Cat-Operated Cat Food Dispenser

Tired of being harassed by your cat? [MomWillBeProud] made a cheap, effective — and more importantly cat-operated — cat food dispenser.

The feeder is of an efficient construction — a double cat food dish, one container to store the electronics, and a Pringles can to act as the hopper. A simple servo rotates the hopper thirty degrees and back on each button press; using gravity to drop food through an opening that appears due to this motion. The button itself is an old IKEA timer and a piece of plastic large enough for a hungry cat to swat.

An Arduino controls the servo, and while [MomWillBeProud] skips over going into detail on his code, you can check it out here.

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Antenna Rotation Arduino Style

Back in the days when you didn’t pay for your TV programming, it was common to have a yagi antenna on the roof. If you were lucky enough to have every TV station in the area in the same direction, you could just point the antenna and forget it. If you didn’t, you needed an antenna rotator. These days, rotators are more often found on communication antennas like ham radio beams. For terrestrial use, the antenna only needs to swing around and doesn’t need to change elevation. However, it does take a stout motor because wind loading can put a lot of force on the system.

[SP3TYF] has a HyGain AR-303 rotator and decided to build an Arduino-based controller for it. The finished product has an LCD and is able to drive a 24 V motor. You can control the azimuth of the antenna with a knob or via the computer.

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Pan and Tilt with Dual Controllers

It wasn’t long ago that faced with a controller project, you might shop for something with just the right features and try to minimize the cost. These days, if you are just doing a one-off, it might be just as easy to throw commodity hardware at it. After all, a Raspberry Pi costs less than a nice meal and it is more powerful than a full PC would have been not long ago.

When [Joe Coburn] wanted to make a pan and tilt webcam he didn’t try to find a minimal configuration. He just threw a Raspberry Pi in for interfacing to the Internet and an Arduino in to control two RC servo motors. A zip tie holds the servos together and potentially the web cam, too.

You can see the result in the video below. It is a simple matter to set up the camera with the Pi, send some commands to the Arduino and hook up to the Internet.

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Tricking Duck Hunt to See A Modern LCD TV as CRT

A must-have peripheral for games consoles of the 1980s and 1990s was the light gun. A lens and photo cell mounted in a gun-like plastic case, the console could calculate where on the screen it was pointing when its trigger was pressed by flashing the screen white and sensing the timing at which the on-screen flying spot triggered the photo cell.

Unfortunately light gun games hail from the era of CRT TVs, they do not work with modern LCDs as my colleague [Will Sweatman] eloquently illustrated late last year. Whereas a CRT displayed the dot on its screen in perfect synchronization with the console output, an LCD captures a whole frame, processes it and displays it in one go. All timing is lost, and the console can no longer sense position.

[Charlie] has attacked this problem with some more recent technology and a bit of lateral thinking, and has successfully brought light gun games back to life. He senses where the gun is pointing using a Wiimote with its sensor bar on top of the TV through a Raspberry Pi, and feeds the positional information to an Arduino. He then takes the video signal from the console and strips out its sync pulses which also go to the Arduino. Knowing both position and timing, the Arduino can then flash a white LED stuck to the end of the light gun barrel at the exact moment that part of the CRT would have been lit up, and as far as the game is concerned it has received the input it is expecting.

He explains the timing problem and his solution in the video below the break. He then shows us gameplay on a wide variety of consoles from the era using the device. More information and his code can be found on his GitHub repository.

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Arduino Versus Logic: The Coil Gun War Continues

Looks like another shot has been fired in the simmering Coil Gun Control War. This time, [Great Scott] is taken to the discrete woodshed with a simplified and improved control circuit using a single CMOS chip and a few transistors. Where will it end? Won’t somebody think of the children?

The latest salvo is in response to [GreatScott]’s attempt to control a DIY coil gun with discrete logic, which in turn was a response to comments that he took the easy way out and used an Arduino in the original build. [Great Scott]’s second build was intended to justify the original design choice, and seemed to do a good job of explaining how much easier and better the build was with a microcontroller. Case closed, right?

Nope. Embedded designer [fede.tft] wasn’t sure the design was even close to optimized, so he got to work — on his vacation, no less!’ He trimmed the component count down to a single CMOS chip (a quad Schmitt trigger NAND), a couple of switching transistors, the MOSFETs that drive the coils, and a few passives. The NANDs are set up as flip-flops that are triggered and reset by the projectile sensors, which are implemented as hardwired AND gates. The total component count is actually less than the support components on the original Arduino build, and [fede.tft] goes so far as to offer ideas for an alternative that does away with the switching transistors.

Even though [fede.tft] admits that [GreatScott] has him beat since he actually built both his circuits, hats off to him for showing us what can likely be accomplished with just a few components. We’d like to see someone implement this design, and see just how simple it can get.

Rainy Day Fun by Calculating Pi

If you need a truly random event generator, just wait till your next rainstorm. Whether any given spot on the ground is hit by a drop at a particular time is anyone’s guess, and such randomness is key to this simple rig that estimates the value of pi using raindrop sensors.

You may recall [AlphaPhoenix]’s recent electroshock Settlers of Catan expeditor. The idea with this less shocking build is to estimate the value of pi using the ratio of the area of a square sensor to a circular one. Simple piezo transducers serve as impact sensors that feed an Arduino and count the relative number of raindrops hitting the sensors. In the first video below, we see that as more data accumulates, the Arduino’s estimate of pi eventually converges on the well-known 3.14159 value. The second video has details of the math behind the method, plus a discussion of the real-world problems that cropped up during testing — turns out that waterproofing and grounding were both key to noise-free data from the sensor pads.

In the end, [AlphaPhoenix] isn’t proving anything new, but we like the method here and can see applications for it. What about using such sensors to detect individual popcorn kernels popping to demonstrate the Gaussian distribution? We also can’t help but think of other ways to measure raindrops; how about strain gauges that weigh the rainwater as it accumulates differentially in square and circular containers? Share your ideas in the comments below.

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VFD Clock Only Speaks Romanian

There’s no shortage of clock projects, but [niq_ro] has his own take using a vacuum fluorescent display (VFD), and Arduino, and a pair of MAX6921 ICs. Those chips are made to drive a VFD, and the use of two of the ICs required a bit of work. The Arduino is not a great time keeper, so the clock also uses a DS3231 clock module and a humidity and temperature sensor.

The clock is in Romanian, although there are some options for different text. You can find the code on GitHub and can see the result in the video below.

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