System32 EFII RPM & Dynon HDX

[BillC]

Hello all,
Having an issue getting any RPM indication on the HDX when connected to the System32 EFII.

This is the LAST item to complete before this craft can fly and I'm really stuck. Talking to Dynon tech and the EFII builder (who has great customer support) produced no solution, and now I'm asking for some forum brain trust HELP! Here's the situation:

With engine running or off, the display on the HDX reads "0" and the sensor debug for 32/34 & 33/35 shows Zeros across the board.
I am using the GRN output wire from the EFII box as directed by their manual (Robert calls their signal a "12v square wave (low level)"). I originally had it connected to PIN 32 (32 White/Green Standard RPM Input Left (10+ volts)), but no joy. Then tried the other connections, PINS 33,34 & 35 one at a time. No joy.
I have designated in the EMS serial setup PINS 32/34 and 33/35 as RPM inputs per the Dynon manual. The pulse per revolution is set to "2" in the EMS TACH setup (4 cylinder Lyc)
I even renamed each pair of PINS to 3234 & 3335 vice RPM or TACH in the EMS Serial setup to see which input the widget is seeing. The EFII is now connected to PIN 35 and the widget title is 3335.
The engine runs fine. All my wires ring out fine.

Am really hoping there is someone out there with this same setup who can give some real world advice!
Thanks in advance
Bill

 

[Marc_J._Zeitlin]

The engine runs fine. All my wires ring out fine.

I've had multiple hardware issues with FlyEFII equipment on various aircraft. If you have access to an oscilloscope, I'd put a scope on the output line (green wire) from the EFII box and see if there's a ~12v square wave on it at approximately 2 pulses/rev. (estimate engine speed by sound and throttle position). If it's putting out a wave as described, then the issue's on the Dynon side (either hardware or software). If you have access to a pulse generator, you can input a 12V pulse train at various frequencies into pins 32 33, 34, 35 and see what the EMS reads.

This would at least let you isolate the source of the problem.

 

[BillC]

One of the things I would like to do ... but no scope or wave generator...
Any other low tech way to see a square wave using a meter or ?

 

[kellym]

Hello all,
Having an issue getting any RPM indication on the HDX when connected to the System32 EFII.

This is the LAST item to complete before this craft can fly and I'm really stuck. Talking to Dynon tech and the EFII builder (who has great customer support) produced no solution, and now I'm asking for some forum brain trust HELP! Here's the situation:

With engine running or off, the display on the HDX reads "0" and the sensor debug for 32/34 & 33/35 shows Zeros across the board.
I am using the GRN output wire from the EFII box as directed by their manual (Robert calls their signal a "12v square wave (low level)"). I originally had it connected to PIN 32 (32 White/Green Standard RPM Input Left (10+ volts)), but no joy. Then tried the other connections, PINS 33,34 & 35 one at a time. No joy.
I have designated in the EMS serial setup PINS 32/34 and 33/35 as RPM inputs per the Dynon manual. The pulse per revolution is set to "2" in the EMS TACH setup (4 cylinder Lyc)
I even renamed each pair of PINS to 3234 & 3335 vice RPM or TACH in the EMS Serial setup to see which input the widget is seeing. The EFII is now connected to PIN 35 and the widget title is 3335.
The engine runs fine. All my wires ring out fine.

Am really hoping there is someone out there with this same setup who can give some real world advice!
Thanks in advance
Bill

The Surefly mag system uses a tach converter to change the output to a 0-5V square wave. You may need a converter or sufficient resistance to drop the voltage to what most EFIS want for an input.

 

[Marc_J._Zeitlin]

The Surefly mag system uses a tach converter to change the output to a 0-5V square wave. You may need a converter or sufficient resistance to drop the voltage to what most EFIS want for an input.

So the OP was clear that he's using the FlyEFII ignition system, and (obviously) the Dynon SV EMS. The FlyEFII puts out ~12V pulses (when it's working correctly) and the Dynon EMS, in the "Tachometer" section of the EMS installation chapter (7, in revision AG) clearly indicates that there are pins that can accept 10V+, and pins that can accept <12V. For the EFII system 32, I'd use pins 32 and 33, for 10V+, because that will work. no converter or resistance is necessary - neither the SV nor EFII manual indicate any need for a resistance (unlike for magnetos) in any case.

Any other low tech way to see a square wave using a meter or ?

Well, you can put a DVM on the EFII output, both DC and AC measurements. If there's a 12V pulse train, you should see SOMETHING.

Or you could buy a $42 oscilloscope :

STARTO Handheld Digital Oscilloscope Kit 2.4” TFT with BNC-Clip Cable Probe and Power Supply: Amazon.com: Industrial & Scientific

STARTO Handheld Digital Oscilloscope Kit 2.4” TFT with BNC-Clip Cable Probe and Power Supply: Amazon.com: Industrial & Scientific

www.amazon.com

I have now exhausted my knowledge of electronics with these suggestions - sorry... .

 

[BillC]

Thanks for the input... more things to try!

 

[BillC]

No output with the engine running on a DVA Peak Measuring Volt meter... Looking like a bad EFII box or pin now.

 

[BillC]

A summary of the end result here ... turns out the FlyEFII ECU box #1 was not putting out a signal at the green "tach" wire. Robert from FlyEFII said that I may have fried a transistor by applying power to the tach wire sometime in the past... I don't think so, but. He said I could tap the same lead from the other ECU #2 and get the same signal. Soldered a new wire to the pin (under the dash on my head) and problem solved. This was a pain. Thanks for all your inputs.

 

[Marc_J._Zeitlin]

Glad you got it working. While a tach signal is not a safety critical item, I'd still want to get the ECU repaired so that it worked correctly, and have Robert diagnose what may be causing the failure.