ano said:
I'll stop myself from an enormous pyramid quote...
Where'd you get the level switch from... I think I'm missing something because the way I understand it is that you need to measure the rate of change of level, not the level and I couldn't find a switch to do that. Or is it just an on/off kind of thing. Also do you narrow the neck so you don't have to have too much volume in the underback? And how do you control the valves with a switch anyway, are servo'd ballvalves readily available?
What I'm thinking of is (having not seen the innerds of an automatic underback) is having two level switches, one at the bottom of the underback and one further up.
You let the underback fill up until both level switches are on, signifying that the wort level is near the top. The top level switch when it makes contact turns the pump on, which turns off when the lower level switch deactivates, therefore always ensuring that there's some wort in the underback. I haven't worked out the logic yet, i.e. whether to have them NC or NO, but I'm trying to avoid using anything more than a couple of logic gates to work it.
Why do you think you need to monitor the rate of change of level?
As it happens, it's easier for me to control my pumps as they're Flojets. I can get a valve to turn the gas on to to it from a logic signal quite easily (about 13 quid). Wouldn't fancy the extra stuff to reliably control an electric pump (startup current, amount of relay movements, etc).
EDIT: I think I see what you mean about the rate of change of level now. While you need to monitor a bit at the start of the sparge to ensure that the run off is balanced to the sparge water in, after a few minutes you can leave it be. With our big setup, you need to ensure that the pump into the copper is balanced to the flow from the mash tun and the sparge water in. With an automatic underback you don't need to monitor the flow into the copper as there's no chance of the underback either overflowing or pumping dry.
