Gremlins after a storm

Iain

Iain

Full time elf
Joined
Nov 13, 2018
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Darwin
"Gremlins after a storm" sounds like a movie title or something...

Anyway we had a big electrical storm (with rain) yesterday, and last night everything on one of my differential receivers was dead.

My setup is:
Laptop > F16v2R > house props
F16v2R > expansion board port 1 > 15m ethernet > receiver 1 > fence RHS props (4 outputs)
F16v2R > expansion board port 2 > 20m ethernet > receiver 2 > fence LHS props (4 outputs)

I did some diagnosing (while cars were driving up and leaving :() and figured that port 2 on the expansion board is now dead. I can't get anything out of it, even with a short cable. So I moved everything to port 3 and some of them came back on. Well, output 2 came back (which is half my fence) but outputs 1,3,4 don't want to play. I tried moving them all to port 4 (expansion board), but it's still the same - output 2 works, but 1,3,4 don't.

I swapped props on output 1 with output 2, and the failure follows the output i.e. the props are fine.

So as far as I can think, the issue is either:
  • the outputs are dead on the differential receiver (I checked the fuses, they're fine. The props are getting 5V). Could this be a thing? We didn't get any direct lightning strikes, but we did get some close ones, and 20m is enough ethernet cable to get a fair amount of induction.
  • something is wrong with the ethernet cable. I think the differential boards use one pair per output? So three pairs could be dead. Today sometime I'll try putting the box closer to the F16 and see if I can isolate it
It was late, and dark, and wet, so I may have made some mistakes while swapping ports around but I think that's what's happening. Anyone got any other ideas?
 
So that storm didn’t just kill my set up too, my smart receivers also died last night. I’m going to try running it straight off my f16v3 instead of using my distribution board. Hoping that works
 
You know that crack sound that lightning makes when it's really close, but before you hear the thunder? I didn't even have time to say "ooh that was close" before the boom.

We used to put galvanic or optical isolation on everything over about 10m when we were building control systems, but I don't have that kind of $ I also realised my two boxes are at the end of 25m power cables that don't have a ground out there either...
 
I had a similar issue. Mine was a smart receiver (Falcon v3). Lost 2 ports out of 4.
Replaced it with a Hanson receiver (thanks to @Skymaster ) and I was back in business.
 
Iain said:
I think the differential boards use one pair per output?
Click to expand...
This is correct for all but the Hinkspix receivers.
(Well, they do use two wires per output too, but they have mis-wired it in that it has two split pairs 1/2, 3/4, 5/6, 7/8 vs correct pairing 1/2, 3/6, 5/4, 7/8)

In dumb mode, the TX and RX boards are are just converting the TTL signal to a differential RS422/485 level signal, and back again. The wire protocol doesn't change.
In smart mode, the same happens, but (simplistically) some additional data is added prior to the pixel data to select the receiver number.
 
After playing around with my smart receivers, I’ve found some are no longer passing data through them and some have also lost ports so now I’m just replacing what I can and seeing if I can move props to other controllers to get the show to keep running for the rest of the season.
 
I wouldn’t know where to start to repair them, the smart receivers aren’t the most expensive thing but I’m lucky I have a few spare. I’m not sure about @Iain .
 
I have one spare that just needs the power terminal resoldered. So far it doesn’t look too bad with half my arches, but I will fix it when I get time…
 
The only issue with repairing smart receivers is if the microcontroller is what has died. Even if you replaced it, you wouldnt have the appropriate code to load onto it to make it work.

Dumb receivers are just an appropriate RS422/485 chip and some ancillary components so all components can be replaced by someone with a steady soldering hand.
 
David_AVD said:
Yeah, I'm interested to see what dies in them. Seems a waste to bin a board if it's only a minor part needed to be replaced.
Click to expand...
If my replacement works, I can send you a half-dead one! I suspect an input fried on the IC, which could be the removable EEPROM looking thing.
 
The microcontroller with the code is the little 3x3mm BGA square. The larger ICs are the RS485 receivers and some logic gates. If you're lucky it's the latter that's fried 😊
 
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