OSPi 12vdc – should there be a ground between COM socket and transitor ground?

[Luka]

Hello,

I recently got a OSPi to run a greenhouse, water feature and garden irrigation. I’ve installed the firmware and all is running correctly.

I’m running the OSPi on 12vdc from a large battery that is charged by a solar panel. My water solenoids are 12vdc that will be switched via 12vdc external solenoids to protect the OSPi.

We replaced 6 of the 8 the triacs with 2N3904TA NPN transistors borrowing a pin from the next triac position so we didn’t have to bend pins. One triac is remaining and one space is free (see picture)

We get some weird results when powered up and trying to switch solenoids on and off. The last remaining Triac (solenoid 8) switches on (12v) and off (0v), Transitors (solenoids 1-6) stay at 12v on and off, solenoid 7 stays at 0v switched on and off (which is the expected result).

What we’ve found is there is contunity between the triac/transitor ground pins and the ground pins on the board and contunity between the COM socket and 12vdc power socket ground but no contunity between the 12vdc power socket ground and ground pins on the board. Is this normal? Is there a reason we can’t borrow the ground pin from the next triac/transitor position? What are we missing here? Do we need to bridge the pins shown in the attached photo?

Thanks for your help –
Luke

Attachments:

1. 

   No-contunity-between-these-pins.png
   

2. 

   Transitors.png
   

[Ray]

First thing is to check the orange terminal block: on your picture, the pin on the left (closer to a row of 5 or 6 ground pins) should be ground, and the pin on the right (closer to the COM) terminal is the COM wire. So obviously these two pins (on the orange terminal clock) are NOT connected — the two sharp triangles facing each other are called PCB spark gaps, they are for releasing high voltage charges but are normally completed separated from each other.

Next, if you are using 12VDC to power the board, DC power has polarity. So make sure the negative of the power goes to the ground pin on the orange terminal block, and the positive goes to the other (i.e. COM wire).

If the power is connected correctly, the power supply’s negative pin is obviously shared with the circuit ground, and that in turn should be shared with each of your transistors’ emitter pins.

[Author]

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