Sand rail glowing spark pugs...

[hybridtoys]

Hey guys, I`m just a tinkerer and definitely a newbie with complex style`s of electronics I`m rebuilding my sand rail,and I`m pretty good with automotive applications, as I`m rewiring the whole rail as the guy who had it before me used a lot of jumpers and house wiring.... I`m a fan of clean and efficient, and function over form.
However there is a project I have been working on building a fun little project that is purely just for fun and looks. I have only seen this one time when I was a kid and have always wanted to do it on one of my rigs. Its basically spark plug wires that light up every time the cylinder is fired. I put a link to a guy that makes them, but the ones he makes are actual neon tubes and I would like to use LED`s in a polished aluminum tube housing.

I know its not the best idea but I thought crap, I`ll just use 8 timing lights gut them and then wire them up to the LED string and mount the guts in a small hidden box. BUT I thought no, I'm gonna try and do this right..... Or as right as my limited ability will allow. I have a decent soldering gun and can do basic stuff, but really only have a Fry`s electronics and Radio shack locally. Normally I`m harvesting parts out of other electronics
So, the motor I have is a Northstar V8 with coil packs 2 plugs per coil, so I'm thinking this is a (wasted spark) system? Also I know I could probably build a processor that would mimic some random firing order but I would rather have the actual real time firing order.
ANYWAY sorry for the long winded start but that's just how I roll Any help would be great, Thanks Guys!

 

[duke37]

What is a sand rail?

The spark can be detected with a small capacitance to the plug lead. Some experiment will be necessary.

The pulse could go to a fet to turn on a led.
The main problem will be getting sufficient pulse which does not blast the fet to oblivion, a good protection circuit will need to be developed.

If two plugs are fired at the same time, I do not see an easy way of separating them.

 

[hybridtoys]

LED spark plug wires

This is a sand rail/ or sand car..... This is a link to a video of playing in the sand.
http://www.glamisdunes.com/invision/index.php?showtopic=286611&st=0&p=4461032&#entry4461032
I was thinking of using a micro processor that would kill the spark that is not used, Vive seen some simple programs I can try and program it to make it alternate and only light the LED every other time. BUT I'm not sure what I would need. This is the part I need help with I guess. Not sure the parts to buy....

 

[duke37]

You should consider the rate at which persistance of vision becomes a problem. You may want to use just one plug and use a Johnson counter (4017) to give a walking (running) display.

An intermittent light at more than about 30Hz will appear to be on continuously.

 

[Mongrel Shark]

You could probably get enough induction from a plug lead with a small coil around it? Would be worth a try, just wind 20-50 turns of 30(ish) gauge enameled wire on the spark plug lead, and put the led on the ends. You would have to play with number of turns and gauge to get the brightness you want.

It may reduce the performance of your spark a bit.

As Duke pointed out though, after 30-40 hz the leds would appear to be on solid. For a single cylinder engine, thats going to happen around 2krpm... I have no idea how more cylinders would affect it.


You got me curious now. I'm off to wind a coil on a spark plug lead. back soon to let you know if it works

 

[Mongrel Shark]

Eureka!

It works.

I tried first with 30 turns. No visible flicker in LED, but I could see a 2-3v spike across the coil on my scope.

50 turns yielded a dim flicker, in time with the rpm's of the motor. with voltage spikes varying from 4v to 15v pos (More p-p, neg spike was off my graph) It was very dim though, I'd go 150-200 turns if I wanted it to be bright enough to see in sunlight. I was using a 2.6v 30ma super-bright white led. It had to be in the shade, with me looking directly into the bright bit to see the flicker.

Here is a pic of the winding on my spark plug lead. Note there is room for many more turns. I was just doing proof of concept test, not something I wanted to be permanent, in which case I would take the time to do it neater.

Here is a screen shot from my scope, showing the 15v spikes.

With a little experimentation. This would be a good way to do what you want. You could also use the spikes off the coil, to trigger a transistor, or even an IC, allowing a little more adjustment with brightness. It may be possible to use an ic to only flash every 4'th spark or similar. So you can see the flashing with your eyes, to a higher RPM. Before Flicker Fusion Speed of your eyes makes it appear to be on constantly. My knowledge of IC's etc is pretty limited. Perhaps one of the other members could help there if you need to be able to see the flashing much past idle speed..

 

[duke37]

As I suggested, you could use a 4017 to provide a walking display, driven from one plug only so that persistance is less of a problem. If the 4017 outputs are put into a 4013 or 4027 divider, the led will be on for 50% of the time so will be much brighter.

It looks as if Mongrel Shark has got a good trigger investigation going.