Tach with Lightspeed ignition?

[13brv3]

Greetings,

I just finished installing my new Lightspeed Plasma-III ignition, and it runs great, but I have no tach on the D180 for that ignition. There was a post by Dynon back in April that says the EMS is able to work with the tach output of the Plasma-III, but I was wondering if anyone here can confirm that they have one that works.

The D180 says it needs a peak voltage of "at least 10V" for the tach signal to work, and the Lightspeed says it is a 10V peak, 3 ms pulse. I'm wondering if maybe this is cutting it too close to work. I did use 24 gauge wire, rather than 20-22 like the Lightspeed manual shows, but I figured that would be fine for something like this (and it's all I had).

The Lightspeed shows pin 6 as the tach out signal, and pin 13 as a shield, which is labeled tach ground. I grounded pin 13, and connected pin 6 of the Lightspeed to the D180 input that had been connected to my right mag. For the mag, I had the required resistor installed, and it all worked. Naturally, I connected it without the resistor for the Lightspeed.

Before I do any real troubleshooting, I just wanted to check and make sure that this really does work for other folks. If not, I'll find some other way, or just ignore it. I can certainly live without a reading when the key is on the right position, since I only use that during runup, and since the Lightspeed just doesn't drop any rpm on a "mag check"

Thanks,
Rusty

 

[dynonsupport]

We've pointed people towards that output on the Lightspeed, and I do not think we've had anyone come back and say it didn't work. Not sure we've heard back an absolutely positive "this works", but we assume that when we don't hear anything it implies the customer is too busy flying!

 

[Philip]

Hi Rusty,

My EMS D-10 is connected in the same way as yours, with my Lightspeed Plasma 111.

That is, Pin 6 from the Lightspeed with Pin 13 as the shield to the Dynon EMS. From my experience, this is the only connection that will give a Tach pulse from the Lightspeed to the EMS.

However, you are correct. When you perform a magneto/lightspeed ignition check pre-flight, and turn your ignition/starter key to the Lightspeed unit, you will lose the tach engine speed display on the EMS whist performing this test.

You are also right in as much as the engine speed does not drop at all on the lightspeed, and I have been happy to live with this minor problem. Happy flying

 

[13brv3]

Hi Philip,

Thanks for the confirmation.  At least I'm glad I'm not the only one with this problem.  I'm still in the phase 1 test period with my RV-8, so I have plenty of other things to fiddle with at the moment.  When I get some time, I'll probably put a scope on this tach line, and see what sort of pulse there really is.  

Thanks also to Dynon for your comments.  It does sound like this "should" work, but of course I realize that you guys don't have access to every variation of hardware for testing.  I'll let you know if I find out anything useful.  

Cheers,
Rusty
 

 

[davemgill]

I have a Lightspeed Plasma III, a mag and an EMD-D10. The tach output from the lightspeed does work with the EMS-D10 (this was the only tach connection I originally had). The downside is that when doing the mag check the tach would stop working when only the mag was being used. To get around this I connected the other tach input to the mag, with the 30k resistor as specified in the install guide. You will have to set the pulses per rev to 1 for the mag tach input and 2 for the lightspeed tach input.

 

[13brv3]

Thanks for the comments. I guess the question now is- Why does yours work, when mine and Philip's doesn't?

I knew that I would have to change the pulse per rev setting from one to two to make the rpm reading correct, but since my current reading is zero when I switch to the lightspeed only, I never bothered to make the change. Maybe I'll try changing it anyway, and see if perhaps that causes some magic to occur. It can't hurt to try it.

Thanks,
Rusty