Obey Your Cat's Demands and Build an Automated Food Dispenser 14632

DN Staff

November 9, 2016

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

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 the image below to see the build process for the cat food dispenser. 

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

 

Photo22-zzzzzz-su-dispenser-04_0.jpg

 

 

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 DispNHD-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

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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