Obey Your Cat's Demands and Build an Automated Food Dispenser

By: 
September 27, 2016

Cat owners know that few things make their pets happier than getting their food on time. But sometimes those times aren't always the most convenient (for humans at least). You can't leave a bowl full of food (if you want to still be able to lift your cat anyway). So it needs to be dealt out in small portions.

Gadget Freak contributor Kerry Erendson combined some engineering know-how with some skilled 3D printing to create an automated cat feeder for his cat, Squishy - who prefers to be fed precisely at 10 a.m. and 3 p.m. every day.

The goal was to be able to set the unit to vend dry cat food at programmable times throughout the day. To allow this, there is an LCD on the front panel with three "soft switches," i.e. switches whose functions are defined by software. These buttons take on the functions labeled above them on the bottom line of the display.

The main screen's top line shows current time. The bottom line labels the left button "MENU" and the right button "ON/OFF." Pushing the right button on this screen toggles the label between ON and OFF. The bipolar LED to the right of the display is green when the unit is ON and unlit when the unit is OFF. This ON/OFF status determines whether the unit will "vend" when it reaches a programmed vend time. The LED allows you to check its status from across the room without looking at the LCD. The LED turns red if an error is detected.

The "MENU" button takes you through a series of choices "Program?", "SetTime?" & "VendNow?" (see "Dispenser Operation Manual.doc" for details).

Well, Squishy loves her feeder, finding it far more reliable than the humans who used to do that job.

The unit uses eight different 3D-printed parts:

1) Food Bin that sits on top under the clear cover.

2) Top Surround that you slide up & off to get at the cover and bin.

3) Spacers are little tabs/washers under the Top Plate's screws (8 screws total)

4) Top Plate has the round area where the Food Bin sits and rotates.

5) Enclosure is the white bulk of the housing, has integral curved chute inside.

6) Bezel has LCD window opening and holes for pushbuttons, all matching the PCB layout.

7) Bottom Surround provides the base structure and solid cross member to support the motor.

8) Rotator has a D-shaped hole all the way through to mate with the motor's output shaft. At the bottom it has a section with 8 "bumps" which actuate the microswitch. The rest of the length is a square that matches the center of the Food Bin that slides down on it.

Click here to download the full build instructions, including SketchUp files, firmware, and schematics.

Parts List:

Part Value Device/Package   Description
BAT1 BR1225A/FA Battery   Allied #70196821
         
C1 0.01 CNONPOL-0603   Capacitor, Non-Polarized, SM
C2 0.1 CNONPOL-0603   Capacitor, Non-Polarized, SM
C3 10µF CPOL-3216/A   Capacitor, Polarized, SM
C4 0.1 CNONPOL-0603   Capacitor, Non-Polarized, SM
C5 0.1 CNONPOL-0603   Capacitor, Non-Polarized, SM
C6 1µF CNONPOL-0805   Capacitor, Non-Polarized, SM
C7 1µF CNONPOL-0805   Capacitor, Non-Polarized, SM
C8 0.01 CNONPOL-0603   Capacitor, Non-Polarized, SM
C9 0.1 CNONPOL-0603   Capacitor, Non-Polarized, SM
C10 0.01 CNONPOL-0603   Capacitor, Non-Polarized, SM
C11 0.01 CNONPOL-0603   Capacitor, Non-Polarized, SM
C12 0.01 CNONPOL-0603   Capacitor, Non-Polarized, SM
C13 0.1 CNONPOL-0603   Capacitor, Non-Polarized, SM
C14 0.1 CNONPOL-0603   Capacitor, Non-Polarized, SM
C15 10µF CPOL-3216/A   Capacitor, Polarized, SM
C16 0.1 CNONPOL-0805   Capacitor, Non-Polarized, SM
C17 10µF CPOL-3216/A   Capacitor, Polarized, SM
D1 S1GB-13-F Diode, S1BB   Allied #70438453 1A 100V Diode SMB pkg Diodes Inc, notch or line is cathode
J1,J2,J3,J6,J7,J8,J9,LED1 .1" sp. 2-way male header     (J7,J8,J9 used on hand-wired bd., put at LED1 to allow harness to front panel)
J4 .1" sp. 6-pin dual row male header BKGD-1-JDR6 (µC prog. conn.)    
J5   .1" sp. 16-way male header    
L1,L2 MI0603J600R-10 INDUCTOR-0603   ferrite, Allied #70065459
         
LCD1 LCD 8-char. by 2-lines New Haven Disp
NHD-0208AZ-RN-YBW-33V
  Allied #70518050, non back-lit, Dispenser PCB has circuitry for a backlit LCD module but will need firmware mod to control it. Location also implies 16-way .1" sp. dual row female conn. for PCB and .1" sp. dual row male header for LCD module.
LED1  T 1-3/4 Bipolar Red/Green thru hole   needs wiring harness to get it to front panel, also plastic LED panel mount 
PZ1 AI-1440-TWT-12V-R PIEZO2LEAD-.3"LS, .543" dia.   Piezo buzzer, 2 Leads, self-osc.
Q1,Q2 DNI*,Q3 MMBT3904 MMBT3904-SOT23   Transistor, NPN, General Purpose
Q4 2N3904 2N3904-TO92 thruhole   Transistor, NPN, General Purpose, TO92 pkg. (used on hand-wired Relay Bd.)
R1 4.7K RESISTOR-0603   Resistor, SM
R2 220 RESISTOR-0603   Resistor, SM
R3 100K RESISTOR-0603   Resistor, SM
R4 10K RESISTOR-0603   Resistor, SM
R5 4.7K RESISTOR-0603   Resistor, SM
R6 4.7K RESISTOR-0603   Resistor, SM
R7 10K RESISTOR-0603   Resistor, SM
R8 10K RESISTOR-0603   Resistor, SM
R9 10K Trimpot   horiz., thruhole
R10 10K RESISTOR-0603   Resistor, SM
R11 10K RESISTOR-0603   Resistor, SM
R12 10K RESISTOR-0603   Resistor, SM
R13 DNI* 10K RESISTOR-0603   Resistor, SM
R14 10K RESISTOR-0603   Resistor, SM
R15 10K RESISTOR-0603   Resistor, SM
R16 10K RESISTOR-0603   Resistor, SM
R17 10K RESISTOR-0603   Resistor, SM
R18 DNI* 0ohm RESISTOR-0805   Resistor, SM
R19 200 RESISTOR-0603   Resistor, SM
R20 3.3K 1/4W 5% RESISTOR-thruhole   Resistor (used on hand wired relay bd.)
RLY1 NAIS TF2-5V Relay DPDT   Relay DPDT 10-pin DIP NAIS TF2 (used on hand wired relay bd.)
S1,S2, S3 SWITCH-PUSHBUTTON    
U1 MC9S08QE128CLH MC9S08QE128CLH, LQFP64 pkg   64 lead µC, Motorola/Freescale/NXP
U2 TC54VN3002ECB TC54VN4502ECB-SOT23   Volt. Detector, 3-pin Allied #70046939
U3 AT25256AN-10SU-2.7 EEPROM, 32768 x 8 bits, SPI interface   SO8 pkg. (could use much smaller device but might need to mod. firmware)
U4 LP38690DT-3.3 LP38690DT-3.3-TO252   Volt. Reg. 3.3V fixed, LDO National LP38690DT-3.3
U5 DS1338Z-33+ RTC, I2C, SO-8pkg   RTC, I2C, 3.3V
         
U6 LM340T-5 7805V-TO220S-1   Linear Voltage Regulator, thruhole, TO220 Standing up (vertical) Allied #70099955
XOSC1 4 MHz Crystal Osc., 3.3V   7 x 5mm pkg.
Y1 32768Hz Crystal, SM    
         
MOTOR1 gear reduction motor 6V   this was one I had in stock, don't know the specs, possibly 5 sec/rev
  microswitch     microswitch with curved end actuator to detect "Rotator" bumps in both directions
AC adapter 6V 400mA      
         
         

 

Don't forget these are native SketchUp files, so you can open them to take measurements and modify them any way you wish. They were composed in the free version of SketchUp. You will of course also need the free plug-in / extension STL Exporter to create files for your CAM program. These designs are somewhat complex, so you should really have some level of 3D printing experience behind you before tackling them.

The Composite file is great for seeing how it all goes together, but don't forget to do any modifications in the individual file for that specific part. I would save modified files with a personalized name so you don't get versions confused.

Do you have a cool, original, homemade gadget you'd like to share with the world? Give us the details at DesignNews.com/GF, and you may receive $500 and automatic entry into our $6000 Gadget Freak of the Year contest!

[All images courtesy of Kerry Erendson]

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