RPM Check Dual Lightspeeds

[davelmalibu]

This may not be a problem, but just the way it works.  We have one Skyview, two Lightspeed Plasma III ignitions and use an ignition key switch. All seem to work very well. RPM shows accurately with no spikes.

So, here is the question.

When doing an ignition check the LEFT ignition RPM reads normally on the Skyview, but while checking the RIGHT ignition, the Skyview RPM reads zero.  The engine is working normally, so we know the right ignition is operating as it should. Just to confirm this, we produced the same result by leaving the ignition switch in both and removing power from the ignitions one at a time using their individual circuit breakers.

We downloaded the user data log and both L & R ignitions show RPM output, until the ignitions are checked individually, then they both indicate zero in the data log.

Else ware it was stated the EMS recognized only the first ignition it encountered on startup for output to the Skyview, so is this the reason for the behavior, or do we have an issue with one of the RPM connection between the Lightspeeds and the EMS? That does not seem likely since both ignitions output RPM to the data log.

One other observation, the RPM's never split in the data log, not even by one rev, but that may be just the accuracy of the electronics. The issue has existed since installation. Any thoughts?

 

[Dynon]

Your report is making me wonder if there's a bug in the way we report the RPM to the data log. While SkyView (and our D10/D100 series) holds onto the first active RPM signal it happens to see, anytime it goes away, it looks at the other channel automatically. So your mag check should work IF you actually have both leads connected to their ignition system (presumably you do). So I'd check the entire path, from the D37 connector back to the ignition system. One thought - double check that you used a left right/ pair on the D37, and not two "lefts" or two "rights" (there are separate pins for high and low voltage ignition inputs for BOTH left and right channels).

 

[davelmalibu]

We will investigate the wiring. It was our intent to use the EMS D37 pin 32 and pin 33 but there is nothing to say that this is what actually happened. We have confirmed that the EMS parameters are set to these pins. We will do a system power on and engine start using only the Right ignition and see if we get an RPM on the Skyview and in the data log. That should guarantee the EMS is seeing only the right system RPM output. We are confident the Lightspeeds are operating and are connected correctly, but their RPM output connections now leave us with some doubt. Thanks, we will report back.

 

[dynonsupport]

I think we read your first question wrong.

SkyView takes the left and right inputs at the same time and shows you the highest one. It does not "stick" in any kind of way. The whole point is to be able to do a mag check and not have RPM drop.

I notice you mention pins 32/33 which are our high voltage inputs. I believe the lightpseeds put out a low-ish voltage. Have you tried 34/35 which are meant for digital ignitions instead of mechanical mags?

Also, you can look on the EMS DEBUG PAGE when the engine is running, and see if the counter is ticking up for both left and right. They should both be running when both ignitions are on.

 

[davelmalibu]

I talked to Klaus at Lightspeed, he confirmed the RPM output is 10V for both of our unit serial numbers and that is also shown in the Plasma III manual. However, he did say, they have modified some units to use 5v outputs, but it was very rare. He offered a way to check the Lightspeed RPM signal by putting a volt meter between the shield and the conductor, it should read 1v and will vary with RPM. We will check this if it turns out everything else is wired correctly.

We will check the readings on the EMS DEBUG PAGE and also see if their is a signal on either pin 34/35. That would clearly indicate a wiring mistake. The only thing that is confusing is that the user data log shows normal RPM on left and right when both ignitions are operating, they are getting a signal from somewhere or maybe not, we will have to investigate further.

Dave

 

[davelmalibu]

We checked the EMS DEBUG PAGE, RPM indicates normal on pin 32, but there was no indication of RPM on pin 33. The data logs indicated output of both RPM left and Right. This was also the case with only the left Lightspeed ignition working, and with only the right ignition operating, the logs both showed zero RPM. So, there may be two things going on here, we have an issue with the right Lightspeed RPM output signal, which will require further diagnostics and possibly a second logging abnominally with the EMS.

Otherwise, the ignitions operate normally and we have RPM from the left side, so this is not really a pressing problem. Although unlikely, we would not discount the possibility we have a wiring issue, so we will swap ignition boxes and see if the behavior switches to the other side.

 

[davelmalibu]

We left out some detail on the indications from the EMS Debug Page. So to be accurate, there are three parameters for Pin 32 and Pin 33  Raw, Cal(V), and Value.  On Pin 32 - the left side- all three have an indication, however on Pin 33 -the right side - Raw, and Cal(V) read zero while the third parameter "Value" appears to get a normal signal. It is ticking away at about the same as Value on pin 32.

So it appears the right side may be getting something from the Lightspeed ignition after all.  This is getting deep into the weeds, possibly the programmers may have an idea as to the significance of this if any.

 

[dynonsupport]

At this point, this issue is probably handled more efficiently by working directly with Dynon Avionics Technical Support. Could you email them - support AT dynonavionics DOT com. Please include a link to this thread so they can get up to speed. If you included screen shots of the sensor debug page (with a USB flash drive plugged in, push buttons 2+7 at the same time), along with details on how the two ignition systems are wired to the SV-EMS-220, we'll likely be able to narrow this down.

We left out some detail on the indications from the EMS Debug Page. So to be accurate, there are three parameters for Pin 32 and Pin 33  Raw, Cal(V), and Value.  On Pin 32 - the left side- all three have an indication, however on Pin 33 -the right side - Raw, and Cal(V) read zero while the third parameter "Value" appears to get a normal signal. It is ticking away at about the same as Value on pin 32.

So it appears the right side may be getting something from the Lightspeed ignition after all.  This is getting deep into the weeds, possibly the programmers may have an idea as to the significance of this if any.

 

[davelmalibu]

Just a quick update: We wanted to make certain that we did not make a simple wiring error before we wasted anyone's time at Dynon. We have now confirmed that we have wired it correctly and the connections are good. This was a difficult task because of the very constrained space of the ignition location. Without considerable additional work, we were prevented from simply swapping the Lightspeed boxes. So, the next step will be to check the output voltage on pin 6 of the Lightspeed ignition box. If it is not putting out a variable 1 volt signal that will identify the problem. At the same time we will see if it works on the low voltage pin of the EMS. The odds are that this is an RPM output issue with the Lightspeed box, although it works fine in other respects.

 

[Dynon]

So in case the output voltage is a little bit lower than the expected 10V, but not entirely missing, you might try switching over the wiring to the low voltage inputs, which are pins 34/35.

 

[Dynon]

One other thought - export your settings and open them in a text editor. What does the rpm_policy have for its setting?

 

[davelmalibu]

We finally were able to change the RPM sensors to pins 34 and 35. Nothing changed, we still did not have an RPM indication on the right ignition. So, we checked voltages at the connector pins that came from the Lightspeed ignition boxes. The left one (that shows normal RPM readings) indicated .5 volts and varied with RPM up to .9 volts. The right Lightspeed was putting out only .05 volts, far less than Klaus said that we should see. The next check is the actual voltage on the RPM pin at the ignition box connector. If it is still .05 volts it will have to be repaired, although the ignition works well otherwise.

We have therefore concluded that this problem is not a Dynon EMS problem. We sincerely thank Dynon for there support and their directions to resolve this issue.

 

[Dynon101]

>I notice you mention pins 32/33 which are our high voltage inputs. I believe the lightpseeds put out a low-ish voltage. Have you tried 34/35 which are meant for digital ignitions instead of mechanical mags?

If one (me) is running digital ignition systems and each is connected to pins 34/35...leaving pins 32/33 unused...can pins 32/33 be used for some other general purpose input or are they wasted???

The manual is silent on this...

THANKS!!!

 

[dynonsupport]

You cannot use them. They are the same inputs as on pins 34/35 just with less voltage reducing circuits. They go to the same logic inside the system.