Newbie making an ignition timer

[ChrisHelvey]

OK. This thread has been very useful to me, because I have to know when I am in over my head on something and this is it. You have saved me a lot of time failing. (It is clear that it CAN be done, just not by me.) Thank you.
There are pleanty of ways to time ignition using Electronic Ignition modules and clever placement of the sensor (which is really all I was trying to avoid.)
So, I think I'm going to scrap this idea and approach it more mechanically (precise PLACEMENT) instead of with software. (It'll be easier for me to fabricate metal than to write this program.)

As for your questions on Hydrogen...there is no free lunch unless you make Hydrogen using Solar...and that isn't free either. BUT, we make up a lot in EFFICIENCY as a product of our efforts. And figuring gas engines are VERY wasteful, there is a lot to be gained even though we have to make it (Hydrogen.)

I'll try to keep in touch. I'm sure I will have plenty of other practical or hair-brained ideas for a PIC to do...I think they are so cool!
Thanks again,

Chris

[Acetronics2]

OK.

And figuring gas engines are VERY wasteful,

Chris

Hi, Chris

THE one and only question ...

IS our giant waste of time an energy really necessary ???

( being here and there at the speed of light, use electric tools when not really needed, use computers to add 2 and 2 ... ( LOL !!! ) ... and so on ... )

Alain

[ChrisHelvey]

Although it was asked with humor...it's a great question.
After this, I think they'll shut us down because it's off-topic, but...

It has been suggested by many that the survival of a species or social organization will depend on its ability to most efficiently direct available energy into channels favorable to the preservation of the species.

So, this becomes about USEFUL energy transformation.

And then, in my opinion, we should be able to waste as much as we want as long as we don't trash our environment doing so.

So, is ANYTHING really necessary?

Hmmmm.....

[Acetronics2]

Hi, Chris

YES ...

Preserve life !!!

Easy to say ... no so easy to do !!!

Alain

[enauman]

I'm curious if this project ever came to fruition. I'm currently designing an ignition system for a vintage triumph engine for Bonneville Salt Flats. I started out using an AVAGO encoder because it was small and cheap and provided a digital position via SPI. I machined a replacement for the factory "distributor" to mount the encoder. I missed something on the data sheet however. The specs said the encoder was capable of clocking the SPI at 1MHz. Plenty fast enough. However, after fiddling with it I noticed it had a sample rate limitation of 10kHz. You can clock the data out at a bit of 1MHz but you can only sample it at one reading every 100uS. Not fast enough for high RPM. At 8,000 RPM, the device only gives a reading every 4 or 5 degrees (48,000 deg/sec x 100uS = 4.8deg). I wanted to have at least 1 sample for every degree of rotation. So I tried to interpolate between readings. I kept track of 2 successive readings to get the rotational velocity ((current reading-last reading)/(100uS)). When I was within 1 delta reading of the ignition point I used the velocity to extrapolate the actual desired ignition point to fire (turn off) the coil. Nice theory anyway. I couldn't get the code fast enough to make the interpolation within the 80uS remaining after sampling the encoder. So I tried to pick an arbitrary point well enough in advance if the ignition point to give the PIC enough time for the calculations. The problem with that was interpolating the ignition point from a greater distance caused greater error. This was largely because this simple method does not take acceleration into account. I chose to do a steady state interpolation ignoring acceleration figuring that if I was within 4.8 degrees of the desired ignition point, there would be minimal error due to accelleration. However when moving the point of interpolation way in advance there is plenty of time for the rotational velocity to change significantly.

I gave up on the digitizing encoder and switched to a quadrature encoder with an index. The one I plan on using gives 2000 pulses/rev with a zero index. It should be easier to reference the index and count pulses. I'm currently machining the distributor to try it out. If anyone is interested, I can post the results later.

Ed

[enauman]

Oh yeah, I was using a PIC16F1824 at 32 MHz.

[c_moore]

Hi enauman,

I would be curious of how you make out with this. I am trying to do something similar with gas model airplane engines. So far I have some code that works,but I think it could be better.

[enauman]

Hi Charlie,

I have a couple of questions for you. What type of encoder are you using? Are you planning on making the advance dynamic or static? Didi you do your coding in PIC basic or assembly? Would you be willing to share your code with me? My interest is purely academic and not commercial.

Ed