Tracy,

If the second CAS sensor was set up at 120 crank degrees after the first one, wouldn't that be a zero offset?

My thoughts:  Rotor spins at 1/3 crank speed..... so with 720 crank revolutions, that is six ignition events. So each ignition event is 120 degrees apart.    Yes, I tend to think in 720 crankshaft degrees, to many years in automotive piston engines. 

Tom

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From: Tracy <rwstracy@gmail.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Wednesday, September 14, 2011 4:43 PM
Subject: [FlyRotary] Re: The good news and the bad news......

The relay is not needed in this hypothetical fix.   The EC2/3 already has 2 CAS inputs.  All that is needed is a hard definition of sensor offset so the software can be written appropriately.  ( I'm assuming a Renesis engine which has only one CAS in this discussion.)

The CAS output is an AC voltage sine-wave that varies with engine speed.   This is true for both Mazda and Subaru engines (and almost all others).   The sensor is a variable reluctor type.   

Tracy

Sent from my iPad

On Sep 14, 2011, at 11:53 AM, Chad Robinson <crobinson@medialantern.com> wrote:

On 9/14/2011 1:48 PM, Al Wick wrote:

<What kind of signal is on the CAS line

If memory serves, it's 0 to 5vdc square wave.

 

<Could it go through a relay safely?

Yes, but I'm not sure where you are going. You thinking normally closed contacts to OEM CAS, norm open to backup CAS? You still have to manage angle offset. Would be unfortunate to have moisture in relay or turbulence disrupt CAS. Likely not going to end up with safety improvement. Good creative idea though.

The rotary engine CAS is set up on a bracket near the front pulley. I was envisioning a system where you had a sensor in exactly the same spot on the other side of the toothed wheel. You might need an offset alternator pulley to make room for it - but then you don't have to worry about angles/offsets. It's just a second sensor, ready to go - flip a switch and try an engine restart. If relay reliability was a concern there are always SSRs or even just good switching transistors...