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  #1  
Old 06-12-2012, 07:54 PM
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Location: Elavil, Ga.
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LED tach...

One of my tachs is dead and the other one flops around from time to time so I figure it's just a matter of time before it's kaput. I was considering just ditching the tach and going with a big clock in that spot but I do like having an indicator of engine speed so I cooked this up:

tach2 - YouTube

That was just some testing of the LED's to get a feel for it but I finally got it nailed down using a Hall effect sensor to pick up RPM.

I was thinking about putting it (Well, a more refined version) in the PRNDL spot in the dash because it's unused in a 116 SD.

Any input? I'll probably have to dim the LED's at night or something and I was just going to trigger it off a magnet epoxied to the PS pump pulley.

I had also considered gutting the tach and putting the LED's around the outside of the dial on the hash marks and a shift light in the center but the asymmetry would probably bug me...
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Old 06-13-2012, 03:07 AM
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Very Knight Rider...

May be you need less diodes so that one lit bulb = 1000 rpm?

May be you need more diodes so that one lit bulb = 500 rpm?

May be you need even more diodes so that one lit bulb = 250 rpm?

Do you see what I'm saying? It is pretty in a 1980s Subaru / Knight Rider kind of a way at the moment but it is difficult to get a real impression of engine speed from the set up at the moment. All I get from it is "way too fast" / "way too slow" etc
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1992 W201 190E 1.8 171,000 km - Daily driver
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1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
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Old 06-13-2012, 09:41 PM
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I understand what you mean but there is only room for 9 round LED's in the PRNDL spot. The spot is occupied by a black painted piece of styrofoam from the factory

I figure have the green illuminated at idle and have it register in the yellow at hwy speeds and maxed out red at 6000 RPM. I may stick it on the car tomorrow.

Believe it or not this is an offshoot of my ACCII experiments...
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Old 06-14-2012, 02:40 AM
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I'm no electronics guru but I thought it was possible to get smaller LEDs. How much space do you have to play with (dimension in inches / mm)? Is it the same size as the one on a W123?
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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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