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Hello fellow makers,

We recently welcomed a stray kitty into our home and while he adjusted to being a house cat just wonderfully, he's still a endless ball of energy!

I decided he needs a new toy that would keep his attention and hopefully burn some energy off.

If you have a cat you will know that they LOVE smacking things around, so the idea was to make a toy that would start moving when it was bumped, wouldn't need input from the human slave, doesn't need constant battery replacements and be as indestructible as possible.

Join me to find out how you can make one for your furry friends...

Step 1: What You Will Need:

To make this pet toy you will need the following:

- Access to a 3D printer

I used PETG and TPU filament in my build

Amazon - Ender 3

- 5v motor

I salvage mine from old pc cd-roms

Amazon - Motor

- 555 timer relay board

Amazon - Timer board

- Soldering iron and solder

- Thin long spring

- Piece of copper wire

- 16340 Li-ion battery

Amazon - 16340

- Battery tabs

Amazon - Tabs

- PNP transistor

- 1k Resistor

- Wire

- Adhesive

*As an Amazon Associate I receive a small percentage from sales made through provided links at no cost to you, this helps fund future projects.

Step 2: Design and Print:

I used both Fusion 360 and Tinkercad while designing.

The design is made according to the products linked, other versions will require some changes to be made.

The main body of the toy will need to be printed with some supports for the roof.

I printed the "wheel" part using TPU to dampen the noise a bit and add some grip....and protect the furniture 😸

My print settings are as follows:

Material: PETG and TPU

Speed: 40mm/s

Temp: 250 degC (220 for TPU) Nozzle and 85 degC Bed

Nozzle: 0.4mm

Step 3: The Brains Behind It All:

The main control for the toy will come from a 555 relay timer board.

Unfortunately the board will need some modifications in order to work for our application.

To cut down on space and weight I started by removing the parts that we will not be using, I disordered the relay as well as the terminal block. Removing these also gave us some nice mounting points for the parts we need to add.

When I was done I quickly powered it on via the micro USB port just to make sure everything is working correctly and to adjust the timer via the potentiometer to stay on for around 3 seconds when it is triggered.

Step 4: Modify the Timer Board:

Now to add the all important SMACK sensor!

You can buy these vibration sensors online but they are so easy to make that I decided to make my own and as an added bonus you can adjust the sensitivity by varying the size of the copper loop depending on how aggressive your furry friend is.

I started by rummaging through my hobby drawers for a small spring that had a lot of sideway movement when bumped, I cut it down to about 20mm length and soldered it to the "TRIG" pin on the board.

Whenever the trigger pin on the board is grounded it switches the 555 timer on.

Next I took a piece of bare copper wire and bent a small loop on the one end of it, I soldered it to the ground pin on the board so that the loop sits around the top of the spring.

Power it on via the USB and see if the trigger light goes on when bumped.

Next I had looked up the transistor that triggers the relay coil and was happy to see it is rated for 500ma and my motor only draws 400ma at stall so I just extended the relay coil pins and soldered the motor directly to that....

BUT...

When I finished assembling the entire toy and turned it on for the first time it just didn't have enough power to start spinning, I saw the trigger LED dim as soon as the motor started pulling power so I immediately knew that transistor was the problem.

Back to the hobby drawer we go to find a higher power transistor to drive the motor.

Because the pin pulls to ground when the timer is triggered we will need a PNP transistor ( mine is rated for 1amp ). The emitter of the transistor get soldered to the relay pin next to the potentiometer, the collector gets soldered to the pin across from it at the output side and finally we solder a 1K resistor from the ground pin of the relay coil, the pad next to the LED to the base of the transistor.

I then soldered a wire on the bottom from the ground pin to the one output pin of the relay as pictured.

Finally as you might have noticed in the pictures I also had to desoldered the potentiometer and resoldered it slightly looser in order to bend it over as it was was just slightly in the way of the battery holder.

Step 5: The Battery Holder:

Now for the power source.

I wanted to make the toy rechargeable as to not have to keep replacing batteries, but also had to keep it as small as possible and needs to be able to supply enough current.

I found that a 16340 Li-ion battery to be the perfect solution, it has a large enough capacity, it is the correct voltage for the motor and timer circuit, rechargeable and is a nice compact package.

I printed the holder for the battery and then simply soldered wires onto some battery tabs, to hold the tabs in place I simply pushed them slightly into the holders sides using the hot soldering iron.

Step 6: Assembly:

Now to assemble everything.

First the battery holders wires get soldered to the boards voltage in and ground respectively. I popped the battery in for a second just to make sure everything works.

Now you can slide the holder with the board and motor through the front hole, the pcb should slot into place and I added some hot melt glue just to make sure it doesn't come loose.

Next I pushed the motor into place and also secured it with some glue.. I know it's going to take a beating!

Adjust your vibration sensor so that the spring is not touching the copper.

Now align the tabs on the battery holder and the slots in the main body and push it into place until it clicks into place.

Step 7: Almost Done:

We're almost done!

Now you can put in the battery ( negative side goes to the spring ) and slide the lid into place, I find the because the pin on the lid is such a small feature sometimes it can overheat when printing causing it to deform a bit so I just use a sharp hobby knife to reshape it to fit into its slot.

I use a tiny 2.5mm screw on the end of the lid just to keep it in place.

Push the wheel onto the motor shaft and you're done....OR you can decorate it a bit.

I simply painted the raised paw print a little but you can also add some fur, feathers, ribbons or even some bells!

Step 8: Modifications:

Later on I decided to print an additional cap for the other side of the toy as to make it roll better and it varies the direction in which the toy spins, sometimes the motor side spins and sometimes the body spins.