# Stop electric motor when toy elevator reaches end of travel

I'm working on a simple toy elevator powered by some small DC electric motor. I know basic electricity. I figured out how to set up simple circuit with 3-position switch so I can turn on the motor in both directions or turn it off.

Is there a simple way to stop the motor when any extremum is reached? I thought that maybe it would be fine if the force becomes too big for motor to handle (e.g. elevator is blocked and can't move any further) but I'm not sure what would happen with such motor turned on but blocked. From what I read motor would start heating up and may be damaged?

Is there any smarter simple way to stop the motor when elevator goes too low or high?

• Why not use limit switches? When the elevator reaches the end of travel, it hits a reversing switch. Commented May 27 at 18:06
• I tried to separate electric circuit from the elevator.
– Ari
Commented May 27 at 18:17

simulate this circuit – Schematic created using CircuitLab

If SW1 is in the centre-off position the elevator does not move

If SW1 is in the 'up' position (shown) the elevator goes up until limit switch SW2 opens

If SW1 is in the 'down' position, the elevator goes down until limit switch SW3 opens

Yes, you could put a current sensor in series with the motor that opens the circuit after a current-limit is exceeded, or after a fixed time.

One simple way to do that would be using a relay to hold the circuit closed, but with a positive temperature coefficient (PTC) thermistor in series, and the PTC thermistor taped to a resistor in series with the motor. If the current were to increase, or the motor run too long, the relay would open.

This is not as great solution, as you'd still need to manually change elevator direction. Limit switches could provide automatic reversing.