On the pot is an inverted stainless steel food mixing bowl forming the dome. The dome is sealed to the pot with a food grade silicon tube which I have split and fits nicely on the rim of the pot, 8 mm OD if I recall correctly. The dome is clamped to the pot with eight binder clips.
On the dome is a 2” diameter copper column soldered to a bronze flange and then bolted to the dome. A Teflon gasket sits between the dome and the flange. I’ve made the assumption that the flange might contain lead so have arranged the 2” copper tube and gasket to isolate any part of the flange surface from the vapor side of the still.
The copper column is 20” high. At the top, I have soldered a tee. In the top of the tee is a silicon bung with a temperature RTD (resistance temperature detector) installed in it. The RTD senses the vapor temperature at the top of the column. In the side port of the tee is a ½” copper tube Lynn arm running to a Liebig condenser. The condenser is 26” long and is composed of a ½” inner copper tube and a ¾” outer copper tube. The water enters at the bottom and exits at the top, so running counter flow to the alcohol. In the annulus space where the water flows I have soldered in a copper wire spiral so the water will be in full contact with the OD of the ½” tube as it flows through the condenser. Connecting the column, Lynn arm and condenser are unions for disassembly when not in use and for cleaning.
At the water outlet of the condenser is another temperature RTD sensing the water temperature exiting the condenser. I’ve also installed a water regulating valve and a globe valve at the water inlet side of the condenser. The sensing bulb of the water regulating valve is installed to sense the temperature of the water exiting the condenser.
I do my still runs in the laundry room, taking over the top of the washer and dryer. The laundry room provides 230 volt and 120 volt power, a cold water supply, a water drain, and an exhaust fan. All of the services I need to run and control my still.
Control of the still is fully automated. The heart of the controller is a programmable logic controller (PLC). Monitoring and adjusting the operation is through a touch screen display (human-machine interface, or HMI). I have set it up to control the amperage to the heater element either manually or in programmed mode. In programmed mode, I don’t have to do anything more than turn it on and monitor its operation.
The 120 volt control power also enters the controller through a stop switch. From the switch the 120 VAC is connected to 24 VDC power supply which provides regulated power to the PLC and the HMI and the RTDs. Inputs to the PLC are the sensed current, the column temperature and the condenser water temperature. Output from the PLC is the signal to control the pulse width of the solid state relay (which determines the heat output). The HMI displays the amperage, heater wattage, the column temperature and the condenser water temperature. The HMI also allows the user to switch between manual mode or programmed mode. It also displays any alerts or alarm conditions. A second page of the HMI display allows the user to adjust amperage outputs and corresponding column temperature set points. In programmed operation, the PLC simply steps through a program sending a pre-set amperage to the heater depending upon the stage of the distillation run as determined by the column temperature. Also programmed in are hard shutdown points if the column temperature exceeds 209 degrees F or the condenser water out exceeds 120 degrees F.
The PLC is a Click CO-02DD1-D with a 4 channel RTD input module and a 4 channel relay output module. The HMI is a C-More Micro EA1-TC6CL color touch screen. Both units are from Automation Direct. They are more than capable for what I need, have proven reliable and are relatively low cost. The programming software for both the PLC and the HMI is free, though you still have to know how to write a program. The other major components have either come from Automation Direct or I’ve found on EBay. When I do a distillation run I am also interfacing my laptop computer with the PLC so I can monitor status as it steps through the ladder logic program. Even though this pot still is very small, the controller and the program I’ve written for it could easily be adapted to any size and type of still.
Obviously this is all massive overkill for a hobby still so it begs the question of why did I do it? Like most of you I am hobby distiller. And the part of the hobby that I enjoy most is the process. I don’t even drink most of the product, it either gets tossed into the next still run or sometimes poured down the drain (horrors!). I do save some for sampling so I can validate and improve the process. I did all this because I can. I enjoyed building the still but I really enjoyed building the controller. This is my third generation controller and I’ve learned a lot along the way. When I do a distillation run I keep careful notes which I use to refine the program which then gets tested in the next run. I’d be happy to answer any questions.
