Beginners who wish to learn about electronics are going to enjoy this post!
It explains how to construct a simple circuit for a magnetic field sensor.
Because they are simple to construct and provide a wide range of uses these circuits are well liked.
In the exciting field of electronics they are a great place to begin.
What is a Magnetic Field Sensor:
Magnetic field sensor circuits are mainly used to detect and measure the strength of magnetic fields in their surroundings.
These circuits normally use Hall effect sensors which are devices that produce a voltage proportional to the strength and polarity of an external magnetic field.
Electronic compasses, industrial automation, robotics and automobile systems are just a few of the applications for magnetic field sensor circuits.
Circuit Working:
Parts List:
| Component Type | Component Details | Quantity |
|---|---|---|
| Resistor | 1k 1/4 W CFR | 1 |
| Semiconductor | IC LM339 | 1 |
| LED Red LED 20mA 5mm | 1 | |
| Relay 12V | 1 |
This creative circuit design smartly generates a magnetic field sensor circuit by replacing a relay coil for the standard meter as previously explained.
The sensitivity of this arrangement to changes in magnetic fields is amazing.
The light from LED1 is an indication that is triggered when a small permanent magnet passes near the connected relay coil.
The sensor works similarly to the previous version which used a mobile coil meter while the coil stays fixed during the magnets transit.
Any relay coil can be used with the circuit but the best sensitivity is achieved by choosing one with the highest resistance and maximum inductance usually 400 ohms.
By placing a permanent magnet a few inches from the relay coil parallel to the coils pole the circuit is converted into a sensor that can detect an iron item moving between the coil and magnet.
The coil experiences tiny alternating current (AC) voltage potentials with every change in the magnetic field.
The operational amplifier (op amp) boosts these weak electrical signals which causes LED1 to dim and brighten sometimes.
Follow the construction details to clear up the complexities of the design and provide a thorough knowledge of this magnetic field sensor circuit.
Formulas:
The following formulas are used to design a Simple Magnetic Field Sensor Circuit:
Magnetic Flux (Φ):
Φ = B * A * cos(θ)
- B is the magnetic field strength.
- A is the cross sectional area.
- θ is the angle between the magnetic field and the coils normal.
Induced EMF (ε):
ε = −NΔΦ / Δt
where:
- N is the number of turns in the coil.
- ΔΦ is the change in magnetic flux.
- Δt is the change in time.
Resistance (R) – Ohms Law:
V = I * R
where:
- V is the voltage across the coil.
- I is the current flowing through the coil.
- R is the resistance of the coil.
How the Circuit is Build:
To build a Simple Magnetic Field Sensor Circuit the following steps are helpful while designing the circuit.
- Select a relay coil with a resistance of around 400 ohms and maximum inductance.
- Gather all the common electronic parts including LED1s, operational amplifiers, resistors and capacitors.
- Replace the traditional meter in the circuit with the relay coil.
- Connect the relay coil to the op amp, resistors, capacitors and other components as needed.
- A few inches from the relay coil place a permanent magnet parallel to the coils pole.
- Give the circuit the necessary voltage while making sure the chosen components are suitable.
- Slowly move a tiny permanent magnet across the relay coil to observe the activation of LED1.
- To check the circuits operation place an iron object between the coil and magnet and see how LED1 reacts to the changing magnetic field.
Conclusion:
Since the circuit is simple and can adjust to even the slightest changes in magnetic fields it is a valuable tool in many fields including electronics and materials detection.