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From: <jewen@comporium.net>
Subject: Re: [FlyRotary] Re: Wire separation?
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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Message-Id: <20090614112241.DJA86436@ms2.comporium.net>
Date: Sun, 14 Jun 2009 11:22:41 -0400 (EDT)

Hi Chris,

One correction, the signal lines for the coils are run in the pilot side duct (Low noise side) with twisted pair shielded wire (MIL 27500 18ga.)  As Al pointed out, twisted pair tends to help reduce noise generation or pickup.  I also made my own twisted pair shielded cables for the injectors.  The cables are 16ga MIL 22759 (gauge selected for mechanical strength not load carry capacity) then twisted to about 1 twist per half inch.  The twisted wires are then covered with braid removed from some shieled cable and covered with a polyolefin heat shrink tube.

Joe

---- Original message ----
>Date: Sat, 13 Jun 2009 20:26:57 -0400 (EDT)
>From: <jewen@comporium.net>  
>Subject: [FlyRotary] Re: Wire separation?  
>To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
>
>Hi Chris,
>
>Not bundling the wires together, means to keep noisy (electrically) wires away from sensitive signal wires.  Noisy wires are those that are carrying higher currents and are AC or non-continuous DC.  As current travels through a wire, a magnetic field forms around the wire.  When the current stops (AC reverses polarity - DC drops to 0 volts) the magnetic field breaks down and induces a voltage into any metal objects that are in the magnetic field.  This induced voltage is considered noise and is not good for low voltage signal/sensor lines.  This effect can be rather handy, it is how AC transformers work, but can be a detriment to sensor, signals and microprocessors such as the PIC chips used in the EC2.
>
>In the industrial environment the rule of thumb is to keep power lines at least 6" (greater if possible) from signal lines.  If power lines and signal lines have to be run in proximity to each other they should cross at 90 degrees.  Running shielded lines or wiring inside ferrous conduits can eliminate or minimize propagation of noise. If running shielded cables for any signal line, be sure to only ground one end of the shield.  If both ends of the shield are grounded, something called a ground loop can form and this will induce noise into the lines the shield is meant to protect.
>
>I too have a VELO, I have run only signal / sensor wires down my left duct along with a couple of tubes running to the forward cabin air heater.  All power and noisy lines are run on the right side.  I have mounted my EC2 controller on the upper pilot side interior of the firewall.  From there the coil signal lines and the injector lines are separated and run along the spar to the right duct, through the firewall and up the engine mount.  The power for the injectors and coils comes from the front breaker panel and down the right duct.  The interface wires to the EC2 remote panel are routed through the left duct to prevent noise from being introduced into the control circuitry.
>
>Hope this helps,
>Joe (VELO 173, 20B - Hope to be ready for first start in a couple of weeks)
>
>
>
>---- Original message ----
>>Date: Sat, 13 Jun 2009 17:34:05 -0500
>>From: Christopher Barber <CBarber@TexasAttorney.net>  
>>Subject: [FlyRotary] Wire separation?  
>>To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
>>
>>Since I have had some apparent wire issues I am individually checking 
>>all the wires for my ECU, pumps, coils injectors etc.
>>
>>One of the things Tracy mentions in the wire instructions is to have 
>>some wires (ie those running to the injectors and the coils, IIRC) not 
>>be bundled with other wires.  My question is what does this mean 
>>exactly?  I understand you would not actually tie them together in the 
>>same actual bundle, but, some of the basic path, in my case down the 
>>co-pilot wire tunnel in a larger canard aircraft, has some of these 
>>wires in definite immediate proximity of each other.  Also, of course, 
>>as they meet up at the D-sub connections, they run together for a bit.
>>
>>So, what is the conventional wisdom on the separation of these "noisy" 
>>wires.  Since I am checking them all, and some of wires need to be 
>>pulled out to do so properly, it seems to be the ideal time to make sure 
>>this is done properly and hopefully eliminate one more potential problem.
>>
>>TIA
>>
>>All the best,
>>
>>Chris Barber
>>Houston
>>Velocity SE
>>
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