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Use a thermal time delay relay to prevent filament flash. This is a video response to Mr. Carlson's Lab - Tech Tips Tuesday: Dirty Little Secrets:
   • Tech Tips Tuesday Dirty Little Secrets  

Amperite thermal time delay relay datasheet:
http://www.amperite.com/assets/Docume...

Other videos on thermal time delay relays:
   • (#0123) Thermal Relay Astable Multivibrato...