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enigma1406
03-07-2007, 12:18 AM
I'm building a circuit to turn a momentary switch into a latching switch. That part I think I have down pretty well. My problem now is where I'll be getting the power from. I need a 12v line and it will use close to, but less than 1A.

I'll be powering some LEDs, so will I have to worry about regulating the voltage? I've read that the voltage on some car lines gets up to 100v. Is this true?

Also, can I just tap off of a fuse in the fuse box and not have to worry about regulating the voltage or using an inline fuse? Thanks for the help.

If you have any suggestions on what line to tap that would be appreciated. This is a switch that I bought from nsxjr, so it will be going next to the passenger airbag light and I'll have access to all of the center console wiring. It shouldn't be too hard to get power from the fuse box to the center console either.

int2str
03-07-2007, 03:31 PM
I'm not sure I fully understand everything, but I'll try to answer what I can:


I'll be powering some LEDs, so will I have to worry about regulating the voltage?

Unless you get 12V LEDs (rare) you will indeed need to regulate your voltage. If you have more than 1 LED you want to hook up, you can connect them in series and thus drop the voltage. If not, you may need resistors.

Here's a good explanation:
http://www.theledlight.com/ledcircuits.html


I've read that the voltage on some car lines gets up to 100v. Is this true?

No. Well, sort of. Car electricity is somewhat regulated and usually hovers somewhere between 11.5 and 13V. But, car alternators can be erratic and in connection with ignition interference can generate voltage spikes. That usually does not happen though - especially in modern cars.


Also, can I just tap off of a fuse in the fuse box and not have to worry about regulating the voltage or using an inline fuse?

It is always prudent to use an inline fuse when you do aftermarket wiring. It's easy and protects your car from shorts etc. in what ever you are hooking up to it. Just do it ;)

enigma1406
03-07-2007, 05:59 PM
Unless you get 12V LEDs (rare) you will indeed need to regulate your voltage. If you have more than 1 LED you want to hook up, you can connect them in series and thus drop the voltage. If not, you may need resistors.

Here's a good explanation:
http://www.theledlight.com/ledcircuits.htmlYea, I know how LEDs work. [;)] The LED array consists of 5 LEDs, so there's a chance there are no resistors in the array. Either way, it is meant to run off of a 13.5V line, and can be dimmed using a PWM controller to lower the voltage. I have them sitting on my table hooked up to a 12V battery and everything is fine. I'm not worried about that part.


No. Well, sort of. Car electricity is somewhat regulated and usually hovers somewhere between 11.5 and 13V. But, car alternators can be erratic and in connection with ignition interference can generate voltage spikes. That usually does not happen though - especially in modern cars.
That's basically what I wanted to hear. Obviously, given what I said above the arrays can take small voltage spikes, so anything from 0-15V (maybe higher) should be fine.


It is always prudent to use an inline fuse when you do aftermarket wiring. It's easy and protects your car from shorts etc. in what ever you are hooking up to it. Just do it ;)Yup, that's the plan. The fuse doesn't really add any complexity, but a voltage regulator does. That's the main reason I wanted to avoid it. I ordered parts (including some voltage regulators just in case) today and will let you know how it goes.

Thanks for the reply.