Non contact voltage checker - Electronic Circuits Projects Diagrams Free

Tony 100 · 11th February 2008, 03:52 PM

Hi everyone (new user)

Need some help manufacturing a non contact voltage checker but are unable to find out what type of sensor is used in the "sniffing" of the voltage. I have tried an Hall effect sensor but this is not sufficient. anyone help?

Regards
Tony

ronsimpson · 11th February 2008, 04:49 PM

A hall effect sensor will only work if current is present.
DC is hard to sensor at low voltages.
I assume you want to fine 120/220 volts A.C. 50/60hz.
I used an amplifier with very low input current like the LMC6442. Use high gain! Add some capacitors to make a band pass filter centered around 60hz. You need to remove high frequencies and DC. I used a 2 inch piece of heave wire or a 2x2 inch piece of copper as an antenna. I was able to find wires buried in the ground. I think with less gain you can find wires in a wall.

Boncuk · 11th February 2008, 11:57 PM

Best bet would be a combination of voltage detector and metal detector. If the wire has no electric field around it (unpowered) the metal detector will find it. To find low voltages you must cascade a lot of amplifiers to a gain of finally 1.000.000.000:1.

I did a circuit some decades ago indicating voltage walking on a carpet caused by friction. (that circuit used transistors) Use a twin circuit of low noise OpAmps, one for positive going voltage and another one for negative voltages or use dual power supply for one circuit. For detection use antennas as already posted here.

jpanhalt · 12th February 2008, 04:20 AM

I think the OP needs to clarify whether it is current or voltage s/he wants to detect. Current lead to magnetic fields and Hall sensors. Voltage (charge) leads to capacitance and electrometers, such as: http://en.wikipedia.org/wiki/Electrometer

John

on1aag · 12th February 2008, 06:24 AM

Hi Tony,

The mystery is solved, the sensor is nothing more than a 6n8
ceramic capacitor.

on1aag.

Tony 100 · 12th February 2008, 10:26 AM

sounds right because the one i stripped down had some sort of antenna Do you have a circuit diagram.

Tony

Tony 100 · 12th February 2008, 03:44 PM

Quote:

Originally Posted by on1aag

Hi Tony,

The mystery is solved, the sensor is nothing more than a 6n8
ceramic capacitor.

on1aag.

Hi
Can you tell me a little more about the theory behind the circuit, how does the Capacitor sense the presence of the supply

ronsimpson · 12th February 2008, 03:52 PM

The capacitor is just an antenna. You could use a piece of copper. A metal button will work.

If you hold a metal frying pan close to an AC wire some energy will be transferred into the pan. (antenna)

Tony 100 · 13th February 2008, 10:21 AM

Quote:

Originally Posted by ronsimpson

The capacitor is just an antenna. You could use a piece of copper. A metal button will work.

If you hold a metal frying pan close to an AC wire some energy will be transferred into the pan. (antenna)

Hi
Thank you for the information, what a great site with a great response. Thank you again, i will let you know how i get on.

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11th February 2008, 03:52 PM	(permalink)
Tony 100	Non contact voltage checker Hi everyone (new user) Need some help manufacturing a non contact voltage checker but are unable to find out what type of sensor is used in the "sniffing" of the voltage. I have tried an Hall effect sensor but this is not sufficient. anyone help? Regards Tony

11th February 2008, 04:49 PM	(permalink)
ronsimpson	A hall effect sensor will only work if current is present. DC is hard to sensor at low voltages. I assume you want to fine 120/220 volts A.C. 50/60hz. I used an amplifier with very low input current like the LMC6442. Use high gain! Add some capacitors to make a band pass filter centered around 60hz. You need to remove high frequencies and DC. I used a 2 inch piece of heave wire or a 2x2 inch piece of copper as an antenna. I was able to find wires buried in the ground. I think with less gain you can find wires in a wall.

11th February 2008, 11:57 PM	(permalink)
Boncuk	Best bet would be a combination of voltage detector and metal detector. If the wire has no electric field around it (unpowered) the metal detector will find it. To find low voltages you must cascade a lot of amplifiers to a gain of finally 1.000.000.000:1. I did a circuit some decades ago indicating voltage walking on a carpet caused by friction. (that circuit used transistors) Use a twin circuit of low noise OpAmps, one for positive going voltage and another one for negative voltages or use dual power supply for one circuit. For detection use antennas as already posted here.

12th February 2008, 04:20 AM	(permalink)
jpanhalt	I think the OP needs to clarify whether it is current or voltage s/he wants to detect. Current lead to magnetic fields and Hall sensors. Voltage (charge) leads to capacitance and electrometers, such as: http://en.wikipedia.org/wiki/Electrometer John

12th February 2008, 10:26 AM	(permalink)
Tony 100	sounds right because the one i stripped down had some sort of antenna Do you have a circuit diagram. Tony

12th February 2008, 03:52 PM	(permalink)
ronsimpson	The capacitor is just an antenna. You could use a piece of copper. A metal button will work. If you hold a metal frying pan close to an AC wire some energy will be transferred into the pan. (antenna)