DIY volt meter

[tombrown]

This is a simple build it yourself volt meter:

http://www.mindspring.com/~wayne.orwig/utils.html#voltalrt

I'm regauging and choose not to buy a volt meter because I found this circuit. There just wasn't room for another round gauge in my panel. This is a 3 LED meter, but keep in mind that as voltage rises, the lower LED will FADE OUT and the higher LED will FADE IN, making this a variable voltage display (within the adjusted range).

I'm going to mount the three LEDs in the dash using round LED clips that require a 1/4" mounting hole. It will take more space for the legend than it will for the actual gauge.

[Techno]

I like the idea but I think that a low voltage reading would be more important. My engine failed to start at 11 volts once.
As far as I know LEDs have steel leads, you have to seal them also.
Another option is to place them in another gauge. one you can take apart and put back together.

[tombrown]

The LED leads aren't the only items that will need to be coated with a barrier finish. I was just going to use 5 minute epoxy.

The reason I chose this design is it's simplicity. There are several CMOS volt meter ICs (don't remember the specific IC) that make for a fairly simple circuit too. They only require some LED driver transistors and a voltage reference. This sort of design would be easily built in 8 to 16 segments.

This discrete component design has a total component count of 12 (including the LEDs) and only requires 3 - 1/4" holes in my dash. I think I'll use super bright LEDs for daytime viewing, so I'll adjust R1 as required.

The battery should float over 12 volts so this circuit will reveal battery undervoltage situations, although it won't reveal detailed information below 12 volts. The bottom line for me is that I'd rather have water temperature gauged instead of volts. I'm with you, however, in that a best case situation would have a full range volt meter.


[Edited by tombrown on 07-15-2001 at 06:44 PM]