A light-dependent resistor detects cacti in the Google Chrome Offline Dinosaur game.

Jump Cacti With An LDR And A Pico

September 6, 2024 by Kristina Panos 6 Comments

By now, probably everyone is familiar with the “You’re Offline” dinosaur that stars in Google’s T. Rex game. You know — jump cacti, avoid pterodactyls. Repeat until you lose, or, we suppose, make the leaderboard. Well, what if you theoretically couldn’t lose? That’s kind of the idea behind [Bas BotBerg]’s cactus detection-and-avoidance scheme (translated from Dutch).

Like many of us, [Bas] firmly believes that repetitive tasks should be automated, and that includes the controls of the famous T. Rex. Since the cacti are always dark gray and appear along the same plane, it’s easy to register the difference between cacti and screen electronically. In order to accomplish this, [Bas] is using a light-dependent resistor and a pull-up resistor to create a resistance bridge, which is then connected to an analog input pin on a Raspberry Pi Pico.

But [Bas] didn’t do this just to cheat at Offline Dinosaur. Really! It’s for educational purposes, to get people comfortable with embedded processing, sensors, and interfaces between different devices. Check it out in brief action after the break.

Once they get familiar with these concepts, maybe introduce the ESP32 version of Offline Dinosaur.

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A Simple Laser Harp MIDI Instrument

June 19, 2024 by Dave Rowntree 5 Comments

Craig Lindley is a technical author and a prolific maker of things. This simple project was his first attempt to create a laser harp MIDI device. While on vacation, Craig saw a laser harp with only three strings and decided to improve upon it by expanding it to twelve strings. The principle of operation is straightforward: twelve cheap diode laser modules aim a beam towards an LDR, which changes resistance if the light level changes when the beam is interrupted.

The controller is a simple piece of perf board, with a Wemos D1 mini ESP32 module flanked by some passives, a barrel socket for power, and the usual DIN connector for connecting the MIDI instrument. Using the ESP32 is a smart choice, removing all the need for configuration and user indication from the physical domain and pushing it onto a rarely-needed webpage. After a false start, attempting to use a triangular frame arrangement, [Craig] settled upon a simple linear arrangement of beams held within a laser-cut wooden box frame. Since these laser modules are quite small, some aluminium rod was machined to make some simple housings to push them into, making them easier to mount in the frame and keeping them nicely aligned with their corresponding LDR.

Sadly, the magnetic attachment method [Craig] used to keep the LDRs in place and aligned with the laser didn’t work as expected, so it was necessary to reach for the hot glue. We’ve all done that!

An interesting addition was using an M5 stack Unit-Synth module for those times when a proper MIDI synthesiser was unavailable. Making this luggable was smart, as people are always fascinated with laser harps. That simple internal synth makes travelling to shows and events a little easier.

Laser harps are nothing new here; we have covered plenty over the years. Like this nice build, which is more a piece of art than an instrument, one which looks just like a real harp and sounds like one, too, due to the use of the Karplus-Strong algorithm to mimic string vibrations.

Simple Hack Lets Smartphone Take Resin Printer Time-Lapses

October 26, 2023 by Dan Maloney 5 Comments

With how cheap they’re getting, everyone seems to be jumping on the resin printer bandwagon. They may not be able to fully replace your trusty old FDM printer, but for certain jobs, they just can’t be beaten. Sadly though, creating those smooth time-lapse videos of your prints isn’t quite as easy to do as it is on their filament-based counterparts.

Not as easy, perhaps, but not impossible. [Fraens] found a way to make time-lapses on any resin printer, and in a wonderfully hacky way. First, you need to find a smartphone, which shouldn’t be too hard, given how often we all tend to upgrade. [Fraens] recommends replacing the standard camera app on the phone with Open Camera, to prevent it from closing during the long intervals with nothing happening. The camera is triggered by any readily available Bluetooth dongle, which is connected via a simple transistor circuit to an Arduino output. To trigger the shutter, a light-dependent resistor (LDR) is connected to one of the microcontroller’s inputs. The LDR is placed inside the bed of the resin printer — an Anycubic Photon in this case — where light from the UV panel used to cross-link the resin can fall on it. A simple bit of Arduino code triggers the Bluetooth dongle at the right moment, capturing a series of stills which are later stitched together using DaVinci Resolve.

The short video below shows the results, which look pretty good to us. There are other ways to do this, of course, but we find the simplicity of this method pleasing.

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A Flex Sensor For A Glove Controller Using An LDR

January 15, 2023 by Jenny List 14 Comments

When most of us think of glove controllers, the first which comes to mind is Nintendo’s PowerGlove, which promised much more than it delivered. But the idea persists, and from time to time we see them here at Hackaday. [Gord Payne] has one with an elegant sensor solution, it detects finger movement using a light dependent resistor.

The cleverest designs are those which are the simplest, and this one eschews complex mechanisms and exotic parts for a simple piece of flexible tube. At one end is an LED and at the other the LDR, and when attached to a glove it provides a finger sensor without the fuss. The amount of light reaching the LDR from the LED decreases as the pipe is bent, and with a simple divider circuit a voltage can be read by an Arduino. You can see it in action in the video below the break, where the glove flexing controls a servo.

Perhaps this might revitalize a bit of interest in glove controllers, something we probably don’t see too many of. Those Nintendo PowerGloves do still crop up from time to time though.

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This Simple Light-Controlled Synth Has A Surprisingly Rich Sound

September 15, 2022 by Dan Maloney 5 Comments

Audio synthesizers can range from vast racks of equipment with modules stitched together by a web of patch cords to a couple of 555s wired together in an Atari punk arrangement. This light-controlled synth comes in closer to the lower extreme of that range, but packs a sonic punch that belies its simplicity.

The project is the latest version of [lonesoulsurfer]’s “Moog Light Synthesizer,” which shares a lot of the circuitry found in his first version a couple of years ago. This one has a lot of bells and whistles, but it all starts with a PWM oscillator that contributes to the mean, growling quality of its sound. There’s also a low-pass filter that’s controlled by a couple of light-dependent resistors, which can be played by blocking them off with a fingertip. A couple of inverters form a drone oscillator that can be switched into the circuit, as well as a 555-based arpeggiator to chop things up a bit.

All those circuits, as well as support for a thirteen-key keyboard, live on one custom PCB. There’s also an off-the-shelf echo/reverb module that’s been significantly hacked to add to the richness of the sound. The custom wood and acrylic case make the whole thing look as good as it sounds.

We noted that [lonesoulsurfer]’s previous “Box of Beezz” drone synth seemed to evoke parts of the “THX Deep Note” at times; similarly, some of the sounds of this synth sound like they’d come from the soundtrack of a [Christopher Nolan] film — check it out in the video below.

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Fytó Is Fido For Phytophiles

August 15, 2022 by Kristina Panos 5 Comments

On the surface, most plants really aren’t all that exciting, save for maybe the Venus flytrap. Sure, you can watch them grow in the long run, but for the most part, they’re just kind of there, quietly bringing peace and cleaner air. Day by day, they hardly move at all, although if you’re one of those people who likes to get the Sim into the pool and take the ladder away, you could always play the drought game just to watch it droop and come back to life a half hour later.

Fytó the smart planter is a much more cool and far less cruel way of spicing up your plant life. The idea is to turn a plant into a pet by giving it an expressive face. Sure, plants have needs, but they communicate them more subtly than the average Earthing. By assigning animated emoji to various conditions, the plant becomes more familiar and in turn, feels more like a pet. Plus, the whole thing is just so darn cute.

Fytó runs on a Raspberry Pi 2W and has six emotions that are based on a capacitive soil moisture sensor, an LM35 temperature sensor, and an LDR module to detect light levels. If everything is copacetic, Fytó puts on a happy face, and will lick its lips after getting a drink of water. If the light is insufficient, Fytó looks sleepy; if the plant needs water, Fytó appears sweaty, red-faced, and parched. Don’t conflate this with the temperature-taking emoji, which indicates that Fytó is too hot. Finally, if the spot is too drafty and cold, Fytó looks like it’s nearly frozen. Be sure to check out the video after the break and watch Fytó work through their range of emotions.

Would you rather hear your plant complain in English? There’s a build for that.

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Four Servo Fingers Play Simon Better Than You Ever Could

May 10, 2021 by Dan Maloney 10 Comments

Remember Simon? We sure do. Simon — as in “Simon says…” — from the leading edge of electronic games in the 1970s, which used four buttons, colored lights, and simple tones as the basis for a memory game. Players had to remember the specific sequence of lights and replay the pattern in order to advance to the next round. It was surprisingly addictive, at least for the era.

For those who never quite got into the Simon groove, fear not — the classic game has now been fully automated. While there were plenty of approaches that could have taken to interfacing to the game, [ido roseman] went with the obvious — and best, in our opinion — technique and simulated a human player’s finger presses with servo-controlled arms. Each arm carries a light-dependent resistor that registers the light coming from the key it’s poised above; the sequence of lights is sensed and recorded by an Arduino, which then drives the servo fingers’ replay attack. The fingers aren’t exactly snappy in their response, which might cause problems — if we recall correctly, Simon is somewhat picky about the speed with which the keys are pressed, at least at higher levels of play.

On the whole, we really like this one, not least for the nostalgia factor. We’ve had a lot of recreations of Simon over the years, including a Dance Dance Revolution version, but few attempts to automate it. And a crazy idea: wouldn’t it be fun to replace the replay attack with a machine learning system that figures out how to play Simon by randomly pressing keys and observing the results?

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