In this Instructables I will be describing how to build an automatic dog treat/food dispenser using an Arduino Duemilanove (the Uno is the newest version of the same board). The timer interval can be adjusted via a potentiometer and can be set to any min or maximum value in the code. This project does not require extensive coding knowledge knowledge and leaves a lot of space to be modified. It is also designed to use as few parts as possible while trying to keep costs down and dogs happy :)
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Step 1: Parts Needed
Step one is to gather the parts needed.
1 or more dogs (these are imperative for quality control and testing purposes! Cats can be used as a substitute in a pinch but results cannot be guaranteed)
1 Arduino board (any arduno board will work i used an older Duemilanove )
1 Standard servo
1 potentiometer (any valued potentiometer will work, i used a 50kohm)
1 9v battery and holder
1 LED (not required but fun for blinking)
1 1/4 (6mm) x 3.5" x 36" Plywood
2 sheets of acrylic 11" x 14" (you can use any thickness or even substitute it with plywood however you wont be able to see into the case)
*NOTES* - templates are provided as a reference when cutting the various parts however always double check as they may not be 100% accurate.
Step 2: Build the Base Box
Cut the parts for the outside box out of the 1/4 (6mm) x 3.5" x 36" Plywood sheet. Glue the bottom and the two sides together but don't add the top piece yet.
*Notes* - Acrylic can be used here for a fully clear box
Step 3: Build the Servo Holder
Cut the parts for the servo holder and glue them together using hot glue, super glue and acrylic don't mix :( it causes the acrylic to go white)
Cut the parts for the back and front acrylic sheets.
Mount the servo holder to the back plate (horizontally centered ), and approximately 1 inch from the bottom
Glue the back piece to the outside box
*Notes* - don't use super glue!! i made this mistake :( it was the first time i have used acrylic in a project
Step 4: Cut Out the Servo Wheel
Cut the circles out of acrylic. Use a cd to trace out the size of the circle. I used a pare of wire cutters and very carefully cut out a rough circle which i then sanded to a smoother circle as shown in the pictures.
*Notes* - This takes a little while to get right, i recommend practicing on some scrap pieces or use a band saw if you have one (on my wish list :) )
Step 5: Build the Wheel
Attach the servo arm to one of the circles making sure it is centered.
While that is drying cut out the rest of the pieces for the in the wheel. Fit one piece into the other to create an X and glue this to the wheel (see pictures).
Once the wheel is built use a 2L coke bottle to cover 3 of the 4 quadrants of the wheel as represented by the red in the picture. This leave one segment open for the food to fill
*Notes* - I didn't screw the servo arm back into the servo which allows me to remove the wheel, so far it hasn't fallen off yet (touch plywood:), this also helps when it has to be cleaned
Step 6: Mount Arduino Board and Connect Servo
Drill holes (carefully) to mount the Arduino board.
Attach the 9V battery holder to the side wall with a little hot glue and connect it to the arduino via an old ac adapter end piece
You can either create a servo harness out of some old rc parts laying around (see picture) or cut the connector off the end of the servo wire
Attach the black wire from the servo to GND on the Arduino, the red wire to VCC or 5V, and the white wire to pin 3 on the arduino
Optional: attach the led to pins 10 and 11 (the long pin or anode to pin 11 and the short pin or cathode to pin 10)
*NOTES* - You can install a switch by splicing the 9V battery wire and mount it to a hole in the side (see pics for the addition)
Step 7: Install Top Ramp
Mount the wheel to the servo
Cut out the parts for the top (feed) ramp.
With the wheel mounted on the servo carefully position the pieces for the top ramp (the two square ones) and glue them (see pictures)
Once these have dried glue the third piece
*NOTES* - you may have to sand down some pieces to create a snug fit
Step 8: Install Exit Ramp
Attach the 9V battery clip/holder as shown
(i used a 9v clip and attached it to an old ac adapter end)
Install the exit guard that guides treats to the hole, also install the exit ramp which help prevent treats getting stuck on the ledge as shown in the pics
*Notes* - Make sure to fit everything before you glue it, also test it with the wheel on to make sure it doesn't get stuck
Mount the potentiometer to the front acrylic piece. (i used some hot glue)
Attach the leads from the potentiometer to the Arduino. The first pin should go to pin 4, the middle pin should go to A0 (analog 0 ) and the third pin should go to ground (GND)
You can attach the front piece to the unit using either tape or glue. I'd recommend using tape or adding a set of hinges to give easy access to the Arduino board for reprogramming of testing. However be careful as the acrylic can crack very easily when drilling it
*NOTES* - you may not want to glue on the front piece as this may make getting into the box to modify the code difficult
Step 10: The Code
Connect the Arduino to your computer via USB ( if you don't know how or are not sure as to how to do this see http://arduino.cc/en/Guide/HomePage )
Download and open the Arduino IDE from http://arduino.cc/en/Main/Software
Copy and paste the code below:
//BEGINNING OF CODE
//Author: Shane Halse
#define fill 155 //the position in degrees to fill the hopper
#define empty 20 //the position in degrees to empty the hopper
#define potPin A0 //this is the pin (must be analog) that the middle of the potentiometer is connected to
#include <Servo.h> //this is a library used to control a servo (for more information see www.arduino.cc for more info)
Servo mainServo; //declare the main servo
int trigger = 0; //this is used to switch between fill and empty
int potIn = 0; //this is the data read from pin A0 (the potPin)
int count = 1; //used as a time muliplier
mainServo.attach(3); //tell arduino which pin the servo is on (the white wire from the servo)
//set the pin modes
pinMode(4, OUTPUT); //used to output 5V or High to the potentiometer
pinMode(10, OUTPUT); //used for the led
pinMode(11, OUTPUT); //used for the led
digitalWrite(4, HIGH); //set pin 4 high
digitalWrite(10, LOW); //set pin 10 low
potIn = analogRead(potPin); //read the position the potentiometer is at
//if the trigger value is 0 fill the hopper
mainServo.write(fill);//move servo to fill position
//this is used to setup the delay
//count = 171 //uncomment this to set the max delay to 3 hours
//the delay below is calculated using potin (which can be 0-1024) as delayinseconds ~= 0 - 64 seconds
//this is to make the LED flash every 100+potIn miliseconds
digitalWrite(11,HIGH); //set led to on
digitalWrite(11,LOW); //set led to off
count = 1;
trigger = 1; //change trigger to 1 to setup empty
digitalWrite(11,LOW); //set led off
mainServo.write(empty); //set the servo to empty position
delay(1000); //delay while servo sets position
trigger = 0; //change trigger to 0 to setup fill
//END OF CODE
Connect the Arduino to your computer
click the compile button
Upload the compiled code to the board and it should start working automatically
You can then mount the unit to the wall, place a bowl under the unit and let the fun ensue!
*NOTES* - If you want you can add some sort of button your dog presses to get a treat rather than waiting and you will have just made the famous Skinner box!