Let's Make Robots!

Start Here Robot Urgent Issue

I began programming my picaxe. I came into some problems...

1) When i ran the servos program (at 75) it only turned a quarter of an inch in that direction.

   a. the servos cant be turned past that direction manually either

2) When I tried running the high and low commands

   a. one wheel turned slightly and stopped

   b. the board went hot so i quickly disconnected it and took out the batteries


The servos issue is beyond me. Does the board getting hot while attempting to run the motors imply there is a short on the board? Back to soldering? (this is my first time and there is a fair chance they suck) What should I resolder in that case and have I destroyed my board?




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Not sure if everything is now resolved, but a couple things. First, I agree with what the others said.

Second, the problem of over-heating sounds like either a wiring problem, or you are using motors that are too heavy for the motor drivers. If it is only from one side, then it is more likely a wiring error.

The servo should get repeated pulses until the servo has time to move to that position. I would not advise forcing the servo to turn by hand. They usually have very small plastic gears that can be stripped if forced too far.  There is a physical stop that keeps a servo from turning too far either direction. Using a bright light try to see through the case (if it is one of the transparent ones) to tell if the top gear is at the stop in one direction. If the servo indeed does not turn as far as it should, then you may have a bad servo and need to get another.

I would also like to see pictures of what you have built and what your program looks like. Your problems could be either place.

you take a clear, focused picture of your solder side? At least we will get some idea of what it looks like rather than just guessing. :)

tell your servo to center itself without having the servo horn installed. Once you have done that, install the servo horn, and, you should get 180* of motion give or take.

I did that. It still wont turn much to the left and cant be forced by hand past that direction by hand. Further when I put in the batteries, the servos turns to the right slightly upon its insertion. Any thoughts on why one of my wheel motors isnt responding?

Servos usually twitch when power is first applied. This is because they are getting power before they are getting a clear signal about what postion to be in. I agree with the advice you received about being sure you have centered your servos before you put the servo horn on.

Regarding your motor issues, I suggest you isolate the symptoms and test. Try connecting the batteries directly to the motor wires (nothing else). Does the motor turn? Try testing the other motor with the suspect motor output pins.

Double check that you have each of the four motor pins connected correctly. Read through the Picaxe for Dummies post. Note that one motor's leads should be across the two pins labeled 'A', and the other motor's leads should be across the two pins labeled 'B'. If you have the motors connected instead so that one lead from each motor is connected to the 'A' pins and the other lead from each motor is connected to the 'B' pins, you will get weird results. 

THANK YOU. The problems with the servos have subsided but it took working with my hands- and not programming. The pin problem is isolated to a motor pins- should they be resoldered?

Impossible to say without a clear, in focus picture. Or if you have a multimeter, you can disconnect everything from the board and run a continuity test between the pins to be sure they are not shorted.

The actual plastic wheel or arm on your servo, did you put that on straight, it might be wonky.

I ran into another issue-

I desoldered the pins which were done together. Then ran commands for the servos to make sure I didn't destroy the board. It still doesnt turn left, and cant be forced in that direction. I ran high 4 low 5- and instead of turning slightly it didnt move at all. The other motor runs perfectly. I soldered and resoldered the connections to the first motor. Whats happening?

I was discussing this with my tech savvy brother and (brace yourself for mild retardation) I had soldered 3 of the motor pins in such a way that the solder was encompassing all 3. I assume is the problem and have to remove the solder with a solder remover (or turkey baster- as it was described to me).


Thanks for your reply about the servos. I'll be playing with it as soon as I get the board back in order.