A 24VDC relay can be used to trace electrical wires up to several meters long. This makes it suitable for detecting electrical wires in structures such as houses, factories, warehouses, big buildings, or other structures, including electrical wires on ships.
This method allows to check a single wire path. Unlike a typical multitester, which requires two wire paths: a positive wire and a negative or neutral wire, to check continuity.
Photo of a 24VDC relay circuit that produces high voltage, transmitted through the power cable, and can be detected with just a voltage tester screwdriver. No multimeter is needed. The short power cable in the photo, in practice, will be a long power cable with both ends separated by several meters.
The induced voltage generated by the coil is relatively safe to touch. Although the voltage is high, the current is very weak, so the power is very small. It does not cause injury if touched, but usually only causes a bit shock.
The 24VDC relay is powered by two 9-volt batteries connected in series to produce 18 volts.
The relay is set to vibrate to generate an electromagnetic field (EMF). The relay pins are connected as follows:
The Common (Com) pin is connected to one of the coil pins. The high positive voltage (H) is generated from this Com pin, and can be detected with a voltage tester screwdriver.
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 kiloohms.
The Normally Closed (NC) pin on the relay is connected to the negative terminal and ground. The NC pin is connected to the Com position when the relay is inactive. When the relay operates or vibrates, the resulting induced voltage illuminates the voltage tester lamp.
The negative terminal of the battery must be connected to ground, which can be connected to a nail in a concrete wall, a steel frame, a metal water faucet, or something else. If the negative terminal is not properly connected to the ground, the voltage tester lamp will be dim.
Video of a 24VDC relay on YouTube during an NCV test.
The electromagnetic field generated by the relay can be detected with a digital multitester with a Non-Contact Voltage function. If the cable is connected directly to the Com terminal on the relay, the NCV on the multitester will detect a strong electromagnetic field.
The photo of the NCV function on Aneng's multi-tester detects an electromagnetic field in a piece of black insulated cable whose conductor is connected to a long coil of cable. The multi-tester display shows a very strong electromagnetic field detected, reaching full scale.
Also, read various other relay circuits for detecting long, hidden electrical cables.
In a long double-core (twin) cable, a weak electromagnetic field is detected in the adjacent cable not directly connected to the relay's Com pin. This type of cable is often used in electrical networks, usually with the code NYMHY, which is a double-core stranded cable with an insulated layer.
If the cable is broken, the electromagnetic field will be very weak in the broken section.
No comments:
Post a Comment
Your positive comment will be highly appreciated to improve this site