topic Re: Frecuency issues with a QG8 in 8-bit Microcontrollers

Frecuency issues with a QG8

neocronos — Sat, 06 Dec 2008 04:41:31 GMT

Hello.

I've been having frecuency issues while running my hardware. This is what I get from the debugger:

RUNNING
Frequency change to ~0hz.
Frequency change to ~4386382hz.
ILLEGAL_BP

I'm guessing it has to be with some kind of noise caused by these motors that I'm controlling using H-Bridges. The question is: What could be the most common cause for this issue? or what you guys would advice me to check in first place?

And besides that problem, I'm also having another one which I'm pretty sure that it has to be with the same thing and is that when I'm controlling the motors, they suddenly stop working after an instruction, but there isn't a reset or a frecuency change, and they start working again if I turn on the H-Bridges again. It could be an H-Bridge issue or some code error too.

I have to check well and ask at college also but I wanted to hear some inputs here since in most of cases those problems are easy to solve (problems because of my lack of experience )

Thanks!

Message Edited by neocronos on 2008-12-05 08:42 PM

Re: Frecuency issues with a QG8

peg — Sat, 06 Dec 2008 05:28:17 GMT

Hi,

The most obvious culprit here is problems caused by switching the inductive load of the motor.
However, before you go down that long and tortuous path it might be an idea to temporarily replace the motors with some very light resistive loads with some LED's to indicate direction etc.
This way you can prove your application actually works properly before worrying about any other issues with the motors.
We would need to know more info about your circuit anyway before any other help could be provided.
What sort of motors? Stepper? brushed DC?
Power stage isolated from control?
or
Common power supply?
What noise mitigation have you done already? If any.

Re: Frecuency issues with a QG8

neocronos — Sat, 06 Dec 2008 06:44:48 GMT

Thanks. It makes lots of sense. Yes, I missed the old LED's test. I'll try it.

I've been testing several things through this whole afternoon and each time it seems more likely it's gonna be an inductive issue (for instance, the hardware works fine with just one motor connected).

The motors are brushed DC (I think. I know them as DC motors with reduction). The project as well is about a couple of robots (two motors per robot), controlled via wireless (using ZigBee) and using a PC. Both robots will work with a single battery and for test purposes I'm working with a DC adapter.

Common power supply (it should go separeted but during the first tests it worked quiet. Power supply has 12v, motors work with 9v and control with 3.3v).

I'm using a bunch of filters to keep the noise away from the control stage. The main one is at the beginning of the whole circuit (next to the power supply) and has a diode and a 100uF capacitor. The regulators and the microprocessor also have their own little filters.

I'll check if I can try the LED's test right now, if not, until sunday! .

Thanks again!.

Re: Frecuency issues with a QG8

neocronos — Wed, 10 Dec 2008 01:33:16 GMT

LEDs test done (one motor and one led). Worked fine.

I had included two little filters in the design which I hadn't been using so far (thought for these cases). I'll try them out. Wish me good luck.

Re: Frecuency issues with a QG8

neocronos — Wed, 10 Dec 2008 02:18:52 GMT

Worked like a charm. Problem solved!

Thanks!