Ultimate SodaStream Mod for Endless Seltzer

I upgraded my seltzer machine by hooking it up to a 50lb CO2 tank, with the help of my friend Ian. We're calling it "Endless Seltzer". We both really love fizzy water.

Ian Charnas is a YouTuber who does mechanical engineering, electrical engineering, and computer engineering. In his videos he makes these super fun inventions and raffles them off to support good causes - so you can win almost everything you see on his channel.

We did some research online and found this adapter you can get that connects the SodaStream to a more industrial standard type tank. That's all that's really required for the minimum viable product, but naturally, we wanted to add a bit more engineering so we also built an internet-connected scale that keeps track of how much CO2 is left.

Supplies and Tools:

• SodaStream or similar sparkling water maker
• Tank-to-SodaStream adapter hose
• Crescent wrench
• 50lb (or another size) CO2 tank (from local welding supply)
• Tank safety bracket with strap
• CO2 safety monitor/alarm
• 4x Load cells
• 4x Load cell amplifiers
• ESP8266 microcontroller (we're using the Feather Huzzah)
• AC adapter with microB connector
• LCD display with i2c/SPI backpack
• Solderless breadboard for prototyping
• Solder-type breadboard for finished circuit

Check out the electronics components in a saved list on Digi-Key.

Although you don't have to build the electronics part of this project to enjoy the fizzy benefits, you must understand the dangers of working with a pressurized tank of gas. If it falls over and the valve is damaged, the whole thing could become a dangerous projectile. Basically a missile. The main precaution we're taking is to install a tank strap to the wall. Don't skip this step. I'm also setting up a CO2 safety monitor/alarm just in case there's a leak.

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At my average consumption rate of one bottle (840mL) per day, this tank should last me almost seven years.

I was also interested to calculate the cost savings this setup would generate over time. The big tank works out to about 18 cents per liter of carbonated water before the equipment cost is recouped, where the subscription canister produces seltzer that is about 38 cents per liter all the time. 

We drove the van over to our local welding supply shop to pick up the tank, which although called a 50-pound tank, that's just the weight of the gas inside. The full tank weighs 160 lbs. So by far, the hardest part of this project was hauling it up the stairs. At least it'll be about one-third lighter when it's empty!

We did some research online and found an adapter that connects the standard industrial-type tank to the SodaStream.

The SodaStream end of the hose has a separate piece that screws in where the small tank normally would. The tank end of the adapter hose tightens onto the tank valve with a crescent wrench. I couldn't get a crescent wrench into the tight spots on the SodaStream, so I used a pair of vicegrips to tighten that. Lastly, the hose end's quick-connect plugs into the end piece.

That's all that's really required for the minimum viable product here, but we wanted to add a bit more engineering so we also built an internet-connected scale that keeps track of how much CO2 is left.

Although you don't have to build the electronics part of this project to enjoy the fizzy benefits, you must understand the dangers of working with a pressurized tank of gas. If it falls over and the valve is damaged, the whole thing could become a dangerous projectile. Basically a missile. The main precaution we're taking is to install a tank strap to the wall. Don't skip this step.

Since we're mounting to brick, we picked up a specialized masonry drill bit in the size specified by our mounting hardware instructions, and used the hammer setting on my drill to make the holes. The strap bracket then screws into the anchors, the tank and scale get into position, and the tank gets strapped in.

I intend to keep the tank valve closed when I'm not actively carbonating, but just in case there were to be a slow leak, while it's not terribly likely, I wanted to take one more safety precaution since this thing is in my house. I picked up a carbon dioxide monitor with an alarm, and installed it low to the ground near the tank.

To build our scale, we're using load cell sensors. These are the same types of sensors as in your typical bathroom scale. They convert pressure into millivolts, a signal that is then amplified by a load cell amplifier before outputting to our microcontroller. We wired up a solderless breadboard prototype to test out these load cells, and amplifier, as well as the LCD screen.

The microcontroller connects to the wifi and lets me know how much CO2 is left.

We goofed and got the type of load cells that can't be combined through a single amplifier, so we made do with the two amps we had and attached them in opposite corners of the scale. It'll reduce the accuracy of the scale, but then again I only need to know when it's getting close to empty, not right down to the gram.

Next up, it's time to build the scale, starting with the electronics. We soldered up a perfboard version of our earlier circuit prototype and attached the load cells with long wires.

Typically you would use four load cells to build a scale, one in each corner. Then a plate presses down evenly on the sensors, and there isn't a lot of clearance between the tall part of the sensor and the rest of it. We constructed the scale from pieces of scrap plywood I had around, and then we reinforced the corners with pieces of metal so that the heavy tank doesn't just deform the plywood onto the sensor. The scale consists of a base piece, the top plate, four sidewalls, and a middle piece where the load cells will live, which has a cutout for the electronics. No fancy woodworking here, just a few pocket holes to stick everything together.

This design is also suitable for building a scale inside a kegerator, just adjust the dimensions to fit the size of your keg.

Thanks for reading! I'd love to hear your thoughts in the comments below.

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