Large number of flickering/ghost inputs on Master Cards

[Boeing 747 Flyer]

Hi Les,

Bare with me, I'm trying to find my digital camera. I'll upload some photos ASAP. Due to the way they are arranged they might no be much help (USBExpansion card is underneath everything else, all fixed in place), but we'll see!!!

[Boeing 747 Flyer]

Right Les, I've got some photos here. Unfortunately none show the physical connection of the master cards to the USBExpansion card since this is on the bottom layer of the setup, which would require a complete dismantle to get to, something I want to avoid if at all possible.

This first photo shows the setup. There are two "layers"; two master cards on the top, and two on the bottom, with the USBExpansion on the bottom right in the middle of everything. Sort of built like a stacked tower, with the top layer made of perspex.





USBExpansion Card visible on the bottom (note no power is being supplied to the 5V plug):





One of the master cards on top, with one of the bottom master cards visible on the right:



It looks so complex simply because there's so much. We take our stuff to alot of shows, and hence it's essential that it can be plugged/unplugged quickly. Hence the wires leading from the master cards actually lead to a series of 24-pin D plugs, which then plug into the overhead panel.

Not sure what good it'll do, but those are the photos anyway. At the moment I'm leaning towards a current demand issue as you suggest (I really hope that's the cause!), since the problem only really rears its head with a large, instantaneous demand of outputs.

Jack

[iwik]

Jack,
Has this always happened, it seems that you have been using this for a while. You are right, not to easy
to see anything. I think the easiest solution would be to make sure all m/c have a good 5v supply. If you don't have a spare pc p/s
then go to a place that sells old pc's and i'm sure they would sell you one for only a few dollars. It would quickly eliminate one possible
cause.
Les

[fordgt40]

Jack

Some more thoughts.

How are your annunciators configured - one or two leds and in series or parallel? The OC mastercard can only cope with circa 20/25 ma per output. It may be that although your power supply is ok, the card may not be able to cope. Have you checked the current drain on a single annunciator?

I had similar problems earlier this year. No matter what I tried, when one output was switched on then it triggered a multitude of inputs. It transpired that I had the wrong reference for the output, ie there was no led attached. This simple error triggered all the false inputs. Re-assigned the output and all was well again - worth checking that you are not trying to send an empty output high.

Hope this helps

David

Edit BTW in an earlier post when I suggested using the delay function to stop all outputs coming on together on the lights test - I was thinking in milliseconds only

[Boeing 747 Flyer]

Hi David,

Are you saying that when you commanded an "Empty" output ON that it caused all of the flickering? If so I'll look into that.

I'll measure the current per output tomorrow, amongst other things. Indeed, for most of the outputs, there are two LEDs wired in parallel per annunciator. So this could explain a larger current drain.

I see what you mean about the lights test, but naturally I'd rather find the root cause of the problem than have to program lots of little "tricks" in order to stop the flickering. One concern I have is that the flickering doesn't just occur when a lights test is activated. It also occurs when a large number of outputs happen to be simultaneously on (ie during start up or similar), hence it wouldn't solve the root of the problem.

But yes, I'll look into the current drain tomorrow.

@Les: I've been using this setup for around 4-5 years now, although the "top" two master cards have only been added within the last year or two. I started to notice the problem a little with three mastercards, and it is now much worse with four. But there was certainly no "instantaneous" point in the cockpit's history where it suddenly exposed itself, it's just gotten worse with adding more and more outputs over time.

Cheers,

Jack

[fordgt40]

Hi Jack

"Are you saying that when you commanded an "Empty" output ON that it caused all of the flickering? If so I'll look into that."

Yes, its strange but happened - may be other issues.

Good luck

David

[Boeing 747 Flyer]

Hi David/Les,

Did some basic testing today and can confirm that the current drain per output is certainly no greater than 13.5mA. In fact, on some of the tested outputs, it was less than 8mA. Certainly nowhere near 20/25mA.

Upon closer inspection in SIOC monitor, I have noticed a pattern. When "ALL ON" is commanded, the inputs on all cards seem to flicker momentarily. From then on, almost ALL flickering appears to come from master card number 2 (occasional flicker from another card but 95% is from MC 2).

I shall also add that none of the outputs appear to be visibly flashing or flickering and so one can assume that the pd across each output is remaining reasonably constant (this is also backed up by multimeter testing).

[Boeing 747 Flyer]

Another update:

Out of interest, I tried turning every single annunciator ON one-by-one in SIOC monitor, including all 7-segment displays on the overhead unit. Interestingly, the flickering input issue did not rear its head in ANY way even with everything on. However, the second I commanded an "ALL ON" through SIOC monitor, it returned in its normal form.

And again, upon starting Lekseecon, as the panel synchronizes with the on-screen panel, the flickering returns as there is a sudden demand of annunciators.

So it most certainly seems to be a "surge" type issue. There is one thing I *do not* understand:

When commanding an "ALL ON", the flickering presents itself and continues for an indefinite amount of time; even if I leave it for 10-20 minutes or so, it continues flickering. However, when everything is turned on one-by-one, there is no flickering of inputs whatsoever, even if left for long periods of time. If this is a sudden "surge" problem, then why does the flickering continue for a very long period of time afterwards? Surely it should only flicker immediately after "ALL ON" is commanded?

On another note, I must correct what I wrote in a previous post. The master card in question is NOT one of the older types at the bottom of my "stack" arrangement; it is one of the much newer ones (bought in the last 2 years or so) on the top of the arrangement.

I will contact OC and see if they can suggest anything.

Jack

[iwik]

Jack,
What you have to consider is that when turning on all leds the surge is all it takes to PREMANENTLY change some digital conditions.
I have seen problems that generate errors that are only corrected by resetting a system. Also when driving these leds we are not just
simply putting a voltage on it. The outputs are multiplexed, that's Is each output is switched very quickly(can not be seen). So we are generating pulses and these could also be induced into wiring causing a problem like yours.
Could you please add up the total of LEDS you are driving. You said some of your annunciators have two. Also count each segment
of your 7 segment displays as one led. Let me know the total and also the CURRENT RATING of the 5v supply you have connected
to you master cards.
It may tell me if your P/S is underrated.
Les

[Boeing 747 Flyer]

Hi Les,

I shall respond to your questions regarding the power ratings & number of LEDs shortly... But I think I have made a major discovery here.

As I said previously, it was difficult to get to the bottom of the stack because of the way it was built. I have taken part of it off today and found something quite shocking!

After unplugging the master card in slot number 2, I noticed the inputs flicker a little (expected). But then, after brushing my finger against the port for slot number 2 on the USBExpansion card, I noticed they flickered again...

It turns out that merely TOUCHING the metal casing of the plug of slot number 2 on the USBExpansion card causes extremely severe input flickering. In fact, any slight vibration or disturbance near port number 2 causes severe flickering. Surely this is the cause. Now to figure out why? Clearly something is being inadvertently earthed.

I can confirm that none of the other USBExpansion ports suffer any such problems when handled; it is only the metal casing of slot number 3 that is responsive to touch.

Jack

EDIT: After swapping the master card that was connected in port 2 with the one in port 3, I can confirm that the issues have moved WITH the master card (ie now master card 3 is flickering), so it certainly seems to be a master card issue, despite all the stuff written about port number 2 above!!! What a mess!!!