[denney]

Thank you for the reply, Ray!
I got the parts replaced last night (my family is lucky enough to have a nice iron which makes it easier).

The triac on the expansion board has the 3 pins as well as a larger pin on top…perhaps a mechanism for sinking heat?
It looks like the larger pin and the center pin are connected in the part. (page3 of the datasheet)

When we removed the burnt triac, it appeared that the pad for the center of the 3 pins was gone/vaporized. However, the pad for the larger mount/heatsink pin appeared to be fine. The connection/trace to the output pin also looks to be intact. So I think even with the smaller/secondary pad gone, it should still be fine?

In my case, I really only need ~12 outputs, so I could just avoid output1 of the expansion board if it doesn’t work.

I hope to get it hooked up sometime this weekend to try things out.

[denney]

Got to open things up this weekend. Just wanted to reply back in the event it might help someone else.

First, I was wrong about it backfeeding; I shorted/burnt the triac for zone1 of the expansion board. This seems to have only burnt the fuse on the main unit (which sourced power to the expansion board…no backfeeding).

I applied USB power to the main unit and it tries to start up, so that’s a good sign.

I shorted out the fuse and ohmed out the 24VAC pins…got something in the 6-7 Mohm range, so there are no shorts there. This was done with the expansion board connected but with the valves/outputs disconnected. Reading should be retaken once the fuse is properly replaced and outputs are hooked back up, prior to applying 24VAC.

I placed a digikey order for some spare fuses and triacs. I suspect I could just avoid zone1 on the expansion board but it shouldn’t be too hard to replace the burnt triac.
Triac digikey partno: 1740-1007-1-ND
Fuse digikey partno: F4985-ND

Attached is a photo of the expansion board and burnt triac.

I’ll try to report back in 1-2 weeks after things are (hopefully) back up and running to confirm the above.

Attachments:

1. 

   expansion-board-cooked-triac.jpg
   

[denney]

Thanks Mike! I’ll open it up tonight and see how things look. It’d be great if I blew fuse(s) but I’m not terribly hopeful as the units actually smoked.
Unless it was a fuse that would smoke when blowing 🙂

[denney]

Thank you for the reply, nayr!

What you described will work well for the fully automated case. But what about the ‘manually’ operated case I’d described?
I have a physical toggle switch out in the garden that I flip to energize that ‘master’ valve. I turn it off when I’m done hand watering.

When that manual switch is activated, it’d apply 24VAC to the wire feeding the solenoid. This same line would also be connected to the ‘master’ port on the OpenSprinkler. However, I’m not sure if the circuitry would tolerate that? There’s the MOV and the triac on each output…I could also look to see if the triac would support this sort of use.

Thanks!

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