Ok so i have a dc motor, pic is my motor. Im trying to make it variable speed. I bought a bridge rectifier and it works great at full speed. Now i tried using a rotary dimmer with a capacitor with little sucess at low speeds and torque. So im going to get a pwm but not sure how to wire it. Do i still need the bridge rectifier? Or does pwm act as one.
>>900816
what kind of rotary dimmer? like a lightswitch?
not a good idea uts not designed for inductive loads like a motor
you can use an autotransformer instead.
pwm is a technique not an object, the components you need depend on what pwm driver you buy or build but if it requires dc you will need to rectify it.
Op here. Is this how to wire it?
>>900816
PWM is still DC. As you can guess from the name, it's just variable pulses from 0 volts to whatever your max voltage is.
>>900818
So if i use this one. Sorry im not too knowledgable on this
http://pages.ebay.com/link/?nav=item.view&id=301390515744&alt=web
Yes all you do is connect the negatives and positives. Maybe you should read a book on electronics or something...
>>900820
Pulses to max voltage of motor? Or outlet?. My motor is 90v and outlet is 120
>>900825
Maybe a book a being helpfull works too. Did i need to put every minuté detail for you?
>>900826
Saying your motor is 90 volts doesn't really mean much, it's just designed to tolerate a maximum of 90 volts. Your outlet's at 110-120 volts, and the rectifier is going to drop that a little, because that's how diodes work. So let's say you have 110 volts on the modulator, then assuming it can handle that much, the output signal will be 110 volts ideally. The motor and modulator might not be able to handle ~110 volts since they're rated for a max of 90, so if that's a problem you need to reduce the voltage with a transformer before the rectifier. Read the sticky/google next time, it'll do ya good.
>>900816
To change the speed of a DC motor all you have to do is vary the VDC voltage. The simplest was is to just put a potentiometer in series with the motor... Not really any need for anything else. Pwm is more efficient than this method but for one motor I don't think there will be a huge difference in what you end up paying for energy.
>>900824
that one is the same one I happened to find on aliexpress (pic related)
you need two things to do this: 1) a DC motor speed controller, and 2) a DC power supply.
both need to be able to put out the voltage and current that the motor needs.
the bridge rectifier is wrong, shit's gonna burn up. Also wrong is "an autotransformer" and "a potentiometer". They won't work either.
If I bought a generic-China motor controller rated for 10 amps @ 90 volts, I would try to keep it to maybe 75% of those values. The motor current is only 2.6 amps so that's no problem. I would recommend using a 60v power supply instead of a 90v though.
The China stuff is low-priced but not built perfect.
If you MUST run the thing at 90 volts, then you want a cooling fan on that motor controller (you should probably put a little fan on it anyway)
![183349[1].jpg](https://i.imgur.com/myqfEzA.jpg "183349[1].jpg")
>>901588
just rebuilt a new control box for a superfinisher. the germans apparently thought it was a good idea to mount all their components directly onto a machine that is made to vibrate like a motherfucker and the components would just shake right off the board, but i digress...
in looking for new pwm control boards i came across both those products in your image. i ended up going with exactly that pwm board and it works great, got it off amazon for something like 14 dollars because reviews were good and im not waiting on shipping from china. that power supply was also on amazon with pretty shitty reviews. i ended up getting an ac step down transformer, 120 to 24, and using a rectifier to convert to dc for the input to the pwm boards.
of course this was all for 24v motors but the end result was great speed control and much improved motor operation at low speeds compared with the amplitude modulation(?) control boards that came with it.
>>900830
You're fucking wrong on that mate, when rectifying AC you'll get the voltage multiplied by the square root of 2 minus the diode drops, which means you'll get a voltage of 170 volts when rectified, meaning that indeed OP will need a transformer. You'd better not help anyone when lacking this basic knowledge.
At least the motor will not be likely to tolerate this voltage for a long duration.
>>901751
Yeah, OP will break his motor going straight from a rectifier. Don't do that shit!
Plus there's the whole issue of not having any isolation from mains...
>>901751
>which means you'll get a voltage of 170 volts when rectified
Only if you insist on adding a capacitor after the rectifier. If you omit it, the rectified AC is from motor's standpoint worth the average value, or around 100V.
>>902165
I mean over a maximum of 50% pulse width.
