Fear the Scary Cat!

After visiting a local Halloween store, I thought it would be cool to create my own interactive scary cat with lights, sound, and movement.

Description

While designing this project for fun, I never really thought about sharing it with other makers and the public. This is my first project submission, and I would have documented the process in greater detail if I had planned ahead better. The hardware and software are fairly straightforward, but developing the 3D printed parts in Tinkercad turned out to be the greatest challenge. As a maker hobbyist with no formal training in electronics or programming, I really enjoyed doing some Arduino programming and integrating various types of hardware, including a sound recording module, servo motor, LEDs, and a passive infrared sensor. Giving birth to this cat was a frightening labor of love!

Details

Before getting started, I thought it would be helpful to explain the features of the scary cat and and provide an overview of how it works. When first powering up the cat, its eyes will fade in and out for a short time before the servo motor resets the head position to face the front. The PIR sensor on the base of the unit then monitors for infrared movement/changes. When the sensor is triggered, the cat's head will move side to side, while the LED eyes slowly fade in and out. Concurrently, the ISD1820 sound record module will playback whatever sound was previously recorded. The cat has a built-in speaker and electret microphone. I simplified ISD1820 functions, such as recording and playback, by wire a couple of switches and the microphone to the enclosure. I programmed the scary cat using the Arduino IDE and decided to use an an ATtiny84 microcontroller instead of a full-blown Arduino. The circuit includes an ICSP programming header for users to modify/improve the code and upload it directly to the cat with the appropriate programmer. Finally, I included a TP4056 charging module to use a 3.7V rechargeable LiPO battery. The cutout in the base of the unit permits the charging LED to be monitored instead of having to remove the cover. That about sums it up!

Files

Servo-Horn-Bracket.stl

Standard Tesselated Geometry - 28.01 kB - 08/24/2021 at 00:10

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Dual-Servo-Horn-Final.stl

Standard Tesselated Geometry - 22.25 kB - 08/24/2021 at 00:10

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Cat-neck-support.stl

Standard Tesselated Geometry - 6.33 kB - 08/24/2021 at 00:10

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Neck-Middle-Marking.stl

Standard Tesselated Geometry - 6.33 kB - 08/24/2021 at 00:10

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Head-Motor-Mount.stl

Standard Tesselated Geometry - 28.01 kB - 08/24/2021 at 00:10

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Components

Build Instructions

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1

Preparation

Start by reviewing the parts list and carefully selecting the necessary components. For example, there are several versions of the ISD1820 sound recording module, so be sure to purchase a kit with all of the necessary external pins needed to interface with the ATtiny84 microcontroller. I could have purchased the ISD1820 IC separately and developed a custom PCB that included all necessary functions. However, for this unique and likely onetime build, I decided to hack an ISD1820 kit and interface it directly with an ATtiny84. Since the ISD1820 kits are fairly easy to build, I recommend putting together one for testing and then another to use for the project. After obtaining all parts list, review the schematic that I created on EasyEDA to identify any potential issues.
2

Construct an ISD1820 Kit with a Few Modifications

Put together an ISD1820 like the one in the components list. Other kit variations will likely work just as well, but the PCB size may not match the mounting holes in the base unit of the cat. DO NOT populate the three momentary switches used for "E" and "L" playback and the one used for recording. Those connections will be wired externally to the scary cat. Also, I recommend using female JST connectors on the PCB to simplify connecting the sound indicator LED, speaker, and the microphone. Please review the photo below.
3

Assemble the Prototype PCB

Using the schematic from EasyEDA, the hand-drawn board layout, and the photos below, populate the prototype PCB. You will have quite a few wires soldered and extending from the PCB to connect the main power switch, PIR sensor, servo motor, eye LEDs, and the interface connector to use with the ISD1820.

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Fear the Scary Cat!

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