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shobley
02-01-2007, 12:05 PM
I'm working my way through a robotics project - and finding that I have a lot to learn about the electromechanics of motor control. :)

Originally I was going to create a simple H-bridge and control some trico wiper motors through relays on the Phidget 8/8/8 board.

I've since learned that this is a bad idea, as when the motors get "loaded" after final assembly, the initial surge could burn them out.

Someone recommended this motor controller:
http://www.robotstore.com/store/product.asp?pid=264&catid=1565
as a nice high ampage controller.

I own the Phidget servo controller, and the 8/8/8 board. It seems that using the 8/8/8 board is not reallly viable as a PWM signal needs to be generated to control the MAXI.

I read somewhere that the servo board actually puts out a PWM signal for the small servos and maybe this could be connected to drive the system.

Does anyone know if this can be done?

...and if not how can I control the motor speed through a USB device/software?

Thanks in advance,
Steve

Matt
02-01-2007, 06:54 PM
Hi Steve,

You are half way there with the phidget servo controller. That's some good news :) The phidget servo controller does output a PWM signal. The same one a DC motor controller needs for input.

Take a peek at the picture and description at the top of the motor controllers page (http://www.trossenrobotics.com/store/c/2664-Motor-Controllers.aspx). On there we explain exactly how to accomplish what you are asking about. You just need to select a motor controller which can accept a PWM signal. The MAXI says that it does so I assume it would work. Of course, I say buy something from us :)

Robot Magazine published an article on this exact topic in the winter issue of 2006. It's not online yet, but hopefully soon.

In the Phidgets examples.zip download there will be an example servo controller project. Use this to send some output from the phidget servo controller and you should be up and running. You just write your own custom program from there!

shobley
02-02-2007, 12:59 PM
Thanks, I managed to solve my problem by getting the Sabretooth controller and an RS232->TTL cable - I'm going to plug the controller into the serial port on my PC and controll things that way...