Well after finishing, what I guess you call, the mini 120V hybrid PID BrewTroller controller I had to keep going since I was on a roll. When I decided to integrate the basic BrewTroller BX1 board into my system so I could begin to see how I can exploit all it’s features. Well one of those features is it’s ability to measure volumes in a vessel using pressure sensors. Volume measurement is not only convenient it helps improve brewhouse efficiency through the ability to accurately determine strike water volume, pre-boil and post-boil volumes. Volume measurement is achieved by using pressure sensors and a vertical small diameter tube mounted in the vessel with the end of the tube as close to the bottom as possible. When height of the liquid increases in a vessel the pressure also increases in the tube as the liquid rises in it. The tube is connected to the sensor with flexible tubing. The sensor sends a signal to the BrewTroller and it is interpreted by the BrewTroller software. After entering a few reference calibration points in the BrewTroller software it is very accurate. One problem is when temperatures in the vessel decrease a vacuum can be created in the tube but if a steady stream of low pressure air is fed into the tube the interference is eliminated. This is accomplished by using a small air pump like those used for aquariums. The diagram below, from Open Control Systems, shows how a “bubbler” system is setup.
Armed with this knowledge, and a couple free scale sensors, I was ready to build the sensor enclosure. I decided to do a remote enclosure for the volume measurement components for a couple reasons. First of all there is no way it would fit in my latest creation and secondly the motor on the pump could cause EMI interference with the BrewTroller itself when in the same enclosure and sharing the same power supply. An added benefit is if I’m not using the BrewTroller I can just disconnect the sensor setup and if I ever built another BrewTroller control panel I would already have the volume measurement part ready to go. Having two sensors gives me the flexibility of monitoring volumes in two vessels when brewing two vessel Brutus 20 style.
First obstacle was what to use for an enclosure? Well since everything else in my system is compact it was obvious I would need to keep this project the same. Luckily the local Radio Shack had a plastic project box for $6.00 that is 6″ x 4″ x 2″, perfect. Next was the air pump and even the smallest aquarium air pump would be too large for the small project box. Well we had a dead Keurig coffee maker and I knew they had an air pump of some sort. Score! After tearing it apart there was a small 12V air pump and a bunch of small silicone tubing in the thing. Easiest way to power the air pump and keep things compact was just to use an AC wall adapter I had laying around. The sensors would get their 5V power through the data cable from the BrewTroller. I had the panel jacks for the power and data cable connections as well as a power switch for the pump. The data cable was four conductor cable from a dead computer keyboard. The only other thing I needed was a couple small tees and valves for the air lines and a quick trip to the pet store solved that. The valves allow you to adjust the flow of air going to the stainless tubes in the vessels to a slow flow of only a few bubbles a second.
The assembly was very straightforward after a couple quick mockups. I did decide to use some quick disconnect fittings, I found on eBay, for the tubing that will go from the box to the vessels to keep things cleaner and easier to store when not being used. The only difficult part of the build was constructing the cable that goes between the sensor enclosure and the BrewTroller control panel. The 4-pin mini XLR connectors have tiny solder connections that are embedded in a not so heat resistant plastic and they are very close together. After some very careful soldering it was done and everything worked as it should, the BrewTroller detected the sensors and the air pump worked great.
As soon as I finish some work to the kettles it will be time to brew a batch and try everything out. Meanwhile a brew day on the previous system is definitely in order since the beer reserves are running low.
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