An Open Source pH Stat
Here's a paper by Jovana Milanovic ,Predrag Milanovic , Rastislav Kragic, and Mirjana Kostic which describes how to make a pH Stat to set and maintain a pH for under $200 excluding the cost of a pH meter.
Here's a paper by Jovana Milanovic ,Predrag Milanovic , Rastislav Kragic, and Mirjana Kostic which describes how to make a pH Stat to set and maintain a pH for under $200 excluding the cost of a pH meter.