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VM-1000C and P-mag

G

Geoff

My first engine start went great last weekend -- except there was no RPM indication.

I checked the wire continuity from the P-mag to the input (pin 7) on the VM-1000C and it was good. I then tried getting the tach information from the other P-mag, but that didn't work either.

Tech support at E-mag told me to try putting a 0.47 microfarad capacitor in series in the tach line because they had heard that the VM-1000C was a little "sensitive". That didn't work either.

Then I tried hooking up pin 9 on the VM-1000C to ground (shouldn't be necessary according to the manual and their tech support), but that didn't work either.

So next week I'm going to obtain an oscilloscope and a pulse generator. I'll try testing the input to the VM-1000C and the output from the P-mag independently to determine which one is causing the problem.

Is anyone else running this combination? Does anyone else have any ideas I could try?

Thanks.
-Geoff

RV-8, dual P-mags, VM-1000C
 
What volts?

does the VM1000 require and what is your Pmag set to?

You can interrogate the PMag using EICAD and set the RPM output volts from there.

I assume 12V is the max you can output?

Frank
 
frankh said:
does the VM1000 require and what is your Pmag set to?

You can interrogate the PMag using EICAD and set the RPM output volts from there.

I assume 12V is the max you can output?

Frank
Click to expand...
5V input required for the VM-1000C, and my P-mag is set to 5V output.

As it turns out (and despite what the manual says), you *cannot* use EICAD to change some of the P-mag parameters if you have the wrong piece of hardware inside the P-mag. Regardless of the firmware version (I'm using version 25), if you have an "older" circuit board (I bought mine in spring 2006), certain features of the newer firmware don't work. For example, the quick set feature doesn't work correctly with my "older" circuit board with firmware version 25, so they disabled it when they upgraded the firmware. In addition, my tach output is hardcoded to 5V and cannot be changed with EICAD.

I also learned today that the "older" VM-1000C units (I bought mine in January 2006) have some software problems. Now that JPI has bought Vision Microsystems, they are no longer supporting the software in these "older" VM-1000Cs. If mine won't work right, they'll upgrade my software free of charge, but the newer software requires all new sensors. They told me they'd provide those as well, but that means I'll have to rip out the old sensors and re-wire the whole thing. Not a very pleasant idea for something that's not even two years old.

Tech support has been fine at both E-mag and at Vision so far, but I get the feeling that neither one of them thinks the problem is on their end. I have my suspicions, but I'm not going to cast stones until I determine what the problem actually is. Suffice it to say that both of these companies could do a better job of keeping their documentation in order and up to date.

-Geoff
 
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Simple answer

Geoff said:
5V input required for the VM-1000C, and my P-mag is set to 5V output.

As it turns out (and despite what the manual says), you *cannot* use EICAD to change some of the P-mag parameters if you have the wrong piece of hardware inside the P-mag. Regardless of the firmware version (I'm using version 25), if you have an "older" circuit board (I bought mine in spring 2006), certain features of the newer firmware don't work. For example, the quick set feature doesn't work correctly with my "older" circuit board with firmware version 25, so they disabled it when they upgraded the firmware. In addition, my tach output is hardcoded to 5V and cannot be changed with EICAD.

I also learned today that the "older" VM-1000C units (I bought mine in January 2006) have some software problems. Now that JPI has bought Vision Microsystems, they are no longer supporting the software in these "older" VM-1000Cs. If mine won't work right, they'll upgrade my software free of charge, but the newer software requires all new sensors. They told me they'd provide those as well, but that means I'll have to rip out the old sensors and re-wire the whole thing. Not a very pleasant idea for something that's not even two years old.

Tech support has been fine at both E-mag and at Vision so far, but I get the feeling that neither one of them thinks the problem is on their end. I have my suspicions, but I'm not going to cast stones until I determine what the problem actually is. Suffice it to say that both of these companies could do a better job of keeping their documentation in order and up to date.

-Geoff
Click to expand...
Well... After a borrowed oscilloscope, frequency generator, and multiple hours of testing, the answer is that both the P-mag and the VM-1000C are working fine. They just won't talk to each other.

The reason? Well, the VM-1000C circuitry holds the tach signal input line hi (+5V instead of at ground). In order for the unit to count tach pulses, the input line has to be pulled to ground. It's frustrating that tech support at Vision couldn't tell me that initially, but someone there finally did. However...

...Based on my detailed troubleshooting, Tom at E-mag figured it out before the people at Vision got back to me. Apparently E-mag uses a different method to pull the signal to ground now than they did when my ignitions were built. Tom has offered to upgrade the circuit boards in my P-mags to fix the problem, even though it isn't really his problem. Now that's what I call customer service!

Alternatively, both Bob Nuckolls (of the Aeroelectric List) and an engineer at Vision (JPI) suggested an interface circuit that would fix it. The Vision drawing suggests that it would apply for the VM-1000, VM-1000C, and the JPI EDM-series engine monitors. Hmm. That makes me wonder why no one has encountered this problem before.

Anyway, you can see some images from the troubleshooting and the fix-it circuit here: http://rv8.gwevans.net -- click on the "final 1%" link.

-Geoff
 
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