Coffee Ground Arm

The purpose of my device is to aid with making coffee in the morning. Specifically, it helps with transporting coffee grounds from the container it is in to the coffee machine in a spoon. In order to know where the coffee machine is, and how much coffee is on the spoon, an ultrasonic sensor and a force sensor are utilized. The assembly consists of a base made out of cardboard, and popsicle sticks to create the arm. At the end of the arm a plastic spoon is attached. The force sensor is attached to the spoon, and the ultrasonic sensor is connected to the arm.

There are two positional servo motors that control the movement of this arm. One motor controls the up and down motion of the popsicle stick that the spoon is connected to (servo 1). This motor is programmed to start pointed down, directly at the coffee container. Once the force sensor registers a significant force this servo rotates 90 degrees, raising the spoon to be parallel with the countertop.
The other positional servo motor (servo 2) controls the left and right movement of the whole arm. At the start, servo 2 rotates back and forth until the force sensor registers a significant force. Once it does, servo 2 stops movement while the other servo rotates the spoon, containing a spoonful of coffee, up. Next, once servo 1 reaches its 90 degree position, servo 2 continues to move left and right. The extent of its movement depends on the reading from the ultrasonic sensor, if it doesn’t find the coffee pot (the reading is not equal to the correct distance that the coffee pot is away), servo 2 continues to move. It continues to 180 (the full scope of its rotation) if the angle it stopped at is less than that value. If it is already at 180, or reaches it before finding the coffee machine, it will then turn back towards the 0 degree position. Once the reading from the ultrasonic sensor is in the correct range, servo 2 stops. Servo 1 then moves the spoon down to once again be perpendicular to the ground, dumping the coffee in the coffee machine.

1 Force Sensitive Resistor DF9-40

1 Ultrasonic Sensor

2 Positional Servo Motor

4 Tongue Depressor

Cardboard ~ 230in^2

1 Plastic Spoon

1 Toilet Paper roll

1 Small Item for Weight (I used a York Patty)

1 Arduino Board

1 Breadboard

1 10k Ohm Resistor

1 Wire Kit

1 3-wire extender

1 USB Cable A to B

1 4-wire harness for color sensor

1. Connect both servo motors to the breadboard and the arduino, each in an individual port.

2. One servo should be taped to the inside of the toilet paper roll, and the rotating part should be taped to the underside of one tongue depressor. On the top side of the depressor, tape a counterweight, in my case I used a York peppermint patty, but anything small that has some weight would work.

3. At the other end of this same tongue depressor, the other servo motor should be taped to the top side, but the servo should be positioned on its side. The rotating portion of the servo should face you as you build it.

4. On the rotating white portion of this servo, another tongue depressor should be taped.

5. At the end of the depressor, a plastic spoon is taped to the short side of the tongue depressor. The spoon should face up towards the sky.

6. Connect the ultrasonic sensor to the breadboard and the arduino, the echo pin and the trigger pin in one port each. The ultrasonic sensor should be taped to the top of the first tongue depressor, on top of the counterweight, facing the second servo and the other tongue depressor.

7. Connect the force sensor, including a 10k Ohm resistor between the sensor and ground.

8. The force sensor should be placed in the spoon, and loosely taped. The force sensor is very sensitive, so it is important to not place too much force on it with the adhesive. However, it is also important to make sure it is flat on the spoon, so that coffee grounds do not get under it.

Once assembled, the machine is easy to use. Simply place the mechanism above the coffee container, and in close proximity to the coffee machine. It should begin with the spoon/tongue depressor facing down, perpendicular to the countertop. The spoon should be touching the coffee itself. Once the code is sent to the arduino, it will start. The force sensor will search for enough force (coffee), and once it does it rotates the spoon up. Next, the arm will search left and right until it finds the coffee machine, and then dump the coffee in the proper place. It is important to make sure the coffee machine is close enough for this, so that coffee does not go flying all over the kitchen.