Voltage leakage

[[email protected]]

I have a situation where I have a 440V power source. I want to tap
into a breaker and power an LED which needs only about 2-5 volts. Is
there a way that I can measure the voltage given off if I were to wrap
a wire around the 440 source?

 

[Terry Pinnell]

I have a situation where I have a 440V power source. I want to tap
into a breaker and power an LED which needs only about 2-5 volts. Is
there a way that I can measure the voltage given off if I were to wrap
a wire around the 440 source?

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.

 

[John Larkin]

I have a situation where I have a 440V power source. I want to tap
into a breaker and power an LED which needs only about 2-5 volts. Is
there a way that I can measure the voltage given off if I were to wrap
a wire around the 440 source?

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

 

[[email protected]]

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
http://www.djandassoc.com
Home of http://www.discovercircuits.com A collection of over 9,000
schematics.
Home of the Imagineering on-line magazine:
http://www.imagineeringezine.com

 

[Guy Macon]

This would allow you to tap into the AC source through some
high voltage capacitors.

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.

 

[Robert Baer]

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.

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

 

[Mark Jones]

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).

David A. Johnson, P.E. --- Consulting Engineer
http://www.djandassoc.com
Home of http://www.discovercircuits.com A collection of over 9,000
schematics.
Home of the Imagineering on-line magazine:
http://www.imagineeringezine.com

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