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Automotive LED Project Help

 
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Captainmurphy
Newbie


Joined: 19 Oct 2006
Posts: 4
Location: Denver

PostPosted: Thu Oct 19, 2006 5:14 pm    Post subject: Automotive LED Project Help Reply with quote

I need help with a project I would like to do.

I've just started in electronics and know just enough to not kill myself.

What I want to do is have the gauges on my mustang change color depending on where the need is.

Example: My water temp gauge, when it is at normal temp it would be green, when is starts to go higher it would turn yellow and at over heating or a temp I don't what to go past it would be red.

I am not doing this to the factory gauges. I have 2 Autometer phantom gauges. If this works when I add more I would do the same.

The back of the gauges have signal, power and ground. These are analog gagues( I want to keep the analog look, I'm not much for the digital read outs) There is a hole for the light to go in. I want to put either just the LEDs in the light hole or if it is small enough the whole electronic piece.

I could be wrong but I imagine the the power changes on the signal line for how hot or cold it is.

I know some of the gauges like my volt gauge would be opposite red when low and green when just right.

Any ideas or plans would be great. I have looked all of the internet, but seeing as I just got into electronics im not sure what to look for.


Thanks


Last edited by Captainmurphy on Thu Oct 19, 2006 6:06 pm; edited 1 time in total
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Captainmurphy
Newbie


Joined: 19 Oct 2006
Posts: 4
Location: Denver

PostPosted: Thu Oct 19, 2006 5:30 pm    Post subject: One more thought Reply with quote

I just remebered one more thing.

Could I either dim the LEDs with the factory dimmer switch or maybe use a relay to have the LEDs turn on when the car starts up.

On the back of the gauge besides power signal and ground, the light socket uses it own power.
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Alan
Site Admin


Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB

PostPosted: Thu Oct 19, 2006 8:46 pm    Post subject: Reply with quote

Hi Captainmurphy,

Do you want (or need) gradual changed between colors? If you do a microcontroller is your best bet.

But if you just need the lights to turn on at different temperatures you could make a separate comparator circuit for each light. I am assuming that the signal is a voltage output that has a good swing from cold to hot (not sure since I have never metered an automotive sending unit output).

Here is some comparator information:

http://en.wikipedia.org/wiki/Comparator
http://hyperphysics.phy-astr.gsu.edu/HBASE/electronic/compar.html#c1
http://www.bcae1.com/opamp.htm

You will have to wire it with a circuit that allows the higher priority LEDs to kill the lower priority ones. For example if the red light turned on it would have to kill the green and yellow ones.
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Captainmurphy
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Joined: 19 Oct 2006
Posts: 4
Location: Denver

PostPosted: Thu Oct 19, 2006 9:04 pm    Post subject: Reply with quote

I dont need gradual changes.

I plan to meter my gauge after work tommorrow. But thanks for the information.
All I could come up with, and I'm not even sure if I was on the right track was a bunch of relays and transistors. But I'm not even sure it would work untill I meter the signal line from the sensor. Hopefully none of this will weaking the signal to the gauge. If it does I would even know how to tap into the siganl line without loss.
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Alan
Site Admin


Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB

PostPosted: Thu Oct 19, 2006 9:11 pm    Post subject: Reply with quote

Captainmurphy wrote:
I dont need gradual changes.

I plan to meter my gauge after work tommorrow. But thanks for the information.
All I could come up with, and I'm not even sure if I was on the right track was a bunch of relays and transistors. But I'm not even sure it would work untill I meter the signal line from the sensor. Hopefully none of this will weaking the signal to the gauge. If it does I would even know how to tap into the siganl line without loss.


Op amps have very high input impedance, so there should be no significant drain on the sensor.
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Nginuity
HG Ruler


Joined: 13 Nov 2006
Posts: 224
Location: Dallas, Texas

PostPosted: Wed Nov 22, 2006 9:27 pm    Post subject: Reply with quote

FYI, the shift lights they put on some tachometers work using this very same methodology. Sorry, I know it's an old topic but I'm killing time Smile
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