CO2 Bottle Scale

This is a scale for 500g CO2 bottles which I use with my fish tank. I wanted to receive an alert, when bottle goes empty and digital pressure gauges in the required range are expensive so I built this little scale.

The bottle will need to be stabilized - the scale fixture will not be sufficient to keep the bottle standing. I have a simple ring mounted to the enclosure wall which keeps the bottle upright.

It is designed for a load cell like this one which is 12,7mm (½ Inch) square cross section and 80mm long. The measurements are then received by an ESP32 with an TX711 break-out board and are then transmitted to my home automation using Tasmota Firmware and MQTT.

Assembly Hints

To assemble insert the clamp part into the base from below and glue those parts together using epoxy or similar glue. After the glue has set use bolts (cylinder head hex bolts) to attach the load cell to the clamp from below. The cup attaches to the other end of the load cell through the washer part using two more cylinder head screws (the washer is separate to avoid the needs for supports). I used M4/M5 cylinder head screws for all connections, but I had to recut the threads in the load cell. So maybe these are tapped for some imperial size. YMMV.

3MF Prusaslicer File

The included 3mf file prints in PETG with an 0.4mm nozzle without supports, but with a lot of infill for stability. Print uses approx. 180g of PETG and takes 16h. A full bottle clocks in at slightly below 4kg, so the print is rather solid.

Model Source

You can download the Solidworks Assembly file here. As it was created with the Maker Edition of Solidworks it will also only work in the Maker Edition. Printables.com does not accept the file as "corrupt".