Indicator question on my first build

[winterc]

I have a 115 volt indicator light, is there anything wrong with attaching it to one leg between the contactor and the element, and the other to neutral? I'm trying to avoid the light being on through SSR leakage.

 

[ajdelange]

A cool way to do this is to go to Radio Shack and buy a cheap 'filament' transformer for a couple of bucks or take the transformer out of a wall wart you aren't using any more. Disassemble the transformer and remove the secondary winding. Now wind the wire that carries your load once or twice around the center of the core where where you removed the original transformer's winding (note: you don't have to remove the winging if you can slip the load conductor between the winding and the core but it is probably better to do so as you can then use tape or something else to prevent the wire from rubbing against the core's steel). The core looks like a squared off 8. The load wire should go in the upper loop and come out the lower but if it only goes through one loop that's OK (but you'll get half the current). Now connect a LED (or a pair of LED's) back to back across the primary. The LEDs will light if sufficient current flows to the load. SSR leakage is not sufficient to light the LEDS. If you find that you are blowing LEDs then use a resistor to limit the voltage across the LED.

This scheme has the advantage of giving you an indication only when the load is actually drawing current. If you apply voltage to an open circuited element a lamp across the element will light indicating that voltage is there even though no current is being drawn. In the LED circuit no current means no light from the LED.

To answer your original question: If you have a valid neutral (and whether you do or not is a question I refuse to discuss) then yes, that will work fine.

 

[winterc]

To answer your original question: If you have a valid neutral (and whether you do or not is a question I refuse to discuss) then yes, that will work fine.

I suspect by valid neutral you mean connected to ground in the main panel and nowhere else. I have 4 wires going to the box, with neutral separate. I've seen enough electrical arguments that I don't want to get into one, I don't know enough to have an opinion, just enough to do basic house wiring.

Thanks for the awesome idea about the LED, perhaps I'll have to incorporate that idea into version 2.

 

[ajdelange]

Yes, that's what I mean.

One additional comment about the transformer scheme: make sure the transformer you modify is physically small. This automatically limits the voltages and currents that can be developed (the core saturates).