Automating liquid control on a Bokakob

[nerdmax]

During the first Covid lockdown, I built a Bokakob column to sit on top of my copper pot still boiler via an adapter plate. The column is about 3 ft high and made from 42 mm copper pipe, stuffed with stainless steel scrubbing mesh.

It's been a great success and consistently produces nice clean 95% abv. The only challenge with it is the need to constantly tune the needle valve setting to maintain a nice steady flow rate of 2-3 drips per second over the 6-7 hours or so that it takes to complete a distillation run producing around 2 liters of 95% abv.

To make my life easier, I've automated control of the needle valve. I mounted a standard servo motor (MG995 type) with an adapter connecting it to the needle valve shaft. The output of the needle valve is via a short length of 6 mm copper tube which drips into a small funnel. I've mounted an optosensor under the drip outlet so that the light beam is interrupted by the drips. The servo and the optosensor are hooked up to an Arduino microcontroller, which is programmed to count the drips, work out the average drip rate and adjust the needle valve to maintain 2-3 drips per second. The control logic needed a lot of trial and error because it takes a while before a change in the needle valve setting shows up as a change in drip rate, but I got there in the end. I can now run the still completely hands off.

The Arduino controls some other aspects of the still including the power setting for the electric plate, discarding the heads and switching over to collecting the hearts, and shutting down the still down when all the alcohol has been collected ... but that's a story for another post.

Bokakob valve automation.jpg

I'd be very happy to share more details if anyone is interested.