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  #23  
Old 04/10/2006, 01:22 PM
BeanAnimal BeanAnimal is offline
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Join Date: Feb 2003
Location: Pittsburgh
Posts: 11,710
The diode is to help abosrb the back emf (inductive kick) that occurs when the relay field colapses. This will help protect the delicate reed switch in the float assembly.

Explanation:
When the power is removed from the relay, the armature is quickly shoved back through the bobbin (the coil) by the return spring. This action produces electricity. In addition the relay bobbin and armature are saturated with electrons that are released when the electromagnetic field colapses.

Any small 2n series should work.

For those interesed:
There are many relay coil supression methods... this is one will work well for our purposes. You should not that ANY supression slows down (dampens) the field collapse and therfore slows down the movement of the relay. This in turn can cause arcing at the relay contacts. This should not be a problem in our application... but HIGH VOLTAGE HIGH CURRENT applications can be affected. In those cases stronger relay springs, contact configurations and other suppression menas should be explored.

Bean