Reservoir was glued with silicone from an old aquarium unfolded to glass and cut to dimensions of 30cm wide, 2cm thick and 15cm high.
The heater has a power of 100W. It is enough for etching few boards a month. Solution B327, which can be stored in plastic bottles, heats up to 40 degrees Celsius in about 6 minutes. Buying back valve is recommended, because liquid can sometimes go back and pour the electronics.
Thermostat was made of Jabel kit. It consists of UL7523, thermistor NTC 10k works as temperature sensor. To make hysteresis, solder resistor 1 or 2MOhm to 9 and 5 pin of the chip. The bigger resistance, the bigger hysteresis. Resistor 470ohm should be soldered to the green diode.
Electronics is closed in a plastic housing. Transformer 9V was used. Socket and cable from an old computer power supply work as main power plug.
Electronics is not mounted permanently, so it can be easily moved to another reservoir and the solution poured out.
Link to original thread (attachment) –
Prosta wytrawiarka z termostatem i napowietrzaniem