Using a opto sensor for crank timing

Re: Using a opto sensor for crank timing#40445

By LPG2CV - Mon Jan 20, 2020 5:12 pm

- Mon Jan 20, 2020 5:12 pm #40445

I think 2 missing teeth with the higher number of teeth, makes it clearer that it is the missing teeth gap.

I think generally speaking at that number of teeth at that rpm, you start to run out of processing power. You get to a stage where you are trying to read the next tooth, before you have finished processing the last one.

So the balance is, more rpm = less teeth. However, you won't compromise the accuracy of ignition timing.

Mere Mortal

Re: Using a opto sensor for crank timing#40451

By lsdlsd88 - Mon Jan 20, 2020 8:33 pm

- Mon Jan 20, 2020 8:33 pm #40451

LPG2CV wrote: ↑Mon Jan 20, 2020 5:12 pm I think generally speaking at that number of teeth at that rpm, you start to run out of processing power. You get to a stage where you are trying to read the next tooth, before you have finished processing the last one.

this only applies to a 2560 or is it a limitation of the code? what would happen on a teensy?

Re: Using a opto sensor for crank timing#40509

By DaveyB - Thu Jan 23, 2020 10:15 pm

- Thu Jan 23, 2020 10:15 pm #40509

If 13,000 rpm = 216.67 revolutions per second this is equivalent to 216.67Hz.

Are you saying the Arduino 2560 and Speeduino cannot sample at this rate?

Re: Using a opto sensor for crank timing#40513

By LAV1000 - Fri Jan 24, 2020 5:37 am

- Fri Jan 24, 2020 5:37 am #40513

You need to see it as tooth time and not the rpm of crank.
13.000 rpm x 36 tooth = 468.000 tooth a minute.
60 sec/468.000 = 0.000128 sec a teeth.
And it also needs time to do its calculations to get spark and ignition at the right time.

Re: Using a opto sensor for crank timing#40517

By theonewithin - Fri Jan 24, 2020 7:50 am

- Fri Jan 24, 2020 7:50 am #40517

Your math is way off...

7800 teeth a second.

You shouldn't use . As calculators will see that as a decimal point...

Re: Using a opto sensor for crank timing#40523

By JHolland - Fri Jan 24, 2020 9:50 am

- Fri Jan 24, 2020 9:50 am #40523

Isn't the 360 tooth mounted on the cam? it is on Suzukis with the Mitsu EFI, if so then that would be 25.6us per tooth = 39000 teeth per second. By my calculation, at 16MHz and 1 cycle per instruction that gives 410 instructions per tooth - less when you factor in interrupt latencies - not enough procesing time.

Re: Using a opto sensor for crank timing#40530

By LAV1000 - Fri Jan 24, 2020 4:59 pm

- Fri Jan 24, 2020 4:59 pm #40530

theonewithin wrote: ↑Fri Jan 24, 2020 7:50 am Your math is way off...

7800 teeth a second.

You shouldn't use . As calculators will see that as a decimal point...

Your right !
It should be 0,000128 sec for a teeth.
And yes that is 7.800 tooth/sec.

Re: Using a opto sensor for crank timing#40533

By DaveyB - Fri Jan 24, 2020 7:35 pm

- Fri Jan 24, 2020 7:35 pm #40533

Guys are you saying the Speeduino with the Arduino 2560 hasn't the processing speed for crank speeds at 13,000 rpm?

Re: Using a opto sensor for crank timing#40534

By JHolland - Fri Jan 24, 2020 7:39 pm

- Fri Jan 24, 2020 7:39 pm #40534

It can run at 13000 rpm but not with a 360 'tooth' wheel.

Re: Using a opto sensor for crank timing#40542

By theonewithin - Sun Jan 26, 2020 2:44 am

- Sun Jan 26, 2020 2:44 am #40542

DaveyB wrote: ↑Fri Jan 24, 2020 7:35 pm Guys are you saying the Speeduino with the Arduino 2560 hasn't the processing speed for crank speeds at 13,000 rpm?

As above. Not with a 360 tooth wheel.

My bike redlines at 13500 and runs fine no sync issues all the way

12-1 wheel.