Simple 1A Throttle
This circuit connects an AC transformer (or a DC supply) to a track to provide a voltage from 0v to max voltage (depending on the voltage of the transformer).
The transformer can be AC or DC and any voltage from 12v to 18v.
The throttle handle connects to the 1k pot.
The diode on the output protects the transistors from reverse polarity (if another controller is also connected to the rails).
Note: The circuit is limited to about 1amp due to the 1N4004 diodes.By changing the diodes, a higher current can be accommodated, This Circuit is however not optimized to handle high currents.