Let's Make Robots!
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Ahoy!

what I am trying to do is make a mobile platform with a little breadboard on it so that I can try different projects. Underneath I have a l298 motor driver kit from solarbotics attached to the standard fa-130 motors that came with the tamiya gearbox. I had a hard time soldering the one lead of the caps onto the motor chassis, but the lead-to-lead caps are ok.

 

Im about to cut a hole in the front to mount the ping sensor and servo.

 

Everything works great when I have 2 seperate power sources, but ideally in the end I will have just one rechargable pack. Right now if I try to run both the Stamp project board and the motorcontroller from the same source, the stamp resets itself a couple of times a second. One person suggested a filtering capacitor for the motor controller, but I dont know anything about this.

 

My knowlege of electonics is really limited, but If you bear with me Ill be sure to keep you posted!

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voodoobot's picture

This is what people where talking about with the smoothing. 

http://www.elecfree.com/electronic/wp-content/uploads/2008/07/power-supply-5v-2a-by-ic-78s05.gif

Note that c1 and c2 go from + to -, these help to make sure you get continuos power to the chip...but you're also using the boe(homework board doesnt have these from my recolection), so you have the caps on the board already, and that board should be fairly solid.  What power source are you using? 9v batteries might not do it(low current) if thats what you use, if anything at least a 7+v power source(though 6 should work). 

 btw, check out this site for some useful knowledge on electronics!  I've found it very useful.

http://www.kpsec.freeuk.com/index.htm

Nice to see another proc on here!

OddBot's picture

G'day Frank, I read about your power problem and have a possible solution.

Power_Schematic.jpg When your running of a single battery pack and a motor draws a lot of current e.g. starting or stalling it can cause the voltage to drop briefly. This circuit will compensate for tempary voltage drops by storing a charge in the capacitor. When a motor draws excessive power e.g. stalls, your stamp runs from the charge in the capacitor. When voltage returns to normal the capacitor recharges. The bigger the capacitor the longer your stamp can continue without reseting.

It also pays to have one or two 0.1uF monolithic capacitors on your stamps 5V supply to help absorb spikes and transients.

If your still having problems then give us some more details such as type of battery pack eg. 4xAA battery and method of voltage regulation. Does a stamp have an on board regulator or is it external?

rik's picture

Could you explain the use of the diode as well? Is it to prevent the motors drawing from the C? Or is it to create a different voltage on the regulator's input?

8ik

OddBot's picture
The diode prevents the heavily loaded/stalled motor from feeding off of the capacitor. It does also drop the battery voltage by about 0.6V but this circuit still needs a proper voltage regulator. I've had this same problem recently with only one battery pack for everything and there is no substitute for a good regulator.
Ant's picture
my guess is so the motor driver can't 'steal' the caps power?