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Inductive load

geochurchi

New Member
Hi All, we are trying to power some restored RR crossing bells from a 12 VDC power supply and the power supply burned out, I doubt it was due to the load, some suggested that we can’t do that with an inductive load, any thoughts?
Geo
 

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ronsimpson

Well-Known Member
Most Helpful Member
I think there is not a problem with inductance in the load. The Bell probably pulls too much power.
 

AnalogKid

Well-Known Member
Most Helpful Member
12 V across 10 ohms is only 1.2 A. A more likely cause is the back EMF spike when the contacts open. There is an R-C snubber in there, but this thing was designed way before switching or other regulated supplies. A fast diode directly across the coils, like a Shottkey or a tranzorb, would be better protection. However, this now makes the device polarity-sensitive. Placing the diode across the power supply output still lets the spark happen across the timer contacts, but should be enough protection and it doesn't force polarity sensitivity onto the device.

ak
 

Pommie

Well-Known Member
Most Helpful Member
Do you have access to a multimeter? If so, can you measure it's resistance?

Mike.
 

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