A Steady Hand Game is shown below. The aim is to move the handle around the wire shape without touching it. If the handle touches the wire a buzzer sounds. This is the type of game that contains a thyristor circuit. When the handle touches the wire the buzzer will sound until the reset push switch is pressed, even if the handle is moved away from the wire.

The circuit for this type of game is shown below. The main component is called a thyristor. This is a special type of switch. When it is activated it cannot be turned off unless electrical power is removed from the whole circuit.

The symbol that represents the thyristor is shown opposite. It has three pins. The ANODE, CATHODE and GATE.

1. Using circuit simulation software draw the thyristor circuit.
2. Close switch ‘A’ to supply power to the whole circuit.
3. Close switch ‘B’ to allow current flow into the thyristor’s gate.
The buzzer should sound.
4. Open switch ‘B’ - the buzzer should still sound because the thyristor cannot be deactivated until all power to the circuit is removed.

COMPONENTS

Three 1K resistors.
One thyristor.
One 6 volt buzzer.
One battery snap.
One 9 volt battery.
Red and Black wire.