This might be an odd question, but does anyone know how the signal is coming from the RPM signal wire on the dizzy? Is it a sine wave or pulses or what? Just tinkering with an idea here. If anyone knows it would be great. -25C is not an ideal tempature to be fiddling under the hood of a car in so I'm asking.
RPM signal from dizzy. Blue wire.
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I should write the reason I wanna do it is a custom shift light. If I can figure out the pulse I can produce LED shift lights for under 5$ lol. Why wouldn't I go down this route and have it hidden exactly where I want rather then a clunky dash mounted shift light. I wanna make the bezel around the cluster light up with yellow LEDs when I hit 8200rpm (my B16 shift point for me).
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-25C? Is that all? It was -24F when I got up this morning. Does tend to dampen the desire to head into the garage though. The manual says the signal from the igniter to the tach is 200 pulses/minute == 100 rpm. I believe it's more like a short square wave pulse when the ignition fires. I have a cruise control (aftermarket) in my CRX that I hooked to this signal, seems to work fine. I think at most you might want to use something like an LM339 ($1.29 at radioshack) to clean up the input. How are you planning to implement your shift light? Counting the pulses directly with a cheapo single-chip microcontroller is one way, plenty of those could be had for less than $5. You could do a pure analog thing where you gate pulses into an RC combination and then turn on the light when that exceeds some threshold (essentially converting RPM into an analog voltage) but it wouldn't be too accurate. Inquiring minds want to know...ludesrv said:
To be honest I'm not the one building it. I get an electrical engineering friend who is doing it for me. I just build the casing and where I want it, he builds the module for it all. All I have to do is help him replace some parts on his bike and he will do 100% of the work.
So it's pulses, 200ppm (pulse per min) = 100rpm. So for 8200rpm I should be looking for 16400 ppm?
So it's pulses, 200ppm (pulse per min) = 100rpm. So for 8200rpm I should be looking for 16400 ppm?
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Yeah. Another way to think about it is to remember that this is the same signal that fires the ignition coil. 4 cylinders, one spark per cylinder per 2 revolutions = 2 sparks per revolution.ludesrv said:
I like the idea of illuminating the cluster with a different color for the shift indication ...
Ah I get it now. Makes sense really. Since 2 cylinders fire per revolution you would get double the signal per revolution, so 100rpm = 200 pulses. Simple math, just needed to understand how it worked.'9445 said:
Ya I like the idea too. It's either that or I make all my vents glow yellow when it's time to shift. I can place LEDs anywhere really and I can make any light go on/off with the system he is building me. It's super cheap and is custom to anyones desire. I'm gonna test it on my own engine. The only thing that sucks is to make it cheap and accurate I cannot adjust it on the fly. So I'm setting it to 8200 and leaving it there. If I want it different I have to change the programming. Oh well, how often do you change it? Never really. You set it to what your engine redlines at. And when you mod the engine to go hire you can just fix the shift light haha.
Ah work is killing me!
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