Riley, an 8 lb pug, has more beauty than brains, and a palate as unrefined as crude oil. While we hate criticizing others’ interests and tastes, his penchant for eating cat poop needed to stop. After a thorough exploration of a variety of options, including cat food additives that make its excrement taste worse (HOW? WHY? Clearly taste wasn’t the issue!), automatic litter boxes that stow the secretions, and pet doors that authenticate access to the room with the litter box, [Science Buddies] eventually settled on a solution that was amenable to all members of the family.

The trick was in creating a door mechanism with a blacklist of sorts rather than a whitelist. As the cat didn’t like to push the door open itself, the solution needed to have the pet door open by default. A magnet on Riley’s collar would trip a sensor attached to an Arduino that would control servos to swing the door shut immediately if he attempted to access the defecated delights. Of course safety was a consideration with the door swinging in Riley’s face.

We’ve covered a few pet screeners, including one for the same purpose that used IR sensors (but a much bigger dog also named Riley), and a flock of solutions for chickens. We’ve also seen [Science Buddies] in previous posts, so they’re not on the tips line blacklist.

Magnets (especially those ball magnets!) are endlessly fascinating, aren’t they? It’s almost dangerous to combine them with LEDs, because how are you supposed to get anything done with something like [andrei.erdei]’s Arduino Magnetic Board beckoning from beyond your keyboard?

This tons-of-fun board uses ball magnets to light up RGB LEDs as they roll around on the sexy Plexiglas field. Underneath the LED matrix is an orchestra of 36 reed switches — those little glass gas-filled grains of rice with axial leads that snap together or fly apart in the presence of magnetic fields. The LEDs are controlled with an Arduino Pro Mini, and so is the 8Ω speaker for sound effects.

[andrei.erdei] has already developed a few applications for this delightful desk toy, and they’re all on GitHub. There’s a chase game that involves tilting the board to catch the next red dot with the magnet, a light painting game, and a sequencer that mimics the ToneMatrix. Roll past the break to check out the series of short demo videos.

Want to play with reed switches but can’t source any at the moment? You could just make them yourself.

Some dogs have no sense of self-preservation. Given the opportunity, they will eat until they’re sick. It’s up to us humans to both feed them and remember doing it so they aren’t accidentally overfed. In a busy household with young children, the tricky part is the remembering.

[Bryan]’s family feeds their dog Chloe once a day, in the mornings. She was a rescue who spent a few years scrounging for meals on the street, so some part of her is always interested in finding food, even if she just ate. Each morning, the flurry of activity throughout the house is compounded by Chloe’s repeated requests for food, so [Bryan] got his kids involved and built a simple circuit that lets everyone know—at a glance—whether Chloe was fed.

Chloe’s kibble is kept in a touch-top wastebasket that flips open at the press of a button. [Bryan]’s dog-fed detector uses a reed switch and an Arduino clone to detect when the lid is opened. When the reed switch goes, low, the Arduino lights up an LED. The light stays on for two hours and then shuts off automatically to get ready for the next day. You don’t have to beg for a demo video, because it’s waiting for you after the break.

Since Chloe devours a bowl of food in about two minutes flat, maybe the next project for [Bryan]’s family could teach her to slow down a bit.

It takes a lot of power and energy to keep grass levels down to an appropriate level; especially when it’s hot out. If cool glasses of lemonade aren’t around, the task at hand may not be completed any time soon causing the unkempt blades of green (or yellow) vegetation outside to continue their path of growth towards the sun.

Instead of braving the oven-like temperatures which will inevitably drench the person in sweat, this solar powered robot has been created ready to take on the job. With the heart of an Arduino, this device shaves down the grass on a regular basis, rather than only chopping down the material when it gets too long. This helps to save electricity since the mower is only dealing with young and soft plants whose heads are easily lopped off without much effort.

Internally, the robot’s circuitry interfaces with an underground wiring system that defines the cutting zones within the lawn, and proves to be a simple, accurate, and reliable approach to directing the robot where to go. If the device travels under a shaded area, a battery kicks in supplying energy to the engine. When sunlight is available, that same battery accumulates the electricity, storing it for later.

There is also an interesting mechanism in place that allows the controller to detect if the wheels are moving properly or if one or more of them have locked up. This is done by using a reed sensor that has been added near the rear-pivoting wheel which is then operated by a small magnet that is inserted into that same wheel.

Obstacle recognition is accomplished in the front by an ultrasonic sensor that is connected to the I2C BUS. A brushless motor, used in the field of aeromodelling, was coupled into a cutting blade. With everything set up, the solar powered lawn mower is ready to be unleashed into the outside world of unsuspecting, growing plants.

Now sit back, relax, and let the robot do the work for you.

For more grass cutting related hacks, be sure to check out this remote-controlled lawn mower, and this monster truck lawn tractor that can go through water.