Automatic French Press
Joseph Stull & Tusharika Tiwary
TA: Tom Houlahan
• To automate the process of brewing
French press coffee.
• Combine quality coffee with convenience
• PIC controlled Stepper motors used to move the
plunger and bean dispenser.
• Automatic coffee bean measurement and brewing
• Adjustable coffee strength.
• Displays time left for brewing and the temperature
of the water using a seven-segment display.
• Dispenses automatically through a solenoid
Power Supply Circuit
Heating Element & Thermistor
• Thermistor linearized at 99⁰C
• Negative temperature coefficient:
Higher temp. → Lower input voltage
• 10 A
• 120 VAC
• 1200 W
• Controlled by relay
• Pins 1,16 -12V Supply.
• Pins 6,11 -12K pull up resistors.
• Pins 4, 5, 12,13 - GND.
• Pin 9- GND (full steps).
• Pin 10- direction of motion of the
-bean dispenser : CW
-plunger motor : CW (down)
: CCW (up)
• Pin 8- irrelevant (relevant only
when voltage at pin 9> 2V)
• Rubber wheel with teeth(for Friction)
mounted on plunger motor.
• Plunger supported by 2 rubber
wheels with built –in teeth.
• Gear mechanism in motors- Torque
• Built-in triangular mesh on heating
• FDA approved parts.
Observations and Testing
• Power Supply
Output of Transformer:-
12 V Regulator Output: 5V Regulator Output:
- At 5Hz, takes 285 steps to move to
the bottom of the beaker.
– 57/12=4.75 secs at 60 Hz.
– Factor to be considered- Finely ground coffee beans.
Motor gets jammed otherwise.
• Motor Drivers
– Pin 10 to ground- CW
– Pin 10 to 5V- CCW
– Solenoid valve needs voltage >=12V to open.
Voltage we provided- 12.425V
– Pressure it can take- 0-0.005 MPa
– Tested with multimeter
• Worked modularly.
• Difficulties with integrating the PIC to the
• Modular breakdown before testing.
• Finalize elements values before ordering the PCB.
• Choose thicker traces to safeguard circuit.
• For better connection, solder on both sides of
• Transistors over relays.
• Gear mechanism to provide more torque
• Adjustable steeping time
• “Beep” when coffee is finished
• Touch screen interface
• Built-in milk frother
• Built-in coffee grinder
• FDA approved food grade parts
• Insulation on heating element
• Grounded body for safety
• Circuit protection
• Prof. Scott Carney
• Tom Houlahan
• Mark Smart (Parts Shop)
• Craig Zeilenga (Machine Shop)