Build Meow! A Step-by-Step Instruction

Introduction
Meow is a little modified Maneki-Neko. At first glance, she looks like any other happy lucky cat but once she’s connected to a WiFi network and integrated into your Slack environment, Meow starts to wave when you receive a Slack message. So before you start, you might have a quick read about the idea and the full story behind Meow.

You already did? Nice! So let's jump right into the building process!

Disassembly
Right after you've unpacked your lucky cat, it should look something like this.

The first thing we need to do is to disassemble the paw from the body. Slightly twist the paw backwards until you see a little plastic knob. The paw is held by a special mechanism as you can see in the image [2]. You might have to block the rotating counterpart at the inside of the lucky cat to release the mechanism. After that, just pull the paw out. That enables us to easily take off the body in the next step.

For this, just loosen the screw and take the body off. What you'll see inside is the structure of the lucky cat including the magnetic coil.

Simple coil test
To detect a damaged coil we'll run a simple coil test. I uploaded a little sketch file to test the functionality of the coil. You can find it down in the 'code' section.

To do so, we need to prepare our TinyPICO first. Solder the JST connector onto the board. We're going to need this one later for battery operation.

Unsolder both cables from the battery compartment of the cat. Afterward, extend both cables to put them into the breadboard later.

To fire up the coil with the provided code, make sure you also solder two cables onto the TinyPICO. We're going to need a GND and a data pin. For this, we pick pin 14. Then just connect as shown below [7].

Preparing all the cables
We're now going to take care of the two custom USB cables we need to upload the code and charge Meow later on.

Please note the USB pinout for the male and the female jack. And if possible, stick to the cable color code.

The solder work is a bit tricky but self-explanatory. Just make sure your cables are long enough and have the right diameter to fit the pins on each jack.

After that, just connect both cables and verify the work with a multimeter. Pro tip: While testing, mark each cable with its corresponding pin names like VCC, GND, or D+ as shown above [11].

Power switch and USB case
Pull the female USB cable through the opening of the battery cover as shown below [12].

Now it's time to print the first model I've provided down in the 'custom parts and enclosures' section. For this, we're going to need the 'Meow-Switch-USB-Case'. Once printed, slightly put the female USB jack into its place. It should be a tight fit.

Solder two cables directly on the two adjacent pins of the switch. Then place the switch in the case. If the components are a little loose, you can use hot glue additionally.

On the left, you can see the first prototype of Meow [15], which basically was a proof of concept. For this one, I've used only components I've already had laying around. For this particular iteration, I did some research on several components for a better look and fit.

Battery operation
Let's now turn to the battery operation. I've developed a little clip-and-click system to make use of the bars inside of the lucky cat.

Simply attach the battery holder to one bar as shown above [17]. Insert the battery and shorten the cables a little bit to provide a better connection for the JST cable.

The Power-Switch-USB-Case is already in its place so we can now proceed with the cables to connect the power switch with the battery. Remember: Always use the VCC lane to equip your battery with a switch.

The TinyPICO finds its place right on the opposite side of the battery. For this, we're going to print the provided 'TinyPICO-Clip'.

Make sure the red-colored connection of the JST cable directly runs through the power switch. This is necessary because we want to be able to control the flowing current with the switch. In other words, to switch it ON and OFF. So, if everything is in place, we can move on to the next step.

The marriage
Solder both USB cables together. Don't rush though! First, trim all cables to an appropriate length. By doing so, we don't need to fit too much cable inside of the cat later on. And, I recommend using a heat shrinking tube to support the solder connection.

Where do I start? Our previous preparations come in handy now, because we marked our cables before and we already know which cables we need to connect. This method is useful for the female USB jack coming out of the power switch and USB case. For the male jack, I've used the color code as shown in the pinout image [9].

After everything is set up, just run a quick uploading test to verify your solder work.

Last steps and fine-tuning
Before we can run our final test, don't forget to connect the magnetic coil with the TinyPICO. The red cable goes to pin 14 and the green one to GND. If there are any protruding cables, you can simply store them between the battery compartment and the coil.

Additionally, you can add some extra bump stops to provide a better stand and to make sure the power switch does not touch or scratch on the ground.

In the video above [28] you can see me running the last test to check everything is working out. I hope you enjoyed this building process!

Check out the Meow git repo for the source code and additional instructions or visit the special themed landing page and play around!

Thanks very much for reading! I’d love to hear your thoughts in the comments.

Stay safe ✌