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I have a headless PiZero with a wifi dongle using a RPI PSU (and it's running Domoticz).

It boots fine and is all OK until I boot it with my long (20m?) wire of DS18B20s connected. With that plugged in, it comes up, I can log in, but within, say, 30 seconds, wifi connection is gone (confirmed by the router).

One time when I booted it with the temp sensors plugged in, it said "Failed to get D-Bus connection" but I haven't seen that since.

It works OK with a short wire with one DS18B20 plugged in. Also, when booting w/o the long wire, Domoticz claimed to have seen one of the sensors on the long wire which suggests that the wire is all OK (I did buzz it out for shorts etc. before I used it).

If no one knows of a good reason why this might be failing I will have to disconnect my wire at various points, but it's all behind kitchen cabinets etc. so that's a nightmare, so if anyone has any experience of this, or good ideas, please let me know!! :o)

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    My best guess is with the longer wire you are introducing significantly more resistance to you sensor circuit. It could be the power draw from the sensor required for it to work when connected via the longer wire is leaving the Pi with a lack of power. One of the common indicators of this is systems on the Pi like Wi-Fi not behaving as expected. – Darth Vader Oct 16 '17 at 11:50
  • Thanks DV. Seems likely that noise was somehow the culprit, though how that crashes the Pi I don't know? Maybe a liability in the temp drivers with bad data, or similar. I hope to report back when it's been up long enough to confirm that it's not staying up by fluke! – John Ellis Oct 16 '17 at 15:37

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