Author Topic: How to build a safe knife switch?  (Read 26028 times)

Keith_Beef

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Re: How to build a safe knife switch?
« Reply #25 on: February 24, 2014, 03:43:25 pm »
I just remembered that one of my childhood books on electricity described how to make sparks with a battery, some wires, and a nail file; I tried it back ten, and it worked. Wire file to one battery terminal; brush wire lead from other terminal across the rough side of the file. Small sparks fly from where the wire contacts the file.

This method could possibly be employed to produce a spark effect for mock-up props.

A piece of very fine steel wool and a little 9V battery can make a useful firestarter.
--
Keith

Peter Brassbeard

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Re: How to build a safe knife switch?
« Reply #26 on: February 24, 2014, 07:18:26 pm »
I just remembered that one of my childhood books on electricity described how to make sparks with a battery, some wires, and a nail file; I tried it back ten, and it worked. Wire file to one battery terminal; brush wire lead from other terminal across the rough side of the file. Small sparks fly from where the wire contacts the file.

This method could possibly be employed to produce a spark effect for mock-up props.
Put a good inductor (coil) inline and a modest current will produce a surge of high voltage when the current is interrupted.  The energy stored in the inductor will be dumped into a spark across the opening gap, unless it finds an easier discharge path.

cossoft

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Re: How to build a safe knife switch?
« Reply #27 on: December 10, 2015, 03:12:16 am »

 
So to combine dramatic sparks from high voltage with safety from low current, my idea would be a circuit to transform 240V (or 110V for you colonials) on a 5A circuit to supply the blade switch with something stupidly dramatic like 1000V at 100mA that then energises the relay.


  >>> This will KILL you immediately <<<





High guys.  I joined this forum just to post this message.  1000V @ 100mA = 100W. 

You will indeed provide a stupidly dramatic spectacle.  This post and it's quotes should be removed /corrected if a typo.  Sorry to put a downer on it.  Good forum.