DIY Pet Treat Dispenser

When I first saw Internet-connected pet treat dispensers like PetCube, I laughed them off. “Who would ever want such a thing?” I have cats, but this just felt silly.

Then we went on vacation and left our cats at home (we hired a sitter, of course). There was one day where our sitter’s car broke down, and wasn’t able to come on the day he’d planned. We have an automatic food dispenser and a water filter, but we naturally started worrying about the furrier members of our family. Then I understood why these goofy treat dispenser products exist.

You’re a kitty!

I’ve seen PetCube used, and it seems like a good product. But cloud-based home video products aren’t something I’m terribly comfortable with. So I set out to build my own. (Also, if I’m being honest, I was looking for a tinker project anyway).

Design

The list of features I wanted were:

  • 3D-printable. I wanted to make as much of the body out of 3D-printable parts as possible.
  • Local control. Cameras that phone home spook me. I planned on hooking it up through HomeAssistant to allow remote access.
  • Camera. Of course the whole point is to spy on cats.
  • Audio. Play short sound clips to let the kitties know they’ll get a treat if they come look cute in front of the camera.
  • Dispense on command. No stringent requirements on treat size, consistent dispense count, etc. Enough to make it worth Eleanor’s while, but not enough to make her too fat.

There are readily available components for all of these things. Tying them together on one perfboard was a pain in the butt, but doable. If I were competent at circuit design, I’d probably have done that instead.

Shopping List

These are the components I used to get the job done. (note that any links contain Amazon Affiliate referral codes.)

All told, this was probably around $50 in parts, plus a bunch of crap I already had lying around.

Printing and Assembling the Body

STLs are on Thingiverse.

I did not adjust parts to be in the proper printing orientation. It’s usually mostly obvious which way they should be oriented. The only slightly tricky ones are the upper half of the main body, which should be printed with the top facing the printbed (i.e., upside-down), and the hopper, which should also be printed upside-down. There are 10 parts in total

These parts are not very difficult to print for the most part, but there are some bridges that are a stretch. Make sure you’ve got your cooling settings dialed in. PLA is probably fine for everything, but I used PETG for the gears and shaft.

Assembly should be mostly straightforward, but I can post some pictures or a video if there’s confusion.

Controller Circuit

There’s nothing fancy going on here. It’s just connecting components together, but there are quite a lot of things to connect. There’s a sloppy Fritzing diagram and a pin mapping table on the Github project, so I won’t rehash it here.

I soldered everything together on perfboard. For what it was, it came out reasonably clean, but it was definitely a stretch. If I were doing this again, I might take the time to lay out an actual PCB and have one printed.

Software

I have the ESP32 controller firmware I wrote on Github.

When first connecting, a setup AP named ESPXXXX (with random XXXX) will appear allowing you to enter your wifi details.

There’s currently no UI. After connecting to your wifi, the easiest way to configure it is via the REST API (use PUT /settings).

The REST API is documented in the Github README. If there’s enough interest, I can document the setup procedure in greater detail.

The Finished Product

Here are some additional pictures of the guts:

Conclusions

This was a really fun and challenging project. The end result is certainly not as polished as an off-the-shelf product, but I’ve been pretty surprised with how well it works.

My cats are unfortunately only occasionally interested in treats, but when they are, they come running. It serves the intended purpose as well as it can.

There are a ton of independent steps you’d need to follow to reproduce this. Honestly, I wouldn’t recommend it unless you’re looking to get your hands really dirty–no really, like encased in dirt.

Links

Custom Prusa IKEA Lack Enclosure Parts

Earlier this year, Prusa released their take on a 3D printer enclosure made from the famous IKEA Lack tables and printable parts.

There are a wealth of printable accessories for this enclosure.  I’ve found these ones really nice:

I’ve designed a few parts of my own that I’m pretty happy with.  I would not be surprised to learn there are equivalent or better alternatives to these.  I did try looking, but not too hard.  I was happy to have the design challenge.

Fan Mount

Thingiverse link.

Enclosures get hot enough to screw with PLA print quality.  I added a ventilation fan which is capable of keeping the temperature in safe ranges (~27 C).

This is a mount for a standard 120x120mm computer case fan.  I’m using this Corsair AF120 fan*.

The mount slides into a centered cutout approximately 129x129mm on one of the acrylic sheets (I’m using the rear one).  

I had intended for the cutout in my sheet to be closer to 122x122mm, but the company I bought the sheet from didn’t get the measurements exactly right.  It was nice to be able to easily resize the part in Fusion 360 and print it out to-size.

1″ Grommet

Thingiverse link.

I drilled a 1″ hole through the bottom table to feed these cables through:

  • Two Logitech C270 * USB cables
  • LCD ribbon cables
  • 24v cables from the PSU

To make the hole look nicer I “designed” a grommet to fit the crappy hole my 1″ drill made.

Birdseye Mount for Logitech C270

Thingiverse link.

The Logitech C270* is a super cheap (~$20) 720p USB webcam that works really well with Octoprint.

I have two of them in my setup.  First, the aforementioned x-axis mounted camera.  Great for making sure the print is looking good where it’s at.  Example view:

And the one placed in this mount, which gives a birds-eye view of the whole print bed.  Example view:

Modified Door Handles

Thingiverse link.

I redesigned the included door handles from scratch, mostly in order to improve my Fusion 360 design skills.

There are a few aesthetic differences, but the functional difference is that there are recesses appropriately sized for some 20x10x2mm N50 magnets* I had laying around.

Control

I’ll share how I’m controlling the fan and lights in a future post.  Long story short, it’s an ESP8266 with some MOSFETs and ancillary circuitry.

[*] Contains affiliate link

Reusable Dash Button Case

I use Dash Buttons* in quite a few places around my home — mostly as a substitute for a light switch where one is inconveniently located, or not present at all.

I prefer them to alternative options like the Flic Button* because they’re dramatically cheaper (a Dash is $5, compared to $35 for a Flic).  They’re also occasionally on sale for $0.99.

My only frustration with Dash buttons is that they’re meant to be disposable, despite being powered by a replaceable AAA battery.  The electronics are encased by two pieces of welded plastic.  It’s easy to break the weld, but difficult to reassemble in a pretty way.

Having recently started dabbling in 3D design and printing, I decided to create a reusable case.  The humble fruit of my efforts is here:

https://www.thingiverse.com/thing:3079607

I’m happy with how this turned out — it’s easy to open the case and replace the battery without damaging anything.

(Dis-)assembly

Pretty straightforward.  I took apart the stock case using some channel locks to break the welds:

With a little bit of elbow grease, and a T5 screwdriver to remove the battery enclosure, it comes apart like so:

A pry tool can be used to remove the PCB if it doesn’t come off by itself.

Assembly is straightforward.  First, put the plastic button and the rubber seal in place.

Then the PCB is placed back on the pegs, battery enclosure placed on top, and T5 screws added back.  Do not over-tighten the screws!  The printed pegs are quite fragile and will break under too much pressure.

After adding the battery back, the lid can be pressed onto the body:

And that’s it!  Fully assembled Dash case.

Update: Sept 4, 2018

I’ve uploaded a slightly modified version.  The main change makes it harder to over-tighten screws making the button unpressable.

[ * ] Contains Amazon affiliate link