Quite some time ago, I described in detail the wiring of my neon shop’s bombarder control panel. (see http://www.novioljourneys.com/?p=1034) I have received a bit of recurrent requests for the schematic or other details of it over the years…while there are many ways to address such a set up, the use of multiple safety switches to provide decision points to make an inadvertent activation of the transformer unlikely is a good idea….and evidently others feel similarly enough about it to have sought out the advice.
Recently I was in a discussion about the switch used for the final activation. Some like push buttons, others prefer a guarded footswitch, and of course we all had some horror stories of shops that had absolutely rotten arrangements that could have easily killed someone. (the regular toggle lightswitch that is not momentary and the handheld push button “pickle switch” come to mind as the worst I have witnessed)
I have, for at least 25-ish years used and been a proponent of the heavy duty guarded foot switch with a momentary action. You must place a foot in it to activate….the guard prevents an errant misstep of the clumsy from turning it on when you don’t want it, etc. …and if you step back, it turns off. All well and good, and many shops have them. But… There may be a better way.
The problem that came up in the discussion was the possibility of the grounded metal parts of the switch providing a path for current if you came into contact with one of the high tension leads. Suppose you somehow put your hand where you shouldn’t and got a shock there. (Yes, I know….I am also careful not to….but accidents do happen and mitigating them is the purpose here, so just humor me.) …anyway if you came into contact with part of the HT circuit this current could then flow through your arm and down your body through the leg and foot that are on that grounded metal guarded switch, thus providing an excellent current path and likely a horrible day for you, if you lived to tell of it.
One suggestion to mitigate this was to buy one of the guarded switches with the plastic housing. All well and good, but there is still an electric switch inside with a cable going back to the control panel….and 20,000 volts can easily blow right through that under the right conditions. The amount of material to insulate against that would be less practical and perhaps require building something of a custom nature.
Here is my solution. It is an air operated switch. Such switches have been used in wet locations like hot tubs and drain clearing machines where the very nature of the use dictates that the operator will be activating an electric device while soaking wet! What I found was a heavy duty momentary air operated switch with a foot bulb that was meant for one of these “roto-rooter” type machines that plumbers run to fix your other mishaps. It cost all of about 30 bucks to buy.
Rather than tear apart my existing control panel to install it, I instead opted to put a set of twist-lock plugs on the cord between the panel and a box with the air switch in it and I also provided a like plug on my old conventional switch’s cord so that I can put it back in service if I have a reason to. The twist-locks were not my ideal choice of connector but they were handy and since I have no other outlet or hardware here that takes that type of plug, the possibility of them being misused is reduced.
The air switch itself is mounted into a small plastic box, and the hose then runs to the foot bulb. I mounted the foot bulb inside of a plastic box to make a guard….I may opt to build a better guard, but this one did pass my “stand on it” test so it’ll do for now I guess.
The air bulb and 10 foot hose allows far more distance of electrical isolation between the operator and either the low or high voltage parts of the circuit. In tests, kinking the hose does not affect the operation and stepping on the hose does not cause an unintended activation. This was a fairly easy and quick project to put together and it seems to work very well.
