# Thread: Lighted rocker switch question

1. gotcha.. that was what I needed. Thank you!

2. No problem, glad to help.

Hope it works for ya!

3. just thought I'd add something here. I cut the wires from the switch. This has nothing to do with the 12V+ and Ground coming in to actually power the inverter.

4. Okay, well at any rate, theory should be the same

5. Also, propbably wont apply to a pep boys switch, as they're probably all designed for in car use, but rat shack lighted switches can either be for automotive (+12vdc power the light) use, or for ac use (120vac powers the light).

6. Man I searched far and wide to find the answer in this thread. I was on the 12th. page of my search, a pic truly is worth a thousand words to me. Now that I know how to wire a 12 volt three prong LED rocker switch, I need to know what the amp limit means. The switch I want is here: http://www.autobarn.net/plsw22.html

They haven't called me back to answer my question yet, but other switches much like this one online said they had a 16 amp limit. What do I do with that number?

After my auxilary deep cycle battery I will have a solenoid relay switch. I have no idea if that relay reduces the flow enough to use a switch rated for 16 amps??

7. You compare that 16 amps to the fuse that is on the circuit that you will be controlling with the switch. If you don't have a fuse on the circuit, stop now and put a fuse on it. The only thing that determines current draw is the load (an inverter and whatever it is powering; a fuel pump; a battery being charged; neon lights...)

For instance, when connecting a power inverter with a peak wattage of 1400 watts, you need to build it's power circuit around 1400 watts, or 116 amps. You get 116 amps by dividing the watts (1400) by the voltage (12). So therefore you need to be sure that the fuse you use exceeds 116 amps, but not by too much. 150 amp would be acceptable. Then you need to make sure that your wire, switch, relay, or whatever else you may have in that circuit, is capable of carrying more than that fuse that you chose. Should you happen to use one of those 16 amp switches in this mockup circuit, that switch would more than likely become somewhat of a combustable fuse. It would probably melt something due to the >16 amps going throught it and could easily start a fire.

8. Thank you for your response, it explains a lot. My planned set up here:

Power Question, Two Battery Set Up

Will probably be a 600 watt inverter, divided by 12 is 50
And a 150 watt PSU divided by 12 is 12.5
Total amps 62.5 right?

http://www.installer.com/stinger/stingerbattery.html

I'd also planned on 0 gauge wire from battery to relay. But I was under the impression that once you get the 0 gauge wire on the relay u could use a smaller wire for the smaller screws. I thought the theory was low current being used to switch high current? Maybe I'm not saying it right, high current relay.

9. Ah yes. I remember reading that a few days ago. Kudos for being a cool dad.

I think you've just about got it. I'll take the blame for having a confusing post, and apologize in advance for another confusing post...

Remember that anything on this power circuit will need to be rated for a higher current than the fuse. Using an 80 amp relay with a 90 amp fuse is not generally acceptable. Think of it this way: say something in the invertor should happen to short or otherwise draw more current than it was supposed to. This is exactly why we have fuses. Lets say the short causes a current draw of 98 amps. Well it doesn't cause it for long because 98>90 and that means your fuse blows, thus interrupting the circuit and saving the other components from a dangerous over-current condition. Now lets say that instead of 98 amps it causes a draw of 87 amps. 87 is smaller than 90 so the fuse remains intact. However, 87 is greater than 80, and this puts your relay in danger of overheating, melting, or in the worst case starting a fire. The 80 amp rating of the relay (or of any component that carries current rather than using it) is not saying that up to 80 amps will flow through and no more. It is saying that if you run more than 80 amps through it you are putting it in danger because it was not designed to carry more than that. Again - is the load and the load alone which dictates how much current is drawn through the circuit.

One more thing - you need to go by the maximum peak current of the inverter. The 1400 watt inverter I used as an example was actually a 700 watt invertor. Your 600 watt inverter may actually have a peak wattage of 1200 or so. All this means is that for no longer than a fraction of a second the inverter is able to supply about double what it can supply at a sustained rate. Even though it can only supply this double wattage for a split second, you still need to base your power circuitry on that peak wattage. Check your inverter manual for specifics. And actually - I think most manuals should give you a suggested value for the fuse. If it does, just use that fuse and base the rest of the circuit on that. (wires, relay, etc.)

Oh yeah. I lied. Last thing... I promise: I think you've got it down about the relay using low current to switch high current, but we just want to be sure. The point of a relay is to be able to use a very small amount of current (usually a fraction of an amp at 12v) to switch on a circuit with a larger current potential. A relay is quite literally an electronic/mechanical switch. It uses the small current to create a magnetic field that moves a mechanical switch. I guess you could say it is much like how you exert a very small amount of force on a light switch in your house, thus allowing as much as 15 amps at 110 volts to flow to your lights.

10. Thanks again for answering Numbers. So if the peak of my 600 watt inverter is 1200 divided by 12, that's a 100 amps. Plus 150 watts for the PSU? Or does that have a peak also? So if the PSU doesn't have a peak, I'm at 112.5 amps?

So according to http://www.bcae1.com/ fuse section, I should use 4 gauge wire and a 125 amp fuse?

My total amp power is 1200 inverter and 150 PSU, so that puts me at 1350. So according to http://www.bcae1.com/ wire section, I should go to 3 gauge wire?

I only saw two choices of high current relays, 80 amp and 200 amp. Should I get the 200 amp high current relay and a 125 amp fuse? I haven't bought the car yet, so I don't know how many amps the alternator puts out.

If I have that much straight now, I still have the question of the high current relay. What gauge wire should I put on the smaller connectors? And what amp switch can I use to control that relay?

BTW, you haven't confused me, I saw a diagram of the inside of a relay at http://www.bcae1.com/ relay section.

The inverter will be used for Playstation2. Playstation2 uses 79 watts. I could always go down to a 400 watt inverter, right?

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