Looking for a low battery voltage switch

[Daox]

I'm looking for a switch that monitors battery voltage. At a set voltage the switch would trigger a LED or relay. Anyone have any ideas on where I could get something like that? I know autospeed has one but I'm really not looking to order something from Australia.

[tasdrouille]

I can confirm that getting something from Autospeed can take a while. My order was shipped via airmail 11 days ago. Must have been shipped in a Beaver.

[NiHaoMike]

A simple comparator circuit is all you need.

[cfg83]

Daox -

Here's 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.

Jaycar electronics is "joined at the hip" to Autospeed.

CarloSW2

[Daox]

Yeah, I know autospeed carries two versions of the voltage switch. I like the one I posted more because its all solid state construction and thus I don't have to worry about the relay ever dying. Also, I just would like to find a place in the US that has this sort of thing. Someone has to have something like it on this side of the pond.

NiHaoMike, I know I need a voltage comparator and that it would be a relatively simple circuit. However, I don't know enough about electronics to build one myself. The problem being that the reference voltage will vary. Unfortunately, I don't even know enough to look at a circuit and know if this problem has been solved. Lastly, I'm willing to pay a bit (not a ton) just to have it premade so as to save me the time and hassle. If you have any suggestions, or a diagram that would be great.

[NiHaoMike]

Use a zener diode as a reference.