pwm motor controller project - Page 1
Forum section: electronics / projects

author: jackbob
author_rank: Regular Contributor
timestamp: November 05, 2011, 01:39:27 am
content: A while ago i made a few posts asking questions about building a pwm motor controller and finally built it and here it is. So frst off lets just say the construction is a little janky ... i know but it is half way good. anyways it has 20 IRFP250 mosfets to power it and I dont have the large power connectors on yet nor are the solder tracks large enough yet ( I need to buy more solder). it works great, the little green terminal post in the front is where the 12v rails and 5v pwm arduino signal hook up to. There is also a picture of one of the two blowers I will be using to cool it down. I have ran it at 120vdc but not too much current yet. Its mainly just for hobby not a real professional job on construction but it is pretty good just for a project ( remember i'm only 15) I have sort of a low budget not enough to make pro pcb's but its god for me. there are two tc4422 mosfet drivers in the bottom left corner and one for each 10 mosfets (only on is visible). The yellow caps and resistor between the heatsinks is a small snubber circuit, it probably doesnt help much but I put it anyways. The diodes are reversed biased on the output to cut out any voltage spikes generated by an inductive load. I could only post 10 pics so I couldn't post one of the solder tracks on the bottom when I finished. All worked out well and best of all it didn't blow up which is great. Feel free to make suggestions or whatever you think about it, I want to know what you people think.

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 05, 2011, 03:58:14 am
content: You'll probably want something with a faster CPU than an Arduino for motor drives. The Microchip dsPIC is a popular choice for such an application.

author: IanB
author_rank: Super Contributor
timestamp: November 05, 2011, 05:48:05 am
content: Neat, except solder is reallynota brilliant conductor of electricity (the resistance is about ten times greater than copper for the same cross-sectional area). I highly recommend that when you lay down tracks you do not use great globs of solder, but rather lay down a length of copper wire and solder it in place, especially when you intend the tracks to pass significant currents.

author: jackbob
author_rank: Regular Contributor
timestamp: November 05, 2011, 07:19:04 am
content: I was thinking about copper and ended up not doing it. The large solder tracks are already finished just not pictured. I figured I probably won't ever use it on that much power and it could easily handle about 150amps as is but that's good for me. It's mainly just for practice and fun. I might use it in a go kart but nothing more. If I were going to make one intended for use I would put a lot more time into constructing a good board. @ NiHaoMike I don't understand what you mean. Are you talking about pwm freq.? If so, the arduino 500Hz does fine for me. I haven't had any problems with the arduino and I have it doing a lot of other stuff too. There are actually 5 pcb's total for the project that are not pictured. I built themall and each one does something different. One is the homemade arduino I builtWorks pretty good. I also added a thermistor to the heatsinks to control fanspeed and temp. Cutoff. I don't know much about pics yet, just getting started on them.

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 05, 2011, 02:13:19 pm
content: An Arduino is not going to be fast enough to perform FOC (Field Oriented Control). If all you need is V/Hz or Hall based control, it should work fine.

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 05, 2011, 05:52:48 pm
content: Quote from: NiHaoMike on November 05, 2011, 02:13:19 pmwhat is Field Oriented Control?

author: jahonen
author_rank: Super Contributor
timestamp: November 05, 2011, 06:18:05 pm
content: Quote from: Mechatrommer on November 05, 2011, 05:52:48 pmIt is a clever method to control AC motor torque to get faster torque response than with conventional methods. Difficulty here is that you must perform a vector rotation operations, PID controller calculations and sampling of phase currents something as fast as your PWM goes. Generally you want the torque control loop (the loop which controls phase currents) to be as fast as possible to get best dynamics. If the ADC is capable of synchronous sampling with PWM (sampling is timed so that the phase currents are sampled in the exact moment the lower switches are active), it greatly simplifies analog electronics for the phase current measurement. Digital Signal Controllers (Microchip dsPIC and TI C2000 etc.) are designed to perform these tasks and have suitable peripherals.But this is of course not necessary if one uses a brushed DC motor, FOC is only relevant with AC machines, like PMSM or induction motor.Regards,Janne

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 05, 2011, 07:32:10 pm
content: he, thanks janne. whats the purpose of "torque control loop"? and "faster torque response" of what?edit: ok! got it in wiki.http://en.wikipedia.org/wiki/Field-oriented_control

author: jackbob
author_rank: Regular Contributor
timestamp: November 05, 2011, 08:10:40 pm
content: Yes this was made for dc brushed and series motors not ac. I do want to make an ac controller next but it's my first time doing so. I'm not sure yet how I will do it but I want to build a variable frequency drive. I might make it 3 phase but I will start out building a simple single phase ac controller.