Levitate a magnet with an Arduino

---

Watch this Maker suspend a neodymium magnet in midair with the help of an Arduino Mega.

---

If you went to enginering school, you probably remember a class called “Control of Dynamic Systems” or something similar. One of the most common concepts that you likely forgot the math behind was the “PID,” or proportional-integral-deriviatave, loop. This crazy-sounding name basically means that it takes three mathematical concepts, factors them into an equation, and outputs the correct amount of power to, say, a heating element on an oven.

If you have forgotten the math behind this, you can conveniently just buy a box called a “PID controller,” tune it, and forget all about Laplace transforms. On the other hand, as shown in this Instructables piece, you can make your own PID controller using an Arduino Mega.

As if controlling one power source wasn’t challenging enough, the setup shown below can balance four electromagnets’ power outputs to keep a neodymium “floater” suspended between them. The suspended disk wobbles slightly in the video, so it’s possible that a more developed setup or different tuning values could cut down on these vibrations. Maybe this could even be perfected to the point where these oscillations are nearly imperceptible.

Oscillations or not, it’s really an amazing project, and showcases what can be done with a firm grasp on PID-mathematics and a low-cost microcontroller setup! Mesmerized? You can check out the entire build here.

Maker builds an automatic feeder for his cats

---

If you’re a Maker and you have three cats with various dietary needs, what do you do? Build an automated feeder, of course!

---

Jamie Navarro faced a dilemma. His three cats needed to be fed at the same time every day, but sometimes he wasn’t able to accommodate them. Add in the fact that Navarro’s cats had different dietary requirements, and it became a problem that was just begging to be automated. He looked for an off-the-shelf product, but they were either too expensive, not flexible enough, or insecure against cat-raids.

Since Navarro claims to be a “nerd” as well as a “control freak,” the only option was to build it himself. His setup, as seen in the video below, uses an Arduino to control two motors, each attached to a paddle. These paddles, at the bottom of their respective tubes of food, turn a certain amount to allow the right amount of food to drop. A system of cardboard tubes distributes the correct type of “kibble” to each feline’s bowl promptly at 5:15am and 5:15pm.

The machine is laid out using a piece of plywood, allowing easy access to the electronics as well as the mechanical components. Although certainly his own project, Navarro gives credit to the creator of the Internet-Enabled Cat Feeder for figuring out much of the dispensing mechanism.

If you want to attempt this build, Navarro has links to the Arduino code as well as the circuit used and a bill of materials in various formats. The entire project price came out to nearly $200, but that’s definitely worth it for the extra few hours of sleep in my opinion!

[h/t Hackaday]