The Magnetic Proximity Switch Sensor Circuit detects magnetic fields to operate in factories, security systems and automation applications; also a magnetic reed switch serves as its main sensing component.
ICs like 555 timer and CD 4013 flip-flop turn relay ON/OFF when magnet is close by and then relay control other device ON/OFF.
Moreover, circuit need stable 12V power for good working.
Circuit Working:
Parts List:
| Components | Values | Quantity |
|---|---|---|
| Resistors (All resistors are 1/4 watt unless specified) | 1k | 1 |
| 470k | 1 | |
| 10k | 1 | |
| 2.2k | 1 | |
| Capacitors | Ceramic 0.01µF, 2.2µF | 1 each |
| Semiconductors | IC 555 | 1 |
| IC CD 4013 | 1 | |
| Transistor BC547 | 1 | |
| LED 5mm 20mA any color | 1 | |
| Diode 1N4007 | 1 | |
| Relay 12V SPDT | 1 | |
| Magnetic Switch Reed Switch | 1 |
To begin with, when magnet is near S1 then switch closes and circuit starts.
Pressing S1 triggers IC1 555 to function as a monostable and generate a single pulse and each pulse from IC1 then causes the IC2 CD4013 flip-flop to change state.
Then Q1 BC547 works like switch to control 12V SPDT relay and LED1 shows magnetic field found and relay working.
When pulse end IC1 output goes low and LED goes OFF, then D1 1N4007 stops relay coil spikes from damaging the circuit.
Formulas with Calculations:
IC1 555 pulse time:
T = 1.1 * R2 * C2
where,
- R2 is 470k
- C2 is 2.2µF
- T is 1.1 * 470000 * 2.2×10⁻⁶ = 1.1374 s = 1.14 s.
So 555 output is HIGH to about 1.14 seconds per trigger.
Q1 base current:
Ib = (Vin – VBE) / R4
where,
- Vin is 12V
- VBE IS 0.7V
- R4 is 2.2k.
- Ib = (12 – 0.7) / 2200 = 0.005136 A = 5.14 mA.
Transistor gain is 200 hFE, so collector current is plenty enough to drive the relay.
How to Build:
To build a Magnetic Proximity Switch Sensor Circuit follow below steps for connection:
- First, put all parts like the circuit diagram and assemble parts on board.
IC1 555:
- Next, pin 1 connect to GND.
- Then pin 2 connect between R3 and S1.
- Now pin 3 connect to pin 3 of IC2.
- Also, pin 4 and pin 8 connect to +12V.
- After that, pin 5 connect to GND through C1.
- Further, pin 6 connect to pin 7 of IC1.
- Positive of C2 connect between pin 6 and GND and then R2 connect between pin 7 and +12V.
LED and R1:
- Then one end of R1 connect between IC1 pin 3 and IC2 pin 3 and other end of R1 connect to LED anode and LED cathode connect to GND.
IC2 CD 4013:
- Pin 1 connect to base of Q1 through R4.
- Pins 4, 6, 7, 8, 9, 10 and 11 connect to GND.
- Pin 2 connect to pin 5.
- Pin 14 connect to +12V.
Transistor Q1 BC547:
- Collector connect to +12V through D1, emitter connect to GND, and base go to IC2 pin 1 through resistor R4.
- Relay coil connect with one side to collector of Q1 and the other side to +12V.
Diode D1:
- D1 connect across the relay coil cathode to +12V and anode to Q1 collector to stop spikes.
Conclusion:
Overall, Magnetic Proximity Switch Sensor Circuit detects magnet and flips relay using 555 timer and CD 4013.
Here, BC547 drives the relay, LED shows detection and 12V supply keeps circuit stable; also this circuit is useful for security, automation and smart control.