VOLTMETER HOOKUP ?

[2windy]

I just got a cheap $20.00 digital panel meter to read the voltage of my 12 volt battery bank. It has 4 wires coming out of it, [no instructions with it of course] 1 set of wires are labeled + and - for 5 volts and the othe set are + and - and not labeled. Do I need some type of a resistor or something to get this voltage down to 5 volts or will it work if I just hook it up to the battery? Waiting til I get some advice before hooking it up and frying it.Thanks for the help!

[nanotech]

I hate to say it, but I don't think that meter is going to work all that well.

I think the other two wires are for a back-light (think the gauges in the dash of your car at night).

I maybe blowing smoke, but I don't think you're going to be able to use it for measuring 12V....

[2windy]

I forgot to tell you the meter says on it 0 to 20 volts DC.

[jimjjnn]

You say wires going into the meter?

Most automotive gauges only have 2 large terminals for batt voltage and 2 wires for light.

If the 2 large terminals are like screw type, those should be your battery connections and any wires that are coming out should be for the light.

[2windy]

It has a small pigtail that plugs in to 4 pins on the back of the meter. It says this  + 5v -   + in -     The wire size is the same for all 4 wires, about the size of telephone wire.

[SamoaPower]

Many (most?) of the cheaper DPM's (Digital Panel Meter) require that you use a completly separate power supply for the meter itself and won't measure it's own supply voltage. The general rule is that none of the supply leads should be common to the voltage you want to measure. There are models that don't have this limitation. You can either use a battery to supply it or, if it's an LCD (Liquid Crystal Display) type, a small, simple isolated supply can be built to power it from your 12 volt battery. DON'T hook the supply leads directly to your 12v battery.

LCD DPM's can be found all day on eBay for US$6.00.

[DaveW]

The problem with panel meters is that they have no internal battery. the + and - inputs are for a battery voltage to make it work.  The problem with cheap panel meters is that they have no internal isolation.  So do not use the same power source as the voltage you are trying to measure.  Else you will see a puff of magic smoke, and no longer have a working meter.  You can use small batteries, most 5VDC panel meters will work with about 4.3 to 6 volt inputs... Just make sure that the grounds are not referenced together with that of the voltage to be measured.

[commanda]

The problem of dpm's and isolated supplies is why I designed & built this.

http://www.fieldlines.com/story/2004/9/14/23945/6905

If you must use the dpm, you need a dc-dc converter. You can buy these. 12 volts in, 5 volts out. Or 4 ni-cads. Take them out & charge them every few months.

Amanda

[ElSenator]

http://www.rc-cars-planes.com/rc-watt-meter_n.html?wurd5

I'm on my second one now(I did bad things and let the smoke out of the first one) and am VERY happy with it! Lot's of different displays (amps,volts, watts, amp hours and a few more. It's about 60 bucks I think.

[Shadow]

Sounds like I have the same digital meter as you. I got mine off Ebay,burnt the first two up as posted in above posts. I got the 5 volt regulator with next set, now I use a 9 volt battery to the 5 volt regulator  on each gauge,(Volts and Amps) also got the shunt with the amp gauge. Hooked up well over a year now with no problems. Battery lasts a long time if you put in a rocker switch and dont leave them on all the time.

[2windy]

Where can I buy one of these dc to dc converters 12 volts to 5 volts?

[commanda]

Any of the better online electronics component suppliers.

Farnell.

Radio Spares.

Digikey.

They all accept credit cards & post anywhere.

You only need the low-power version. I think 1(one) watt is toward the lower end without actually digging out a catalog.

Amanda