voltage activated circuit

can anyone help me with a problem? im looking for a circuit that will detect a drop in voltage and then activate a switch on when the voltage below certain voltage (let say 8 V)

the source voltage can be 22V

**broken link removed**

I have one. Although I've never used it other than testing it. I ordered the kit, but they sent my an assembled one. Well made. It operates a relay above or below a set voltage. You can set it to trip on a rising or falling voltage. and it has a wide adjustable hysteresis.

I have the instructions and diagram, but I'm not sure I'm allowed to post them here. I think I've seen them posted other places.

May be overkill for what you want to do.

use a voltage reference chip for reference, comparator to compare the actual voltage with reference voltage and use the output from the comparator to do whatever you want (turn on relay or whatever) ...

HerfGun said:

**broken link removed**

I have one. Although I've never used it other than testing it. I ordered the kit, but they sent my an assembled one. Well made. It operates a relay above or below a set voltage. You can set it to trip on a rising or falling voltage. and it has a wide adjustable hysteresis.

I have the instructions and diagram, but I'm not sure I'm allowed to post them here. I think I've seen them posted other places.

May be overkill for what you want to do.

Click to expand...

dam.. the stupid office internet not allow me to go to the page. is it possible for you to tell me what the exact name in the catalogue. i got 2008 one in front of me

thanks

CAT. NO. KC5377 cost: $18.95 for one

Universal Voltage Switch

Ref: High Performance Electronic Projects for Cars - Silicon Chip Publications.

This is a universal module which can be adapted to suit a range of different applications. It will trip a relay when a preset voltage is reached. It can be configured to trip with a rising or falling voltage, so it is suitable for a wide variety of voltage outputting devices eg., throttle position sensor, air flow sensor, EGO sensor. It also features adjustable hysteresis (the difference between trigger on/off voltage), making it extremely versatile. You could use it to trigger an extra fuel pump under high boost, anti-lag wastegate shutoff, and much more. Kit supplied with PCB, and all electronic components.

Here's a little article about it.

Voltage Switch

Google "jaycar voltage switch" or just "voltage switch"