volt gauge (mini) install (1 Viewer)

lx450landcruiser

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Well finally got around to installing this. For those who dont know i was given a few of these by a friend and after some talk looks like some mudders were able to find them on ebay for about $10 ( http://www.lightobject.com/3-digit-Mini-Green-LED-100V-Volt-Meter-P52.aspx )These run off 5 volt so you have to buy a resistor at radio shack ($1.60) I ended up wiring it to a 3 way switch so i can now check both batterys voltage off the one gauge. Its really easy to see at night and day (the pics make it look hard to read but thats due to the flash) I did have to file a bit of the plastic to get it to fit but its a nice snug fit and im happy with it. Ill be installing another in the trailer.
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The 7805 Voltage Regulator (not a resistor) he gave the part number to has three pins: in, out, & common or ground. In goes to your 12V supply, out to your device and common to ground - simple as that. You can also add a couple of caps on the input and output to further stabilize the power supply.
 
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Quick update - I was emailing George thanking him for his quick service on the domelight LEDs and asked him a question about the 78xx voltage regulators in a different application - his reply is pertinent here:

"well, a voltage regulator would work, but it would be better to use something like the lm2931 series that is designed to withstand the automotive electrical environment (reverse polarity, load dumps etc)."

The circuit is wired the same as the 78xx.
 

TrickyT

Hate that mud...
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I installed a similar digital panel meter a few months ago so that I could monitor the state of charge in my battery (battery voltage is a reasonable measure of charge state), although mine is made by Datel and is 3 1/2 digits (p/n DMS-20PC-2-GS-C). A couple of things to note. First, these meters draw ~100ma, so the voltage regulator must dissipate about 3/4 watts (7.7v x 100ma), which means they get pretty hot - too hot to touch. So to insure the regulator doesn't burn up it should be mounted to a metal heat sink. Just use a little thermal mounting compound under the regulator and bolt it to metal framing somewhere behind the dash. Secondly, it gets pretty hot inside the engine compartment and these meters are typically rated for a max temp of 125*C. If you want your meter to lead a long life, I'd avoid putting it inside the engine compartment.
 

Lka1988

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So, how did you wire this up? I got mine in the mail today. There are four wires on the pigtail, Red, Black, Green, Blue.
 
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So, how did you wire this up? I got mine in the mail today. There are four wires on the pigtail, Red, Black, Green, Blue.
Probably too late to help you - but here it is:

Red - +5V
Blk - Gnd
Blu - Gnd
Gre - voltage to measure.

It looks like you can measure voltages not tied to ground as well. The power leads are red and black - the measurement leads are green and blue.

The non-mini version of this can use 12V as the power supply. Too bad the mini needs 5V.
 
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Radio shack part number is 276-1770

5 volt
Do you know if the mounting tab/heat sink can be grounded without causing a problem ?

you know, bolting it to some dash bracket to use said bracket as a heat sink?

Thanks

***Update yes I can mount it to ground with no problems :) ***
 
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Do you know if the mounting tab/heat sink can be grounded without causing a problem ?

you know, bolting it to some dash bracket to use said bracket as a heat sink?

Thanks

***Update yes I can mount it to ground with no problems :) ***
Hello folks:

This is Ligthobject and I'm the one who is selling that mini meter. If you're concerning the heat that a 7805 generated, then you may consider a dc-dc isolated power module. 7805 is a passive regulator while the dc-dc module is employing switching circuitry so that there is much less heat generated. There is about 0.7Watt heat wasted on the 7805 which is fine as my 7805 module comes with a little heatsink attached to it.

FYI, I got a Blue 100V available. I do have 7805 module with cables ready for the meter.

Feel free to drop me email for question. I'll try to help as much as I know:beer:
 
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I really dig the mini-size of the LCD... been searching around for a solution for some time without success.

So, I think i'm still not clear on which mini 12v gauges will fit in the OEM switch holes; not require external power source and won't melt the dash plastic.

I'm looking for a design to accomplish the monitoring of a dual battery set up. If that can be accomplished with a single display, great. If it needs two, then where to install them?

Also, besides being illuminated with ignition on, has anyone wired in a temporary push-button or momentary rocker that'll allow seeing the voltage measurement while the engine is off & no keys in ignition?

Come to think of it, I'd considered getting an meter with Red display for better night-vision. Anyone using red that could speak to it's visibility during the day? Any difference than with the green or blue?

Thanks!
 
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alia176

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I think a simple two position maintained (with center off) switch for monitoring dual batteries will suffice (wired constant hot). I'm not sure if you want to see a voltage display all the time, maybe you do! You have many options.
 
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