Tea Timer for Breville HotCup Water Dispenser

Overview

This is an automatically triggered tea timer for use with the Breville HotCup hot water dispenser machines. It fits on top of the cup holder of the VKJ318 & VKJ784 models, and the cup is then placed on top of the timer. When the water is dispensed, the cup gets heavy enough to press a button inside the tea timer, and the timer starts. When the time has run out, the timer beeps for a short while and then goes back to stand-by mode. Three different times can be selected either before or during brewing time using the three buttons on the front. A flashing LED above the active time shows that the timer is currently running. If the cup is removed before the time has run out, a long beep indicates that the timer has been aborted.

Mechanical Parts

I recommend printing in PETG for improved robustness and heat resistance. All parts should be printed in the orientation provided. Several parts must be superglued:

• Glue the clips into the recesses on the platform.

• Glue the axles into the recesses on the base (be careful not to get any glue onto the exposed part of the axle, the clips must be able to turn freely on the axles).

• Glue the feet into the recesses on the bottom of the base.

After installing the electronics, push the clips onto the axles.

I 3D printed a battery holder because I didn't have a proper one in stock when I made the timer. While it has worked for several years now, the contact isn't great (you can hear voltage fluctuations in the beeping frequency), so I recommend using a commercial battery holder (2x AAA) if possible. The clips need to be adjusted depending on the type of battery holder, or you can remove the clips and just glue the battery holder.

Electronics

A simple circuit based on an ATtiny13 (or ATtiny13A) microcontroller must be constructed on a piece of perfboard. There are 4 small pieces of board holding the buttons and LEDs, and a larger piece for the remainder of the circuit. In the schematic, each piece of board is indicated by a dashed line. The boards are connected together with soldered-on pieces of stranded wire (0.14mm² works well). Short screws (5mm or less) are used to mount the boards to the 3D printed base, the corresponding holes in the board must be drilled out to 3.2mm (or 3mm if no 3.2mm drill bit is available). The correct positions for the buttons, LEDs and screws can be seen in the photos.

The button for the cup detection may require some experimentation to get the trigger point right. If the button can be pressed too easily, an empty cup will trigger the timer, and if the button is too stiff, the timer might not trigger at all. Depending on the weight of the cup, it can also help to position the cup further to the back (towards the HotCup machine, for heavy cups) or to the front (for lighter cups) on the platform. As a starting point, a switch with a 2.5N actuation force (usually the "stiffest" ones available) should be selected.

The microcontroller must be programmed with the provided firmware, and AVR ISP programmer is necessary for this. By default (when using the hex file), the three times are set to 3, 5, and 7 minutes. They can be adjusted as desired in the source code. The source code also provides an adjustment factor for the (rather inaccurate) internal oscillator of the ATtiny13. 

Bill of Materials