How to control a servo with a switch?

As above i was wondering how to fully turn a servo and turn it back just with a switch
It's for a dashboard sat nav box that flips up (Might add it on here)

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rickharris4 years ago
In view of what your making you might find smart grease an interesting product.

Jayefuu4 years ago
Here's another diagram (click to enlarge) in case Rick's is hard to follow. DPDT = dual pole, dual throw. They're fairly common. LS1 and LS2 are limit switches. These will need to be incorporated into the mechanical design of your unit. They will be activated when the box opens and closes to stop the motor, they're just SPDT or SPST.

If you wanted it so that you had 3 switch positions: open, close and stop you could get rid of the limit switches if you wanted and just put the switch back to the middle when it was opened or closed enough. Let me know and I'll draw a diagram for that.

Jayefuu Jayefuu4 years ago
Here's an improved schematic for Frollard's suggestion 3. The limit switches have been turned around and connected so that the NO contacts will short the two motor terminals together, braking (not breaking ;) ) the motor so it doesn't overshoot. I think it's right, Steve or IcEng should be able to confirm.

Nope. Missing a couple of vital bits. Consider what happens when the motor HITS the limit switch..
Diodes across the limit switches?
frollard4 years ago
Servos need a very precisely timed pulse train to get them to go to specific angles, you have 2 options to do this:
1) microcontroller that takes the switch input and converts it into the pulses required by the servo. Easy and can be cheap.
2) analog circuit that varies in frequency at the flip of a switch. Possible, but pain in the butt to get right.

A third option that ignores using a servo:
Use a DC gearmotor with 2 endstops, and a dpdt 'updown' switch. The updown switch will cause the motor to turn on and go to the end of its travel where it will have the circuit interrupted by a limit switch, then turn off.
Varies DUTY cycle, not frequency....

Me, I'd go for option 3....I may even have a circuit.....
+1 for option 3.

Connect it like this The double pole double throw center off switch will allow yu a middle position that is motor off. Or you can use a second on off switch as DPDT Co are hard to find.
yeah, it's the useless box circuit, but instead of the top of the throw reversing the switch it just interrupts the OTHER side of the dpdt so it ends up bistable.