Sound Voice Activated Relay Switch

This mini-VOX - voice operated relay - is based on a circuit published in Silicon Chip, 9/1994, p31. We have improved it by putting an on-board Koa potentiometer in order to adjust the sensitivity. The idea behind a VOX is that instead of the user pressing a switch to activate a relay, the sound of the users voice itself activates the relay. This gives hands-free control over devices like lights and tape recorders. Relay stays on for 1 or 5 seconds (depending on components used) then shuts off. Different time values can be realized by using different value components (read pdf file for more information).

Specifications:

• L: 2-1/4" W: 1-1/4" H: 5/8"
• Requires 12 VDC Power Supply
  (Need a Power Supply?)
• Current drain when off is 5-7mA and 35mA when activated
• Relay output rated at 12VDC/10A or 240VAC/5A
• Microphone can be connected on leads up to 2 feet away from the PCB.
• Off time delay adjustable by changing component values.