Using a Reed Switch as a Current Monitor Circuit

Reed switch can be used to sense current.

It is like a tiny magnetic switch.

When current flows in a wire nearby, it creates a magnet field.

This magnet field triggers the reed switch to turn on or off depending on the design.

Circuit Working:

Parts List:

In this current monitoring setup we employ a reed switch alongside an LED and a resistor to indicate the presence of current in a circuit.

A Reed switch typically demands between 10 and 100 AT ampere turns which corresponds to the current in a coil multiplied by the number of turns.

The lower the AT value, the more sensitive the reed switch becomes.

For instance, consider a car headlight system where each light bulb draws a current of 7A or 8A at 12V.

Therefore, a 50 AT Reed switch necessitates 7 or 8 turns to effectively monitor the current.

If one bulb malfunctions and the current drops below half the switch opens its contact.

Formulas and Calculations:

From the above circuit, formula for calculating the current in the circuit is:

I = V / R

where,

• I represents the current in amps A.
• The voltage expressed in volts is V.
• In ohms Ω, R represents the resistance.

From the circuit above 470 ohms of resistance and 12V of power, so the current is:

I = 12V / 470Ω = 0.0255 A

or 25.5 milliamperes (mA).

There will be around two volts across the LED.

Thus, the LEDs current is:

I = 2V / 470Ω = 0.0043 A

or 4.3 milliamperes (mA).

Note:

A quick and efficient method for determining if a current is there is the reed switch current monitor circuit.

Numerous applications, including industrial controls, alarm systems, and security systems are possible for it.

How to Build:

To build a Reed Switch as a Current Monitor Circuit you need to follow the steps mentioned below:

Gather Components:

• You will need a reed switch, an LED a resistor the value depends on the LED and the desired brightness, and a power source such as a battery.

Connect Reed Switch:

• Wire the reed switch in series with the circuit you want to monitor.
• The reed switch should be positioned so that it opens or closes based on the current flow.

Add LED and Resistor:

• Connect the LED in parallel with the Reed switch.
• The resistor should be in series with the LED to limit the current and protect the LED from burning out.

Test the Circuit:

• Apply power to the circuit and test its functionality.
• The LED should light up when there is current flowing through the circuit.

Install and Monitor:

• Once the circuit is working correctly install it in the desired location and monitor the current flow as needed.

Note:

• Remember to take proper precautions when working with electricity, and if you’re unsure seek the help of a qualified electrician or technician.

Conclusion:

Employing a reed switch as a current monitor circuit offers a simple yet efficient method to detect current flow in a circuit.

By utilizing the reed switch’s magnetic sensitivity to open or close in response to current this setup can provide valuable monitoring and control functionality in various applications.

Its basic design and ability to be adjusted for sensitivity make it a practical choice for tasks requiring current monitoring.

References:

Circuit to turn microcontroller on when reed switch state changes (to monitor door lock state)

Reed switch as over current detector ?