Making Membrane Keypads From Scratch

A few years ago, [Paul]’s son got a simple electronic toy that plays funny noises and sings to him. The son loves the toy, but after months and months of use, the toy was inevitably broken beyond repair. Figuring an ‘electronic box that plays sounds’ wouldn’t be a hard project to replicate, [Paul] set out on making his own. The electronics weren’t hard, but custom membrane keypads are hard to come by. No matter, because it’s actually pretty easy to build your own.

Membrane switches are usually made with silkscreen conductive inks on fancy plastic, but that’s not a requirement to build your own. All you really need are four layers – a ‘front decal’, a ‘top foil’ layer for the rows, a ‘bottom foil’ layer for the columns, and a ‘cutout’ layer that provides enough separation between the rows and columns.

[Peter] laid out the four layers in Illustrator, printed the layers, and covered the rows and columns with copper tape. The cutout layer is the crucial part that keeps the layers separated until the button is pressed, and that was just a piece of card stock with strategically placed holes.

Once the rows, columns, and other layers were glued up, [Peter] could connect this keypad up to a microcontroller. The code is very easy with the Arduino keypad library, and should stand up to the rigors of being handled by a child.

Ask Hackaday: Your Very First Microcontroller

Necessity is the mother of invention. It is also true that invention necessitates learning new things. And such was the case on the stormy Tuesday morning our story begins.  Distant echos of thunder reverberated in the small 8 x 16 workshop, drawing my attention to the surge suppressor powering my bench.  With only a few vacation days left, my goal of finishing the hacked dancing Santa Claus toy was far from complete. It was for a Secret Santa gift, and I wanted to impress. The Santa moved from side to side as it sang a song. I wanted to replace the song with a custom MP3 track. In 2008, MP3 players were cheap and ripe for hacking. They could readily be picked up at local thrift shops, and I had picked up a few. It soon became clear, however, that I would need a microcontroller to make it do what I wanted it to do.

Continue reading “Ask Hackaday: Your Very First Microcontroller”

DIY Hot Wheels Drag Race Timer

[Apachexmd] wanted to do something fun for his three-year-old son’s birthday party. Knowing how cool race cars are, he opted to build his own Hot Wheels drag race timer. He didn’t take the easy way out either. He put both his electronics and 3D printing skills to the test with this project.

The system has two main components. First, there’s the starting gate. The cars all have to leave the gate at the same time for a fair race, so [Apachexmd] needed a way to make this electronically controlled. His solution was to use a servo connected to a hinge. The hinge has four machine screws, one for each car. When the servo is rotated in one direction, the hinge pushes the screws out through holes in the track. This keeps the cars from moving on the downward slope. When the start button is pressed, the screws are pulled back and the cars are free to let gravity take over.

The second component is the finish line. Underneath the track are four laser diodes. These shine upwards through holes drilled into the track. Four phototransistors are mounted up above. These act as sensors to detect when the laser beam is broken by a car. It works similarly to a laser trip wire alarm system. The sensors are aimed downwards and covered in black tape to block out extra light noise.

Also above the track are eight 7-segment displays; two for each car. The system is able to keep track of the order in which the cars cross the finish line. When the race ends, it displays which place each car came in above the corresponding track. The system also keeps track of the winning car’s time in seconds and displays this on the display as well.

The system runs on an Arduino and is built almost exclusively out of custom designed 3D printed components. Since all of the components are designed to fit perfectly, the end result is a very slick race timer. Maybe next [Apachexmd] can add in a radar gun to clock top speed. Check out the video below to see it in action. Continue reading “DIY Hot Wheels Drag Race Timer”

Budget Wrist-Controlled RC car is a nice touch

Does your RC car’s crude, push-button controller make you feel like you’re mashing tv remote buttons like a caveman? We think so too, but [Noel] has actually done the heavy-lifting to fix just that. He’s revamped his kids’ rc controller for gesture control. Now their rc car can be guided by the crisp, intuitive control of one’s wrist movements.

To tackle this project, [Noel] has integrated a gyroscope and accelerometer, an Arduino, and the existing remote. Data from the gyroscope-and-accelerometer limits are mapped to the buttons through an Arduino, which parses the raw data and triggers the controller’s switches, now wired directly to the Arduino and pulled up with resistors. In his overview video, [Noel] tells us that he’s binarized the gyroscope-and-accel data to trigger at certain limits, a choice that adequately suits the controller’s original push-button controls. Finally, the entire setup is cleanly strapped to a 3D-printed case. Not bad, for a grand total of $20 and a quick trip to Target.

[Noel]’s custom wrist-controller takes its place on the shelf of many other unique controllers, and his demo is a great example of using existing open hardware to tailor our toys to more personal tastes. After all, the hardware shopping list is just a breakout board, an Arduino, and a few jumper wires. When the next zombie apocalypse hits, we can easily see some practical components like these making their way into our suitcase. At the very least, we’ll be able to build a few wrist controllers and dispatch some toy cars to greet the undead.

Continue reading “Budget Wrist-Controlled RC car is a nice touch”

Measuring the Planck Constant With Lego

For nearly 130 years, the kilogram has been defined by a small platinum and iridium cylinder sitting in a vault outside Paris. Every other unit of measurement is defined by reproducible physical phenomenon; the second is a precise number of oscillations of a cesium atom, and a meter is the length light travels in 1/299792458th of a second. Only the kilogram is defined by an actual object, until NIST and the International Committee of Weights and Measures defines it as a function of the Planck constant. How do you measure the Planck constant? With a Watt balance. How do you build a Watt balance? With Lego, of course.

A Watt balance looks like a double-armed scale where one weight can be compared to another weight of known mass. Instead of using two arms, a Watt balance only has one arm, brought into balance by a current flowing through a coil. The mechanical power in the balance – brought about by whatever is on the balance plate – can then be compared to the electrical power, and eventually the Planck constant. This will soon be part of the formal definition of the kilogram, and yes, a machine to measure this can be made out of Lego.

The only major non-Lego parts in the Lego Watt balance are a few coils of wire wound around a PVC pipe and a few neodymium magnets. These are placed on both arms of the balance, and a pair of lasers are used to make sure both arms of the balance are level. Data are collected by measuring the coils through a few analog pins on a Labjack and a Phidget. Once the voltage and current induced in each coil is measured, the Wattage can be calculated, then the Planck constant, and finally how close the mass on the balance pan is to a real, idealized kilogram. Despite being made out of Lego, this system can measure a gram mass to 1% uncertainty.

The authors have included a list of Lego parts, most of which could be found in any giant tub of Lego in an 8-year-old’s closet. The only really expensive item on the BOM is a 16-bit USB DAQ; apart from that, it’s something anyone can build.

Thanks [Matt] for the tip.

Pandaphone is a DIY Baby Toy

[Tyler] was looking for a gift for his friend’s one year old son. Searching through the shelves in the toy store, [Tyler] realized that most toys for children this age are just boxes of plastic that flash lights and make sound. Something that he should be able to make himself with relative ease. After spending a bit of time in the shop, [Tyler] came up with the Pandaphone.

The enclosure is made from a piece of 2×4 lumber. He cut that piece into three thinner pieces of wood. The top piece has two holes cut out to allow for an ultrasonic sensor to poke out. The middle piece has a cavity carved out using a band saw. This would leave room to store the electronics. The bottom piece acts as a cover to hide the insides.

The circuit uses an ATtiny85. The program watches the ultrasonic PING sensor for a change in distance. It then plays an audio tone out of a small speaker, which changes pitch based on the distance detected. The result is a pitch that is lower when your hand is close to the sensor, but higher when your hand is farther away. The case was painted with the image of a panda on the front, hence the name, “Pandaphone”. Based on the video below, it looks like the recipient is enjoying it! Continue reading “Pandaphone is a DIY Baby Toy”

Developing Film With Lego

Developing film at home is most certainly a nearly forgotten art nowadays, but there are still a few very dedicated people who care enough to put in the time and study to this craft. [Jan] is one of the exceptional ones. He’s developing 35mm film with Lego (Dutch, Google translate).

For the build, [Jan] is using the Lego RCX 1.0, the first gen of the Lego Mindstorms, released in the late 90s. According to eBay, this is a significantly cheaper option for programmable Lego. The mechanics of the Lego film developer consisted of multiple tanks of chemicals. The film was loaded on a reel, suspended from a Lego gantry, and dunked into each tank for a specific amount of time.

A second revision of the hardware (translate) was designed, with the film loaded into a rotating cylinder. A series of chemicals would then be pumped into this unit with the hope of reducing the amount of chemicals required. This system was eventually built using the wiper fluid pump from a car. Apparently, the system worked well, judging from the pictures developed with this system. Whether it was easy or efficient is another matter entirely.

You can check out a video of the first revision of the Lego film developing system below.

Thanks [Andrew] for sending this in.

Continue reading “Developing Film With Lego”