Airlock Bubble Sensor Mount

One of the most useful things I have made for homebrewing is a device that counts the bubbles as they pass through an airlock during fermentation. I find this to be a great way of monitoring yeast activity and for telling me when the fermentation has finished. It also allows me to estimate the strength of the fermented beer. I could sit and count them visually I suppose, but the record this device has counted is about 250,000 bubbles for a single 6-gallon fermentation. The sensor used to detect bubbles passing through is a simple HY810A I.R. opto-coupler of the type used on a lot of electronic devices to detect movement (e.g. tachometers) or when a cover is closed or a part is properly installed. Originally, I just taped the sensor to the airlock using black electrical tape—but that was messy and tedious. I eventually 3D-printed a mount for the sensor that just clips onto a standard S-shaped airlock in seconds and does a great job of detecting bubbles as they pass through.

An STL file