Harry Potter HAPOMAGMG Self Stirring Mug, Metal, 450mililiters

Product Information

Tip: If you don't have access to a 3d printer you can simplify the mechanical assembly by salvaging a large cog or wheel from a scrap printer. Fix this to the motors drive shaft then glue on your spoon, simple!

The drive plate assembly consists of two pieces that are glued together. Make sure that the centers are aligned to allow the motor shaft to fit. You may need to use a countersinking tool to make a recess in the base of the smaller plate, this will allow the assembly to slide further down the motor shaft if necessary. Ever since I discovered the joys of etching my own PCB I never miss an opportunity to make one, so if you're well practiced you could probably churn out the whole circuit in under an hour. I've included the PCB file as well as ready to print PDFs of the PCB layout. If you're stripboarding I've also provided the circuit schematic for you to follow. For the lighting we are using a SMD 5050 light strip. These are really versatile light strips that are bright, offer RGB colour and can be cut to the desired length. As water is also used in this project I'd recommend getting the waterproof ones. The strips often come in kits that include a controller, you can put that to one side for another day as we don't need it, ours will be driven by a PICAXE microcontroller. For anyone who is not familiar with the Self-Stirring Cauldron, it appeared in Harry Potter and the Philosopher's Stone. It was invented by Gaspard Shingleton and was sold in cauldron shops to assist the owner in the stirring of his or her potions. But of course, you could always use a potion stirring charm. The cauldron also has a choice of three stirring actions, making it suitable for mixing almost any potion. The Cauldron is made up of four main elements, the Stirring Action (we'll be using a stepper motor for this), the Lighting (LED strip lighting) and the visual Fog Effect (here we'll be using dry ice, more on this later) ohh and of course the Cauldron (ideally a witchy type one but you can use anything you can get your hands on, I hear saucepans are all the rage amongst muggles!).For this I salvaged some cables with 2-way header connectors from a scrap PC (they are used to connect the PC front panel to the mainboard). Cut the cable to around 70mm length (connector included) then strip and tin with solder as shown in the photos provided. The motor and the lights are controlled by the PICAXE microcontroller, to achieve this we use two separate programs that run as parallel tasks on the PICAXE (I believe this is only possible with the newer M2 chips).

To create the stirring effect we are using a stepper motor, I've opted for the 28BYH-48. These motors are manufactured in large volumes so they are so cheap they're practically giving them away. They are known for missing the occasional step so not great for high precision tasks, but they are small and provide a lot of torque thanks to its 64:1 gear reduction ratio. You can read more about this motor here. The motor is commonly supplied with a ULN2003 driver, which is perfect for using with our PICAXE. The motor control is covered in more detail in the next step when we program the PICAXE.

The circuits are fitted to either side of the main enclosure, there are pilot holes to enable the PCB's to be screw mounted, but I opted to use hot-melt glue to secure mine. To summarise, we have a PICAXE directly controlling the Motor Driver board via four outputs. The PICAXE is then switching a pair of darlington transistors via another two outputs to control the LEDs. We have a switched 4.5v battery source (3x AA's) feeding the PICAXE, the LED strips and the Motor Driver. Don't be fooled by the PP3 connector in the photos, this does not connect to a 9v PP9 battery!! It connects to a AA battery box. The crescent shape on the front of the enclsoure is a water tank, it also has a Max Fill level marker for your reference. This can be used for the purpose of adding a fog effect to your cauldron with the aid of some dry ice (more on this in the next step). Included with the STL files is the water tank assembly. This consists of a removable tank that has a carry handle to make filling and emptying easier. Just glue the handle bar in place and it can be used to lift the tank in and out. Choose one of the three stirring action pieces and slot it onto the drive plate. Line up the four pins and it should slot on securely. If the fit is too tight, use a round file to make the holes on the action plate a little larger. The cables can been hidden in the battery recess below the motor assembly, I used a cable tie with a self-adhesive tie mount to keep them in place.