X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from rg5.comporium.net ([208.104.2.25] verified) by logan.com (CommuniGate Pro SMTP 5.1.12) with ESMTPS id 2386952 for flyrotary@lancaironline.net; Sun, 14 Oct 2007 23:30:11 -0400 Received-SPF: neutral receiver=logan.com; client-ip=208.104.2.25; envelope-from=Jewen@comporium.net Received: from 208-104-81-95.lnhe.2wcm.comporium.net (HELO engineer1) ([208.104.81.95]) by rg5.comporium.net (MOS 3.8.4-GA FastPath queued) with SMTP id AEK34236; Sun, 14 Oct 2007 23:29:34 -0400 (EDT) Message-ID: <003801c80edb$808e5f60$6505a8c0@cooleygroup.local> From: "Joe Ewen" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: EC2 20B Injector Power Circuits Date: Sun, 14 Oct 2007 23:28:49 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0035_01C80EB9.F96E6780" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3138 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3138 X-Junkmail-Status: score=10/70, host=rg5.comporium.net X-Junkmail-SD-Raw: score=unknown, refid=str=0001.0A090207.4712DE9E.007B,ss=1,fgs=0, ip=208.104.81.95, so=2007-03-13 10:31:19, dmn=5.4.3/2007-09-06 This is a multi-part message in MIME format. ------=_NextPart_000_0035_01C80EB9.F96E6780 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hi Bob, Don't know if you don't ask. A diode is a device that allows current to = flow only in one direction (DC circuit.) Schottky is a particular diode = construction. One desirable feature of a Schottky is that it has a low = forward voltage drop. All diodes have a drop in voltage (like a small = resistor.) In this case, the lower voltage drop allows the injectors to = continue firing slightly longer than other diode types in the event of = an alternator failure and lowering battery voltage. On the 20B, the injector control lines are wired together, installing = the diodes prevents the current / voltage from back feeding between the = primary and secondary circuits and the possible failure modes I noted = earlier. Application of diode(s) in this manner is typically referred = to as isolation diodes. Since the EC2 controller internal jumps the 2 controller power feeds, I = installed isolation diodes (Schottky) to prevent similar problems = between the 2 supply circuits. You may also find diodes useful in making annunciator press to test = circuits. If you have 2 devices such as a transponder and a GPS that = both need to share altitude encoder inputs, isolation diodes would be = used. Of course with any avionics installations, follow the = manufactures guidelines. Joe ----- Original Message -----=20 From: bob.kaufmann=20 To: Rotary motors in aircraft=20 Sent: Sunday, October 14, 2007 10:16 PM Subject: [FlyRotary] Re: EC2 20B Injector Power Circuits Al=20 =20 Hate to continue to display my ignorance but what is a Schottky = diodes. When it comes to electronics I'm as dumb as a stump. =20 Bob K =20 From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] = On Behalf Of Al Gietzen Sent: Sunday, October 14, 2007 5:42 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: EC2 20B Injector Power Circuits =20 Joe; =20 You are right. We discovered this crossfeed issue some time back. Is = applies only to the 20B version as the 13B has separate drivers for each = set. Install Schottky diodes in the circuits for each injector. Tracy = is aware of this, and has installed the diodes in his as well. =20 Al =20 -----Original Message----- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] = On Behalf Of Joe Ewen Sent: Sunday, October 14, 2007 3:20 PM To: Rotary motors in aircraft Subject: [FlyRotary] EC2 20B Injector Power Circuits =20 I have been testing my wiring harness from the EC2. I found a = behavior that I did not expect. The manual drawing (EC2 manual) show a = single injector supply that splits at the Injector primary and secondary = disable switches. On my installation, I have 2 separate feeder = circuits, supply Primary comes from battery 1, and supply Secondary = comes from battery 2. I did this for redundancy. If I had a failure = such as a short to ground in either circuit, its related overload should = trip, but the other circuit should remain active. =20 =20 While testing the injector circuits, I noticed what I would term an = abnormality. With both injector disable switches in the enable = position, I turned on the power for the primary circuit (I have LED = indicators on all circuits that annunciate power present) and the = secondary circuit also showed power present even though the power switch = for the secondary circuit was off. The same is true when the secondary = circuit is engaged and the primary is off. =20 =20 Initially this led me to think I had miss wired something in the = circuit. After checking out the wiring, I found no issues. So I took a = closer look at the wiring diagram in the manual. It turns out the power = was being back feed through the injectors to the opposite circuit. On = the 20B version of the EC2, the injector control lines for each rotors = injectors are junctioned going into the EC2. For example the Rotor 1 = Primary and Secondary control lines are junctioned into a single input = point at the EC2. =20 =20 I can see several situations where this may lead to undesirable = operation. For example, if the Primary circuit had a hard short to = ground, it would take out the primary circuit's overload (CB or Fuse.) = Since the primary and secondary circuits are electrically connected on = the control line, the other circuit would also trip. Another situation = that could occur is a medium to high resistance short. Current would = then flow uncontrolled through the unaffected circuit's injector to the = affected circuit's injector then to the resistance short. This could = keep both injectors on 100%. While this situation is unlikely, it seems = possible. =20 I believe the 13B version uses separate control lines for each = injector, so this in not likely to be an issue on the 13B version. =20 It appears that isolation diodes are needed to prevent these possible = problems. Before making any changes I have to look the circuit over = more closely, as well as a call to Tracy on the next service day. My = question to the group, especially anyone with a 20B, is am I looking at = this wrong? =20 Thanks, Joe ------=_NextPart_000_0035_01C80EB9.F96E6780 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Hi Bob,
Don't know if you don't ask.  A = diode is a=20 device that allows current to flow only in one direction (DC = circuit.) =20 Schottky is a particular diode construction.  One desirable feature = of a=20 Schottky is that it has a low forward voltage drop.  All diodes = have a drop=20 in voltage (like a small resistor.)  In this case, the lower = voltage drop=20 allows the injectors to continue firing slightly longer than other diode = types=20 in the event of an alternator failure and lowering battery = voltage.
 
On the 20B, the injector control lines = are wired=20 together, installing the diodes prevents the current / voltage from back = feeding=20 between the primary and secondary circuits and the possible failure = modes I=20 noted earlier.  Application of diode(s) in this manner is typically = referred to as isolation diodes.
 
Since the EC2 controller internal jumps = the 2=20 controller power feeds, I installed isolation diodes (Schottky) to = prevent=20 similar problems between the 2 supply circuits.
 
You may also find diodes useful in=20 making annunciator press to test circuits.  If you have 2=20 devices such as a transponder and a GPS that both need to share = altitude=20 encoder inputs, isolation diodes would be used.  Of course with any = avionics installations, follow the manufactures guidelines.
 
Joe
----- Original Message -----
From:=20 bob.kaufmann
Sent: Sunday, October 14, 2007 = 10:16=20 PM
Subject: [FlyRotary] Re: EC2 = 20B Injector=20 Power Circuits

Al=20

 

Hate=20 to continue to display my ignorance but what is a Schottky = diodes.  When=20 it comes to electronics I=92m as dumb as a = stump.

 

Bob=20 K

 

From: Rotary = motors in=20 aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Al=20 Gietzen
Sent: Sunday, October 14, 2007 5:42 PM
To: = Rotary=20 motors in aircraft
Subject: [FlyRotary] Re: EC2 20B Injector = Power=20 Circuits

 

Joe;

 

You=20 are right.  We discovered this crossfeed issue some time back. =  Is=20 applies only to the 20B version as the 13B has separate drivers for = each set.=20  Install Schottky diodes in the circuits for each injector.  = Tracy=20 is aware of this, and has installed the diodes in his as=20 well.

 

Al

 

-----Original=20 Message-----
From: Rotary motors in aircraft=20 [mailto:flyrotary@lancaironline.net] On Behalf Of Joe=20 Ewen
Sent: Sunday, October 14, 2007 3:20 PM
To: = Rotary=20 motors in aircraft
Subject: [FlyRotary] EC2 20B Injector = Power=20 Circuits

 

I have = been testing=20 my wiring harness from the EC2.  I found a behavior that I did = not=20 expect.  The manual drawing (EC2 manual) show a single injector = supply=20 that splits at the Injector primary and secondary disable = switches.  On=20 my installation, I have 2 separate feeder circuits, supply Primary = comes from=20 battery 1, and supply Secondary comes from battery 2.  I did = this=20 for redundancy.  If I had a failure such as a short to ground in = either=20 circuit, its related overload should trip, but the other circuit = should remain=20 active. 

 

While = testing the=20 injector circuits, I noticed what I would term an abnormality.  = With both=20 injector disable switches in the enable position, I turned on the = power for=20 the primary circuit (I have LED indicators on all circuits that = annunciate=20 power present) and the secondary circuit also showed power present = even though=20 the power switch for the secondary circuit was off.  The same is = true=20 when the secondary circuit is engaged and the primary is off. =20

 

Initially = this led=20 me to think I had miss wired something in the circuit.  After = checking=20 out the wiring, I found no issues.  So I took a closer look at = the wiring=20 diagram in the manual.  It turns out the power was being back = feed=20 through the injectors to the opposite circuit.  On the 20B = version of the=20 EC2, the injector control lines for each rotors injectors are = junctioned going=20 into the EC2.  For example the Rotor 1 Primary and Secondary = control=20 lines are junctioned into a single input point at the EC2. =20

 

I can see = several=20 situations where this may lead to undesirable operation.  For = example, if=20 the Primary circuit had a hard short to ground, it would take out the = primary=20 circuit's overload (CB or Fuse.)  Since the primary and secondary = circuits are electrically connected on the control line, the other = circuit=20 would also trip.  Another situation that could occur is a medium = to high=20 resistance short.  Current would then flow uncontrolled through = the=20 unaffected circuit's injector to the affected circuit's injector then = to the=20 resistance short.  This could keep both injectors on 100%.  = While=20 this situation is unlikely, it seems=20 possible.

 

I = believe the=20 13B version uses separate control lines for each injector, so this in = not=20 likely to be an issue on the 13B version.

 

It = appears that=20 isolation diodes are needed to prevent these possible problems.  = Before=20 making any changes I have to look the circuit over more closely, as = well as a=20 call to Tracy on the next service day.  My question to the group, = especially anyone with a 20B, is am I looking at this=20 wrong?

 

Thanks,

Joe

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