The Thyristor Latch

This circuit uses a component called a thyristor to latch on an output. A thyristor works a lot like a transistor, however it stays on when switched on, until the power supply has been cut off. It has three legs: Anode (positive connection), Cathode (negative connection) and gate- the middle leg that when triggered by being connected to 0V will allow current flow between the anode and cathode. The circuit therefore uses a switch between the gate and 0V, when pressed the switch will complete the circuit of which the LED is connected to and thus light the LED. The gate of a thyristor should always be protected by a 1K ohm resistor if a 9V power supply is to be used.

Parts List

• 1 Thyristor
• 1 1K ohm resistor
• 1 330 ohm resistor
• 1 LED
• 1 Push to make switch
• 1 rocker switch
• 1 9V power supply
• Breadboard or similar

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