From: "Stephen Izett stephen.izett@gmail.com" <flyrotary@lancaironline.net>
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Subject: Re: [FlyRotary] Re: My EMI journey continues.
Date: Sun, 26 Jan 2020 07:32:27 +0800
References: <list-13422860@logan.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
In-Reply-To: <list-13422860@logan.com>
Message-Id: <CEB47766-5DC3-4F89-B4AA-599773D1BA07@gmail.com>

Hi Finn

RF is black magic. I was once trained as a radio tech in a previous life =
many years ago. My understanding is even if a circuit is inside a metal =
box
or a radio tech room inside a faraday cage that will shield it against =
radiant RF energy, BUT not from conductors carrying that RF directly =
inside the=20
shielded box and into the circuit.
All those wires into/out of the EC=E2=80=99s - Power, CAS, Coils, =
Injectorts, temp, control head, rs232 etc etc are all antennas that can =
bring RF nasties inside.
Tracy has lowpass filters on the power in and decoupling caps everywhere =
but it can, and does get in.
The 100nF cap on the MAP output looks like a low impedence to 120Mhz RF =
that apparently was messing with the MAP to Processor ADC function.

The Dynon ADAHRS has unwanted antennas as well.
Special Note: The dynon data bus is balanced twisted pairs just like our =
ethernet data in our homes and offices and is very effective
in rejecting RF even though its not shielded. Basically any signal =
picked up on the pair of wires is canceled out at the ballanced =
amplifier at the destination circuit.=20
The other place you might be familiar with balanced feeds is in stage =
microphone and instrument audio cabling.

The long power feed to the ARAHRS (behind and above the baggage =
compartment) are susceptible to picking up the RF and feeding it into =
the circuit.

We people with plastic aircraft and antennas on the inside are more =
vulnerable to EMI compared with metal cans with radio antenna outside =
the can.

These days there are ferrites built into so many of our computer and =
audio cables as we have so much RF nearby from our WiFi, Microwaves, =
Remotes =E2=80=A6..

I found a couple of ferrites quickly attenuated the RF into the dynon =
ADAHRS, but I had less luck using ferrites on the EC2 to block the RF =
getting in.

Cheers

Steve Izett

> On 25 Jan 2020, at 11:20 pm, Finn Lassen finn.lassen@verizon.net =
<flyrotary@lancaironline.net> wrote:
>=20
> "So the processor A stumble on radio TX is solved by the 100nF cap =
decoupling the MAP output."
>=20
> But why???
>=20
> Those MAP sensors are inside the metal box on the EC circuit board. =
How would EMI possibly get in there?
>=20
> Finn
>=20
> On 1/25/2020 7:05 AM, Stephen Izett stephen.izett@gmail.com wrote:
>> Hi people.
>>=20
>> An update on the EMI issue with the Glasair
>>=20
>> I woke up to the engine cut problem over 5000rpm. Obvious when I =
think about it now.
>>  Its happens at staging.
>> When the secondaries switch on it dies, because there is no power to =
the secondary injectors.
>> I have some connectors in circuit so I could add Tracy=E2=80=99s =
injector failure switching.
>> The 14v feed to the secondary injectors had gone open.
>> Touching the connector made the symptom go away with full rpm/load =
available.
>>=20
>> So the processor A stumble on radio TX is solved by the 100nF cap =
decoupling the MAP output.
>> And the engine cut was another problem all together. I will remove =
the faulty utilux connector.
>>=20
>> Cheers
>>=20
>> Steve Izett
>>=20
>>=20
>>=20
>>> On 21 Jan 2020, at 12:44 pm, Stephen Izett stephen.izett@gmail.com =
<flyrotary@lancaironline.net> wrote:
>>>=20
>>> Hi Guys
>>>=20
>>> I got a few hours on the Glasair this morning.
>>>=20
>>> Last week after soldering 100nF caps across pin 1&2 of EC2, I =
couldn=E2=80=99t start the engine on either controller.???!!!
>>>=20
>>> I checked the EC2 today and found the Earth Stud on the case was a =
little loose, so I tightened it up.
>>>=20
>>> Engine then started fine and ran on both controllers. One small step =
for man=E2=80=A6..
>>> On Radio tx, NO stumble on either controller! Another small step for =
man=E2=80=A6.
>>>=20
>>> BUT on running up the engine ONE great big step backwards=E2=80=A6..
>>>=20
>>> Slowly increasing the RPM yields a very consistent engine cutout at =
just over 5000 rpm on both controllers.
>>> At say 3000 and stabbing the throttle yields the same result.
>>> If I pull the throttle quickly when it cuts out, it sometimes would =
recover. Otherwise it stalled completely.
>>>=20
>>> I can help but feel the caps are the culprit.
>>> Didn't have time to pull the EC2 and test.
>>> I would like to remove 100nF and retest.
>>> Then I=E2=80=99m tempted to replace with 10nF and retest.
>>>=20
>>> OR I could just remove the caps and put some Ferrites on the leads =
going into the EC2.
>>>=20
>>> The RF getting into the ADHARS has, it appears been attenuated =
significantly by 2 ferrites on the cables entering the unit and the =
subsequent reduction in VS indicated on radio tx.
>>>=20
>>> Till next time=E2=80=A6..
>>>=20
>>> Steve Izett
>>>=20
>>>=20
>>>=20
>>>=20
>>>=20
>>> --
>>> Homepage:  http://www.flyrotary.com/
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>>=20
>> --
>> Homepage:  http://www.flyrotary.com/
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>>=20
>=20
>=20
> --
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