11. Applications and Implications¶
This week I have to propose a final project masterpiece that integrates the range of units covered. The project should incorporate 2D and 3D design, additive and subtractive fabrication processes, electronics design and production, microcontroller interfacing and programming, system integration and packaging
After considering various options, I decided to make an automatic cat litter box, ie. a cat litter box that self cleans after a cat uses it.
Cat Litter Box
I have always loved animals as long as I can remember. Even as a kid I used to sneak stray kittens and puppies into my home without my mom knowing it. As it was very hard to get my neat freak mom to approve of my four legged friends, it was always limited to a cat or a dog at a time. Ever since I moved out and started living on my own, I have been fostering kittens and injured cats. At present I’m the butler to a dog and 6 cats and fostering 4 kittens (from my lab, the Superfab Lab, Kerala) and a paraplegic cat. Living in this multi cat household has made me consider the needs of the individual cats. “Catifying” (This is a word coined by Jackson Galaxy, the cat daddy) a household is a huge task and we have been successful in creating a warm environment for the cats in many ways. But the cat litter box has been an issue. Cat litter box is basically its toilet, a plastic tub where the cat poops and pees and is filled to its one third capacity with a material(called as litter) that mimics the texture of sand will simulate the experience of burying the excreta in soft, sandy soil as they would do in the wild.
The available types of litter in India are
1. Sand- It is the natural litter in the wild but inside aroom it cannot contain the heavy smell of the cat urine.
2. Bentonite clay- these types of clay clumps in the presence of moisture and is ideal as a cat litter but the disposal is a huge problem.
3. Sawdust- Many people use it but as in the case of sand it cannot contain smell, but very easy to dispose of. A very good way of upcycling sawdust waste from wood mills.
4. Wooden pellet- This actually uses sawdust but it compresses it into a small tablet and removes the moisture content. When water falls on it, it will expand and become sawdust again. It can contain the smell as well. This property makes it ideal to be a cat litter. But this is not available in India
Making custom wooden pellets
I was looking for an alternate option for bentonite clay cat litter back in 2015 and read about the use of wooden pellet as cat litter elsewhere in the world. So I decided to work around the problem and approached companies that make Biomass Pellets. These pellets are used as fuel to work large boilers etc. I got the manufacturers to change the properties of the biomass pellets a bit and without adding any kind of chemicals that helps it in combustion. The manufacturers were amused by my call and to hear about this multi-cat circus. A few of them agreed to work with me.
I tested various settings and realised that the moisture content should be much lower than that used for biomass, also the compression needed to be low as I want the pellet to disintegrate as soon as urine falls on it. Then I worked around the size. The least possible size is 6mm and I changed its length to 6mm as well. And I have been using these wooden pellets ever since.
The rule of thumb is that a household should provide one litter box for each cat resident plus one extra. These cat litter boxes have to be ideally cleaned after every use, just like a human would flush down the toilet.
Cleaning the litter box is never a fun task. And leaving it unattended is unhealthy for the cats – and for myself. The solution is an automatic self-cleaning litter box.
Self cleaning Litter Box
Self-cleaning litter boxes are available in the market and they come equipped with a method of detecting when the cat is in the litter box—either a motion or weight sensor. A few minutes after the cat has finished it’s business in the litter box and left, the self-cleaning litter box will rake the litter and deposit the waste in a separate compartment. Some units will rotate to separate the waste. The compartment with all the waste is enclosed and cordoned off, so that the smell is not noxious. Some self-cleaning litter boxes utilize special litter, and others are designed to work with what you already use.
There are some problems with the self cleaning litter boxes available in the market. None of them are using wooden pellets, most of them use bentonite clay and some of them have their own unhealthy choices of litters. Besides they are all super expensive. This is why I needed to design a self cleaning litter box of my own.
What will it do?¶
My self cleaning litter box has to work using wooden pellets and it should sieve the disintegrated saw dust filled with cat urine from the fresh litter. It should also remove the cat poop. And this leaves a good toilet for the cats all the time. What I will need is:
* As input:
Must have: A motion sensor to detect whether the cat is using the litter box. It should only work when the cat leaves the box.
Want to have: A day/night detection system
Nice to have: A height level detection of litter in the box * As Output: Must have: A system that removes cat feces out into the waste bin(may be using a combination of DC motor and servo motor)
Want to have: Lights surrounding the litter box for the cat to see it at night
Nice to have: An automatically filling mechanism for new litter
Who has done what beforehand?¶
Commercial Cat Litter Boxes:
1.Litter Robot A rotating self cleaning litter box
Projects and weekly assignments related to cats by Neil’s students
1.Litter Robot Evo A cat litter Robot repair by Florent Lemaire from agrilab of 2020 batch.
Although he is from my batch of 2020, due to the crazy schedules due to COVID-19, Lemaire had presented it to Neil while I was still considering the cat litter box as an option for the final project. This project is a repair of an existing litter robot.
The following are some projects for catifying the house, but none of them are litter boxes.
2. C.A.Ts Automated cat feeder by Toni F. Barreiros from Fab Lab Aldeias do Xisto of 2017 batch.
3. Mirru in-mirru out Cat entrance door system by Pamela Martello, Shanghai 2019
4. Black Jack Automatics water fountain for cats by Francis Lance from echofablab of 2019 batch
5.“NO RUPERT! Don’t eat that!” Selective Cat Bowl by Camille Henrot from MIT
6. Kitty matics cat feeder by Kayla Proctor from fablab waunakee of 2017 batch
7. Smart Cat Feeder by Mohamed Kamel from Fablab Egypt of 2016 batch
8. Cat cave by Ivan Callupe from Fablab Tecsup of 2019 batch
9. Cat friendly bench by Sara Alvarellos from Fab Lab Leon of 2013 batch
10. Cat tree by Alexandra Coston from Charlotte of 2020 batch
11. Cat Mould by Jeremy Grandclaudon from WoMa Fablab of 2017 batch
This doesn’t help in catifying the house at all, but I thought it can be a nice gift to someone with a cat.
12. Discarded project idea by Lingyu Yue from Fab Lab Szoil of 2019 batch
What will you design?¶
I want to design and make all parts myself. I will need to design:
1. Main box: Size considerations based on the present litter box my cats are using. Minimum length- cm, Minimum height- cm, Minimum breadth- cm
2. Waste box: It has to fit perfectly underneath the main box yet should be easily removable.
3. Sieving system for urine: Fitted to the bottom of the main box this should have holes of diameter less than 6mm as the diameter of litter is 6mm.
4. Feces removing system: This can either be a stationary system, then the litter should move(by tilting, maybe?) and fall into it or it can be a comb piece that moves from one and to another of the box while raking the faeces out.
5. Cat detection mechanism: A sensor that finds whether the cat is present at a time. The idea is that the machine should start the cleaning cycle only after the cat has left the box.
6. Integration for all the electronic components: I do not want the cat to touch any of the electronic components for it’s safety. Also the cat might spray on some electronic components if it is visible. So all electronic components need to be integrated inside one unit.
What materials and components will be used and where will they come from and how much will they cost?¶
1. Main box and a waste box: Made from 12mm thick plywood of 8x4 ft size available at my lab, SuperFablab, Kochi approximately Rs 2000/- for the sheet
2. A sieving area: Acrylic with holes of 4mm available at my lab
3. 3D print parts: Using Ultimaker 2+, or Prusa or Sindoh or Foam Labs or HP available at my lab
4. Guide Rod: The movement will be through this
5. A comb that can remove poop Either 3 d print it or make it using metal wires on a plastic pipe, I will have to purchase the metal wire and plastic pipe from the local hardware shop in Ernakulam. It might require a metre of pipe which should be less than Rs 50 and 2 metres of GI wire which should also be less than Rs 50.
What parts and systems will be made?¶
I’m planning to make all parts of the litter box except the electronics and the guide rod.
What processes will be used?¶
1. Shopbot cnc machining for the making the box and its cover from wood
2. 3D printing for making some moving components
3. Laser cutting acrylic sheet to create a sieve and for beautification
4. The electronics will be designed in Eagle and Milled using Roland Modella.
what questions need to be answered?¶
1. How can I separate cat poop and litter?
2. How will I remove the separated poop into a waste bin?
3. How can I ensure that the electronic components will be out of reach of cats?
4. How can I ensure the accessibility for older cats and younger kittens?
How will it be evaluated?¶
The basic functions required are to separate the disintegrated urine ridden dust from the fresh litter and to remove the poop from the litter. Extra credits can be given if it senses the presence/ absence of the cat and works only when there is no cat around.
The plan I made on my Trello board.