custom shift light question?

[g2_teg_na]

i have an empty space on my dash where a power mirror switch usually goes. to fill it in, i want to make a neat little shift light thing. i dont really need a shift light, i'd just like to rig one up as somethin cool to have. here's my plan: 3 little LEDs -- one red, one yellow, and one green. all three set to light at different RPMs -- red: 100 rpms -- yellow: 5000 rpms -- green: 6800 rpms (redline) one/off toggle switch -- so that i can have them all working, or none. if you guys understand right, then you'll get that im trying to make it look like a stop light, where the light either changes, or the next light comes on at higher RPMs. heres a pic so u can get a better view of what i plan on doing. now here are my question: How will i hook these LEDs up to know what RPMs my car is revving to?

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[VPUPPY]

you need to create a circuit board with a DOT/Bar Display Driver(an actual semiconductor chip) that senses A/C voltage for the leds. this would need to be hooked up to your tach wire(which works on A/C voltage, the higher the voltage, the higher the RPMs are). it would probably be cheaper and easier to buy one off the shelf rather then create your own.

[g2_teg_na]

Originally Posted by VPUPPY

you need to create a circuit board with a DOT/Bar Display Driver(an actual semiconductor chip) that senses A/C voltage for the leds.

how would i do that? u have any websites that'd explain that to me?

[VPUPPY]

to get an idea, take a look at this custom air/fuel meter:
http://www.scirocco.org/tech/misc/afgauge/af.html

[g2_teg_na]

thanks....kinda confused now though.

[bxsnypa]

when u get ur shift light installed please post a pic i would be interested in seeing that

[g2_teg_na]

Originally Posted by bxsnypa

when u get ur shift light installed please post a pic i would be interested in seeing that

if i can ever figure out how to get it done...

[94JR]

I was thinking about replacing a shift light for my dash dimmer nob on my 94LS. It seems to be a good place that would look like it was ment to be there

[VPUPPY]

the basic idea is that you have a chip(driver chip) that gets a signal from a wire(tach wire). when that chip detects a certain A/C Voltage(thats what the tach wire sends) it turns on a corresponding LED. sorry i could not be any more specific but I have never had to build one of these. the hardest part should be getting the chip(one that reads A/C voltage) and programming it. you need to know the A/C voltage output at specific RPMs to correctly program the chip. if you look online for "semiconductor chip" and your city name you may find some places that you could call to see if they offer a LED driver chip that takes A/C voltage as an input.

[VPUPPY]

btw, like I suggested before, it may be easier to buy a off the shelf shift kit and installing that, unless you want to learn how to make them.

[kill_kill_kill]

^ that is good advice.

Another idea is to have a voltage comparator checking the alternators output, my friend created something very much like what you're describing with that as the input. Higher RPM's => higher voltage, but this is coming second hand.

[MarshyTheKid]

You could probobly have the needle of the tachometer hit small switches as it gets to the desired rpms..Like have the power wire run along the bottom of the needle then have contacts for each different LED where the needle would hit the rpms and the lights. That would be a much easier and kinda ghetto way of rigging it. Forgive me if you don't get what I'm saying, I'm tired.

[worm696]

sounds kinda neat. id like to see some pics.