Requires a separate Power Supply
3 digit LED panel Voltmeter
For + Voltage only; Note: Power & Input Share the Common Black lead Black Wire: Power Supply - & Input - Red Wire: Power Supply + 3 to 30VDC White Wire: + Input
Supply Voltage: 2.5-30VDC
Metering Input Range: 0-100VDC (99.9V)
Character Height: .28"
2 screw mounting.
Cutout: 22.5 X 10.5mm
6in. leads W: 33mm O/A H: 11mm D: 9mm WT: .012
WARNING: This product can expose you to chemicals including Nickel which is known to the State of California to cause cancer and which is known to the State of California to cause birth defects and/or other reproductive harm. For more information, go to www.P65Warnings.ca.gov
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I read the reviews above, but I think their explanations were not quite complete. So I grabbed my decent quality Tenma Voltmeter, a decade resistor box, and soldering iron, and started testing. I am using this with my Raspberry Pi, so the RED Panel Meter + wire is connected to the 5.1VDC that powers my RPi. And BLACK to RPi ground of course. Mark M. description above was good, but I d like to add a couple footnotes. This type of meter uses a voltage divider so that the 100VDC input rating is divided down to something the analog > digital chip can handle. I attached the Tenma voltmeter, and the Panel Meter WHITE wire to my voltage source > 3.3VDC from the RPi, and started paralleling the 330K > marked 334 - near the D1, C3, U4 > with decreasing value resistances. I found eventually that that SHORTING OUT the 330K gave me a reading near 3.3V that I expected. Then, using a small plastic tuning tool, I tweaked the potentiometer in the center of the board, and got the Panel Meter reading dead on with the Tenma meter. So it looks like that 330K resistor and the pot is the only thing in the voltage divider to the A > D chip. I tested several other voltages from 0V to 5.1V and found it to track very close. PLEASE NOTE: Since the decimal point cannot be moved, 3.3VDC showed 33.3VDC on the meter readout. CAUTION: Shorting out the 330K probably means that ANY voltage substantially higher that the meter power voltage COULD DAMAGE the meter. > above 10VDC at the input? > Using this on my RPi breadboard, that will not be an issue here. Hope this information is useful...
- Dale Kline, MI
Smaller than expected, very nice!
I ordered 10 because of the sale price, and I was pleasantly surprised by how small these are. That means I can use them in more projects! You could almost call them adorable. Very handy.
- Willie..., CT
Display Voltage Change
I changed the 100v input. In one corner there is a chip resistor marked 334. I placed a 220K resistor across it and changed the display so that 5V input = 10.0V readout. Other values = other display readouts. Initially used potentiometer to find desired readout vs input. No attempt was made to change the decimal but it could be blocked with a dab of black paint. Solder carefully!!!
- Woody, VA
Use of a red filter red gel filter in front of the display will suppress unlit segments. Greatly enhanced contrast! Google red gel filter.
- Woody, VA
Which resistor to short out?
I see a 330k, a 2.2k, and a 12k. Which one should be shorted to change the range to 0.00 - 9.99v?
Versatile, easy to use
I bought a bunch of these because of the three-wire configuration; I wanted to measure voltages other than the supply, which shared a common ground.
Theyre very compact; only the mounting tabs stick out beyond the area of the display itself.
Theyre very easy to use, of course, and also easy to mount. I wanted a somewhat dressier look, so I 3D-printed bezels to allow them to mount neatly through a rectangular hole in the sheet metal panel with no exposed hardware. Unlike other units of this type, the LED segments in these are surrounded by a black background, so no extra smoked lens in necessary for good contrast in bright lighting.
I also modified some of the units to display 0 to .999 volts, rather than the 0 to 99.9 volts theyre designed for. This was very easy, requiring only that a single surface-mount resistor be replaced with a wire jumper, and also had the side effect of increasing the range on the on-board calibration trimmer.
These are great little units, especially at the price. I have taken to scattering them throughout projects Im working on, so I can monitor voltages at various points in real time during development.