Open Source Food Pellet Dispenser

thingiverse

This food pellet dispenser was developed by Dr. Andrew Maurer's Lab in the McKnight Brain Institute at the University of Florida. The dispenser is made up of four separate 3D printed components and uses a bipolar stepper motor to dispense individual 45mg food pellets one at a time. A highly accurate infrared break-beam sensor attached to an external interrupt pin keeps track of how many pellets have been dispensed by the machine. The dispenser is designed to be operated with an Arduino using an Adafruit motor driver shield, or any other micro-controller and H-bridge that can handle the motor control. Parts List and Code Examples Part List 4x - M3 0.5 hex nut (McMaster-Carr part number: 90695A033) 2x - M3 35mm socket cap screw (McMaster-Carr part number: 92095A201) 2x - M3 50mm socket cap screw (McMaster-Carr part number: 92095A475) 1x - 3mm IR break-beam (Adafruit part number: 2167) 1x - Adafruit Motor Shield v2 (Adafruit part number: 1438) 1x - Nema 14 bipolar stepper motor (Pololu part number: 1208) Code Examples Break-beams are interrupt driven to keep track of the number of pellets dispensed by the machine. The Adafruit motor driver library was used to handle all motor control operations. void beamBroken_isr(){ noInterrupts(); pells--; disp++; broken = true; Serial.println("Beam Broken"); if(disp == 5){ disp = 0; rot = !rot; } interrupts(); } The dispenser is set up to switch the direction of the rotor after every five steps, which was found to reduce jamming and crushed pellets significantly. A delay of 100ms was added after each step to help the break-beams detect individual pellets accurately. if (f == "disp" || f == "Disp") { pellsR = param; Serial.print("Dispensing "); Serial.print(param); Serial.println(" pellets"); while(pells>0){ if(rot == false){ myMotor->step(25, FORWARD, SINGLE); delay(100); } else if(rot == true){ myMotor->step(25, BACKWARD, SINGLE); delay(100); } }