This random timer circuit is based on a Atmel ATTINY24 avr driving one power relay. You can use this circuit to switch on and off other circuits randomly. For example, when using this circuit on a model railroad you can turn on and off parts of the animated or moving scenery to create a more dynamic view.
This circuit was designed to be used on a modular model railroad. This model railroad contains different flashing light on ambulances, police cars and fire engines. These lights are on all the time, with this circuit I hope to keep visitors of a model railroad exposition more interested while watching all the action.