January 28, 2008
Ghosts in circuits?
R Y Khan asked:
I have problems with ghosts being found in my electrics circuits. Everytime I build a robot, with it's wheels, gearboxs and microchips, all ready connected and programmed, I end up finding ghosts, the main concern is that they always change the directions of my motors spinning in the another direction My question is how you locate and remove these ghosts?
Pick The Gender Of Your Baby
I have problems with ghosts being found in my electrics circuits. Everytime I build a robot, with it's wheels, gearboxs and microchips, all ready connected and programmed, I end up finding ghosts, the main concern is that they always change the directions of my motors spinning in the another direction My question is how you locate and remove these ghosts?
Pick The Gender Of Your Baby
Written by: John
Filed Under: Robot Programming
Tags: Circuits, Spinning, Wheels
Trackback URL: http://roboticstechnologycenter.com/505/ghosts-in-circuits/trackback/
ia
January 30, 2008 at 6:44 pm
check and rewire carefully
billrussell42
February 2, 2008 at 2:01 am
Do you have any memory/cpu circuits? Motors generate a lot of voltage spikes, and memory circuits, like flip flops are very sensitive to spikes.
Make sure all motors and relays have reverse diodes across them, directly across the terminals.
Make sure all logic and memory has lots of bypass caps on them, across the supply rails. A 100µF cap for each board, 0.1µF for each IC.
Worse case, enclose the memory/cpu circuits in a metal box. Experiment with aluminum foil.
Good secure grounds running between the various circuits and other metal parts. heavy wire or braid.
Small (1nF) caps on signal lines can sometimes help (and can sometimes hurt).
Spikes and their prevention are a ever-present part of an engineer’s job.
An illustration: a friend of mine was experimenting with a simple LS74 flip-flop. He had it wired in the open on the bench, with inputs tied via a resistor to +5. With bypass caps. We discovered we could make the flip-flop change state by waving out hand in the air about 2 feet above the circuit.