I am building a line-following robot using two of these motors:


I had everything on the breadboard and it worked fine - including both motors. Then I built the circuit, soldered wires to the motor terminals, added molex connectors, and one motor doesn't work. I switched the motors in the circuit - same one works, same one doesn't. I stripped off the heatshrink tubing, and connected the bad motor directly to a battery with alligator clips - it still doesn't work.

I am still learning to solder - could I have applied too much heat and melted something important inside my motor? Is there a way to find out?

Moving forward, is it a good idea to solder directly to motor terminals? Should I have used a heatsink clip?

Thanks, Matt

  • \$\begingroup\$ I couldn't open the data sheet properly (1st sign of cheap quality products in my book) but maybe if you have the data sheet for it there may be a recommendation about soldering and soldering times. \$\endgroup\$ – Andy aka Oct 11 '13 at 19:45
  • \$\begingroup\$ Did you melt the plastic around the terminal(s)? \$\endgroup\$ – Dave Tweed Oct 11 '13 at 19:56
  • \$\begingroup\$ Nope, plastic around the terminals is fine. What else could it even be besides too much heat? \$\endgroup\$ – fatman Oct 11 '13 at 20:02

Rather than actually melting something, if you softened the plastic you could have twisted one of the brushes away from the commutator. If you can figure that out (or inspect the brushes if there's a cooling hole) you may be able to apply more heat and twist it back.

Failing that, a small screwdriver can straighten the tabs holding the plastic cap in. Remove it carefully, realign the brushes and reassemble. (On reassembly, look for a couple of holes in the plastic cap, for pins to hold the brushes clear of the commutator. Reassemble, then pull out the pins...)

If the motor's dead anyway there's nothing to lose except the time spent taking it apart.

  • \$\begingroup\$ "If the motor's dead anyway there's nothing to lose except the time spent taking it apart." Absolutely. I took off the gearhead and wondered if I could even manually turn the motor. (The good motor moved manually). I tried, I think I heard a tiny little snap, put it back together, and it worked! Thanks for the prompt! \$\endgroup\$ – fatman Oct 12 '13 at 17:58

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