"Tony Matt" wrote in message
...
| Martin wrote:
| I was trying to run one of the kids toys from a bench supply instead
| of batteries.
|
| Instead of hooking it up to 5 volts I accidentally hooked it to 17
| volts ...
|
| So now I'm trying to troublshoot.
|
|
| The toy is a hotwheels "shooter" ...
| There is a motor driving some gears that then drive two foam wheels
| about an inch apart.
| when the motor and foam wheels are spinning, you feed in a hotwheels
| car and it shoots out the other side at high speed.
|
| The circuit driving the motor is (all in series):
| Battery positive,
| something that looks like a disk capacitor,
| a wirewound rheostat,
| the motor,
| battery negative
|
| I have two of them, the one that is blown up will kind of run for a
| bit, but then pretty much stop.
| At that point the "disk capacitor" will be pretty hot to the touch.
|
| Both of them act/measure the same when the batteries are removed.
|
| It didn't make sense to have a capacitor in the circuit in series with
| everything else, since that would have kept any DC current
| flowing ... but maybe it was it was some kind of wierd reactive RC
| circuit with the motor ... I dunno ...
|
| So I measured it with a capacitance meter ... and it measured the same
| as connecting the probe tips together in a dead short ... so probably
| not actually a disk capacitor after all.
|
| Which made sense, since a capacitor there would have made no sense.
|
| Measureing it with an ohm-meter gives a value of about 1 ohm, for both
| the dead and the good one
|
| So what is it ... I'll guess some kind of current limiter to protect
| the motor if the thing becomes jammed.
| I would guess the resistance goes up if the current gets too high,
| which then reduces the current to the motor.
|
| Anyone know of anything like that, and what to search under in a
| catalog.
|
| Could be a resettable fuse, like a Tyco (Raychem) Polyswitch, Bourns
| Multifuse, Littelfuse Polyfuse, or Optifuse. See
|
http://en.wikipedia.org/wiki/Polyswitch. Most of the radial packages
| are rectangular, but some are discs. Does the part have any markings?
|
| TM
That's my guess too. Here's a pic:
http://www.allelectronics.com/make-a...3-AMP/-/1.html