Hey /diy, I come seeking your wisdom on what is likely a very basic 'problem'. Hope you can help!
I have 5UV LEDs in series and a 3v motor (for a fan) and a Push-Hold switch. Power is 9vDC.
My issue is that I can't get both the LEDs and motor to work simultaneously with LEDs at a reasonable illumination.
I reckon the current demand from the motor is too high. I have tried varying the resistance as I don't mind if the motor runs at fewer rpms but the LEDs do not light up sufficiently.
I am now playing with some transistors to see but I feel like I'm fumbling in the dark.
Voltage drop per LED should be around 3V for UV
You might need more voltage mate
Wire them in parallel you git. 12v = 1 motor || 4-5LEDs or 3LEDs + resistor if you're worried about avalanche
>>1009582
Tip here is that the same current goes through leds and this motor. LED will burn if you apply more than 20mA (it depends on led power, but i assume you are using small ones). On the other hand typical motor needs more than 20mA.
You'd better make it parallel (motor in one branch and leds in another)
>>1009593
I considered this and read up a bit on it and concluded it wasn't as straight forward as that.
I calculate total demand is 20.5v (3.5 for UV LEDs and 3v for motor) although the motor will operate at 1.5v so can be 19v.
Forward currents come to 170mA.
Is there really not a better way like using a transistor as a PWM?
>>1009594
Cheers. Am I right in thinking each led will require a resistor?
>>1009598
Or like pic related is good?
>>1009582
I have seen true horror.
Dog those leds can't support the current that motor wants to pull, first of all.
>>1009609
I posted the image there, because your question is a simple question that does not deserve its own thread.
>>1009601
Try this
Random anon here, would this work? Just interested.
>>1009647
it will be working, but not the way you want.
The current wont go through leds, but motor will be spinning
>>1009625
why use one resistor when you can use three!
>>1009743
Using one R and all LED's in parallel results in unequal brightness due to slight manufacturing differences in the LED's forward V rating.
LED current is not linear. A slight change in LED voltage can cause a large change in LED current.
>>1009625 has it right
>>1009781
normally you can get away with just putting a bunch of leds in series because our eyes perceive increases in light logarithmically. However that will lead to premature failure of the leds, as more current is dissipated in the poorly manufactured ones.
Truthfully it's better to use a current regulating circuit to drive an led. However that's a little above ops current level, so sticking to the parallel led and resistor is the best design.
>>1009582
There was a thread about simulating circuits or some shit, try that out?
>>1009743
Because then you'd have to find a resistor with more than 1/4W rating.
>>1009936
Nevermind I'm retarded
>>1009853
Also, putting resistor in series with motor is usually not a good idea.
wow, lots of replies but not one correct answer so far.
>>1009625 is close but it shows a 3V motor being driven from a 9V battery meaning it'll burn out the motor. to fix that, you gotta put a power resistor (or maybe a light-bulb) in series with the motor to drop 6V. the calculation for the resistor is 6V divided by the motor's rated current. assuming it's rated for 0.2A, then you'd need 30 ohms, the power rating needed is 6V * 0.2A or 1.2W. realistically you'd use 3W or 5W.
other simple options include an LM317 wired as a constant-current source, or 8 diodes in series.
>>1009942
I totally omitted the part that motor is 3V :D
>>1009942
Simple solution to get 3V from 9V is to put some 1n4007 in series with the motor.
>>1009944
and some means about 9 :)
>>1009582
lamps/led parallel
Is everyone in this thread trolling or just really, really ungodly retarded?
UV LEDs typically need ~4V. Two LEDs and a resistor in series is about right for 9V.
But 9V is way too high for the motor, so you'll either need to drop most of the voltage using some resistors or diodes (which will consume twice the power the motor does), or PWM the motor (which isn't trivial if you don't know the first thing about electronics).
You'd be better off using 3x 1.5V cells in series for 4.5V. You'll waste less energy that way. You'll need a 15 ohm resistor for each LED and either a resistor (value depends upon motor current) or two diodes for the motor.
>>1009942
>>1009582 (OP)
here u go amigo. replace ampmeter and 18.7 ohm resistor with your motor.
trust me, I waz engineer
>>1010150
>UV LED
>3-3.6V per LED
>has 5 in series
>actually trying to use a transistor as a current controller
Get real faggot.
>>1010157
u just godda heatsing :D
>imblying dat transformer can't boost 1kV
>>1009834
>sticking to the parallel led and resistor is the best design
holy shit just kill yourself already
>>1009625
OP here. Thanks anon, this works just fine!
Only additional mod was changing the motor to a 5v brushless mini (pc type) fan.
In a few hours will post pics of the build.
Thanks to all anons for your contributions
