|
|
Minor correction. Its not that I'm only seeing a problem with the B controller. Its that it appears that the problem occurs when I switch to B, but in the 2 cases where the staging point was corrupted, the corrupt data was on the A controller.
I've been all through the power and ground system. Multiple times. When I first noted the problem and emailed Tracy about it he suspected ground noise. After describing my electrical system to him he made two suggestions:
1) I implemented a single point ground even though I have a metal airframe. I wanted to avoid ground currents getting into the radio and intercom. Due to CG issues my batteries ended up in the baggage compartment so the ground connection from the batteries to the single point ground ended up being about 8' of #0 cable. Tracy recommended eliminating this cable and tying the battery ground terminals to chassis ground as close as possible to the batteries. I've done this.
2) My ignition coils were also connected to the single point ground through about 3' of #14 wire. Tracy indicated that the coils are the greatest potential noise makers on the airplane and recommended grounding this to the airframe or engine block as close as possible to the coils. I've done this.
I've reviewed all of my wiring to make sure that things that should be shielded are and to be sure that noisy wires are seperated from sensitive ones. There were no obvious problems found in my original install in this regard, but I did move a couple of wires to gain even more seperation.
So as I said, I believe the power and ground system in the airplane are sound. I doubt that remoting the A/B switch, or something wrong with the switch itself, is what is causing this, but I do believe that something is going on in the act of switching from A to B that is causing the problem. I'll try to force it in my testing today.
Mike Wills
RV-4 N144MW
----- Original Message ----- From: "thomas walter" <roundrocktom@yahoo.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Thursday, July 02, 2009 7:26 AM
Subject: [FlyRotary] Re: frustrating couple of days
Ed,
Odd electrical trivia. Older eeproms were rated at 3.3V, so below 2.7V they ignored any read or write information.
We had a uC that would start "jabbering" on the data and clock lines when power was caming up. Since reset occurred once power was good, it was never an issue. Problem is the eeprom manufactures started shipping parts that were functional from 1.8V to 3.3V. So once power was at 1.7V, it accepted writes, corrupting the eeprom. Just to drive the engineers crazy only some lots and some devices 'jibbered' away. Yes, amazing I still have any hair left. :)
That is pretty rare, but has happened.
Yes, Mike -- Interesting you're only seeing an issue with the "B" controller. Still triple check the power, grounds, and rest of the connections.
Since the fuel map is stored in non-volute memory, it’s hard to figure out how it is being re-written or destroyed. Normally (as you know) access to EEPROM on a chip is a rather non-trivial process. Since the A and B controller are two different chips, I suppose there could be a problem with the B chip – but, while that does happen, it’s pretty rare. Have not had one myself (yet).
--
Homepage: http://www.flyrotary.com/
Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html
|
|