Let's take a look at a rather shonky looking electrical test probe and this thing is odd because I don't know if it's based on a another product, but they've basically just stuffed a circuit board inside this and it's not on any carrier reels. it's just literally wobbling and rotating inside. Very strange. However, this is an electrical test probe and it's rated from 3 to 36 volts.

I Have tested it against the fluke and the results were impressive. It was accurate within 0.1 of a volt the flux reading across the full range. So I've connected the black to the red, lead the red to the black the black connector because that's just how this thing is configured. Fortunately, it does have reverse polarity protection, but I'm going to turn the light off and I'll show you basically what this looks like because otherwise it's going to look a little bit flickery.

Actually, you know it's not bad. It is not bad. I Don't think I need to turn the light off. It could do with a red Barrel here or a bit of red photo material, but other than that it's not bad.

The flickeriness and the oddness of the flickerness is because this appears to be a Tri-State rated I Try Tri-State Driven display It's a Charlie plexed which is quite an odd way of driving it. Watch what happens when I connect the priority wrong. you connect the priority wrong and all that happens is a bright green LED Lights to show that it's wrong. It would have been better if it was red to show it's wrong and green to show it's right.

but they've got that Led the wrong way around. Let me open this up. very easy. unscrew the end.

Let's get a little metal plate in here on this. strangely. I Mean it's pleasing. I'm not sure what this cable is.

it's bizarre. It's very translucent and and sort of like candy like stranger. But here's the circuit board module. Very easy to get out.

so for that reason I have jumped straight into actually taking a picture of the back and reverse engineering in advance because it was so easy to get out and that saves a bit of time. It came with a plastic film across the front that's used to seal the front and while they're actually making it, they inject the resin and then they just leave the film on. that stops the resin basically just dribbling over the end. Let me show you the circuit board.

That is a good idea. Here 's the back of the circuit board. I Showed us to mount just a tiny bit here. I Shall also Focus down onto that.

that's better. So look at the circuit board. We have the chip that does everything. We've got One, two, three, Four Five six pins going to that display.

That is all. It's not like a standard Multiplex display. There is a number on the side of it. Two three eight one s Dash Seven or Two Three Eight One S seven I Only found one seller of that? Well, only one reference to it and it was a the is it what is the name of that website? uh or something like that the Chinese uh website that's like AliExpress but for Chinese people and uh, it's not one I really use very much so I don't really can't really remember the name.

but anyway, there was a reference. no data shooter. just said we've got these displays and that was it. However, it has six pins and Charlie plexing is a way that you can switch the pins both positive and negative.

So this thing must be limiting the current as well as switching the pins. Alternative: Negative and negative and positive. Yes, negative and positive. but also it can leave them floating and by using just six pins, you can address a huge number of LEDs Literally six at times, six minus one.

so five gives it can drive 30 LEDs So this display has, um, the seven segment display, so it's effectively with the decimal point eight eight times three, 24 LEDs so it fits nicely in with those six pins. The circuitry, the polarity indicator LED is in series with a massively High 10K LED and it's just a simple dual priority LED It's very sensitive. it's extremely bright, which is good because that is quite a high value of resistor. but keep in mind this is designed to operate from three to 36 volts.

I Only tested it up to 35, partly because it's got a little 3.3 volt regulator here and uh, that would be pushing I think to actually take this up Beyond 35 volts. However, the circuitry looks like this: There is a polarity protection diode, but before the polarity protection diet, there is a resistive divider uh, 20K resistor and a 1K resistor. But this looks as though it may be designed for a potentiometer, so they could actually fine tune it. But they've just used a fixed value here and that goes to the input to the chip.

We've got the power going to the regulator that regulates it to the 3.3 volts and the decoupling capacity across the chip. That's fundamentally it's not even it or starts operating at less than three volts and is still accurate even though it's not even reached the regulation point of that regulator. Um, and there's a diode between the output, the regulator and the input to the regulator. I'm not sure why that is.

Let me show you the schematic you can shame in if you can work out what they've put this diode here for. So here's the incoming: Supply There's the red green Bipolar LED With its 10K resistor, we've got the sense input going over to the potential divider that then provides a lower voltage reference to the microcontroller or indeed a dedicated meter chip. There's a possibility it is a dedicated meter chip specifically designed for use for that display. The accuracy is outstanding.

Really, it is so accurate. it was really impressive. There's the polarity protection diode. There's the regulator.

There's the decoupling capacitor which I'm going to guess based on the readings that I took on it even though it was in parallel. The circuitry is going to be roughly 100 nanofarad and there's this diode now. I've seen that diode used in the past for ensuring a fast reset of the low voltage site when the power goes off because the another a load in the power side will basically shunt via that diode and take it down to zero volts quite quickly. But that doesn't happen with this polarge protection diode.

Is this for leakage priority protection or something? I Really don't know why that diodes there and but let me know in the comments. if you can work out what that is and then fundamentally, that is it. You know there's not not much to it, it's just basically a simple, minimalist low component count voltage meter which makes me think really is probably going to be the same chip and module found in a standard low voltage LED display module. But that's it.

The strange cobbled together spiky electrical test device that could find uses out with the automotive industry. I'm guessing it's aimed at the automotive industry. The 3 to 36 volts is quite generous. It could also find rudimentary use and troubleshooting through control panels, but it is kind of designed to clip on to our chassis or chassis if you prefer.

and for the zero volt reference, but that's it. Interesting little circuit, novel, just not sure without diodes for quite strange.