Voltage leakage

Not an led, but you might get a neon lamp to light up this way. Maybe use foil around the wire to increase the pickup capacitance. But it won't be very bright.

It would be easy to light the LED from a battery-powered circuit that senses whether the 440 is present.

Or a split-core current transformer could sense the *current* in the wire and power an LED. But that wouldn't be safe as a "hot" warning.

John

Is this a 440vac three phase system? If so, then one phase would be about 260vac to 280vac. If you flashed the LED instead of driving it continuously, you can keep the average current draw down of a couple microamps. This would allow you to tap into the AC source through some high voltage capacitors. Even a pair of 1000 picofarad caps (1KV rating) connected to the AC source, would give you enough power to drive an LED flasher circuit. Just connect the two caps to the AC source and to a bridge rectifier (you can use some 4148 diodes if you wish). Place a small 1 uF cap at the output of the rectifier. Then, to limit the voltage to a low level, place a 3.3v zener diode across the cap. This should give you 3 volts with about 20 microamps of DC, which would be enough to drive a LED flasher circuit. I have several posted on my Discover Circuits site.

David A. Johnson, P.E. --- Consulting Engineer

Home of A collection of over 9,000 schematics. Home of the Imagineering on-line magazine:

Wait exactly one week from reading this reply, and then take the following methodical steps:

1. Obtain a standard test tube and a cork or rubber stopper to fit it.
2. Hold the test tube at 45 degrees over the 440V source, for 3 secs.
3. Replace the stopper, capturing the voltage given off.
4. Use a Digital Multimeter/Voltmeter (a DMM or DVM) set to a low voltage range, remove the stopper, and then quickly insert the probes into the test tube.
5. Read the result.

--
Terry Pinnell
Hobbyist, West Sussex, UK

I always like to use two capacitors in series when tapping into an AC line. I don't want to be one component failure away from feeding full line voltage/current into my circuit.

A damn lightning bug beat me to it; got inside before i could, then escped all litup...

1N4148? At -380Vrm (peak)? 1N4148 is only rated for -100v repetitive, -75v/5.0uA.