Electronic – Choosing the right (flyback) diode to stop contacts (points) arcing (sparking) on solenoid (relay)

diodesflybackrelaysolenoidspark

Clock with a simple electric remontoire, consisting of a solenoid, with an arm, that kicks back the main spring, rewinding it.

Solenoid coil data:

  1. operating voltage: 12V-15V
  2. measured resistance: 3ohm
  3. theoretical operating current: 4-5A

(unable to measure current since the coil is energised just for a fraction of a second. Weirdly enough… a lot of current for a small clock).

  1. What would be a good flyback diode to use for this application?
  2. What are the rules/formulas helpful for chosing a flyback diode for
    other characteristics of solenoids (relays).

schematic

simulate this circuit – Schematic created using CircuitLab

enter image description here

THANK YOU!

Best Answer

The peak voltage across the diode is equal to the supply voltage.

The peak current through the diode is equal to the solenoid current.

The duty cycle of the current is very low, so the average current through the diode is negligible.