TreadBot

[JohnH]

I built a walking (biped) robot and had trouble with motor noise causing the A/D signals to vary. (I use two A/D inputs to read pots coupled to the legs for position information.) Adding .1uf caps from each motor lead to the motor's case solved the problem.

My motors are the cheaper hobby motors used with the Tamiya double gearbox. If you are using the Pololu serial motor controller they recommend the caps too. I use an analog H bridge and still had noise issues even with seperate motor and logic batteries.

I don't know if it will help you but it is something to try....

By the way, you did an excellent job on the project, I hope it works out.
--John

[dragons_fire]

thanks for the compliment John, i have added the caps across one motor, and just forgot about the other motor. i usually add one from each lead to the case, and another across both leads. its one of those things i picked up from RC cars and planes.

heres a picture of one of my motors ontop of the scroll wheel on my mouse. i cant remeber if i posted it before, but here it is again..



i would like to see a pic of that biped if you have any.. its one thing i want to do eventually. heres a hexapod i made, its kinda the same as the Lynxmotion hexapod.

[dragons_fire]

so... i havent forgotten about this, im still working on it. I have just had a lot of work and other stuff to do lately. when i use:

For speed = 0 TO 80
'speed up motor to full speed
SerOut2 lcd, baudlcd,[254,"G",1,4,#speed," "]
'display speed on lcd
SerOut2 motor, baudmotor, [$80, 0, lfwd, speed]
'left motor forward
SerOut2 motor, baudmotor, [$80, 0, rfwd, speed] 'right motor forward
Pause 150
next

both motors will speed up to around 45 or 50, and then just shut off. nothing seems to be overheating, and the voltage doesnt drop. the PIC still keeps running because the LCD will still show the Speed Variable increasing. i have tried pulling the reset pin low and then high again at the end of each cycle of code, but that doesnt help either.

if i tell it "speed = 80" then it will run fine, and have no problems.. i think maybe there is an issue with the motor controller recieving too many serial commands in such a short time, or something is getting messed up in the commands.

do hopefully by the weekend, i will have the ultrasonic sensor working and it driving around...

thanks for all the advice everyone...

[JohnH]

If you are using the Pololu motor controller, make sure it's reset pin is held high. If it dips to 0V, it will reset the controller to its inital state (motors off).

If you are using the Pololu Low voltage Dual serial controller:
The green leds on the controller should also be on for forward settings, see if they are still on when the problem occurs.

It looks like you have enough of a delay after the motor serial commands.

--John

[skimask]

Maybe try a little bit of 'DEFINE CHAR_PACING'?
It add x ms between serial characters on the output.
Maybe at the higher settings it doesn't like having x characters in a short amount of time...who knows...

[dragons_fire]

yeah, i have been keeping the reset pin high. i have also tried to reset it after every loop...and i can get it to slow down from 80 to 0 using the same program without a problem.

[dragons_fire]

so i got the motors workign by changing the caps across the leads. i found out a couple days ago that the drawers i keep my caps in got messed up, so i ended up putting in 22pf caps instead of 1uf caps.

so now i added on the parallax ping ultrasonic sensor, and its messing something up. heres the short code for the sensor:

PulsOut ultra, 5
PulsIn ultra, 1, ping

"ultra is the port, and ping is the distance variable. the pulsin line seems to work, and the LED lights on the ping sensor, but everytime i send the pulsout command, it sends wierd characters to the LCD, and the "ping" variable doesnt change from 0.... the LCD is on portf.0 and the ping sensor is on portf.1.... the traces are fairly far apart, and there is nothing touching them.

if i delete the pulsout line, everything displays where its supposed too, and the ping var = 0...

i know i didnt describe it the best, but if anyone has any ideas, please let me know...

[skimask]

so now i added on the parallax ping ultrasonic sensor, and its messing something up. heres the short code for the sensor:

PulsOut ultra, 5
PulsIn ultra, 1, ping

"ultra is the port, and ping is the distance variable. the pulsin line seems to work, and the LED lights on the ping sensor, but everytime i send the pulsout command, it sends wierd characters to the LCD, and the "ping" variable doesnt change from 0.... the LCD is on portf.0 and the ping sensor is on portf.1.... the traces are fairly far apart, and there is nothing touching them.

if i delete the pulsout line, everything displays where its supposed too, and the ping var = 0...

Those ultrasonic transducers generate some fairly high voltages while doing their work. I can easily see one of those dumping current across traces and causing your problems. Maybe try putting a series resistor inline with portf.0 and see what happens. Don't run the transducer, start low on the resistance, work your way up until the LCD doesn't work anymore, then back off one or two values. Then fire up the transducer and see what happens...
Have you ever been 'bit' by one? I wouldn't touch the bare metal on it while it's doing it's 'transducing'.