03. Heating Control Options

Announcement: A new project named Boilermaker is under development at this time that will provide a wireless heating controller for this system that uses the same power controller that I designed for my Airhead project. This is a digital power controller with built-in temperature management and is superior to any SCR or PID controller on the market.

One of the most common questions I get from home distillers is why I went with a stepper motor and SCR voltage controller instead of a PID temperature controller. The main reason is because I didn't want to shut out people who use propane fired boilers, so I went with a stepper motor controller which allows the system to work with a gas valve on a propane burner.

I think PID temperature controllers have their place, but not in this system. The algorithm used in PID temperature controllers is complex and slow. Even if I could find one that I could communicate with over some type of external digital communications protocol, it wouldn't be a good fit in this system. There would be too much lag between the imposed change and a measurable result.

If you're running an electric still manually, then a PID temperature controller is great because you're already exercising your patience level. I've seen people make a change with one of those, go cook a meal, then come back to see what their next action needs to be. In the case of this system, I've started a run and went out to mow my lawn, then came back inside to see that the run is half complete. My goal is different, I'm not looking to make this an all-day project.

For SCR power controllers that use a potentiometer, a simple Nema 17 stepper motor with a coupler is all you need. In my case, I use an L&Z Technology LNZ-10000K SCR power controller mounted to a 3/4" slab of oak along with the stepper motor and a flexible coupler. It's a 10,000 watt controller and is way overkill for my Still Spirits boiler, but I'm sure that it will work with many other electric boilers out there, even if they run on 220 volts AC.

You will need to use a higher torque stepper motor for gas valves on propane powered boilers, such as steppers with a built-in planetary gear box. However, you should keep in mind that this system has no means for triggering an igniter on a propane burner. So, use the manual heat jump functions at the bottom of the Management menu to turn up the stepper motor to light the burner, then return it to zero (your idle burn position) and then start your run. In a gas fired boiler, the zero position doesn't shut off the gas completely, you should have an upstream valve for that.

For SCR power controllers with a potentiometer and propane powered boilers, you want to tell the smart still controller that you are using an analog heating controller, even if the SCR power controller has a built-in digital volt meter. This causes the smart still controller to always turn the heating down to zero and then dial up to the setting. Digital SCR power controllers use an encoder dial and every click will result in a precise change, analog controllers and gas valves are not accurate when randomly dialing in both directions.

In my stepper motor driver circuit and code, I do not use step smoothing (micro stepping) because I want precise steps and step smoothing reduces the torque. You may want to mount your stepper motor with rubber grommets on the screws if the noise bothers you. I'm not concerned with the noise, but I know some people who seem to think that all mechanical noise is a bad thing. I just figured that I would add this note and suggested remedy for those people who actually are bothered by the noise.

NOTE: When configuring the heating in the user interface, remember that a straight stepper motor with no planetary gear box has 200 steps per rotation. If you are using a 4:1 gear box, there are 800 steps per rotation.