uArm Vending Machine

I burned out one of the servos in the arm and uFactory were kind enough to send me another one. As it turns out I had miscalibrated the arm when I assembled it. This happened to more people than me so they made a video explaining how to do it. So that's that problem eliminated.

Our dream is to make a web interface like the one in Yu Jiang Tham's Bar Mixvah:

This should satisfy the Hackaday Prize requirements for connectedness. However, I've only ever programmed in Matlab and Arduino, and the MEAN stack is quite intimidating. Hopefully we can make this work by mostly using Yu Jiang's interface and back end. It's all there on his blog. We met Yu Jiang at Startup Reykjavik 2014, so we might be able to get some tips from him when we run into trouble.

It takes some trouble to get all this software running on a Raspberry Pi, and I'm currently stuck at installing MongoDB. It even took me days just to get Raspbian running on the machine because NOOBS wasn't able to install it. In the beginning we should probably skip the fancy tablet ordering and just use the numpad right on the machine. Just get it making doughnuts, right?

Another aspect of connectedness is using SSH to access the Raspberry Pi. That way you can reprogram the vending machine from any computer.

The third aspect of connectedness is getting push notifications when supplies run out or something goes wrong with the machine. There's no rush to figure out how to do that because this prototype is just a proof of concept and probably won't be used as a commercial vending machine. We'll be around when things go wrong.

We see that the uArm can pick up a frying basket and put it back into the pot:

But is this repeatable?

We need to improve the design of the carousel so that the uArm can turn it. Making the nibs bigger should do the trick.

We used a cheap and simple home doughnut maker.

The dough has to be so runny that it pours through the valve by itself. Yeast based dough is probably a no-go because it expands continuously, making the first doughnuts of the day small and tough, and later on they’re big and fluffy. This recipe uses baking powder: https://uk.answers.yahoo.com/question/index?qid=20061010051311AAEFQb1

This dough is still too thick to flow, so we added some milk.

The fetus-shaped pastry is our first attempt. As you can see they rapidly improved. You only have to open the valve for half a second!

We also tried a thicker mix. Then the valve had to be kept open for five seconds. You got bulkier doughnuts with a crispy crust and they took longer to fry.

This is one way to frost the doughnuts:

But you get frying oil in the frosting. Next we tried a syringe:

The frosting melted in a few seconds. We tried letting the doughnuts wait for 0:30, 1:00, 1:30 and two minutes before frosting. You need at least two minutes, which is too long for a vending machine.

We refrigerated the frosting syringe and tried again. This time 30 seconds is OK. The frosting starts melting after maybe a minute on the doughnut, but by then you have the doughnut in your hand.

All in all, we think we can make doughnuts on demand.