Trace Long Electric Wire, Without Negative/neutral

 

The tools discussed in this article are used to check or trace long electrical wiring networks. Those long wires can't be traced by the continuity function on a multi-tester. Because the wires extend several meters and are passing through different rooms.

Simply by using a voltage tester, the other end of the wire can be found.

The wires being tested are all physically identical, for example: all wires have black insulation.

The circuit discussed here uses high voltage induction from a relay coil. The high induction voltage is fed to the end of a wire, the H-end in the image above. The other end is then traced using a voltage tester.

The negative terminal of the induction voltage is connected to ground (earth), so the voltage tester illuminates brightly.

This method allows one wire path can be found. Unlike a typical multi-tester, which requires two wire paths: the positive wire and the negative or neutral wire, to check continuity.

The induction voltage generated by the relay coil is relatively safe to touch. Although the voltage is high, the current is very weak, so the power is very small. It doesn't cause injury if touched, but usually only cause a shock.

These circuits are intentionally designed to be simple yet reliable and easy to operate. This avoids confusion when tracing electrical wires. Even if this tool damage, it's easily repaired due to its simple circuitry. The components are readily available and inexpensive.

All circuits are designed without transistors or integrated circuit (IC). Transistor and IC can fail when exposed to high voltage, making it confusing when tracing wires.

The voltage tester used is a standard type with a mini neon light, as it's reliable and readily available at a low price. It's not an electronic voltage tester, which is prone to damage and expensive.

Tracing electrical wires is difficult and high-risk job. Therefore, don't let complicated and confusing designs add to the difficulty.

24VDC RELAY CIRCUIT

This circuit uses only one component: a 24VDC relay, designated R in the schematic. The relay is powered by two 9V batteries, connected in series to produce a voltage of 18V.

The Common (Com) pin is connected to one of the coil pins. The positive high voltage (H) is generated from this Com pin.

The other coil pin is connected to the positive terminal of the battery.

The 24VDC relay, as shown in the photo above, has a coil resistance of approximately 1.6 kilo-ohms.

Photo of a 24VDC relay circuit.

The Normally Closed (NC) pin on the relay is connected to the negative terminal and ground. The NC pin is connected to the Com pin when the relay is not active.

To ensure the voltage tester light is bright, the negative terminal must be connected to ground, which can be connected to a nail on a concrete wall, steel frame, metal of water tap, etc.. If the negative terminal is not properly connected to ground, the voltage tester light will be dim.

Video of a 24VDC relay on YouTube.

How It Works:

When the relay coil is connected to the battery, a magnetic field is created in the active coil, as the coil is an electromagnet. The magnetic field will attract the relay switch, thereby cutting off the current from the NC pin. This will interrupt the flow of current to the coil.

The electromagnetic field formed when the coil is activated will collapse and induce current into the coil, resulting in a high voltage induction from the coil.

Because the connection between the switch and the NC pin is broken, the current of induction high voltage cannot flow: through the NC pin, through the battery, to the coil's negative terminal, or to ground.

The high-voltage current will flow through point H, through the long electrical cable being probed. It then travels to the voltage tester, the technician's body, and becomes neutral at ground.

When operating, the relay will vibrate and sound, indicating proper operation. This makes it easier to check if the device is working or faulty.

5VDC RELAY PAIR CIRCUIT

This circuit uses two 5VDC relays in series connection, R1 and R2. The circuit is also supplied with 18V.

In the first 5VDC relay (R1), one pin of the coil is connected to the positive terminal of the battery. The other pin is connected to the second relay (R2).

The 5VDC relay in the photo above has a coil resistance of approximately 125 ohms.

The photo above shows the induction voltage from two 5VDC relays, their coils connected in series, powering a voltage tester through the electric wire.

The first relay (R1) in the schematic uses only its coil; its switch is not used.

For the second 5VDC relay (R2), its pins are connected in exactly the same way as the 24VDC relay in the first circuit.

The above is YouTube video about this two relays device.

JOULE THIEF CIRCUIT

The Joule thief circuit uses a 5VDC relay. It is similar to the circuit in the previous Joule thief article, which was used to power a 3W 220VAC lamp.

The difference is that this circuit uses only the relay coil to produce high voltage.

The high-voltage supply is provided without any additional coils. This simplifies the process.

The 5VDC relay connection on this circuit is exactly the same as the 24VDC relay circuit above.

As shown in the photo above, the voltage tester lights up brightly because the circuit uses a capacitor (C) to collect current. This circuit can be powered by 9V or a single square battery.

The capacitor (C) used is 100 nanofarads and with a voltage rating 220 VAC.

If supplied with 18V, the voltage tester will light up brighter. However, this makes the circuit more complicated and increases the cost.

The diode (D) is a 1N4007; in this circuit, it prevents the high voltage induction energy accumulated in the capacitor from flowing backward, preventing the capacitor from discharging.

The above is YouTube video about this Joule Thief.

OTHER PROCEDURES:

One of the methods is to use two voltage testers, one as a feeder and the other for detection.

The feeder voltage tester is connected to the high-voltage 220 VAC power grid. This voltage tester applies a small current to the wire to be tested. Then, using another voltage tester, the end of the wire is probed.

Other method for source of induction voltage can also be used, such as a soldering iron supplied with alternating current (VAC). The metal tip of the soldering iron can generate an induction voltage to make the voltage tester glow brightly. The metal tip of the soldering iron is connected to one end of a wire. A voltage tester is used to check the other end if that wire. 

However, both of these alternative methods require a high voltage source from the network, even though the wires of that network are being tested. Although this can be regulated using a system of several separated circuit breakers (MCBs), due to the high voltage and high power of the network, any error can result in a fatal accident. Furthermore, electrical wiring is often installed in difficult-to-access locations such as above ceiling, inside wall, under floor, in display case, cupboard, or large cabinet, etc., making it prone to accidents.

CAUTION:

The high voltage from the induction coil, even at very low wattage, can damage sensitive electronic equipment, as it can reach voltage exceeding 220V.

Therefore, before performing the procedure with the tools mentioned above, it's best to unplug all electronic equipment, such as cell phone chargers, TVs, radios/stereos, computers, laptops, and other high-voltage sensitive devices, from the electrical network. This will prevent damage from exposure to high voltage from the coil.