can produce the required supplies by rectifying and filtering 18V AC. You can either use a transformer with a single winding and two half-wave rectifiers (requires bigger capacitors), a 2 x 18V center-tapped transformer and a diode bridge or a transformer with two separate 18V windings and two bridges.
>>928433
Ah, thanks! I assume I'd only need about 1.5 amps at 25VDC to power the amp adequately?
>>928438
No, you need dual supplies, +/- 25V. In other words, 2 x 25V so that the total supply voltage is actually 50V and the ground is the mid-point (so that you have +25V, 0V and -25V).
It also needs something like 2A of current at full power (to 8R load), or around 3A during peaks (or when driven to clipping).
>>928446
Sorry, currents are wrong. I thought it was a 30W amp for whatever reason.
>>928452
>>928450
And, just checking to make sure I didn't go full retard, would these two go together well?
http://www.ebay.com/itm/MINI-TDA7293-100W-Mono-Single-Channel-Amplifier-Board-Module-DIY-Kits-/131564588015?hash=item1ea1dc4bef:g:OQ0AAOSw5IJWe6OX
and
http://www.ebay.com/itm/AC-110V-220V-TO-DC-12V-Regulated-Transformer-Power-Supply-For-LED-Strip-Light-/261470580279
>>928452
The amp needs to produce both positive and negative half cycles and each half cycle gets at most half of the total supply voltage.
Let's say you have an 8R load and you're pumping 30W RMS sine to it. You can calculate from P=I^2R that you'd need 1.9A RMS current. Since it's sine, it means that the peak current is sqrt(2) times higher, or 2.7A. To get that much current through an 8R load you need V=IR=22V peak voltage. And that's your positive half cycle. You need -2.7A and -22V for the negative half cycle, so that the peak-to-peak output voltage is 44V.
The advantage of using a dual supply is that it's simple. If you want to use a single supply, you either need to feed the speaker via a large capacitor (since the amplifier output will be sitting at supply_voltage/2) or use two amplifiers.
>>928459
It's another dual supply amplifier and 2 x 12V is kinda low for it.
>>928462
Dammit, I meant the 10w x 12v version. I'm only powering a 60w rms speaker, so I shouldn't need all 100 watts. And I believe the power supply in question is a dual supply.
Hi /ohm/. I completely forgot about /diy/ and asked a question on /g/ out of ignorance and it seems that this general is fit for my question. Could anyone verify that what this anon said >>>/g/52364029 is correct?
>>928474
It's for LEDs, so I doubt it. It's much more likely that the ground is protective earth and that you'd need two of those bricks.
Try to find a kit built around some car stereo amplifier chip, for example TDA1516. They're designed for single supply operation.
>>928491
It's possible. Another possibility is that moisture/dirt leaks power to it (it's a bathroom lamp, after all). Or you have a dimmer switch.
>>928491
as the other dude implied, your switch is leaking current, which it shouldnt. so, it's either a cheapo dimmer that does not incorporate a switch, or it's a timer switch, or a smart switch, that always passes a tiny bit of current to keep itself powered-up.
if it's not the switch, then there's some non-obvious wiring errors.
Ended up breaking a USB port outta this, how would you guys go about fixing this? She looks pretty fucked to me
>>928674
if you got skillz, and fine-tip soldereing iron, that's not too bad. the power and ground are still in place, so you just have to re-attach the 2 data lines, which you can do by running some fine wire, like 30-gauge wrapping wire, from the connector to the two resistors.
alternately, you can solder the cut-off end of a USB cable to the 4 points, and have a permanent cable hanging out of the unit. (assuming this is not the kind of device you carry in your pocket)
however, if you dont have the skillz, then you will only make it worse. since you have to ask, i assume you're in this category.
>>928529
I can't find any kits that use regular ol' DC, so what if I got two of the 5A 12VDC power supplies and used them to drive the amp? Seems clunky and dumb, but would it work? And how would I go about wiring it up? Just ground to ground, and 12VDC from one to the + terminal on the amp, and 12VDC from the other to the - terminal?
Is it counterproductive to put a heatshrinked 3034 mosfet on a heatsink? I have one pre-wrapped and I would rather have the heatsink if I had to choose between the two. The mosfet would only have 4v going through it at a time if not less.
>>928847
>heatshrinked 3034 mosfet
Why did you put heat shrink tubing on it in the first place?
How can you tell if an LED has a built in resistor or not?
It's rated at 3W 3-5V, so should I just hook it up to 5v and record the amps across it? what should I be looking for?
They're pic related style but I don't have any other info on it.
>>927583
Good for the environment, probably. Not worth your time.
>>927488
nope, they're usually moving a lighter sled, and moving it more slowly.
>>928886
> It's rated at 3W 3-5V, so should I just hook it up to 5v
5V is a maximum, you dont start at the maximum ever, coz that's asking for trouble. so, you'd start low and increase towards the max while checking for temperature. if it's too hot to touch, you've gone too far.
a power LED like that will not have a resistor, and would normally use a constant current source at the appropriate rating for it, so that it doesnt go into thermal runaway.
>>927457
Digikey.
Mouser.
Free TI samples.
>>928880
>I have one pre-wrapped
>>928911
It had a 240V ac to 3-5v(?) converter with it, so would the current limiting happen in the converter?
Here's the stat sheet of a similar one, I'm starting with a 5V powered usb hub just for convenience sake, which I'm assuming is at least 3A (there's three I want to power in total)
Seems like I'll need beefy resistors to bring it down to 3.6v and dissipate that much power?
1A x 3.6v = 3.6w
I'm pretty new to this
>>928939
Alternatively I could gut it and replace them with a few 3.6v 20ma leds and just use 1/4w 100ohm resistors. That's something I've done before so I hope it's the right calculation. I don't think I'll need 2w of brightness for where I'm putting them.
>>928832
Yeah, two separate bricks is one way of doing it, but you need to have bricks which are floating. Those LED PSUs probably are, but I didn't see the ad really mention it.
The solution the Chink was referring to (18V AC -> rectifier) is the typical way to produce the dual supply for non-tiny amplifiers, but it requires a transformer and tinkering with mains voltage. Pic related.
The first amp chip you mentioned can also pretty easily arranged for single supply operation (the datasheet has a schematic), but then you need to wire it by yourself.
>>928973
What would have to change to the first amp to make it single supply compatible? I'm down with some reconfiguring as long as it's not balls-hard, but I don't know much about circuit-making or anything like that.
>>928928
I don't even know what is a 3034 mosfet, but Google suggests it's actually IRLB3034, which comes in a TO220 package.
Yeah, it isn't the greatest idea to have heat shrink tubing between the fet and the heatsink. How bad idea it is depends on power dissipation.
Cutting the heat shrink sleeve away shouldn't be exactly challenging.
>>928976
See the amplifier chip's datasheet.
www.ti.com/lit/ds/symlink/lm1875.pdf
The second page shows the dual supply configuration, which should be pretty close what the Chinaman used. Page 3 shows the single supply version. The principal changes are that the pin 1 is now fed from a voltage divider (R1/R2/C2), output has a large capacitor (C6) and the filter capacitors from the negative side are removed. The feedback thing (R6/R5/C3) is also using different component values, but there's a pretty good chance that the original values would also work.
>>928982
Alright man, thanks for the help! I'm trying to make a mono amp using this spare 60W speaker I've got, and this seemed to be the cheapest solution. I'll probably end up getting a car monoblock and a 12VDC adaptor though lol
I'm not sure if this is the correct thread for this so apologies in advance if it's not.
I recently managed to get an electric scooter for dirt cheap.
I've seen some videos of people with the same model who have tricked them out to got faster by changing the batteries out/ adapting the motor somehow.
Is this something a complete novice could manage to do with out destroying it or should I just find someone with more know how than me to do it?
Model:
http://www.razor.com/uk/products/electric-scooters/e300/
Example of modified one:
https://www.youtube.com/watch?v=DPXLMTt1WRo
>>929054
Based on my limited knowledge of such things, if you do enough research and ask around some more, this sounds like a pretty decent first-ish project. Maybe some fab work involved, but with such a simple concept (scooters in general) to begin with, I don't see how it could end up being that complex.
With that in mind, going 60 mph on one of those things sounds fucking terrifying. But hell, go for it, bro. You only YOLO once.
>>929076
I think he says 16 not 60, pretty sure you'd have to use black magic to make it go 60.
i want to power a circuit via batteries. the microcontroller i use needs at least 2.3V @ 8 Mhz (pic related). since there are some more components Vcc>3V will do (tested it)
now i don't want to use 3 batteries, because thats just too clunky. two batteries work fine, but only if they are nearly fully charged and i don't want to switch them when they aren't even fully discharged. i want to use the full capacity.
so what i would love to use is a boost converter that works from 1,8V-3V and provides around 3V-5V. also i would like to avoid an IC and use a discrete ciruit instead for interest sake.
i know the basic theory about boost converters but haven't tested one myself yet. will a typical circuit do the trick? what do i have to take into account, considering my requirements?
>>929091
The website says 15 mph max speed for the stock one, so unless he's doing all that work for one more mph, I feel like he said 60.
Or maybe I just want it to go that fast for teh lulz.
>>927421
I have 8 of those connected in serial from a thermalcycler. I was planning to use them (+rele +PS + arduino) to chill a few degrees a beer fermenter but I don't have any scheme so far
When you connect a microcontroller pin to something via a resistor in series, then how come the thing you've connected it to still "see" the voltage?
Like with an Arduino - it's 5v out of each pin so you can use it to control something with a 5v logic level. But you usually have to put a current regulating resistor in series (like with an LED), so how does the voltage drop of the resistor not affect the voltage seen?
Is it something to do with the impedance of the IO ports?
>>928258
Would this component work? I watched some youtube videos and think I understand what is needed.
http://www.ebay.com/itm/DC-DC-8-48v-to-12V-50V-24V-Boost-Step-up-Converter-Constant-Current-Power-Supply-/221946904722?hash=item33ad110092:g:pm0AAOSw8-tWUC6u
>>929232
If you're connecting a 5V output to something that actually wants 5V, then you wouldn't use a resistor.
If you use a resistor, then it's going to affect the voltage. That's the point of putting it there.
>>929133
> will a typical circuit do the trick?
Uh, what's a "typical" circuit?
In addition to the basic inductor-switch-diode-capacitor, you need an oscillator, and some kind of feedback to maintain a constant output voltage.
> what do i have to take into account, considering my requirements?
Given that you're presumably talking about very low power, there aren't really many constraints. Most of the design constraints relate to efficiency.
The basic design requirements is: don't exceed the maximum voltage, current or power dissipation of any component.
The capacitor's energy capacity needs to be such that each pulse should constitute a small fraction of the capacitor's total energy capacity, so that you don't get noticeable ripple.
You need to keep the inductor current below its saturation current.
You can operate either in continuous mode (inductor current never reaches zero) or discontinuous mode (let inductor current reach zero before starting each cycle). The latter means that you only get switching losses when turning off, not when turning on.
(tbc, field too long)
>>929312
(Cont'd)
The lower the switching time, the lower the switching losses. When the switch is fully conducting (saturation), there's negligible voltage across it thus negligible power dissipation. When it's off, there's no current and thus no power dissipation. In between (when the switch is in the linear region), there's power dissipation. Transistors (either BJTs or FETs) turn off faster if you actively pull the base/gate to ground than if you just disconnect it.
The higher the switching frequency, the higher the switching losses, but the smaller the required inductor (the inductor needs to be able to store one cycle's worth of energy for discontinuous mode, more for continuous mode). At high frequencies, you may need multiple output capacitors (i.e. something with low parasitic inductance to handle the high frequency components).
The energy dissipation of the inductor and capacitor will be determined by their parasitic resistance. Particularly for the capacitor, you need to average the square rather than squaring the average (nearly all of the power dissipation will occur in the charging spike at turn-off).
Bitches don't know 'bout my new toys.
Didn't come with pre-soldered headers. Included before & after soldering the included headers.
>>928940
Gutted it and replaced it with lower power leds, they're not as bright but the 3w were too bright to begin with. I'm happy with it.
>>929312
>>929313
with "typical" i was referring to pic related. like you said, inductor-switch-diode-capacitor. an oscillator was implied, i didn't think about feedback though
i guess i can't use the µC for pwm/feedback since its the part that actually needs the higher voltage in the first place. maybe a simple 555 circuit will do?
also, aren't there any restraints regarding the load? isn't the boost converter load dependant?
>>929586
>isn't the boost converter load dependant?
In discontinuous mode - yes, otherwise not so much. Basically, if the load is small enough, you need to adjust the duty cycle.
>µC
>555
Weren't you supposed to use discretes?
>>929598
the circuit isn't a task or anything, i'm just doing it out of curiosity. so i'm actually not supposed to use discretes but i feel like i won't learn much when i just buy a DC-DC converter
>>929303
What if the device wants 5v but would draw more current than the uC pin could supply?
>>929658
Then you use some kind of buffer, which can be a mosfet, a bipolar transistor or some suitable IC.
SUP LADS
former EE student here
dropped out of college and got addicted to heroin, spent 3 years in rehab ad forgot everything.
Where do I begin agin?
>>929738
kek
Got a simple question for any RC fags in the thread.
Can anyone identify this connector for me? I think it may be JST, but I'm not sure, and the documentation for the car doesn't say anywhere.
I'm looking to buy an upgraded battery for it and want to know what connector to get.
Hope it doesn't rotate my image...
>>929738
Don't waste your time waiting for the proper connector. You could just bodge something, it's only 2 wires
>>929775
This.
Ask yourself if you ever plan to sell it, if no, just cut that shit and use a terminal block or spades.
>>929780
yes
I think these leaded solder fumes are getting to me
>>929782
>>929783
Okay. Thanks for the advice.
Gonna buy a LiPo Turnigy 2200mAh 2S battery and use it as opposed to shit that Losi gives you.
And lets face it, I'm really just looking for shit that I can use with my new balancer/charger.
Man, fuck Losi for using their own shit mini connector as opposed to a real standard.
>>929775
>>929782
>>929783
Mk, just a quick update. Figured I'd take y'all's advice and rigged up the shittiest connector on the face of the Earth to see if charging using my dedicated charger would be faster, and it definitely is.
But I thought you guys may get a kick out of the shit job I did.
Pic shows the new charger, the shitty connector I made, the perilous way its connected to the battery, and the rating of the charger that the battery came with the 6+ years ago when I bought the rc truck.
>>928977
It is the IRLB3034, sorry for not specifying.
Yeah it's not a challenge, I'll just cut it if it's going to insulate a large portion of the heat instead of dispersing it.
I'm Working on a 8 step CV sequencer for my modular synth project.
simple prototype on my trainer.
>>929958
its a 4516 up/down counter counting through the 3 address pins on a 4051 8 way analoge mux.
the 8 inputs go to a voltage dividing pot each.
when the counter is clocked, the output of the mux outputs the voltages of the pots in sequence.
>>929818
>LiFe
So there's lithium ion and lithum iron? How ironic.
>>929960
working on adding a 40106 hex inverter to use as internal clocksource
as well as buffering for external clock input and gate out.
other plans are latching up/down button and input jack.
reset/count select switch or separate gate outs for each step, haven't decided yet.
also some sort of step indicator. 7 segment maybe.
>>927457
work and ebay
>>929958
Ah yes I remember your awesome breadboard from the previous thread. Rescued from work wasn't it?
>>929970
y-yes, thanks
I can't tell if you are being sarcastic or not.
I guess I'm just 4chan paranoid.
>>927457
I cruise the neighborhood and the college on trash day.
>>929833
Well, a quick calculation suggests that ½mm thick heat shrink tube would increase the thermal resistance about 20K/W, which is about the same as for the tiniest clip-on heatsinks (20x20x20mm). That is, the heat shrink tube alone would turn your infinitely large heat sink to an equivalent of the tiniest heat sinks.
To put it another way, the MOSFET with heat shrink tube would be capable of handling around 5...7W on an infinite heat sink and 2...3W with those tiny heat sinks.
And that 2...3W would correspond to 35...42A current at the nominal Rds(on) @ Vgs=10V.
>>927598
Staples. Rainbow peanut staples.
>>929960
it works.
Does anyone know cheap /diy/ friendly custom MCPCB supplier? Or is MCPCBs even worth it? I found some random article that says that FR4 with plated vias would perform just as well, but that seems bit suspect.
I'm working first time with high-power LEDs (maybe upto 20W total) so that's why I'm bit clueless...
>>930070
sexy as fuck
Got a receiver like this. Same model but not mine.
Overall it sounds pretty good I think, but this is my first fancy audio system.
Sometimes, the left channel will cut out entirely unless I set it to mono, and when I have headphones on I can tell the right channel is significantly stronger.
I was thinking of replacing all the capacitors, but I've never done something like that before. I found this guy http://www.vintageaudiobliss.com/2012/02/akai-aa-1010-stereo-receiver.html has done it, but doesn't list the capacitors you need. Is it as simple as reading the voltage and capacitance ratings and then buying capacitors of the same values, then soldering them in place?
Anything else I should know?
I'm in a microfabrication lab this semester and we get to make any IC we want for a final project. I'm not sure what application I should design mine for. At first I was thinking about making a fizz buzz IC for the novelty, but I might want something more interesting but still relatively simple.
Does /ohm/ have any ideas?
>>930223
weak and cutting out channels are commonly just dirty volume pots or buttons.
A telltale sign of bad caps is a loud humming noise.
>>930285
if you're into RC you can make a controller board that has a microcontroller and 2.4ghz receiver on it so you can mod different stuff to be controllable from a smartphone
>>930223
>Is it as simple as reading the voltage and capacitance ratings and then buying capacitors of the same values, then soldering them in place?
Yes. That said you most likely don't need to.
Give the switches a clean with some of this. Not too much. You don't want it everywhere. Just squirt a little in the switch and push / turn it a bit. I wouldn't put it in the mains switch. Switched headphone sockets can need some on occasions but it sounds like your fault is before that.
Other than that check for dry joints which you want to do anyhow in something of this age.
i've heard multisim can do microcontroller simulation, but since everything in multisim is complicated and unstable i can only assume that is too. can i easily use that feature to have code toggle outputs based on inputs during the schematic simulation?
i'm not doing anything technical, i'm just trying to use multisim to understand switching power supplies better and that requires implementing a PID loop to control output voltage. which i'd like to do in a few lines of C instead of simulating some bullshit voltage controlled pwm circuit if possible.
>>930285
741
555
7805
7474
sampling gate with drivers
time to digital converter or a part of it
1b processor
flash or folding ADC
fast test pattern generator
electrometer amplifier
wide-range hall sensor
"high voltage" charge pump with integrated capacitors
temperature sensor
How do i make LED lamp (only need one) for 12V AC current.
stereo lamp (filament bulb) burnt out and i want to replace it with LED, but i looked everywhere and every site gives this large robust circuits. I need something small and compact so it can fit in receiver
>>930360
Oh you. No you don't. Just keep the rectifier (diode bridge) part outside the tight spaces. That is, put the rectifier somewhere near the transformer where there's space for it and wire the 12V DC output to your LEDs.
Also, since you know your bulbs are 12V, why not use 12V bulbs?
>>930368
because i live in gods forsaken land (croatia) and i just went to our larger store (chipoteka) and i asked for 12 volt light bulbs and they only have 12V DC light bulbs. I guess i will have to order overseas again
>>930377
cont.
I have just returned from my trip to store. Bought AC to DC converter (220V 50Hz -> 12V 600mA)
Will that converter run or burn my gramophone (12V 100mA).
also how can i know which is negative and which is positive. One has straight line like this ___________
The other has straight line ____ and broken line like - - - - - -
>>930384
Dashed line is 0v straight line is +ve
Voltages are the same and current supply should be greater than current load so it looks like its good to go
>>930435
I can check and have checked adapter polarity. I'm worried on polarity of those 2 wires sticking out of gramophone. I can't check those untill i plug them or connect them
>>930447
Use the continuity measurement on a multimeter and see where the wires go inside the gramophone, see of you can find any input filtering capacitors as that will reveal which wire is positive and which is negative.
Is there a model number for this gramophone? One of us might be able to find some schematics.
>>930455
Oh wonderful. How old do you estimate the gramophone to be?
>>930458
sanyo TP59
found it in same attic as this receiver. So I guess they were bought at the same time. My uncle says he doesn't remember, but i guess if receiver is from '72, so is gramophone
it has 3.5mm jack. How can i transform that into those 2 chinch cable so i can connect it to back panel into phono 1/2
complete beginner here: how would i go about making a simple contraption that would have single knob to shift the pitch and would just splice between your speakers/headphones and the audio output (pc/phone)
>>930360
> How do i make LED lamp (only need one) for 12V AC current.
Put a diode and resistor in series with the LED. You don't need a bridge rectifier (half-wave rectification just means that you get 50/60 Hz flicker rather than 100/120 Hz). The diode is there because LEDs are typically limited to ~5 V reverse voltage.
>>928052
I would recomend a breadboard, i started with arduino and breadboard but i already knew programming so meh.
>>928067
Radio shack by me doesnt even have male to female jumper wires
>>928912
Can someone explain how to get free TI samples?
>>930468
You'd need a microcontroller, because pitch isn't a property that can be changed by linear transformations the way, say, volume or EQ can.
Briefly, you'd capture the incoming sound, FFT it, move the FFT up or down, then inverse-FFT it and output it.
There'll be some latency, because FFT is only meaningful over a sampling period.
>>928346
its just the ratio between voltage and current. half an ohm means a conductor that happens to allow 2amps for every volt. wires are probably even less resistive than that.
i shorted a 12v battery once. the plastic melted on the wire and burned me. i dare say there was far more than 12amps drawn.
division by zero means current tends to infinity in theory. 0 ohms = superconductor.
>>930548
fuck, i knew there was a reason i couldnt find a simple project like this
I wanted to control an indicator bulb with a pot so i got this 10A power transistor and quickly realised my 1/4 watt resistors on the base were overheating so i tried this.
By trial and error i got a good pot "mapping" to bulb brightness. Still the resistors get hot though. And the power transistor does too and its not near its rating.
Can some arrangement with 1/4 watt resistors be made with this setup?
What are the key transistor parameters I should understand?
> Can someone explain how to get free TI samples?
search for the part you want on their website, if you hover over a part #, you get this popup which includes Sample and Buy; click and follow instructions. doesnt work with every part.
>>930627
>Can some arrangement with 1/4 watt resistors be made with this setup?
I mean without overloading the resistors. Also the voltage source is a lab power supply.
>>930627
your circuit is wrong. your pot is essentially in series with two diodes to ground, which makes it super touchy and likely to burn up.
you want to put the load on the emitter, and wire it up like this instead.
>>930631
>your circuit is wrong. your pot is essentially in series with two diodes to ground, which makes it super touchy and likely to burn up.
I don't understand. I realise 100ohms is probably too low but when the pot is maxxed it's about 1mA. Should i pad with a 330ohm maybe.
Also why the load on the emitter? So the lamp can use the base current too? Or to add more resistance from pot to ground?
>>930633
you should just try it instead of asking questions. it's faster and you learn better.
having the load on the collector essentially makes it an on-off circuit. as soon as you apply enough current to turn on the transistors, the lamp goes on full power. by putting it on the emitter, you can raise the lamp voltage incrementally from 0 to about +12 so you have a range of brightness.
>>930637
Cool. i will do it thanks.
>>930637
>having the load on the collector essentially makes it an on-off circuit. as soon as you apply enough current to turn on the transistors, the lamp goes on full power. by putting it on the emitter, you can raise the lamp voltage incrementally from 0 to about +12 so you have a range of brightness.
i never knew transistors were magic.
>>930676
care to elucidate on your retard-o comment?
>>930682
ic~=ie
> ic~=ie
true, but so what? the difference is in the transfer function between input current and output current. with an emitter load, it's a nice straight line, with a collector load, it's more like Al Gore's hockey stick graph.
>>930692
maybe if you are dumping the load voltage onto the base instead of working out the current range to drive the load properly.
load on the emitter is just another voltage drop to factor in calculating your base current
you don't need to worry about a the voltage drop of the load on a collector, figure your base current wrt the be drop which is pretty much always .7 or 1.4 or something reliable and boom done. no sweat.
sometimes you can't drive the base voltage up to overcome the load drop either, say you want to switch something with a uC that supplys 5v only? 12v load? tough shit.
load on the collector is better but in theory there is no difference between the two methods.
>>930704
you're not entirely wrong, it's more like they gave you the wrong glasses so your view is hazy, confused, incomplete, incoherent at times.
>>930627
> What are the key transistor parameters I should understand?
h[FE] (i.e. current gain).
The 2SC2625 has a minimum current gain of 10. That's not very high, but it's not atypical for a power transistor.
A 12V 21W lamp will draw close to 2A of current. With a gain of 10, you're talking about 200 mA of base current. With an 11-point-something volt drop across the base resistor, that's around 2W dissipated in the resistor.
In this particular application, you'd be better off using an emitter-follower, i.e. putting the load between the emitter and ground. That way, the base voltage will rise as load current increases, meaning the amount of voltage you need to drop decreases as current increases, which will limit the power dissipation in the base resistor. It will also make the load current less dependent upon the transistor's gain, which varies with temperature.
Another option is to use a MOSFET instead of a bipolar transistor.
What's a good way to start learning to repair electronics? I don't have any broke shit. Do pawn shops carry broken electronics? Do I need to find a junkyard perhaps?
>>930768
in the city, i see old or broken electronics on the street pretty much every garbage day as i walk around; printers, stereos, TVs, VCRs, washing machines, electric gardening tools, etc. a thrift shop will have stuff which is usually ok or half-broken, or missing pieces, very cheap. there's also a repair shop nearby: the stuff that would cost too much to repair, they put outside in the lane.
So i have a 12V powered sign for a car which i want dimmed, preferably with a potentiometer.
I was measuring the current and it is 7A so we are talking about 84W of power, also it is a lightbulb.
I don't really care how complex it will be aslong as it will work.
Pic related is the most related circuit i found but i have a 12V source.
>>930765
>In this particular application, you'd be better off using an emitter-follower, i.e. putting the load between the emitter and ground. That way, the base voltage will rise as load current increases, meaning the amount of voltage you need to drop decreases as current increases, which will limit the power dissipation in the base resistor. It will also make the load current less dependent upon the transistor's gain, which varies with temperature.
That's a lot to get my head around. Any good online guides to help? Transistors are mad.
>>930842
triacs are no good at DC. you need a PWM circuit driving 1 or more FETs. this circuit, for example, with 4 FETs is good for 30A. site is here: http://chemelec.com/Projects/PWM/PWM.htm
>>930765
I changed the circuit so the bulb is on the emitter. It's definitely better - the resistors didn't get hot anymore.
The bulb was a little dim so I played with the resistors. I found that when I took the base resistor off the first transistor, the bulb stayed on.
So that stage didn't seem necessary so I took it out. Now it looks like this and seems to work perfectly. The pot (of which I'm only using the 2 legs) seems fine. I measured the base current and it's only about 63mA tops.
Previously I measured the bulb to draw about 1.6A now in this circuit the whole thing draws about 1.5A.
Is this setup advisable? The power transistor gets damn hot too. still. Is that normal for this application?
>>930971
What are the diodes on the FETs for?
>>930990
protection diodes.
absolutely necessary on with any inductive load.
bulbs you might not need them.
most powerfets have them built in anyway, so no worries.
>>930971
Alright anon, thanks a lot for the answer, i can go on from here with this.
>>930995
Ah yes like the diode across a motor.
>>930986
Does the load on the emitter make a votage divider with the base resistor? Or would it be one anyway? Does a transistor base have an appreciable impedance or is it essentially a wire to ground?
>>931004
The inductive load would be where it says Load, it looks like 1 diode would do the job here too but i believe if you use one at each Source - Drain it would distribute the power equally. Maybe the diodes are just added next to each FET so you know which one you should get more easily since most power misfets have a diode between S- D integrated already.
>>931000
I just experimented with this. Seems like a resistor on the base and on the emitter does act like a voltage divider. When I short the emitter to ground though, I still get some voltage at the base, so the path from base to ground (via emitter) must also have some inherent resistance, right?
>>931008
>The inductive load would be where it says Load, it looks like 1 diode would do the job here too
Yeah that's what I thought.
>>930986
removing the first transistor is not advisable. a pot isnt meant to carry any appreciable current, and 60mA is way too much. if you put back the first transistor, you can reduce that current by about 100 times.
> The power transistor gets damn hot too. still. Is that normal for this application?
it's normal in this kind of setup. at half brightness, the transistor is gonna dissipate about 10 watts. if that's not acceptable, you have to go the PWM route, like the circuit shown at >>930971
>>927598
This is my first time ever on this board and even I know what those are.
>>931033
>I'll see if I can get the Darlington pair setup working
well, using the darlington pair means you lose about 1.4V, so if you start with 12V, you end up with 10.6V on the lamp. but, if you start with 13.4V, then you end up with 12V, so you dont lose any brightness at all.
>>931041
Is the drop the same on the BE and CE junctions of a transistor?
no, BE is almost always 0.6 to 0.7, whereas the CE is 0.2 and up to infinity.
>>931047
Where does the 1.4v figure come from?
there's two transistors, so 0.7 + 0.7 in series
>>931056
But the load only goes through one.
the 'how do i bias an NPN transistor' explanation takes about 5 minutes in person, and a week thru text. so just know this: emitter voltage is base voltage minus 1 diode drop. since you have 2 transistors in series, it's 2 diode drops. the collector drop is of no concern to us (in this configuration) coz the emitter is king (in this configuration).
>>931063
>the 'how do i bias an NPN transistor' explanation takes about 5 minutes in person, and a week thru text
Ain't that the truth. If i just had someone to ask in person.
>. so just know this: emitter voltage is base voltage minus 1 diode drop. since you have 2 transistors in series, it's 2 diode drops. the collector drop is of no concern to us (in this configuration) coz the emitter is king (in this configuration).
Ok I see that now. I thought the transistor was just modulating between short and open crcuit between the collector and emitter - thus letting you go between 0 and the supply voltage,
>>931063
>>931069
Having said that, i thought it was the collector/emitter drop. As in a drop has to exist between 2 points. How can there just be a collector drop?
The only factors are the 2 BE drops, though, you're saying?
Even though most of the current comes via the collector, the collector drop doesn't play a part?
This is confusing.
the collector just deliver what the emitter asks for, or dies trying.
so, putting 8V at the base means 6.6V at the emitter. the collector drops 5.4V in this case, or in general, it drops whatever is necessary to provide what the emitter has ordered.
>>931086
Wow that explains a lot actually.
>>931073
Collector current (Ic) is proportional to base current (Ib). Emitter current is the sum of the two.
Base current is proportional to .. well, unless it's limited in some way, it isn't proportional to anything. It's roughly exponential with base-emitter voltage. In practice, this means that if Vbe is below 0.65V, Ib will be negligible; once Vbe goes over 0.65V, Ib will be whatever it can get.
Putting the load between the emitter and ground (emitter-follower) means that the base voltage will be 0.65V above the emitter voltage (or conversely, the emitter voltage will be 0.65V below the base voltage).
If you try to increase Vbe above that figure, Ib increases, so Ic increases, so Ie increases, so Ve increases, so Vbe reduces. If you try to reduce Vbe, Ib decreases, Ic decreases, Ie decreases, Ve decreases and thus Vbe increases. IOW, you have a negative feedback loop which tries to maintain Vbe at 0.65V.
I'm pretty new to this, sorting out all my bits before I get too into it.
What's the best way to sort capacitors? I have this set of just generic ceramic ones, not sure what voltage they are.
Sorted them by number then looked up what the numbers meant, so the first 2 numbers are exactly what they say, then the 3rd number is how many zeros to add after the first two numbers?
301 = 300
653 - 65000
So would this be the best way to sort them?
101 = 100
121 = 120
102 = 1000
122 = 1200
>>931180
Sorting your caps in ascending order by capacitance is a pretty radical method. Usually people sort them by their relative shininess.
>>931185
Remember when trolling used to be good?
>>927666
The other anons don't know what they're talking about. Topology-wise, that looks fine. Keeping the power amp in the feedback loop like you're doing will greatly help to reduce distortion. If it it simulates OK, I'd go ahead and try it out. Be mindful of heatsinking.
>>927824
Do you even know what you're looking at? Or what purpose the tl072 serves in that schematic?
If you think that's confusing, you clearly have no idea what a power amp schematic looks like.
>>929610
You'll learn as much as anyone that does circuit design for a living. IC boost converters exist for a reason!
>>930704
Are you an idiot? Using the transistor as an emitter follower is probably the best way to do *variable lamp brightness* without resorting to pwm. You have half of the answer yourself - the base emitter drop is .7v. Therefore, the voltage across the lamp is ALWAYS the base voltage minus the base-emitter diode voltage. The transistor's gain will attempt to make this as true as it possibly can.
As for how linearly the voltage across the lamp tracks the brightness of the lamp: I don't know.
>>931028
There is a ~roughly static voltage drop across the base and emitter of .7V (the base-emitter junction is a silicon diode). Hence the bipolar-junction transistor.
>>930619
Hou can find cheep microcontrollers on gearbest id suggest funduino, maybe the uno model...they might have a wearable model...
>>930468
Try and search for Atari Punk Console or any other 555 astable circuit, it should be exactly what you are looking for
I frequently see circuits that use gate drivers following logic outputs to control power fets. Are these really necessary? As I understand it modern mosfets, even for high current applications, still only need logic-level voltages at extremely low currents to switch fully on.
>>931324
I should note that I'm not referring to isolation when I say gate drivers. The particular circuit I'm looking at still had transformers for that.
>>931324
Not all MOSFETs are logic level devices, as logic level drive is a compromise.
Also, while you need only minimal amount of current to keep a MOSFET turned on (or off), you'll need lots of current to make them switch fast.
>girlfriend's dad was throwing away old shit
>I saved this sharp RF-F816 from 1988 ($350 at the time)
I can't for the life of me find a manual, and I don't know how to provide power to it. It's a car radio, so it has a 12V input.
Can anyone help?
It would be a shame not to see if this beautiful radio still works.
>>931242
Not that guy but the tl072 still is a bad choice.
>>931334
It works, it's unlikely to be the limiting factor in that design and it's cheap and easy to get. The primary problem with it is the limited supply voltage range, but the same applies to the most opamps. And if he's unhappy with it, he can always just drop another opamp in its place.
If he wants to improve the circuit, he has plenty of more interesting options to check. Like that level shifter / drive stage and frequency compensation. Short circuit protection would be nice to have in an experimental amp, too.
>>931333
There are three leads coming out of the device. Just open the lid, it shouldn't be rocket science to figure out which one is positive and which is negative. Heck, you could even try measuring continuity against the case with a multimeter
>>930288
>A telltale sign of bad caps is a loud humming noise.
I didn't notice it at first, but when I turn the volume up past about 1/3, I can hear a humming.
Will also clean all the stuff inside.
>>931356
Is that because it is letting lower frequencies pass through?
>>930070
This is amazing. I'd love to make something like this.
I've recently been reading some books on basic electronics as was planning on making some effects pedals, but was only thinking today that maybe making modular stuff might suit me a lot better as I don't play guitar but am into synths and general sound design.
Do you have any advice on where a good place to start would be for learning about electronics for sound generating and processing, preferably euro rack stuff? I have a few pedal kits to build and basic soldering skills.
digikey's product table for all of the transistor categories has a column titled "max power". is that the device's maximum rated dissipation, or the maximum Vds*Id? it doesn't say anywhere, including a datasheet i looked at.
>>931418
whoops nevermind i just found a 125W dissipation limit on that device's datasheet so i'm assuming that's what "Power - Max" refers to.
>>927806
Are peltier coolers a practical method of cooling test tubes by 10-20C or am I better off sticking with an ice bath? Obviously the coolers would allow much more fine tuned control, which would be useful.
>>931418
Correct, this is the devices maximum power dissipation rather than V x I handling ability.
Bearing in mind that these are the absolute maximums under ideal heatsinking and @25c, you won't get anything close to that in a practical application.
>>930986
Look into buck converters instead, they are much more efficient and can be purchased on ebay very cheaply.
>>931324
1. Not all MOSFETs are "logic level".
2. A "logic level" FET typically needs 5V Vgs; if you're using 3.3V logic, it's unlikely to be enough.
3. Even 5V isn't enough to fully saturate most "logic level" FETs; you need more if you want Rds to be close to its minimum value.
4. Large FETs have significant capacitance. If you want them to switch fast (in order to minimise the time spent in the linear region where both Rds and Ids and thus I^2*R are significant) you need to be able to charge and discharge that capacitance fast. A decent driver will push/pull *several amps* to/from the gate in order to achieve fast switching.
5. If you're driving a push-pull pair of FETs, the high-side FET will have its source above ground, maybe even well above the logic level. The gate needs to be 5V+ above that, so you definitely need a level shifter (high-side drivers often also include a charge pump to generate a gate voltage above the supply voltage).
>>931418
It's the dissipation, which will be the integral of Vds*Ids over a cycle (or over the device's thermal time constant, whichever is shorter).
Typically, Vds[max] relates to the "off" state, while Ids[max] relates to the "on" state. You shouldn't be approaching both of those limits *simultaneously*.
What's a good, cheap function generator?
>>931471
>very cheap
Custom mp3 files on an old cell phone, I've used this method before and its fine for basic things.
>less cheap
Chinese kits on ebay or second hand.
>>931473
Explain this mp3 on cellphone method for me. I assume you create a music file with the particular signal you want to create and use an aux cable as input?
>>931474
you assume correctly. you can use programs like Audacity to create sine and triangular waves.
>>931474
Yes. It's a bit cumbersome but in the past I have used audacity to generate waveforms and export them as mp3's, then once transferred to a phone just connect the headphone jack to the circuit (careful not to short it).
I used this method to test a small audio amplifier I was building, if you are feeling confident you can use the audio output of your PC directly using a program called SigJenny.
I want to make an amplifier using a TDA2030. I have this toroidal transformer. It's rated for 60VA and 50Hz. From what I have read, it can run on 60Hz just fine.
It has a wire for the neutral, one for 110V and one for 220V, then two for 12V. I also have some rectifier diode bridges and a few large capacitors.
How do I make it so that the amplifier can run on either 220 or 120v? Is there such thing as a capacitor calculator to determine the optimum capacitance? I assume 35V capacitors will work just fine, right?
>>931478
>SigJenny
Sorry I meant to say SweepGen, SigJenny hasn't been updated in years and give an error on my PC.
http://www.satsignal.eu/software/audio.html
When using a PC soundcard as a signal generation be sure to exercise caution, one wrong move could seriously fuck up the card. That's why I suggest using an old cell phone first just to make sure the circuit works correctly beforehand.
A good start would be making up a custom aux lead with some 1k resistors in series with each channel.
>>931484
Awesome thanks
>>931362
Dunno. I guess I'll unplug the input and check
>>931483
> It's rated for 60VA and 50Hz. From what I have read, it can run on 60Hz just fine.
Yes, running a 50hz transformer on 60hz is fine. You can't run a 60hz transformer on 50hz however.
>How do I make it so that the amplifier can run on either 220 or 120v?
Using a switch like they do on some PC power supplies, make sure its correctly set before powering it on. A metal switch lever must be earthed/grounded for safety.
>pic related
>Is there such thing as a capacitor calculator to determine the optimum capacitance?
Rule of thumb is about 2000uF per amp of DC load, for an audio amp you may want to increase this a little.
> I assume 35V capacitors will work just fine, right?
For 12vac that gives just under 17vdc when rectified and smoothed, so yes 35v capacitors will be fine.
Read up on this guide about transformers and reciters+smoothing caps, you'll need to derate it for DC loads. With a full wave bridge rectifier and smoothing cap that 60va transformer will suddenly become a 37.2 watt transformer.
http://www.hammondmfg.com/pdf/5c007.pdf
>>931492
Thank you very much. Also, where does the ground on the amp circuit go when there's no center tap on the transformer?
>>931494
The protective earthing for a metal switch is different from the circuit ground of the amplifier, which should be left floating.
Are you intending to make a split rail supply with a non center tapped transformer?
>>931495
What is a split rail supply? Is it one with +12V and -12V? If that's the case, then yes, it's what I intend to do.
>>931496
I don't think that transformer is suitable for that, as each rail will only be 8.5v with 12vac on the secondary (excluding diode voltage drops).
You'll be better off with the single ended setup as split rails with that transformer is very close to the minimum voltage for the chip in dual rail configuration (+/-6v vs 12v single ended).
At such a low supply voltage you should really use 4 ohm speakers to increase maximum volume before clipping.
>>931499
Hmmmm, if that transformer is not suitable for that then I bet get another, because it's heavy as fuck and not easy to mount to a chassis. If I made the amplifier single ended I'd need a voltage divider to bias the input stage, right?
>>931503
You mean that potentiometer in the image? If so that's just for volume control, you connect one channel of your audio source to "Vi" and the other end to circuit ground (the power supply negative in this case).
If you're feeling confident you could always add a couple more secondary turns around the core to get more voltage out, you'll want about 22vac for a 30vdc supply.
>pic
The top voltages are for split supply whilst the bottom is single ended, y axis shows max output power compared to supply voltage.
I have 5 or 6 fax modem boards (ISA / PCI) which i want to use up somehow. I have an idea to connect one to telephone line and use it as answering device, but that's only one card. Do you have any more ideas what cool things can be done with them as they are?
I consider to cut their edge connectors and use them for my custom expansion boards, but want to double check if I'm not missing out on something.
>>930545
No.
Free samples for personal projects is a jerk thing to do and is abusive to the goodwill of a company that wants to help other companies make products.
>>931471
555 timer which are usually half a dollar or even less if ordered OTI
>>931645
a 555 only generate pulses which makes it essentially useless as a function generator.
>>928064
Overdriven LEDs (like the ones you find in a typical retail LED light bulb) burn out so you have to buy new bulbs. If you drive them properly, according to the original TI spec sheet, they might get a little dimmer after 50 years. I've never seen one in an indicator application burn out. Never. (Barring massive surges and/or lightning strikes)
>>931642
>abusive to the goodwill of a company that wants to help secure future revenues.
>>931671
Its ok for square and triangular wave.
