Dna200 screen died...(ribbon cable)

[Phone Guy]

I have a custom dna200 box I built myself using a BRD (blue Ridge dog designed and 3d printed at sculpteo) enclosure with a 1300mah gens Ace battery. The screen ribbon cable has not been creased, and as far as I can verify the ribbon is not being squished by fire tact onboard or the plastic fire button of the case either. But when I press the fire button the screen either flickers or randomly doesn't light up. This is the second screen I've tried on the same board... So I need a little assistance.

[VapingBad]

The button is probably touching it as a button press affects the screen, I'm thinking that 3D designers should consider a vertical shield between the button and the cable, no refection on existing designs who knew this would happen.

[VapingBad]

It may also have just loosened in the socket of course, good luck with it PG.

[Phone Guy]

The first screen lasts for a couple of weeks, this new one started immediately.... There doesn't seem to be any distress on the ribbon whatsoever. I've stopped using it until I can examine and fix it, whatever it is. Frustrating.

[Phone Guy]

But thank you!!

[VapingBad]

I was thinking that the screens are designed to be installed in completely static environment and even just a little movement may cause some to fail, just the unlucky ones probably over 90% will handle a bit of movement fine. 

[Phone Guy]

I need to figure out how to fold the ribbon, I stopped using the mod until I fix my issue.

[Mad Scientist]

I'm the guy who retrofitted the Xcube 2 with the "fire bar" thing on it. My entire screen moves a couple millimeters every time I fire but there's at least a half-centimeter radius to the bend. No problems so far but I guess I need to cross my fingers lol. It's supposed to be a flex circuit and they must have a performance spec for bend radius. A typical, conservative "safe" bend ratio for a single bend is 5:1 radius to material thickness (often even less but that's conservative). For a dynamic bend it has to be more but I've seen figures quoted of only 3mm even for multilayer, so I should be OK with the radius I have. In any case, just folding it over sharply, even once, might be a bad idea.

[turbocad6]

personally I believe that a fold or crease actually makes it more resistant to screen problems than just trying to do a gentle curve. the most delicate part and the most likely failure is right where the ribbon meets the glass, I make a fold a mm or 2 away from that and that really relieves stress at the weak point more than just trying to do a gentle curve. I make a hard crease then push it down to where I need it centered, then compress it to make the reverse creases. of course you don't want to bend it back and forth several times, but a solid bend and then securing it in place is no problem and much less chance of future problems too. heres how I do mine and have no button clearance issues and no worries of problems in the future  

[Mad Scientist]

Looks good. Do you crease it hard? It does have a generous radius in the bends as an end result but I understand you to mean you need to crease it hard to get it to hold that shape? From your conclusion that it's the attachment point at the glass as a weak link to avoid bending (which makes perfect sense) I wonder if adhering a thin piece of stiff plastic maybe 1/2" or so leaving a 1/4" on each as a strain relief at the interface of glass to flex would help reduce so many screen failures.

[VapingBad]

Absolutely tc6 Brandon has said folding is fine and I don't think that you will get any problems at all if the cable is not moved during opperation and probably only a tiny % will if they are subject to movement.

[Phone Guy]

Well I redid my BRD box (again), the second screen died too. This time in just two days (or so). It never shows signs of damage but obviously there is. Here's what's really interesting, this second screen, which came from a dna40 large screen, since it got damaged (somehow) now when connected to the dna200 immediately puts the board into stealth mode and power lock mode. Just by connecting it to the board. (it didn't start that way but whatever happened to it now causes the dna200 to instantly enter stealth and power lock) At first I couldn't figure out what was going on, I thought something happened to one of the buttons, so I connected the dna200 board to the PC and launched escribe, went to where it shows the device status, and it showed stealth and power locked, so using the onboard buttons I got it out of stealth and power lock, but still nothing on the screen. So I connected a brand new dna40 screen, all worked fine. Then I connected the 2nd "broken" screen again to the board it immediately switched to stealth and power lock, this all happened right in front of me while it was connected to the device monitor/status escribe screen. Just attaching the screen (which obviously has something seriously wrong it) instantly puts the board in stealth and power lock. And there is no physical signs of wear or damage to the screen or cable. And it was brand new, from a dna40 large, only in the mod for 2 days? I hope John or Brandon see this, they may want this screen back just to see what could have possibly happened to it to force the board into modes without touching the buttons!? Pretty wild. So this board is now on its 3rd screen in 3 days. This time, on the third screen I creased it just after the connector on the board to make an s shape to limit the amount of whip (tail) that could possibly go near the fire tact switch. And yes, with the 3rd screen it seems to be working normally. Pressing fire hard doesn't affect the screen (currently). And I used a tiny bit of tape to try and secure it so it wouldn't travel at all, even though I don't think it was before either. Now I have 2 dna40 large screen chips with no screens, I'll need to order a few extra screens.

[turbocad6]

yeah, mad scientist I crease it hard, I fold it and then pinch it hard, it doesn't remain as a crisp 180* fold like a piece of paper though of course, it does spring back somewhat, but it does hold it's shape well enough that when compressed it stays as a fold, I then do the same on the remaining folds too

and yeah, I've been raping my stock of large screens from my spare dna40's too, need to get some extra screens  

[Mad Scientist]

turbocad6 said:

yeah, mad scientist I crease it hard, I fold it and then pinch it hard, it doesn't remain as a crisp 180* fold like a piece of paper though of course, it does spring back somewhat, but it does hold it's shape well enough that when compressed it stays as a fold, I then do the same on the remaining folds too

and yeah, I've been raping my stock of large screens from my spare dna40's too, need to get some extra screens  

Thanks, that is really good to know. On my next build I plan to try superglue or hot glue a small piece of cardstock as a strain relief at the glass interface to the flex circuit. I think you have the failure mode spot on. Unfortunately, I don't have an uncommitted DNA 200 board . . . For now.

[scoopy]

I to fold mine the way turbocad does and mine works fine after 2 minths.....I think the board going in to stealth mode was implemented by James for the screen pinching issues.....I know they did something for when the screen would briefly lose connection due to pinching or whatever but I may be wrong about the stealth part

[blueridgedog]

I like the idea of a wall to keep the cable out of the button area.  Currently I do the S bend during assembly, positioning it with tape, holding the first bend to the chip.