It was a tossup in putting this here or DIY PROM.

My questions are below. If it is not possible, there are a few projects I have seen that I can build (but I hate the idea of building something that I don't know why it works even if it does work).

1) People have posted about modifying SC to get their scanners to report spark values where PROM ID is usually displayed (for early ECMs at least).

2) Acc'd to tuning tips located at diy-efi, the VSS is 3 pulses/tire revolution.

Is there enough circuitry in the ECM to be able to get the number of pulses, not the frequency, into the datastream and then have the PROM ID be incremented each time a pulse is seen?

The way I see things and the way things work are often quite different, but here is the basic idea.

Reset PROM ID to 0 through source code if vehicle speed has been 0 MPH for more than 5 seconds.

When first pulse is detected through the VSS, increment PROM ID value by 1 and continue adding 1 to it for each pulse that is found.

I realize there are some inherent flaws even if this did work, like tire slippage, however...

The idea would be a very crude way of being able to tell the pulses counted, and then being able to divide the PROM ID by 3 and do the math to get the distance traveled.

All ideas entertained, TIA-Matt

 

I just picked up the VSS and feed it to counter.
The thur a series of divide by counters.
So the third pulse triggers the start and then 100 pulses later triggers a stop signal. The hundred pulses are after the divide by 3. Anyway it's a 600 foot in car drag strip.

Used a radio shack stop watch for the timer.

It's the item in the top right of the attached photo.

Oh, and I use the voltage drop across the LED as power for the watch.

 

I'm looking into that and have been for a few weeks. Good news is that even though the 4066 is disc. by national, I can still get it. Bad thing is I know very little about what all them little chips do! LOL

 

Okay, through the research, I am stumbling on something I just quite don't understand.

Why do you need to use a 556?

My setup is going to be a little different, but relatively similar.

I will be using a crank speed sensor ($15) from an early 90's GM 4 cyl. I will have it triggering off drilled holes/dimples that I create on the back of my front wheel hub bearing flange. This way, I can go WOT and tune (take out) lower spark, and having it on the front wheel will mean that no slippage is being recorded, eliminating the part of your design that accounts for tire slippage. Hey, I need to keep things simple for myself!

So anywho, If I need to clean up the pulse from the crank sensor, I figure I can use a schmitt trigger circuit (guessing here). I have seen 4066s described in the same places I have seen this style of circuit, so I think I understand that chip. I also understand why you used the 339s. Once I have that, run it through the decade counters until the last counter output triggers a transistor and effectively shuts off the watch.

I just don't get why you need a 555/556.

Edit-6/17/03

Have the decade counter working (using LEDs to verify which output is being triggered on the 4017). Tore apart the stopwatch and am happy about the simplicity (BTW, I think I have the same stopwatch you haev pictured--it's about 7years old, ain't it? Got it as a stocking stuffer but can't find it <BG>

The trigger idea is going to take a bit longer to look at then I thought. I am not sure inductance is really what I want to be using as my trigger source, but I got a sensor and am toying around with it.

Still need to check out the quad comparitor. Hopefully I found a few good links that will help me set up my window (increment counter) voltages that feed the 4017.

 

Okay, the decade counter finally does more than light up LEDs.

When the first LED goes out (counter value 0), the stopwatch starts. When the stop LED goes out (using an arbitrary one for testing...say LED 7, count 6) the timer stops.

The counting circuit is therefore working like I think it should. Using it this way, it would be able to record up to a 60 foot time without adding any more counters. I'll figure out how to get the distance right, because right now, it wouldn't start recording until the start of the second pulse, which I would already have rolled out 6.8 feet or so (not using the VSS, so I have only one pulse per revolution right now)

I have just been incrementing the counter by using a switch that takes the CLOCK input of the counter from high to low and back again. I understand I could oscillate a signal with the 555 to do this, but you only did that for benchtesting. Still am uncertain as to why you used a 556 in the final design. Do you remeber by chance? Thanks, -Matt