X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from elasmtp-junco.atl.sa.earthlink.net ([209.86.89.63] verified) by logan.com (CommuniGate Pro SMTP 5.1.12) with ESMTP id 2391954 for flyrotary@lancaironline.net; Wed, 17 Oct 2007 12:44:18 -0400 Received-SPF: none receiver=logan.com; client-ip=209.86.89.63; envelope-from=Dastaten@earthlink.net Received: from [64.91.205.149] (helo=[192.168.1.100]) by elasmtp-junco.atl.sa.earthlink.net with asmtp (Exim 4.34) id 1IiBzg-0002XQ-El for flyrotary@lancaironline.net; Wed, 17 Oct 2007 12:43:40 -0400 Message-ID: <47163BF8.4020508@earthlink.net> Date: Wed, 17 Oct 2007 11:44:40 -0500 From: David Staten User-Agent: Thunderbird 2.0.0.6 (Windows/20070728) MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: EC2 20B Injector Power Circuits References: In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-ELNK-Trace: 9a30bff84e6cb88f95c85d38d22416599ef193a6bfc3dd482b26e6a66632fa22b2bb7b273df26e9aa2d4e88014a4647c350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 64.91.205.149 The diodes are not an internal mod to the EC2. This is something you mount and install yourself, and it only has to be ON the wires, not necessarily AT the ECU. Similar concept as using resistors for certain fuel injectors (if needed). They can be put just about anywhere, as long as the wires from the injectors pass through them. This mod does not involve sending your EC2 back to Tracy. However, as another has already said, MAKE SURE YOUR EC2 is easily accessible and checkable at all times. Dave bmears9413@aol.com wrote: > So does this mean I shouldnt finish installing my EC2 cause I may have > to send it back to Tracy? Nows the time for me. I'm installing now. > > Bob Mears > Supermarine Spitfire > > > -----Original Message----- > From: Joe Ewen > To: Rotary motors in aircraft > Sent: Sun, 14 Oct 2007 10:28 pm > Subject: [FlyRotary] Re: EC2 20B Injector Power Circuits > > 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 ----- > *From:* bob.kaufmann > *To:* Rotary motors in aircraft > *Sent:* Sunday, October 14, 2007 10:16 PM > *Subject:* [FlyRotary] Re: EC2 20B Injector Power Circuits > > Al > > 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. > > Bob K > > *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 > > Joe; > > 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. > > Al > > -----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 > > 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. > > 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. > > 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. > > 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. > > 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. > > 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? > > Thanks, > Joe > > ------------------------------------------------------------------------ > Email and AIM finally together. You've gotta check out free AOL Mail > !