servo/motor problem

[griffin]

hi there im working on a project for science olympiad and i recently got all the electronics done for my robot. what baffles me though is that after about 3 to 4 minutes of controlling the motor (through an h-bridge) and servo all of a sudden both stop working, the motor stops working and the servo makes very jerky movements in one direction. is there anything u can think of that could cause this? i have checked all of my connections which are good, the batteries are still fresh, and i have even swapped out the micro (16f690) all have made no difference.

[mackrackit]

What about the voltage regulator? Is it heating up after a bit and dropping out?.

A schematic might help.

[Archangel]

What about the voltage regulator? Is it heating up after a bit and dropping out?.

A schematic might help.
I think this is likely, are you running the motor's power through the regulator?

[griffin]

the motor does not have a voltage regulator, and i am running everything off of 4 AAA batteries. should i add a voltage reg? how will this affect my battey life?

[Acetronics2]

and i am running everything off of 4 AAA batteries. ?



No need to see further ...

Alain

[mackrackit]

Are the batteries rechargeable? The total voltage could be with fully charged cells 4.8 to 6 volts nominal. One could be a bit low if you are running at 10MHz or above and the other is a bit high.

The 4.8 v will be fine if nothing causes to much of a voltage drop. The batteries may seem fine after everything stops due to rebound. Try a voltmeter when it is running to monitor the voltage to see for your self.

Solution might be to have a separate set of batteries for the PIC and another for the motors. Share the zero rail.

If you are not running rechargables then a regulator is recommended for the PIC. Keep the voltage at 5 volts or less here. If you run the PIC at 4 MHZ or so the voltage can be much lower, check the data sheet under electrical characteristics. A low drop out regulator may also be handy. If the batteries are max voltage 4.8 and you run at 4 MHz then you will not need the regulator.

This "science olympiad ", is this something with a secondary school or university ?

[Acetronics2]

Hi,Dave

The internal resistance of those batteries is FAR too high to power a servo , so a servo and a Motor ...

Want some values ??? just to laugh a bit ...

running the PIC @ 3 v could be a solution ... for the Pic only !!!

Alain

[mackrackit]

The internal resistance of those batteries is FAR too high to power a servo , so a servo and a Motor ...


eYup, I was not really thinking about the motors, more to the PIC browning out. Good point.

[Archangel]

. . . should i add a voltage reg? how will this affect my battey life? No, I thought if you were, then you might be overloading it. Alain is one of this forums R/C and Servo EXPERTS, I would defer to his expertise.

[griffin]

I just got done trying to power the pic seperatly from the motor and servo and nothing changed. also i tried some code to just use the servos and that worked fine, any ideas?

[mackrackit]

Now is the time to post your code and schematic.