Inside a 22mm digital panel indicator/voltmeter

A typical Bigclivedotcom teardown video; but you know it’s serious when he cracks out the big yellow Fluke.  The panel indicators under the figurative microscope are unusual, in that they are not only colourful – but also include a voltmeter and readout rated from 60 to 500 volts a/c.  An astonishing level of functionality given the ludicrously low price – around £1 at the time of the video.

The red version is likely to be the longest lasting – as the LED display is based on older, more reliable chemistry.  All of the versions were within a couple of volts of the readout from the Fluke – so close enough to be usefully accurate as an indicator (though any reading should always be confirmed using a more accurate meter/test equipment – this is, after all, a test panel indicator light and should be treated with caution – just because it’s off doesn’t necessarily mean there’s no current present).

Dismantling required cutting wires the to the terminals, as they must have been soldered on during the manufacturing process.  The voltage ratings of the components used appeared to be sufficient for use on UK 3-phase industrial supplies – but, as always, Clive cautions against using anonymous/untraceable chinese imported electrical equipment in a commercial environment (with the liability implications that could follow a failure).  An unmarked control chip provides the brains of the units.  Overall, the simplicity of the circuit, the quality of the components used, and the price they’re being sold for impressed Clive.

The red, green and yellow versions can be found on eBay from chips-fans (currently for £1.11) and the white version from cayin35 (currently for 99p)


YouTube description

This is neat, and surprisingly cheap too. Instead of just being a panel indicator light it also displays the supply voltage. That’s a very nice solution for quick diagnostics. The quality of construction seems OK. Very simple and well rated components for standard mains voltages, although the sense resistor may not be rated for the higher phase to phase voltages.

Power dissipation is low at about half a watt with predictably poor power factor (0.07) because of the simple capacitive dropper and low circuit voltage. There’s no significant heat being dissipated on the PCB.

The music track referenced is an old fairground classic called Dominator:-…

Carl Cox mix:-…

Here’s a universal ebay search link for the meters:-…

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