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"Dead Man" switch
"Dead Man" switch
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Old 15th June 2019, 06:50 AM   #21
Wavebourn is offline Wavebourn  United States
Anatoliy Lisovskiy
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"Dead Man" switch
I would never rely on such a switch. When current goes through your body, you would not remember to take off your foot from it. Better be careful and know what you are doing. Dead man switch may help, though, to remove voltage from already dead body...
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Old 15th June 2019, 05:59 PM   #22
Windcrest77 is online now Windcrest77  United States
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OK the consensus is that I'm on the wrong track for a lot of good reasons. And I have great respect for the minds here. But nobody has offered where their master cutoff switch actually is or how it is operated or if they have one in their specific bread-boarding arrangement at all that is accessible.

I see bread boarding as being the area most likely to cause a shock, if every project was a chassis build from day one that's inherently safer, of course, then experimenting becomes like a repair job of any existing chassis. I wanted a method where my master switch was "normally open" and required my conscious effort to keep it energized. I feel a master cutoff is always needed and I didnt like that prior to this my master was a difficult, smallish, "grindy", rocker switch on a Chinese power strip that I had to physically find and reach for to de-energize the circuit.

Where is your master cutoff switch when doing bench experiments and how is it operated? So I can do the best here too.
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Old 15th June 2019, 06:48 PM   #23
huggygood is offline huggygood  France
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for me : variac + emergency stop juste dérivé des alimentations de mes multiprises
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Then, I have a specific electrical board for my workbench with differential circuit breaker and two differential switches.
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Old 15th June 2019, 07:04 PM   #24
gabdx is offline gabdx  Canada
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Think about it, a switch like you want is used to do short power up times. It would be a major inconvenient to have to press down on a switch and work on the equipment at the same time...

It would use your concentration, increasing the risk of error, and if it comes on/off rapidly, etc, idk, to me it would cause more problems...

There are almost no reason to work for long period of times on live equipment or open boards.

There is only one way: each time you cut the power / turn it off / disconnect the wires.

If you have only one switch, you can always get a shock upstream, the switch will do nothing.

Just don't work with life wires to open equipment and place your hand in there, 0 need for this.

To take a measurement, I plug the wires where I want them, I can plug many voltmeters, and 2 THD analyser.

I put my electrical gloves, ear plugs, googles, look away and turn slowly the power on:

with bulb first, and variac and a lower fuse.

if this is ok and nothing is shorted out from the prongs I retest without the bulb....

This takes 1 minute of power on, take down the readings shut off all power, discharge etc...

MAX it takes 1 or 2 tests like this to check THD at pre-amp stages and currents in critical areas, check heater voltages, check power on and off for surges, check max capacitor voltage cannot be exceeded by on/off cycles.

If you know what you are doing and why, you don't need any safety kill switch etc it is for industrial application, to do fast maintenance, and place a working personal lock on the machine.

I did have some steel old sewing machine pedal to do a small DC conduction test, the pedal was far from the gears to make sure the operator could not activate it and touch the gear at the same time, but this is crappy cheap solutions...

In good setups you use X-ray screens, they can be set to shut off power.

The best kill switch would be a heart rate monitor with a PLC control, but this could fail too.

Last edited by gabdx; 15th June 2019 at 07:10 PM.
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Old 15th June 2019, 07:32 PM   #25
Bigun is offline Bigun  Canada
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"Dead Man" switch
I work with rubber matt on floor. Never work in poor emotional state or tired. Avoid probing live circuit by using clip on leads installed first, then power up, measure, and then power down (multimeters are cheap). All caps have bleeder resistors. Be paranoid, assume parts may have damaged insulation.

I had a 240Vac mains shock in UK once. I was so startled by it that there would be no chance to think rationally or react in any deliberate conscious fashion.

I have a high voltage warning sign on my hobby room door. No ambulance driver should have to get a shock.
"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.

Last edited by Bigun; 15th June 2019 at 07:35 PM.
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