Author Topic: pwm module (Read 7667 times)

mrbump82 · « **on:** July 31, 2014, 10:07:19 PM »

What do y'all think about using a pwm module for a regulated mod?

CraigHB · « **Reply #1 on:** August 01, 2014, 01:30:36 PM »

Pretty vague question, which part are talking about? PWM controllers can range widely in frequency and can be used in a wide range of applications.

To talk about it in the most general terms, if you want to use a low frequency PWM controller for a PWM driven atomizer, you'd do better using an MCU since you'll need other functions as well. An MCU is perfectly suited for generating a low frequency PWM signal.

High frequency PWM is used in switching regulators to provide a purely DC output. In that case, you'd do better with a controller designed for that purpose. It' possible to design a switching regulator with a PWM controller, but it's hard to do. It's hugely easier to use a converter controller.

Converter controllers are one of those widely produced parts similar to MCUs with many optimizations to make design an easier process. Even so, high power DC-DC converter design is one of the most tricky areas of circuit design. It's really complicated to account for all the things that need to be accounted for. Everything is on the level of second order differentials so the math is crazy complicated.

You can pretty much wing it with a good simulator, but there's always an amount of bench tuning involved to get one working well and there's no guarantee. Sometimes, you have to give up on a design because it just can't meet the specs you're looking for once you get it on the bench. I've had that happen a few times already.

mrbump82 · « **Reply #2 on:** August 01, 2014, 02:04:56 PM »

I'm thinking of usind a 12 dc motor speed controller or an electronic speed controller from a r/c car I'm trying to make the 12 volt rail adjustable but not lose my amp rating from my power supply. Since I don't need batteries in my boxes I'm trying to explore other options. Than using the chips that are usually sold out

CraigHB · « **Reply #3 on:** August 01, 2014, 02:26:21 PM »

Well, there's a pretty big difference in loading between an atomizer and a motor. The RC motors are typically three phase (some are four) so you wouldn't be able to load an ESC properly. You'd only be loading one leg and the ESC would probably have a problem with that. You can't tie any of the legs together since it would short the ESC.

You'd actually have to set up three atomizer coils in a Y or Delta configuration. That would probably work actually. With all the phases loaded properly the ESC would be happy. Problem is you need an atomizer with three connections instead of two which would present a problem.

mrbump82 · « **Reply #4 on:** August 01, 2014, 04:55:01 PM »

Well I've noticed the brushless use three phase the brushed ones use two wires. My buddy actually did it with a dc fan controller but the module he used was pretty big

CraigHB · « **Reply #5 on:** August 02, 2014, 05:08:40 PM »

Should be good then, a single phase controller should do the job just fine.

I never noticed there were brushed single phase motors for hobby use. I don't do RC stuff myself, I have at times in my life, but years ago and it was all nitro-methane powered at the time. I get the Hobby King newlsetter since I've bought stuff from them before. Hobby stuff is pretty interesting anyway and I may get back into RC planes if I ever have the idle time.

If you can find a single phase motor controller small enough, should do the job.