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AC (+) and (-) finder circuit

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Eplanet

New Member
hello all
can you help me for making a circuit for finding AC (+) ans (-) in main power.
thanks
 

BrownOut

Banned
Any DMM will do:

Measure between each phase and ground.

The phase which reads > 0 will be the hot wire. The phase that reads 0 ( or very nearly so ) is the neutral.
 

picbits

Well-Known Member
If your electrics have a ground on them then just connect three neons with limiting resisors across each combination.

The node that has 2 lit neons on it is the live.
 
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Hero999

Banned
There's is no '+' and '-' with AC, only different phases, phase/antiphase or phase and neutral, depending on what system you're using.
 

Eplanet

New Member
i know there is no + and - for AC i mean phase and ground. i need electronic circuit for indicating phase and ground for exp with LED or buzzer. this is tool for repairing electrical device.
and i don't want to use DMM. i need very simple device.
thanks
 

Eplanet

New Member
i have tester but i cant see any light in the sunny day for repairing cooler on the roof.
 

Hero999

Banned
Add a photo Darlington transistor and a piezo buzzer.:D
 

JimB

Super Moderator
Most Helpful Member
Or use a cheap and cheerfull DMM with an LCD display which can be seen in bright sunlight.

JimB
 

Boncuk

New Member
i have tester but i cant see any light in the sunny day for repairing cooler on the roof.
The neon bulb in the tester is fitted with a current limiting resistor since it's operating voltage is approximately 50V. Reduce the value of the resistor until you get a bright orange display. (Additionally you could paint the body (inside around the lamp) of the tester with transparent red colour.)

The light gets brighter if you touch the metal cap on top of the tester and a piece of grounded metal (cooler case)

If that won't help shade the indicator light for better view.

Boncuk
 

Hero999

Banned
Be careful, if you reduce the value of the resistor too much you'll receive a shock.

Make sure the resistor is rated to 2kV as there can be nasty spikes on the mains.

I would just use a 4.7nF Y2 capacitor rather than a resistor.

i haven't 220v piezo buzzer.
Then use a battery, two watch button cells in series will be enough to make a piezo buzzer beep quietly.
 
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