Steamer

[steamer]

Simple diode circuit. Hope I explain it good enough.
1 just a motor and if you reverse polarity, motor runs both ways.

2 if you add in down stop switch, motor power will be cut at bottom stop. Make the switch adjustable to get box to stop were needed. With this setup the box will not go back up again because S1 is now open and no power will flow either way, IE, reverse polarity.

3 A diode is simple blocking device that lets current flow one way, Anode + to cathode - but blocks power from flowing backwards. The power flows toward the white band but not the other way. Because of this if you install one across your switch it will allow the power to reverse the motor and the box will go back up. The diode is out of the circuit as soon as the box starts moving in the up direction and S1 closes. The one I used is a
1N4002 available at Radio Shack.
I've made a rough drawing for the three circuits shown



If there's anything not clear enough, just ask thanks.
Rob