Remember the spell book from Hocus Pocus with the creepy moving eyeball? Since it is the season of Halloween-movie-replica-prop-making, I’ve found a great DIY tutorial that covers the steps required to make a pretty accurate copy! This tutorial doesn’t include how to make the eyeball actually move, but I would […]
Sometimes the best way to learn about a technology is to just build something yourself. That’s what [Dan] did with his DIY optoisolator. The purpose of an optoisolator is to allow two electrical systems to communicate with each other without being electrically connected. Many times this is done to prevent noise from one circuit from bleeding over into another.
[Dan] built his incredibly simple optoisolator using just a toilet paper tube, some aluminum foil, an LED, and a photo cell. The electrical components are mounted inside of the tube and the ends of the tube are sealed with foil. That’s all there is to it. To test the circuit, he configured an Arduino to send PWM signals to the LED inside the tube at various pulse widths. He then measured the resistance on the other side and graphed the resulting data. The result is a curve that shows the LED affects the sensor pretty drastically at first, but then gets less and less effective as the frequency of the signal increases.
[Dan] then had some more fun with his project by testing it on a simple temperature controller circuit. An Arduino reads a temperature sensor and if the temperature rises above a certain value, it turns on a fan to cool the sensor off again. [Dan] first graphed the sensor data with no fan hooked up. He only used ambient air to cool things down. The resulting graph is a pretty smooth curve. Next he hooked the fan up and tried again. This time the graph went all kinds of crazy. Every time the fan turned on, it created a bunch of electrical noise that prevented the Arduino from getting an accurate analog reading of the temperature sensor.
The third test was to remove the motor circuit and move it to its own bread board. The only thing connecting the Arduino circuit to the fan was a wire for the PWM signal and also a common ground. This smoothed out the graph but it was still a bit… lumpy. The final test was to isolate the fan circuit from the temperature sensor and see if it helped the situation. [Dan] hooked up his optoisolator and tried again. This time the graph was nice and smooth, just like the original graph.
While this technology is certainly not new or exciting, it’s always great to see someone learning by doing. What’s more is [Dan] has made all of his schematics and code readily available so others can try the same experiment and learn it for themselves.
The Motion Controlled Ultrasonic Lamp is great for beginners starting out with the Arduino Uno.
It may or may not detect ninjas but will illuminate and follow most everyone else.
This is the story of a group of college students who moved to the Mojave Desert, bought a house, painted it white, and turned it into a make-shift lab. Then they went out to launch rockets.
If you want to channel your inner Catherine Zeta-Jones and give it a shot yourself, take a crack at the Laser Maze.
Hackaday.io blogger 'Risknc' updates his Light Staff prototype, much to the excitement of the LARPing community. It is a 8-foot staff filled with High Intensity LEDs that put on quite a show.
The $80 Head Mounted Display was made with 3D printed frames and component housing modules with the optics bought from eBay.
They are fully adjustable and function with Android or Linux-based mobile devices.
Chuck Stephens is an artist, musician, hardware hacker and small boat builder who specializes in the use of recycled, repurposed and salvaged materials. Exhibiting at Maker Faire Orlando as Nepchune’s Noise Circus, Chuck says noise circuits provided his Eureka! moment in electronics. 
A group of electronics students from HiST brought two very different projects to the faire—an underwater ROV and a bunch of electric long boards.
