# Solenoids - anyone know where to buy the basic parts?

#### Alec_t

Joined Sep 17, 2013
10,918
I don't understand this. How does a diode across the relays coil affect the contacts?

#### wpri268

Joined Feb 18, 2012
30
A relay coil, like a transformer, is a wire wound magnetic component. There are many different types of magnet wire wire insulation available-chosen for things like service temperature ( 80C to 240C ) breakdown voltage rating ( 1.5KV+ ), and manufacturing processes depending on design requirements. A simple solenoid coil is likely random wound on a bobbin with UL Class F (155C ) single layer insulated wire. The gauge and turns are design dependent.
Just as nothing is perfect the same applies to mag wire insulation. Its typically very thin ( .001 in ) which will vary ( tolerance ) and even have tiny pinholes. Winding operations can cause nicks and scratches. It is commonly assumed that the like likelyhood of any defects lining up to cause turn to turn faults is remote. Properly designed manufactured, and operated a coil will last for 20+ years.
However, a solenoid coil is inductive. When power is removed from an energized coil a high voltage discharge is created. Where that energy discharges can be harmless or can damage mag wire insulation. Repeated discharges within a coil can result in turn to turn shorts and failure of the coil. A reverse biased diode is often placed across DC relay power terminals to snub that arc but It has zero effect on the switching contacts.

#### Berzerker

Joined Jul 29, 2018
575