View Full Version : Brushless Motor Microcontoller
05-20-2009, 09:01 AM
I can't seem to find a direct answer to this question, so I have to ask! I want to get into R/C in the offseason, yet I don't simply want to drive the car .. I want it to mess around with autonomous driving. I don't doubt that the micro controller requirements will grow as I get more involved with this, but for the first year I need a controller that's capable of handling 6 analog sensors, 6 digital sensors, 1 servo output and 1-2 outputs for brushless motors.
The problem I have with this is that I'm not sure if a brushless motor control is the same as a brushed motor control, from the communications signal perspective. For instance -- can I use the VEX microcontroller I already have to control a brushless motor controller that supports a PWM input? I've forgotten most of what I learned as an EE where analog circuits are concerned since I've done mostly embedded and upper-level programming since I got out of college ... so purchasing a chip (like an arduino) and designing a circuit is alot more than I'd like to have to do at the moment.
05-20-2009, 10:09 AM
As far as I know, hobby style brushless motor controllers use the same 1-2ms, ~50Hz PWM signal that the brushed controllers use. This is very convenient in that a ton of work has already been done for you.
Additionally, there is already a "motor shield" built for the Arduino that meets many of your stated needs. Although, I am not certain if you will be able to use all your sensors with it AND drive all the motors.
Take a look at what is available with the Arduino, it may just be the ticket you want.
Look at Sparkfun (http://www.sparkfun.com/commerce/categories.php?c=103) and Adafruit (http://www.adafruit.com/index.php?main_page=index&cPath=17&sessid=712ea7d07fb2d3b16d58989e8ea5111d). Both have a good selection of options.
05-21-2009, 06:02 PM
The problem I have with this is that I'm not sure if a brushless motor control is the same as a brushed motor control, from the communications signal perspective. For instance -- can I use the VEX microcontroller I already have to control a brushless motor controller that supports a PWM input?
Yes, VEX should be able to send a PWM signal to a a brushless motor controller.
Look carefully at your motor specifications before selecting a Brushless Motor controller.
I suggest browsing a few of the R/C hobby websites.
TowerHobbies (http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXMKH1) , HobbyLobby (http://www.hobby-lobby.com/jetiblue.htm)
If you want to go into more detail,
Sensorless Brushless Control (http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en022169)
Luminary Micro Brushless Reference Design Kit (http://engineeringtv.com/blogs/etv/archive/2009/05/21/luminary-micro-tempest-microcontroller-kits.aspx)
05-24-2009, 09:02 PM
Looking at the Adafruit link, this (http://www.adafruit.com/index.php?main_page=product_info&cPath=17&products_id=81&sessid=712ea7d07fb2d3b16d58989e8ea5111d) shield looks like it has everything you need. 2 servo ports, those would be your brushless ones, and 4 DC outputs, so you can run either 4 DC motors, 2 stepper motors, or one stepper motor and 1/2 DC motors. It also has 6 analog input ports, and it looks like 14 digital IO (not sure which ones are in, out, or bidirectional). As long as you're on the shy side of that "1-2 brushless" quantity, you'll be fine. I'm guessing the servo would have been for Ackermann steering? Anyway, good luck.
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