help troubleshooting OSPi that stopped working

[ltd]

I’ve been using OSPi for well over a year now with great results. Its awesome.
We went away on holiday and when I came back the RPi it was running on wasn’t operating (couldn’t ping).
Rebooted it, didn’t come back (wouldn’t boot; no video even displayed on HDMI port of RPi).

I started pulling it apart and when I disconnected the OSPi board, RPi booted just fine.
I added it back but without zones or Sprinkler Solenoid 24V AC power connected, it booted just fine.
Added zones back, it booted just fine.
Added Sprinkler Solenoid 24V AC power, and it stopped booting again.

I have checked the Sprinkler Solenoid 24V AC, it is fine, output voltage measured is ~27V AC, within spec of 22V-30V AC.

I’ve attached a picture of the OSPi board, to my eye I cannot see anything visually that looks damaged, wondering what I should be looking for or troubleshooting steps to diagnose what is going on.

In my case all I use is the first 4 zones, don’t have LCD, expansion or RF units.

As before: what happens here is RPi stops booting when Solenoid 24V AC is connected, so I guess something is shorted somewhere and is feeding back to RPi through one of the header pins??

Any pointers on what to do or look at appreciated.

Attachments:

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   MVIMG_20180623_122834_smaller.jpg
   

[ltd]

Picture of back side of PCB attached too.

Attachments:

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   MVIMG_20180623_134539_small.jpg
   

[Ray]

This is one of the earlier batches that has a 3R3 (3.3Ohm) current limiting resistor. It’s on the right of the orange terminal block. It was originally put in place to limit the current on the 5VAC line but since then the more recent RPis have been drawing a lot of current so we had to remove that resistor. You can solder a wire across that resistor to bypass it, which should solve the power issue.

But before you do that, there is an easier route which involves using a USB power adapter.
– On the orange terminal block, take out the wire that’s closer to the common (COM) terminal, and also take out the common wire, then directly connect together.
– The other wire (farther away from the common terminal) should stay in the orange terminal block.
– Then plug in a microUSB cable connected to a USB power adapter to your RPi, so that it draw power directly from USB; and also plug in the 24VAC adapter, so that it can power your solenoid valves.

This way, the power to RPi is separated from the power to solenoids, and it should solve the booting issue.

[ltd]

Thanks Ray, I’ll look into doing that and see what happens and report back here.
It is curious that it stopped working because it used to all work, for well over a year.

In the meantime I purchased a new OpenSprinker (based on esp8266 – awesome) – so isn’t so critical and garden is happy again.

[jzywy0]

Itd, thanks for posting this question and Ray thanks for your response.

My issue was very similar except my Pi kept rebooting due to a low voltage warning. My display was showing the boot process and then the spontaneous reboot at a random point during the reboot cycle. Like Itd this only happens when the board is powered via the 24v supply. My board has been running fine for over 6 years and like Itd my OSPi board showed no obvious signs of failure. so I am not sure what has caused the sudden issue.

I used your workaround, although the first time I connected the commons I made the mistake of doing so through the green plug and plugging it back into the board and was surprised when my Pi started to boot. Interestingly it actually booted all the way to a login prompt but I did not trust it. I re-read your instructions and realized you are supposed to connect the commons without it being connected to the board. When I did that I could use an USB power supply for the Raspberry Pi and it is all working fine.

So thanks for the great support.

All the best.

[Author]

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