Hacked Gadgets Forum

May 24, 2014

Non Contact Voltage Test Pen Teardown

at 9:11 am. Filed under Teardown



If you are doing any electrical work, one of these Non Contact Voltage Test Pens can be quite handy. Just touch the wire that you want to make sure isn’t live and check that the tester doesn’t beep and start flashing. This test pen is on all the time monitoring for AC between 90V and 1000 V. I would have preferred the device to have an on/off switch which would allow the battery to last even longer but I guess they figured that the 1.5 year life that they rate this for when in standby was good enough. This impressive life is because they got the current draw down to under 10 micro amps! Even when operating it only draws a handful of milli amps.

The board is quite thin at 0.8mm, this is half the typical generic PCB thickness which is 1.6mm. In large quantities the thinner board might be cheaper but typically anything thinner or thicker than 1.6mm is a premium price at most board houses that I know about.

The main component of the board is a 74HC14D hex inverting buffer the data sheet (PDF) shows a maximum supply current to the chip of 2 micro amps which makes sense based on our current readings. You can see a schematic below that Warren Young reverse engineered from a similar device (not the same but very similar operation).

You can see full sized tear down images here.







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2 Responses to “Non Contact Voltage Test Pen Teardown”

  1. Howard Says:

    It would be interesting to see a side-by-side comparison between a genuine Fluke VoltAlert and this Chinese knock-off copy. Although they both perform the same function it’s often obvious that the knock-off is not built to the same standards. One wonders if it is built to any safety certification standard or even tested.

  2. k.alajmi Says:

    what is the R2 lead and what the value? …also what are you using for an antenna? based on the circuit draw there is an inductor before the 1M resistor.. if you can explain how is it work.


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