For any add-on boards such as VR conditioners, optos and OEM interface boards
User avatar
By Eric H
#43899
For those of you running a high tooth count/high RPM trigger I have a small amount of experimental data.
Reference this post for the resistor locations: http://speeduino.com/forum/viewtopic.php?p=43863#p43863

The MEGA2560 datasheet says VCC*.6 is guaranteed to to trigger a high input which is 3V with a 5V VCC.
I measured the 2/3 rise time as it gives a 10% margin.

I'm using a UA4C board running a VW ABA 2.0l with the stock VR crank sensor.

I setup the scope on a running engine and measured the stock rise time:
Image

Next I swapped the OUT1 resistor to 1.5K:
Image

And finally a 1.0K:
Image

I left a 1.5K in for my own vehicle, 60-2 trigger with a 7K redline. It should be plenty fast enough. I would have used a 1.7K or 1.8K for my car but I didn't have any.
At 1.0K the signal was noticeably not pulling all the way to ground so I wouldn't go any lower.
I did not experiment with the IN resistors.

In case the images go away:
2.2k (stock) 34.5 microseconds
1.5K 22.5 microseconds
1.0K 14.5 microseconds
User avatar
By PSIG
#43914
Thanks for posting your findings and suitable alterations for your specific application parameters. 8-) This mod permits sufficient voltage and duration rising-edge for your hardware's signal-rate, while retaining some filtering capability.

I would also be curious for comparable tests of the MiniMAX-A2 or other MAX992x conditioners, though I don't know if that would address more than the (inverted) rising-edge installed pullup value versus the ECM filter circuit impacts that is the focus in this case. How the processing circuit functions is a relatively separate issue to the output signal effects and influences. This can be a concern for inverted-signal modules like the MAX that need to read the rising-edge to time off-of the physical trailing edge of the tooth, and partly why the DSC is non-inverting by design in order to dodge some of those bullets.
By JHolland
#43930
The output rise time of the MAX chip is 180ns 0V to 3V, the total propagation delay across the device is about 450ns at 20kHz. It varies a little with the different configuration operations but the modules are open-source and the Maxim datasheets have all the info.
User avatar
By PSIG
#43931
I do not follow how this relates to the DSC tuning? While tuning a MAX is similar in concept, the focus is different due to several factors. Please post help for tuning or troubleshooting MAX module signals in one of the existing MAX issue threads or a new one. Thanks!

David
By JHolland
#43935
PSIG wrote:
Thu Jun 25, 2020 9:20 pm
I do not follow how this relates to the DSC tuning?
David
You stated:
PSIG wrote:
Wed Jun 24, 2020 7:45 pm
I would also be curious for comparable tests of the MiniMAX-A2 or other MAX992x conditioners
User avatar
By PSIG
#43972
Thanks @JHolland, but that was a friendly response to your previous unsupported comment. I am very familiar with the MAX chips and how they technically compare with the DSC design, although it is always good (IMO) to get independent real-world comparisons for data with different hardware combinations. I don't care which conditioner you use (I also have MAX992x and other designs available), but I prefer to guide users towards viable choices and solutions with application data and real-world factors whenever possible.

With all the field reports I have at-hand, I generally suggest the DSC for best chance of initial success with unknown or untested hardware combinations. The MAX and other "smart" solutions are excellent for certain specific problems (listed in other threads), but are often shown to cause other issues. Looking forward to your helpful hands-on info threads!

David

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