How to Be Safe With Projects That Involve Mains AC

Introduction: How to Be Safe With Projects That Involve Mains AC

About: I'm a sophomore in high school. I am proud to be a super-nerd. Things that bore my peers in school, fascinate me. One thing that has really interested me is organic chemistry, it systematic nature is beautif...

If you are a beginner electronics hobbyist, you may encounter some projects that require you to plug right into the wall. This is a potentially dangerous thing if you don't know what you are doing. There is 120 volts in the standard US outlet and 240 volts in the UK (correct me if I'm wrong) this voltage can kill or give a nasty shock depending on the path of the current. In this Instructable I will give you some general rules to follow in order to safely work with Mains AC



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    9 Discussions

    does it help if i attach a wire from my wrists to my boots so the electricity would take travel down the wire instead of through my body?

    1 reply

    Shoes? I think I might have a pair somewhere. It has been a while since I've seen them though. Right now I have to operate on the zero crossing theory. I figure if I only grab the wires while the current is zero crossing I should be OK ...

    Thank you. And yes, it does seem to vary a bit, not sure what causes that either. All the outlets in my house measure 120.

    Power fluctuates depending on grid load, and line loss. When everything is working right you should have 120VAC.

    US residential single phase is 240 but we split it and use a neutral between the 2 hot leads. This is where our 120 VAC comes from. You can experience line loss that will drop your voltage even further than what your electrical service provides too. Of course the grid voltage will vary too depending on the load. I've seen values on appliances that say 115 or even 117VAC on them. I've never had any problems running anything like that on our 120 volt power though.

    With many devices a couple of volts one way or the other doesn't matter much. I did rewire my pool pump because whoever did it ran too long a wire of too thin a gauge to it. What was there was 14 gauge SG stranded cable, I replaced it with solid 12 gauge UF. Induction motors can be sensitive to brown line conditions. They can run hotter, and have a harder time starting if voltage is low to them. I had a 4 volt voltage drop to my motor before I ran a new wire to it.

    I mean it worked with the old wire, but it was kind of marginal. I felt better for changing it. Especially being as the motor is on a timer and I'm not always home.