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Andrew Angellotti has built and documented a DIY Brushless Motor Controller if you ever wanted to understand how a brushless motor controller worked or perhaps build your own this would be a great article to read. Once you have a good understanding of the heavy lifting electronics you should have a look at the second part of the DIY Brushless Motor Controller where Andrew goes over the code that makes the controller tick. “The half bridges use TIP120 darlington NPN transistors on the low side (emitter goes to ground, collector goes to the output/high side), with a 470 ohm current limiting resistor between the base and the input to the board. Bring the corresponding input up to 5 volts or so, and the transistor turns on. Not much to that one. The high side is slightly more complicated. It uses TIP125 PNP transistors. The emitter of these is connected to the controller’s drive voltage, and the collector is again connected to the output/low side. To get these guys to turn on, we need to pull the base below the emitter voltage. This is done with a trusty 2N3904. The base of the TIP125 is connected to the collector of the 3904 through a current limiting resistor, and then the emitter of the 3904 is connected to ground. So when the 3904 is active, the base of the TIP125 is pulled low, and it turns “on.” Of course, don’t forget the 2k-ish current limiting resistor on the base of the 3904. This is then connected to the input to the board. So, looking purely at driving the inputs, 5V on a high-side input means the corresponding transistor turns on, just like the low side would if you applied 5V to a low-side input.” |
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May 29th, 2011
The picture here is not the “brains” of the controller, so to speak, but rather the “muscle” – there is an important part that’s missing on the picture and that’s the circuit that energized the motor’s windings in a particular order. This could be an MCU or, as I think the author has done, a PC with software and a parallel(?) interface.
They tend to call the circuit as pictured here an “amplifier”. A “controller” would be the complete device with both parts – the “brains” and the “muscle”.
That said, great job perf-boarding! Mine usually look like a bunch of spaghetti randomly thrown on a table
Cheers!
June 2nd, 2011
Was trying to control an RC Car with an Arduino. Would this setup work?
June 3rd, 2011
This setup is for a rather large DC brushless motor. You may be able to get away with a much more simple SN754410 – based setup. It’s pretty much the same circuit packed into a 16-pin IC. The only limitation is that you can only have up to 1A per driver. Depending on the size of your car it may or may not be enough.
June 3rd, 2011
Thanks. Looking at YouTube videos no one mentions needing a driver of some kind. It’s a learning curve.
June 6th, 2011
@dustin:
This is probably just a matter of terminology but I hope we’re on the same page here: by “driver” I did not mean a software driver of any kind.
When you’re talking about controlling motors, when they say “driver”, they usually mean the circuit (or a part of the circuit) that literally drives, or energizes, the motor’s windings. Like I said before, for a brushless DC motor to actually turn (and in the right direction), you also need a “controller” that would, with the help of three “drivers”, energize the windings in a particular order with a particular frequency.
The “drivers” are often located on a different circuit from the controller (because of the high currents involved and other practical considerations) and so such collection of “drivers” would often be called an “amplifier” or “amp”. That’s exactly what the circuit pictured above is.
Please note that I’m not claiming any authority in establishing the terms, I just merely came across these while doing my own research. Another thing you’ll notice when you start reading around on the subject is that the terms are pretty flexible and some people use them as they’re pleased. However, the definitions above make sense to me and they seem to be rather commonly accepted. Even then sometimes some device would throw you for a loop because it would have pieces of different control functions in it and the manufacturer would prefer to call it by yet another name.
Hope this helps rather than complicates the issue
June 6th, 2011
Haha we’re on the same page. I didn’t mean a software driver but rather a device to actually get the motors moving. Your terms made sense and like you said they’re commonly accepted. I’m just googling around deciding what H-bridge type chip to use and all that fun stuff.
June 6th, 2011
Haha we’re on the same page. I didn’t mean a software driver but rather a device to actually get the motors moving. Your terms made sense and like you said they’re commonly accepted. I’m just googling around deciding what H-bridge chip to use and all that fun stuff. Thanks for the help.
June 8th, 2011
Just for kicks, I looked up what currents people are talking about in RC cars.
Holy cow! Looks like 2x25A is at the lower end for some people! How big is your RC car, is it one of those monsters? In this case you’re probably going to need a specialized controller – plenty of companies are making those in prices ranging from $60 to … well, there’s really no upper limit there.
Good luck!