Tuesday, September 3, 2013

Motor drive tests with SN754410


With the pic and SN 754410 ready to go it was time for a motor drive test.  But first the motors needed to be fixed up.  I did the standard practice of soldering 0.1uF capacitors from each motor terminal to the motor body and another capacitor across the motor terminals.  Then the wires from each terminal were twisted together and terminated in a 2 pin female header.

For the drive test I modified my full pennybot code and did a simple forward/back/left/right test.  Worked well but forward/back were backwards.  A quick modification in the code fixed that.  Also my dual colour leds were not symmetrical.  On forward one led was green, the other red.  So I flipped around one the leds and fixed that.  Probably could have worked that one out when initially soldering but I knew that I might get it wrong regardless so it was quicker to just do and fix if needed.

The drive test also showed one motor was slightly faster than the other.  Over a number of iterations pennybot was slowly turning around on it's starting position.  Nothing to fix there but it's good to be aware.

Now was time for the push test against Dumbbot, my first sumo bot which has only edge avoidance, no detection of opponents.  Both bots weighted in at 320gm.  Head to head pennybot couldn't move a stationary Dumbbot at all.  Those Tamiya rubber tyres Dumbbot hava obviously grip very well.  Dumbbot however with a much more geared down drive train and rubber tyres can push pennybot no worries at all.  Those skinny tyres Pennybot has just don't have the grip.  I can see why people buy the super sticky version of the tyres.  Hopefully at full 500gm weight things will be different.  As far as speed goes Pennybot approx. three times faster than Dumbbot.  So a design battle of strength vs speed will be had…once Pennybot has some eyes.

Finally since dumb is a rude word for 5 year olds Dumbbot is now know as Slowbot.  Soviet revisionism at it's best.