Cockscomb Mini Blue 0.36 " LED Digital Volt Voltage Panel Meter Voltmeter 0-99V, Three-wires for DIY

These KEEDOX Mini Blue LED digi-volt meters are pretty cool: Blue LED segments, three-wires (V+, Gnd, and Sense), small mounting holes in the perfboard, and AN ADJUSTMENT POT on the back!If you want high-precision voltage monitoring, these are not really for you. Get a true digital (or analog) voltmeter that will cost you, but this is just reality. When I received these the first thing I did was set them up on a 12v gel-cell battery in parallel with a Fluke digital multimeter - they read 1/2 volt from each other. Removing the KEEDOX Mini Blue LED leads did NOT lead to a rise in voltage due to removed load -- so these devices draw little current. I checked in-line to see how much current they drew and it was in the 100ths of amps. For my application, this is acceptable.On the back of each LED's circuitboard is a very small trim pot. You will need a small screwdriver (I used a small flathead driver meant for repairing glasses) and a known-good volt meter. Connect both to the same battery source, using the Orange/Yellow wire as the 'sense' wire, connected to the battery's +V terminal. Connect the volt meter probes to the same battery's terminals. Adjust the trim pot on the LED display CW or CCW until the display agrees with the voltmeter's display.I use these to monitor battery voltage on my deep-cycle gel-cell battery and a bank of smaller 8Ah 12v batteries. After adjustment, a little bit of double-sided tape and some quick connections of the (very thin) wire leads and it was done. They've been monitoring voltage for several weeks now.Good for hobbyist/maker who is not too concerned with accuracy, but needs a reliable ballpark voltage figure.

So far it has worked really well for several months of constant usage (it gets turned on about 200 times per day for around 3 seconds each time) as a voltage monitor in a DIY E-Cig project (I'm quitting smoking, and use the e-cig as a bridge).After all this time it still works acceptably, but I found I have to re calibrate it every few weeks, as it slips by about -0.2V. So that's why it looses a star, because a slip of that much means that I think the 3.7V Lipo charge level is lower than it really is, so I stop using it and recharge (it would be worse the other way around). Honestly, though its a really good deal, and accurate enough for my uses.Its accuracy is 00.0V, so its better geared for higher voltage operations, but still effective in the low Lipo range. For a 1S Lipo battery, you'd be better off with 0.00V precision.

I purchased several of these little panel meters in green, blue and red. These are a great value, and I still cant believe how inexpensive they are. All of mine work perfectly, and they are all accurate to within +/-0.1 Volts of what my FLUKE Multimeter reads. As soon as I received them I connected all of them to the same power source to check how consistent they were. All of them displayed exactly the same voltage of 12.3V, and my FLUKE multimeter showed 12.34V (can't ask for better than that). Just in case one of these panel meters is a little off the mark, there is a tiny trim pot on the back which allows you to adjust the displayed voltage. The only thing that you need to watch out for is the exposed circuitry on the back. Just touching the electronics with your finger causes the voltage reading to go crazy. I recommend that you just put a piece of electrical tape over the back to avoid messing things up.The number one reason why I bought a bunch of these things is because of how small they are. Most panel meters are quite large, making them difficult to use in limited space applications. No more cutting giant square holes into your stuff, these meters are so small they can go almost anywhere. I put three of these in the front of my desktop computer to keep track of the 3.3V, 5V and 12V power supply outputs. I also put one just under the gauge cluster in my car to monitor the battery charge. They're bright enough so that you can easily read them in anything except direct sunlight, but they're also not blinding at night like some other products are.They ship directly from China, so it will take a couple weeks before you receive them. But the bottom line is, for $3.19 this is the best deal out there.

I bought this panel a few months ago to use on a power supply project. It has held up very strong to daily us.It took awhile to ship compared to the other colors as it had to come from China directly.I would have to say, the unit is pretty accurate, but I had to calibrate it (turning the little Philips-head screw on the rear) a little bit using another voltmeter as the 10th place was a little off - not a real big deal to me.When connecting the unit, the black and red wires are for power and the white wire is for voltage measurement on the POSITIVE terminal. Make sure to note that otherwise you can risk burning out the unit.After successfully connecting it, the LED light (blue) is very bright and consistent.I only had one issue with this produce as it had a slightly different form factor as the green and red ones. It did not match the picture as shown. Instead, I got the unit with thin long mounting ears (top and bottom parts cut off). It did not really bother me, but it looks out of proportion to the other colors.I cannot really complain as the price was extremely cheap for the unit.Despite the form factor differences from the photo and the other colors, I still would recommend this product and I won't deduct a star as the price and performance and ability to calibrate it was great. This product is perfect for various electronic project just to mention.