Beer CO2 Saver

1. Have you ever lost all your CO2 due to a leak?
2. Have you had trouble finding a CO2 leak?
3. Have you ever put in a new keg and lost all your CO2?
4. Would you like to know if your CO2 level is dropping?

Well, you are in luck, Beer CO2 Saver fixes all these issues.

Overview

Beer CO2 Saver adds a CO2 valve and a CO2 pressure sensor to your CO2 manifold. The system is controlled by an ESP32 microprocessor, and your phone or computer is used to see status and make settings.

Almost all the time your CO2 system has no CO2 flowing. When you pour a beer a small amount of CO2 is used. When a leak occurs all your CO2 is lost. With this system the CO2 is turned on for a few seconds every hour. During the hour the system measures the CO2 drop. If the drop is too much a leak is likely. When you have a party and are pouring a lot of beers you can turn the CO2 on all the time or set the rate for 5 minutes. 

Features:

1. Provides displays via a VGA Monitor
2. Control via a PS2 keyboard
3. Displays current CO2 pressure in psi
4. Displays when to replace CO2 canister
5. Displays when a leak is detected
6. Turns off CO2 when a leak is detected
7. Displays of plot of the CO2 pressure with a linear regression fit
8. Provides alarms when a CO2 pressure problem is detected

Theory of Operation

The theory of operation is quite simple. The solenoid valve is turned on for 5 seconds and then turned off. The maximum pressure is measured while the valve is on. While the valve is off the pressure is measured every 10 seconds. If the CO2 pressure drops below 100 psi you have a leak. When a leak is detected, the CO2 is not turned on again.

A pressure gauge is installed between the CO2 canister and the valve. This valve will show if there is a leak in this small manifold. When you replace the canister, turn the CO2 on for a few seconds and then off. Wait for about an hour and verify that the gauge reading did not drop.

When a new keg is added and you are over pressurizing the keg to build up the CO2, you will see a very small drop in the CO2 level every hour. After the beer in the keg has become saturated the small drop (a few psi) will stop. If the drop is more than 100 psi in an hour you probably have a leak.

The normal maximum CO2 pressure at room temperature is 1200 psi. When the CO2 canister is put in the keg storage unit the pressure normally drops 300 to 500 psi. So, I choose a 1500 psi solenoid. Higher pressure solenoids significantly increase in price.

I choose a 2500 psi pressure transducer. The voltage range is 0.5 (0 psi) to 4.5 (2500 psi). The ESP32 input pin can read a voltage up to 3.2 volts which is 1687 psi. ESP32 input pins are rated at a maximum voltage of 3.6 volts which is 1937 psi. .Since the normal output voltage is 0.5 to 1.5 volts the ESP32 input pin is safe.

Electrical Pressure Transducer Specs

The following are the specifications for the pressure transducer:

1. Case: 316 Stainless Steel.
2. Connector: water sealed Packard compatible connector.
3. Port thread: 1/8”-27 NPT, can be customized for large quantity.
4. Power: regulated 5V.
5. Current draw: less than 4ma.
6. Output: 0.5 - 4.5VDC, or customized.
7. Input pressure: zero to psi: 5, 15, 30, 60, 80, 100, 150, 200, 300, 500, 1000, 1600.
8. Working temp: -4F (-20C) to +260F (125C)
9. Accuracy: 2% FS
10. Over pressure: more than 150% FS (full scale)
11. Response time: 2ms

The above graph shows the linear response of the transducer:

Solenoid Valve

The following are the electrical specifications for the solenoid valve:

1. Power:                 10.1 watts
2. Holding:               25 VA @ 110 volts = 0.3 amps
3. Inrush:                 50 VA @ 110 volts = 0.6 amps
4. Temperature:        -13˚F to 131˚F (-25˚C to 55˚C)

Solenoid Valve Relay

The following are the relay specifications:

1. 3V Relay Module: Working Voltage: DC 3-3.3V
2. Load: 10A 250VAC / 10A 30VDC.
3. Load Current: 10A max
4. Optocoupler Isolator: 3V/3.3V Power Relay Module Supports Photocoupler Isolation Control
5. High Level Trigger: The Relay Module is Triggered by High Level Signal, Which Can Be Input from Microcontroller IO

Processor Board

Almost any ESP32 processor board will work on this project. The one shown is an example board.

The software is part of my Keg Monitoring software. You can read about it on Instructionables at the following link: https://www.instructables.com/Low-Cost-Beer-Monitoring-System/

The CO2 saver function is included in the Keg Monitor software is available at https://github.com/RickLloyd24/Beer-Keg-Monitor. There are also software writeups to explain key features.

To use the CO2 saver function only, in the “Constants.h” file set the CO2OnlyFlag to true. The above picture is a sample of the main CO2 saver display.

The top line shows the current mean pressure in psi, the slope of the line that fits the current data and the current rate that CO2 is turned on. The slope is determined by a linear regression fit to the data.

The second line show shows the previous CO2 pressure, the previous line slope and how long it will be until the CO2 is turned on again.

The rest of the display is a plot of the CO2 data. The white plot is the current raw measurements from the pressure sensor. The green line is the linear regression fit to the raw measurements. The numbers on the left are the y-axis values in PSI. The numbers on the bottom of the screen are the number of points displayed. The 13^th line provides status information.

The following inputs are available with this display:

1. Pressing the ‘u’ key will update the display and bring the display back from the screensaver.
2. Pressing the ‘a’ key will display alarms.
3. Typing in a number and hitting the ENTER key will update the CO2 on Rate.

If a leak is detected the system turns off the CO2 and sets an alarm that a leak occurred. To find the leak follow these steps:

1. Check the CO2 gauge between the cannister and the valve to make sure you have pressure in the tank. If not replace the tank.
2. Test the manifold first. Turn off all the regulator valves and set the CO2 rate for one hour. Wait at least 5 minutes and then plot the CO2 pressure to see if you have a leak. The pressure should remain constant during the hour. If there is no leak proceed to the next step.
3. If the pressure drops remove the manifold and use soapy water to find the leak. You can hook up a line cord to the CO2 valve to keep it open.
4. After the leak is fixed, turn the CO2 on then off and make sure the pressure does not drop for 1 hour.  Now you know your manifold is good. Proceed to the next step.
5. Turn on the regulator valves one at a time to find which line is leaking. Each time you turn on a line set the rate to 60 to charge the keg. If the pressure drops you know this is the line that is leaking.  When you find the line, that leaks go to the next step.
6. Disconnect the CO2 connector from the keg and repeat the test. If the test passes you know the leak is in the keg. If the test fails, you know the leak is in the CO2 line or connections. You can use soapy water to help you find the leak. If the test passes go to the next step.
7. For Corny kegs the leak is normally around the lid or the relief valve. With the keg pressurized listen closely for the leak. If you don’t hear a leak, use soapy water around the parts. Repair the leak and test the whole system again.