Re: [CAD_CAM_EDM_DRO] Relay question about diodes across the coil

In a message dated 1/11/2004 7:25:08 PM Central Standard Time,
paul_davis@... writes:
Maybe, though, it was the back emf spike which caused the circuit to re
energize the coil?
No, Paul! What PROBABLY happened is that the spike SHORTED the
driver-transistor "on"! This happens sometimes with molded transistors, but in the ones
with TO-5 or TO-39 "cans" where the chip is bonded with tiny gold wires to the
tips of the lead-wires inside, the most common thing is that the tiny wires
will be fuzed like a fuze! POP!

The diode across an inductive load switched by a semiconductor (transistor)
is NOT a luxury! It MUST be there if you ever want to switch that inductor
OFF! (It will survive a quick "bounceless" switching-ON, but NOT off!)


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