Initial Phase
Our very first idea involved a cylindrical container with hollow axis down the central axis and 5 compartments. Four compartments contains one liquid each and one compartment contains cooked tapioca pearls. The bubble tea cup would be carried on a conveyer belt and stop under each drink’s tap to receive the drink. We chose this idea as we thought that this would make the workflow very simple, as well as make it possible for different drinks to be dispensed simultaneously at once. However, we discarded this idea as we later learnt that it would be difficult to customise a hollow exterior of these large dimensions (each compartment was intended to store 5-10L of drink). Additionally, the conveyer belt would be hard to construct mechanically, and the simultaneous dispensing of drinks would be computationally very challenging to code for.
Draft 1: conveyer belt
Hanyang recommended that we bought a watertight exterior that is commercially made and sold. Immediately, we thought of this three-compartment liquid storage container that we can often see at pasar malams, containing drinks like blueberry, bandung and lime soda. We then thought to make the central compartment the electronics box while using the other two compartments to store liquids for dispensing. By using food grade bags, we were able to use an even bigger number of liquids to make more combinations of drinks.
At the same time, we were brainstorming what kinds of pumps to use. Peristaltic pumps are one of the most common pumps for volume-controlled dispensers. We read up on electronic circuits and decided to use a voltage regulator as well.
Draft 2: reality check
Draft 2: Our very first block diagram
Finally, we settled on Draft 3 for the machine. Multiple drinks will be stored inside a large container, and each drink is connected to a pump which channels liquid towards the cup in the middle. Electronics (not shown in the drawing) will be placed behind the liquid storage.
Draft 3: Final design for machine exterior
Prototype
Now that our final design is roughly decided, our next course of action was to test out two key components of the internal mechanics: Dosing control and the pearl transporting mechanism.
We had done a timing-controlled dosing control initially. However, we realised that this was problematic as the volume dispensed was dependent on the length of the plastic tubing connected to the pump as well as the volume of liquid in the container itself.
After which, we switched to a weight-controlled dosing control with the aid of a load cell. The system worked in delivering our desired volume of liquid regardless of external conditions. Here is one of our first successful runs! Initially, we used Arduino IDE to calibrate the weight of the container before each round of dispensing, explaining why we used the computer at the start. And as we had not incorporated the code into Arduino Cloud yet, we used a button in the 4×4 button grid to initiate the dispensing process.
To test whether an Archimedes screw pump was suitable in transporting pearls, we first constructed a plastic prototype with a 3D printed (non-food safe) Archimedes screw. Even though the pearls did not exit through the spout at this stage, we knew it was because the plastic top lid was not secure enough and that the spout was too small.
Once we have confirmed that that approach works in transporting pearls upwards, we bought a chocolate fountain (containing an auger within as the mechanism that transports liquid chocolate upwards, and tested it out using our pearls. Here’s a fun video capturing our delight when we found out that the auger indeed could transport pearls, and that this was a suitable approach. After which, we extracted the auger from a new chocolate fountain machine, and this would be used for the bubble tea machine.
Final Product
A sight to behold – our fully automated bubble tea machine!
Dimensions: 67cm x 41cm x 34cm
Dimensions of machine
Here’s a video of it in action!
Upon the press of a button (Milk tea 50% Sugar), a prefixed weight of boba is seamlessly dispensed, followed by milk tea and finally sugar syrup. This is just 1 out of 9 of our unique combinations of bubble tea!