Hi,
Hi have a Pololu dual motor controller that I’m trying to use to control a Tamiya 70097 twin motor gearbox.
I’ve built two circuits - a test circuit and the robot for which the motors and controller are eventually destined.
The problem is that I’m getting very erratic results. The test circuit has a pic16f818 clocked at 4Mhz powered by a 6V DC mains supply. The code is written in picbasic, and is a variation of the code in the back of the controller manual. Intially it worked fine - that’s to say the motors powered up and seemed happy running indefinitely. But now I get very inconsistent results. Generally if I plug in the power supply the motors will kick for a fraction of a second before stopping. (I know the circuit is still operating correctly because I have an LED pulsing as the code cylces.) If I continue to switch the circuit on and off sometimes the motors will run a little longer each time, and eventually operate indefinitely speeding up and down as intended!
The circuit for the robot controller is a little different: A pic16f876a clocked at 20mhz. Two sets of 4 AAs (producing ~6V each) power the system - one set of 4 goes through a low dropout 5V regulator (with suitable capacitors) and powers the PIC, and the other pack of 4 goes unregulated to the motor controller. The grounds of the two packs are connected together. I get similar results with this set up. At the moment it’s programmed to run the motors at half speed for 3 seconds to verify everything’s working ok. In fact when switched on most of the time the motors just kick before stopping, but a couple of times they’ve run for the full 3 seconds at programmed.
If I consistently just got the motors kicking I’d presume I was drawing too much power, but the fact that sometimes it works absolutely fine is really throwing me. At this stage I’m wondering if my motor controller has a fault.
A couple of other pieces of information that may be relevant: The controller was purchased pre-assembled. It only seems to get warm to the touch after a period of successful operation. I’ve tried powering the test circuit off 4.5V with the same (inconsistent) results. The motor gearbox is configured to a ratio of 203:1, and is well subricated.
Any suggestions? I’m totally perplexed!
Thanks very much for any help - it’s really appreciated.
Luke