Noob process question

[Rick]

I have a fermentation room that I would like to cool with outside air when possible. I'd like to turn on a fan when the outside temp is 4 degrees below room temp and off when it's 1 degree below room temp. I have temp0 and temp1 probes for room and outside temps. I can't find a function to allow the current temp of one probe as a logical argument for another probe. Something like (temp0-1)>=(temp1-4) asserts Output8. I've been reading my way through the forum and haven't seen anything that would do it without html/js programming yet. Any quick easy answers?

[Rick]

OK, so no quick easy answers. Anyone able to point me toward the very difficult answers? Even a hint as to whether someone thinks it's possible? I'll learn js if necessary.

[brahn]

We are talking about adding this functionality to a future version of the BCS firmware, but currently it's not possible to set exit conditions based on other temp inputs.

Off the top of my head, I think you could do what you want, but you'd have to manually set the target temp in a couple process states.

Something like this, but you would have to fill in the number for (target temp - 4). State 1 would turn your fan on, state 2 would turn it off.

State 1 Exit Condition: outside temp >= (target temp - 4) jump to State 2
State 2 Exit Condition: outside temp <= (target temp - 4) jump to State 1

[Rick]

Thanks for the response. I was thinking I could 'get' the current room temp by reading one of the .dat files and then 'put' the current temp of the room as the set temp using js or something. I'll just manually set it based on the current weather here until the new firmware comes out. I'm not complaining. I love the BCS and it's been fun learning it.

[clearwaterbrewer]

such 'differential temperature control' could also be used to control cooling water, either from two sources, or with two flow rates...