AC/DC help

I have the following: 1) 12v DC power source (car battery) 2) 12v DC 1no1nc locking switch with LED light (6 terminals, 1 pair for normally open, 1 pair for normally closed and one pair for LED on the switch) 3) 12v to 35v-70v AC inverter (I guess there is a "range" for the DC too, but I don't recall it and I am running it straight 12v and not varying it) 4) 35v - 70v AC load (smart tint if you are curious)

The short of what I want to do is power the switches LED based on whether the load is functioning or not. When I press the switch and lock it in the 'on' position and the load works as expected, I want the light to come on. However, if I close the circuit and the load fails, I want the light to remain off.

If I wire this on the 12v side, pressing the switch will turn the LED on and the state of the load will be unknown.

I am not an electronics guy really. So talk 9 year old to me please. :) I am really hoping there is an existing item that I can wire up like a relay vs lots of individual components I don't understand.

Thanks in advance for your assistance.


What does it mean for the load to fail? Completely open-circuit?

HI, I'd put some fuses in there as well, if you are using a car sized lead acid battery. Otherwise you may fry something.

Tom... :)


Yes, my expectation is if the load fails that the circuit will be open. If it fails and the circuit doesn't open, I do not know how I could test for that without a camera or something watching it.

I agree Tom, I failed to list the fuse in the equipment list.

The input current to the inverter could be sampled. It won't drop right to zero when the load 'pops' but it ought to be a predictable low value compared to normal operation.

Its easier to measure steady current too.

:o Thanks. But this is ... umm .. where I mentioned I am not an electron's guy. So I have no idea what you just said.

I really just do not understand why there isn't a relay that the input is AC (35-75 vac) and the output is DC (~12vdc). Moreover, I don't even understand why it matters what I put on the output of a relay as the idea of it -- to my minimal understanding -- is that input A causes a coil or similar Solid State device to close a switch for output B while maintaining otherwise separate circuits. Other than capacity, why does output B care if it is AC or DC. It shouldn't matter as it is just a switch that closes to allow current flow. But I digress

It just amazes me that some of the seemingly simple things a person might want to do doesn't already exist. There are solutions to really hard problems, but some of the simple ones are just not there.