This article is perfect for beginners who want to learn about electronics!
It shows you how to build a simple magnetic field sensor circuit.
These circuits are popular because they are easy to make and there are many things you can do with them.
They are a great way to get started in the exciting world of electronics.
What is a Magnetic Field Sensor:
A Magnetic Field Sensor Circuit is an electronic circuit designed to detect and measure the strength of magnetic fields in its vicinity.
These circuits typically utilize hall effect sensors, which are devices that produce a voltage proportional to the strength and polarity of an external magnetic field.
Magnetic field sensor circuits find applications in various fields including industrial automation, automotive systems, robotics and electronic compasses.
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 |
| Other | Relay 12V | 1 |
In this innovative circuit design the conventional meter is ingeniously replaced with a relay coil to fabricate a magnetic field sensor circuit as elucidated earlier.
This configuration exhibits a remarkable sensitivity to alterations in magnetic fields.
The illumination of LED1 serves as an indicator activated by the passage of a diminutive permanent magnet in close proximity to the interconnected relay coil.
During the magnets traversal while the coil remains stationary the sensor functions analogously to the prior design utilizing a mobile coil meter.
While any relay coil is compatible with the circuit optimal sensitivity is achieved by, selecting a relay coil characterized by maximum inductance and highest resistance typically around 400 ohms.
The transformation of the circuit into a sensor capable of discerning an iron object in motion between the magnet and coil is achieved by situating a permanent magnet a few inches away from the relay coil parallel to the coils pole.
Each alteration in the magnetic field induces minuscule alternating current AC voltage potentials across the coil.
These subtle electrical signals undergo amplification by the operational amplifier op amp subsequently causing LED1 to intermittently illuminate and extinguish.
To facilitate a comprehensive understanding of this magnetic field sensor circuit, follow the construction details to elucidate the intricacies of its implementation.
Formulas:
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:
- Choose a relay coil with maximum inductance and a resistance of approximately 400 ohms.
- Acquire standard electronic components such as resistors, capacitors, an operational amplifier, and LED1.
- Connect the relay coil in lieu of the conventional meter within the circuit.
- Establish the necessary connections between the relay coil, resistors, capacitors, and the op amp.
- Position a permanent magnet parallel to the coils pole, a few inches away from the relay coil.
- Provide the required voltage to the circuit, ensuring compatibility with the selected components.
- Gradually move a tiny permanent magnet across the relay coil to observe the activation of LED1.
- Verify the circuits functionality by introducing an iron object between the magnet and coil noting the response of LED1 to the changing magnetic field.
Conclusion
The circuits simplicity, coupled with its ability to respond to minute magnetic field changes positions it as a valuable tool in various fields from electronics to materials detection.
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