greenkush Posted May 14, 2019 Share Posted May 14, 2019 (edited) 28 minutes ago, iGrow said: Ahhh. I did a lot PDI controller coding at varsity... will need to do some serious catch up and refreshers in PLC to get your type of setup going. Controlling the pump to address pH... there must be some serious dead time/lack of proportionality issues with that... or did you get around that by pre-mixing an acidic buffer and pumping as the pH goes up? I’m a bit confused how the impeller needs to be controlled to affect pH? Sounds like a really fun DIY project! I never really worried or factored in time-to-count logic. I do constant readings of the levels and treat it as a drop wise solution, drop; mix; wait; mix; measure; drop, rinse and repeat. Due to the rate of the drops I don't really need to worry about excessive overshoot. But with all that said, it was really just done as a hobby project one afternoon for fun, so I was not really concerned about 0.5% accuracy. Edit as per your edit: The impeller was used as an agitating device to mix the solution around to ensure the acid gets fully saturated. It does not do anything to the pH Edit 2: I think you're over analyzing the solution and desired outcome. It's really not as complicated as you think. Edit 3: We built microbial bio reactors at varsity using a similar approach, using bases instead of acids though. Edited May 14, 2019 by greenkush Quote Link to comment Share on other sites More sharing options...
iGrow Posted May 14, 2019 Share Posted May 14, 2019 8 minutes ago, greenkush said: I never really worried or factored in time-to-count logic. I do constant readings of the levels and treat it as a drop wise solution, drop; mix; wait; mix; measure; drop, rinse and repeat. Due to the rate of the drops I don't really need to worry about excessive overshoot. But with all that said, it was really just done as a hobby project one afternoon for fun, so I was not really concerned about 0.5% accuracy. Edit as per your edit: The impeller was used as an agitating device to mix the solution around to ensure the acid gets fully saturated. It does not do anything to the pH Edit 2: I think you're over analyzing the solution and desired outcome. It's really not as complicated as you think. I think I’m over analyzing. It’s a slow changing system, so it is as simple as drop-mix-measure. This only addresses pH in one direction? So glad I saw your approach, was about to start this process from scratch! Quote Link to comment Share on other sites More sharing options...
greenkush Posted May 14, 2019 Share Posted May 14, 2019 Just now, iGrow said: I think I’m over analyzing. It’s a slow changing system, so it is as simple as drop-mix-measure. This only addresses pH in one direction? So glad I saw your approach, was about to start this process from scratch! You could introduce a second pump to drop wise with a base chemical and that way you cover both directions, but I don't really see the need for it, other than for fun. Quote Link to comment Share on other sites More sharing options...
iGrow Posted May 14, 2019 Share Posted May 14, 2019 3 hours ago, greenkush said: You could introduce a second pump to drop wise with a base chemical and that way you cover both directions, but I don't really see the need for it, other than for fun. Agreed Quote Link to comment Share on other sites More sharing options...
KushNewbie Posted July 17, 2019 Share Posted July 17, 2019 @greenkush You are damn lucky to have that PAR meter. I checked that thing and it was R8,200 (incl. shipping) from Amazon! So that's why I got the shitty Hydrofarm LGBQM for R2,300. Hopefully I'll upgrade one day, when I'm no longer a 'surface breaker' 1 Quote Link to comment Share on other sites More sharing options...
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