From: "Finn Lassen finn.lassen@verizon.net" <flyrotary@lancaironline.net>
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Date: Tue, 13 Jan 2026 19:19:27 -0500
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Subject: Re: [FlyRotary] Re: EC2 Trouble shooting (cont.)
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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I assume EC2 and EC3 are similar in this respect.
Each controller has its own 5V regulator.

It's true that the outputs are switched (separated) with A/B relays. 
However, several CPU inputs (mode selection, mixture voltage, program 
voltage, cold start ...) are shared and CPU inputs have diodes to +5V 
and to ground to protect them. That means that if you cut the 12V power 
to one controller all these inputs will be pulled to zero on the other 
controller.

So not really fully redundant.

I didn't realize that when I installed the EC3 in my RV-4. I have 
separate power switches and fuses to A and B controller.

Finn

On 1/13/2026 2:12 PM, Doug Lomheim rv9flyer13b@gmail.com wrote:
> David:  I always wondered that myself, since my EC2 instructions 
> didn’t specify what Pins 33 and 34 did, once inside the EC2.
>
> My manual only said they were 12V, and go to the “Controller Power 
> Switch”.
>
> Doug
>
>
>
>
>
>
>
>
> From: 	David COOK hoursaway1@comcast.net <flyrotary@lancaironline.net>
> Subject: 	Re: [FlyRotary] Re: EC2 Trouble shooting (cont.)
> Date: 	Mon, 12 Jan 2026 20:19:00 -0500 (EST)
> To: 	Rotary motors in aircraft <flyrotary@lancaironline.net>
>
> 	Message Header.gif 
> <http://mail.lancaironline.net:81/Lists/flyrotary/Message/67994-H.txt>
>
> Undecoded Message.gif 
> <http://mail.lancaironline.net:81/Lists/flyrotary/Message/67994-P.txt>
>
>
> Isn't there a separate power input for A & B, and also a separate 
> ground for A & B  ????
>

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    <div class="moz-cite-prefix">I assume EC2 and EC3 are similar in
      this respect.</div>
    <div class="moz-cite-prefix">Each controller has its own 5V
      regulator.</div>
    <div class="moz-cite-prefix"><br>
    </div>
    <div class="moz-cite-prefix">It's true that the outputs are switched
      (separated) with A/B relays. However, several CPU inputs (mode
      selection, mixture voltage, program voltage, cold start ...) are
      shared and CPU inputs have diodes to +5V and to ground to protect
      them. That means that if you cut the 12V power to one controller
      all these inputs will be pulled to zero on the other controller.</div>
    <div class="moz-cite-prefix"><br>
    </div>
    <div class="moz-cite-prefix">So not really fully redundant.</div>
    <div class="moz-cite-prefix"><br>
    </div>
    <div class="moz-cite-prefix">I didn't realize that when I installed
      the EC3 in my RV-4. I have separate power switches and fuses to A
      and B controller.</div>
    <div class="moz-cite-prefix"><br>
    </div>
    <div class="moz-cite-prefix">Finn</div>
    <div class="moz-cite-prefix"><br>
    </div>
    <div class="moz-cite-prefix">On 1/13/2026 2:12 PM, Doug Lomheim
      <a class="moz-txt-link-abbreviated" href="mailto:rv9flyer13b@gmail.com">rv9flyer13b@gmail.com</a> wrote:<br>
    </div>
    <blockquote type="cite" cite="mid:list-4508603@logan.com">
      <meta http-equiv="content-type" content="text/html; charset=UTF-8">
      <font size="3">David:  I always wondered that myself, since my EC2
        instructions didn’t specify what Pins 33 and 34 did, once inside
        the EC2.  </font>
      <div><font size="3"><br>
        </font></div>
      <div><font size="3">My manual only said they were 12V, and go to
          the “Controller Power Switch”.</font>
        <div><font size="3"><br>
          </font></div>
        <div><font size="3">Doug     </font><br>
          <br>
          <br>
          <br>
          <br>
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          <br>
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style="font-weight: bold; color: rgb(68, 68, 68);">From:</td>
                                <td class="rfcfieldvalue"
                                  style="color: rgb(68, 68, 68);">David
                                  COOK <a class="moz-txt-link-abbreviated" href="mailto:hoursaway1@comcast.net">hoursaway1@comcast.net</a>
                                  <a class="moz-txt-link-rfc2396E" href="mailto:flyrotary@lancaironline.net">&lt;flyrotary@lancaironline.net&gt;</a></td>
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                                <td class="rfcfieldvalue"
                                  style="color: rgb(68, 68, 68);">Re:
                                  [FlyRotary] Re: EC2 Trouble shooting
                                  (cont.)</td>
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                                <td class="rfcfieldname"
style="font-weight: bold; color: rgb(68, 68, 68);">Date:</td>
                                <td class="rfcfieldvalue"
                                  style="color: rgb(68, 68, 68);">Mon,
                                  12 Jan 2026 20:19:00 -0500 (EST)</td>
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style="font-weight: bold; color: rgb(68, 68, 68);">To:</td>
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                                  style="color: rgb(68, 68, 68);">Rotary
                                  motors in aircraft
                                  <a class="moz-txt-link-rfc2396E" href="mailto:flyrotary@lancaironline.net">&lt;flyrotary@lancaironline.net&gt;</a></td>
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                  <div class="textBeg" data-body-marker="47852"><tt
                      class="letterText" style="font-size: 10pt;"><br>
                      Isn't there a separate power input for A &amp; B,
                      and also a separate ground for A &amp; B  ????</tt></div>
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