The MagPi - February 2020

X

ander the cat is a much-loved family pet,

but as his owners live in a flat, he can

get a little bored staying indoors when

they’re out at work. Seeking a way to keep his

cat entertained, Enzo Calogero came up with an

ingenious Raspberry Pi-powered project. “We

noticed that he loves to chase a laser light, so we

decide to create a device to make laser games for

him,” explains Enzo.

The result is the Tri-Lasers for Felines device

which, when the cat’s presence is detected by a PIR

motion sensor, beams a laser dot around the room

for Xander to chase between randomly generated

points. Judging by the video on the project’s

Hackster tutorial page (magpi.cc/trilasers), he

seems to love it.

Pan and tilt

The laser’s main movement trajectory is handled

by mounting it on a Pan-Tilt HAT, which has

vertical and horizontal servo motors. “A pair of

coordinates (x, y) is generated randomly,” explains

Enzo. “The laser point moves from the current

point to a new coordinate, following the segment

that connects the two points, at a speed defined

by a status variable. Once the new coordinates are

reached, we loop back to point one.”

To add extra interest for Xander, its movement

is randomised further by switching between three

laser diodes to perform micro random movements

very quickly. “Switching the active laser among

the three allows extremely rapid movements of the

laser dot, to create an extra variability of the light

trajectories which seems more enjoyable for the

cat,” says Enzo.

While the laser point is visible in daylight, it

shows up better when there’s less light: “Xander

prefers it when the room is completely dark.”

Keeping a modern cat entertained requires

something more high-tech than a ball of yarn.

Phil King wonders if this is a purr-fect project

Tri-Lasers

for Felines

Enzo

Calogero

Enzo is a field

data scientist,

passionate about

microcontrollers,

Raspberry Pi,

and 3D printer

technologies. He

enjoys creating

IoT devices to use

in day-to-day life,

along with robots.

hackster.io/enzo

MAKER

The device’s three laser diodes are set into a

3D-printed triangular holder that sits atop the Pan-

Tilt HAT’s acrylic mount – which would normally be

used to hold a Camera Module. Enzo also designed

and 3D-printed a case for the PIR sensor.

Cat-a-log

In addition to handling laser movement, the

Python script saves a log of Xander’s activity: “We

check it now and then out for curiosity,” says Enzo.

“When Xander was a kitten, he was playing with

it very often. Now he is a bit older and much more

prone to sleep rather than play, we switch it on

when we are out in the evening to keep him busy

during our prolonged absence.”

One issue that came up is that, being naturally

curious animals, cats are prone to investigate

any new objects. “We try to put it as high and

tilt sensor was added to shut down the device if A

interfered with by a curious cat

Warning!

Laser eye!

Don’t look into a laser

beam, and don’t point

a laser beam at a

somebody’s head.

magpi.cc/lasersafety

18 magpi.cc Tri-Lasers for Felines

PROJECT SHOWCASE