Let's Make Robots!

2 Bit Motor Controller Weirdness



I was wondering if some of you guru's could provide some insight as to why (what I thought was simple) motor controller is not preforming correctly.

The problem is, the direction bit is failing.  Or one motor's direction bit... the other is working fine.  I switched direction lines to data pins and now it's all crappy (damaged BBB now?)

I'm wondering if its a problem of not enough current from the BBB board, which leads me to another question....    Anyone have experience on over-sourcing the pins of a BBB board?  Is it now all burned up?

Unfortunately, it will take time to unpack it all and do a decent amount of diagnostics.. 

Here's another question ... How do I determine the maximum amount of current the BBB data pin can source, AFTER I have possibly damaged it, without damaging it further (obvious answers like RTFM will not be accepted at this time) ;D


2 bit F&#(@ ! -  just switched them back and now both direction control lines will not work - both motors will go forward but now (since I switched the bad (right side) with the good (left side)) and now switched them back - they both will not go reverse... only forward..   It appears that it is contagious (yarg) !





Motor Driver Schematic


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I am soooooo done with 754410 and other 1 chip motor drivers (at the moment).   You guys with good hardware karma can have them ! 

Made a mini-boa driver, and it would seem that at a comparable price of the 754410 I can get 5A out of this puppy !   I toner-transfered, populated, and solder these guys, and guess what ?   THEY WORK !  Oooh, notice the hacked-in protection diode too.  I may not have good hardware karma, but I want good hardware karma :)

So 5Amps ... for such a little guy.  The 5A is for the TIP 122, but I don't think the relay has that high of rating, but I am guessing that the rating for the relay is for switching when loaded.  If the software makes sure there is no current running through the relay when direction is changed I "think" I'm good !

Just remember that those TIP-babies will eat a whole lot of voltage!

I'd like to share a wise lesson from my frustrating days with LD293. Pull all your inputs down or up as appropriate. Floating inputs will present you a slew of mind puzzles. As will removing one of the two power supplies.

Nothing was left floating... Nothing disconnected...
I think me and the one chip wonders just don't get along...