I was wondering if anyone had devised a good way of testing motor controllers? If so I’d love to know your method, my team has a couple of controllers that are questionable and we need to test them.
You can build your own test rig. All you need is an old unwanted junker laptop and a couple of motors. (And a battery).
Take the laptop and install FreeDOS on it.
Write a simple app to toggle the RTS pin on the serial port to simulate the desired servo signal (you can code it to simulate both Vic and Jag signals). You can get highly accurate and stable performance because there’s no multitasking going on. You can hard-code a test sequence into the app, or you can read the test sequence from a text-file script, or you can have a simple user interface to change the command.
Build a fixture to hold 2 motors with their output shafts connected together. Drive one motor with the motor controller you are testing. Run tests with the leads of the other motor open. Stop the test and connect the leads together and run another test with the leads shorted.
You can also attach a motor, a battery, and build this. No computer needed.
That looks like a fun project !
The date of your post is 11/05**…**
Has anyone has built one of these lately? Where did you get the parts and what was the total cost?
Why do you need a dual timer? Most circuit I have seen use a 555.
We have something similar, courtesy of our electrical mentor. Unfortunately, I haven’t had the time to become familiar with the circuit itself, so I can’t provide many details.
Parts were salvaged from his inventory as a hobbyist; I believe total cost was in the $20 range.
Here is ours. We use a y pwm cable to the Jags to test ganged motors. We use this device to test our prototypes, motor burn in and robot builds before the electronics go in. All the parts were from Radio Shack under $50
Hi, is there any chance that you/one of your teammates could explain a little about how you built it?
(I’ve seen it before and got excited, but I’m not exactly sure how to implement one ourselves)
Anyways nice idea!
Pololu has several RC servo controllers.
I use one hooked to a lap top to run our motors when the C-rio and the programers are not available. Also can do analog conversions to check sensors. The app that runs on the pc is nice.
Jameco has a tutorial about PWM:
Parts are Radio Shack, cost was about $15 including a nice little case. Can be less fancy if you have a good junkbox.
One timer generates the pulses every x milliseconds, the other varies the output pulse width from 1 to 2 mSec. If you try to do both with a single timer you end up varying a parameter you don’t want to vary. Plus, a 556 is really no more expensive than a 555…
Remember, any device a team makes or buys must be able to generate pulses beyond the 1 to 2 ms pulses that are the hobby standard for servos. The jag has an extended range I believe is .8 to 2.2 ms for full speed. 1 to 2 ms for a victor.
Debugging can issues is a whole other can of worms.