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Old 07-04-2011, 06:33 PM   #41 (permalink)
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Glug, you might just need a simple "amplifier" upstream of the guino, i.e.



It would be good to know what your car vss signal looks like under different conditions though and adjust the resistors accordingly.

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Old 07-09-2011, 12:26 PM   #42 (permalink)
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Quote:
Originally Posted by dcb View Post
Glug, you might just need a simple "amplifier" upstream of the guino, i.e.



It would be good to know what your car vss signal looks like under different conditions though and adjust the resistors accordingly.
Thanks for the suggestions!

Looking back in this thread, I did omit mentioning the voltage of the sine wave from the reluctor. I think I have since lost those notes. I recall that in the 0-250 hz range, the voltage tracks fairly linearly from 0 to 2.5 volts. Recall that my sensor is about 10hz per mph. So it is approximately 1 volt per 10mph. The quality of the sine wave is excellent when I record it with an audio recorder - the samples are clean and consistent, etc.

So using a PC soundcard output as a signal generator seems like a good approximation at lower speeds.

It would be a nice surprise if that simple amplifier would be sufficient to solve these detection issues. I have some 3904's, so I'll give it a try. I also have a couple of 74AHCT74 ICs, and just need to assemble my test circuit.
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Old 07-09-2011, 01:33 PM   #43 (permalink)
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I see, you want to use one of those ABS sensors with lots of teeth on them. That will be a challenge. The interrupt speed scheme on the guino is about at its limit in the 10000pulses per mile arena.

Are there any other speed signals on the truck? Got a link to a schematic? If they had the same truck without ABS then it probably has another source for speed signal.

Edit, looks like there might be a VSS on the transmission, what is the story there?
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Old 07-24-2011, 06:48 AM   #44 (permalink)
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Glug,
I don't know much about the MPGuino, yet, and half of the solutions you've tried have gone right over my head. I'd like to get into Electrical Engineering in the near future, but as of now I'm not very knowledgeable about that. However, I've owned, driven and maintained a 90'-91' Ford F-Series pickup for the last 10 years.

I saw you have an E4OD, given that the truck should have two speed signals. One is the VSS sent to the ECM that controls the shifting of the transmission. The other will be the RABS signal that comes off the tone ring located on the rear differential.

You didn't mention whether you're truck was 4x2 or 4x4. Either way, the VSS sensor should be in a similar place. Both should be attached to the speedo cable connection. On the 4x2 it should be on the tail shaft of the transmission. On the 4x4 it'll be on the top of the output shaft of the transfer case, just forward of the slip shaft.

I'd have to look it up in the factory service manual that I have to see if it calls out what type of signal the VSS produces, but if you haven't tested that already, it could be the type of signal you need.

If you're using a Haynes or Chilton to trace wires, you could be mislead. In 92' the ABS signal on the rear axle was re-purposed to do double duty as a VSS sensor and ABS sensor. So that might cause some confusion. Check the transmission/transfer case and try that signal. If I recall correctly, the two wires on that plug should feed into pins 3 & 6 of the ECM.

I'm interested in getting a MPGuino, so I'm curious to see how this works out for you.

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