Using A Diode With A Solenoid

Using a Diode with a Solenoid

Why Use a Diode?

A solenoid is an inductive load, meaning it generates a high-voltage spike when it is turned off due to the collapsing magnetic field. This back electromotive force (EMF) can damage circuit components, including transistors, relays, and microcontrollers. A flyback diode (also known as a freewheeling diode or clamping diode) protects your circuit by safely dissipating this energy. 

How to Wire the Diode

1. Choose an Appropriate Diode

• IN5400: Common for Neutron solenoid usage
• Schottky diodes: Recommended for faster switching solenoids due to their lower forward voltage drop.
• The diode’s current rating should be equal to or greater than the solenoid’s operating current.

2. Connect the Diode in Parallel with the Solenoid

• Anode (-) to the solenoid’s ground.
• Cathode (+) to the solenoid’s power (VCC).
• This configuration allows the diode to conduct and safely dissipate the voltage spike when the solenoid turns off.

3. Controlling the Solenoid with a Transistor or Relay

If a transistor (e.g., MOSFET) is used to switch the solenoid, the diode should be connected across the solenoid coil, not the transistor.

Example Circuit with an NPN Transistor

  +12V ----->|------ Solenoid -----> Collector (NPN)

                |

              (Diode 1n5400)

                |

  GND <------|------ Emitter (NPN)

Key Considerations

• Do not place the diode in series with the solenoid; this would block normal current flo

By correctly using a diode, you can significantly extend the lifespan of your electronic components and ensure reliable solenoid operation.