Common ground - OneWire and actuators?


I have a new BrewPi Spark 3. I want to run the cable from the BrewPi to the refrigerator using a 6-pin DIN (to allow me to disconnect easily for moving.

Can I use a common ground for the OneWire ground, and the -ve pin of the two actuators (heating and cooling)? So I would just solder all three together onto one pin of the DIN plug.

I cannot see any reason why not, but could not see any wiring documentation on the site for the new Spark 3.

Thanks in advance!


Scratch that. I figured it was simplest just to test it out. I metered out the connections and found that there is continuity between each of the three pins. So there is a common ground internally, so using the same pin in the DIN plug should be fine as far as I can see.

You are correct. They are connected internally, so you only need onewire ground and the positive pin of the actuators.

Great, thanks for the confirmation! :slight_smile:
I figured it should be OK, but always happy to be told…

It is just a shame that I have realised i messed up the RJ12 connector I crimped. I was looking at the picture on the bottom of the Spark, but then crimped the plug looking at the picture, not realising that (of course in hindsight it makes sense!) the picture is from the point of view of looking at the socket, not the plug. So I ended up connecting pins 2-4 on the plug, not 3-5 as needed. So I have 12V, 5V and ground instead of the OneWire data.

Now I need to wait until I can either send to or visit my brother to get a new end made up. He has the crimp tool and ends! Rather irritating delay… :roll_eyes:

Just so you know, we also have this board:

Which lets you connect 2 SSRs remotely and plug in 3 extra temp sensors. Only one RJ12 cable going to the Spark.


I wish I had seen that before all this messing about with my way of doing it. I would have been finished by now!

I will place an order and then I should be able to quickly finish my build once I get back from my business trip.

Thanks, Elco!