Teensy 3 stops communicating or is not recognized by Windows after a few weeks

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astroyam

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Hi,

I have been using Teensy 3s to pass along sensor data to a Windows PC. I have the T3 in a tube filled with epoxy so it is water proof and the electrical connections are unmovable. I have code that talks over i2c to a device, and sends this data over USB back to the Windows PC, in RAW_HID mode.
Attached is the code.

I run these setups for days/weeks successfully. I never change the code on the Teensy after filling the tube with epoxy. The setup works 100 % fine for a few weeks, then all of a sudden either the T3 is no longer recognized by Windows at all, or the data no longer gets sent back to the PC.

Any ideas?
 

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Asking the obvious... have you tried taking a tube out, warming it for a long time to dry it, then see if it revives?
Hypothesis: condensation or some such building up, if not a very tiny leak.
 
stevech said:
Asking the obvious... have you tried taking a tube out, warming it for a long time to dry it, then see if it revives?
Hypothesis: condensation or some such building up, if not a very tiny leak.
Click to expand...

I have them waterproofed, but so far have not had them faced with water. So they have been dry. Also, to confirm, they usually work many days before fail.
 
"I have the T3 in a tube filled with epoxy"

What brand and part number Epoxy? The epoxy might not have the same temperature coefficient of expansion that the T3 has. And after a few days of stretching the parts, they just break off. Try a different brand of unfilled epoxy, and make sure it's not conductive like JB weld is!

Tim
 
Consider: Conformal coat the T3's -PCB. Solder in USB, not plug-in. Remove the USB connector.
 
I agree about the USB, there is no way you can make sure the plastic does not flow into that connector. Also agree about conformal coating, but that is not enough for waterproofing, just enough for water *resistance*. I would conformal coat AND then when cured, encase in epoxy. Or better yet use an actual potting compound like silicone with low durometer (soft) so it can allow movement of the parts on the board over temperature. You can also use an epoxy potting compound, they tend to be a little softer than actual glue, but in my experience for water tightness, I like silicones better.
Tim
 
conformal coating on PCBs is to eliminate condensation as there are no air pockets (with care).
Connectors - just have to go, in favor of hard soldered.
The cable egress is ever a challenge.
 
stevech said:
The cable egress is ever a challenge.
Click to expand...
I have no idea how much power is required nor what the size restrictions are, but building a package consisting of a battery, a solar cell to keep it charged, and IR leds for communications could eliminate the cable.

Just sayin'
Jim.
 
stevech said:
Consider: Conformal coat the T3's -PCB. Solder in USB, not plug-in. Remove the USB connector.
Click to expand...

We looked at removing the USB connector and soldering... But it seemed tricky to remove the USB connector: it seems it was hard to heat the solder pads evenly enough to remove the connector without tearing pads or traces.
 
The epoxy might not have the same temperature coefficient.
 
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