Prolific Hack a Day author [Mike S] has been playing in his lab again and he’s come up with a neat way to talk to microcontrollers with an LCD monitor. The basic idea behind [Mike]‘s work isn’t much different from the weird and/or cool Timex Datalink watch from the 1990s.

Despite the fancy dev board, the hardware is very simple – a photoresistor is pointed at a computer monitor and reads bits using Manchester encoding. The computer flashes a series of black and white screens thanks to a simple Javascript/HTML page, and data is (mostly) transmitted to the micro. [Mike] says he has about a failed message about 60% of the time, and he’s not quite sure where the problem is. He’s looking into another kind of Manchester encoding that uses samples instead of edges, so we hope everything works out for him.

This build is very similar – and was inspired by – an earlier post about microcontroller communication with flashing lights. Still, [Mike]‘s build reminds us of the strangely futuristic Ironman watch we had in ’97. Check out [Mike]‘s demo of his computer/micro comm link after the break and his code on github.

You’re out at night and playing a boisterous game of flashlight tag. But how can you tell if you’ve been mortally wounded by your opponents light beam? [Kenyer] solved this problem by building a flashlight tag damage sensor which is worn by each participant. It adds a bit of the high-tech equipment used with laser tag while keeping a low-tech price tag.

The sensor relies on a light dependent resistor to register hits when a flashlight beam passes through the round window. It will only register one hit in a three-second time period. At the end of the game, the total number of hits recorded can be flashed back using an on-board LED to see who is the victor. You can see a demo of this functionality in the clip after the break.

[Kenyer] started with a breadboard prototype using an Arduino as the driver. Obviously the cost of an Arduino for every player is a bit ridiculous. He scaled down the project, running the Arduino code on an ATtiny microcontroller.

The latest offering in glove-based noisemakers forsakes commonly used flex sensors in favor or photoresistors. [Bruno Ratnieks] is responsible for this musical glove and his methods will be very easy to recreate. He used an Arduino to interface with it while providing a USB connection to your audio software. The sensors themselves couldn’t be easier to throw together, with each photoresistor creating a voltage divider when combined with a fixed-value resistor. That’s all the hardware you need, and with some creative coding you can making it do much more than the effects heard in the video after the break.

Some will say that [Bruno] simply didn’t used enough duct tape with his project design. Be we liked how he wove the wiring into the mesh of these knit gloves to keep it firmly in place.

[Julien] built an input device that uses reflected light detected by some photoresistors. Placing your hand above the device will reflect light from the LED back down onto the cadmium-sulfide sensors. The resistance of those sensors is read by four ADC pins on a Teensy microcontroller and translated to mouse movements. In the video after the break you can see that this works rather well in controlling the cursor. The source code is available on pastebin but we’re also going to host the code for posterity.

[Thanks Patrick]

[Shay] and his friend built some battling robots for a school project. Instead of destroying each other’s robots with saws or torches, they are playing laser tag. Each robot sports an eeePC, a laser pointer on a movable arm, and some photoresistors. The goal is to get your laser to hit the other robot’s photoresistor to lower its health towards a kill. A server keeps track of the bout, monitoring shot fired because you won’t find unlimited ammo in this game. As for piloting the rig, the netbook webcam is streamed to a control station with an Xbox 360 controller for motion, aiming, and firing. Check it out after the break.

This peculiar setup allows [Ben Krasnow] to control an alternating current device using one pin on a microcontroller. He’s experimenting with a power drill and has relocated the trigger circuitry that makes it spin. On that board he found a variable resistor combined with a capacitor which control a triac, actuating the speed of a drill. [Ben's] solution works great and isolates the drill from the control circuitry. He replace the variable resistor with a cadmium sulfide photoresistor (basically a variable resistor whose resistance depends on the intensity of light). Pulse-width modulation is used to adjust the brightness of an LED shining on that photoresistor and thereby affect the speed of the drill. This is such as simple alteration to the drill we’d call it MacGyver-esque.

See a demonstration after the break.

[Alex] continues to delight us with his projects. His third-generation tiny Braitenberg vehicle, a light seeking robot, is a big improvement over its predecessor, the mini Braitenberg vehicle. He’s moved from an Arduino based design to using the AVR ATtiny25v, replaced the breadboard with a PCB, and reduced the parts count. We think it was a great idea to use shrink tubing to shield the back of the photo-resistors from ambient light. Don’t miss the video of these little guys chasing a flashlight beam after the break.

[vilxes91] sent in this cool little false-theremin (translated). Its a pretty simple circuit, that can fit in really small places. It isn’t a true theremen because it uses the amount of light coming in around the lid for the modulation. To play it, you turn it on and open it up, the more open the lid, the higher the pitch. You can see a video of it in action after the break.

The NoiseAXE is a miniature synthesizer based on the Picaxe 08M microcontroller.  Its operating principle is fairly simple: a conductive stylus touches the leg of one of eight resistors to play one of eight notes, while a photoresistor controls the amount of modulation, creating a variable vibrato effect.  While the synthesizer’s output is rather limited (the NoiseAXE isn’t exactly a Yamaha DX7), it’s still a pretty cool little project; you could use its unique sounds to add that gritty analog touch to your next electro hit.  Check out the video clip below to see and hear it in action.

[photo: rarebeasts]

The ThingamaKIT is an anthropomorphic analog synthesizer kit from Bleep Labs. Using “LEDacles”, photoresistors, knobs, and switches, it generates interesting high pitched vocalizations. Bleep Labs sent us a review unit and this article shares our experiences building and using the kit. We’ve also included a tutorial on making some hacks, modifications, and circuit bends to it. Skip to the end to see a video of our hacked kit in action.

Using the ThingamaKIT

While it may not be that useful for serious musical composition, the ThingamaKIT makes some nice bleeps and blips, even without modification.The LED to photoresistor input/feedback method is enjoyable to play with, by repointing the LEDacles and waving hands around the photoresistor. The ThingamaKIT is very easy to start using; just twiddle knobs, and it starts making its characteristic ridiculous sounds.

The ThingamaKIT is an simple but fun circuit, and schematics are provided. Three Schmitt trigger oscillators, like the ones used in the previous Hack a Day synth article are used to control the first LEDacle. Because they have different frequencies, the LEDacle blinks in an interesting manner. A Schmitt trigger and op amp generate a triangle wave for the other LEDacle, with controllable waveshape and speed. Another Schmitt trigger generates the modulating wave, with a frequency based on either Photocell 2 or a potentiometer. The main oscillator, the XR2206, has a pitch controlled by Photocell 1, except when the output from the modulation is high, then it switches to a different pitch.

Embedded above is Bleep Labs official demo video.

Building the ThingamaKIT

The instructions for building the ThingamaKIT are printed well and easy to follow. [Surachai]‘s build time lapse, shown above, gives a nice overview of the process. We had no problem finding components and soldering them to the board. Though troubleshooting instructions are provided in the manual, our device worked fine, and we did not need them.

If you are assembling the ThingamaKIT with the intent to hack it as shown in the rest of this article, there are a couple things you should do differently than shown in the instructions.

• Cut the 4” wires a little longer, closer to 6”. You’ll need the extra length when fitting components.
• Do not install the waveshape switch, unless you want to test the default ThingamaKIT unit without modifications.
• Do not proceed to the casing steps until you have made modifications.

Hacking the ThingamaKIT

Bleep Labs has designed the ThingamaKIT to be easily circuit bendable, and there are many fun hacks that can be done with this unit. A few are briefly presented in the extra information given with the kit. While playing around with it and assembling it, we also discovered several more. We’ll show you a few different hacks and circuit bends that you can do with an assembled ThingamaKIT.

Adding an audio input

Our favorite hack for the ThingamaKIT is to add an audio input. The ThingamaKIT will completely warp any audio input, crushing it to lo-fi fuzz and crunches. Here is its emotional rendition of The Police’s “Every Breath You Take”:

To do this, you’ll need a 3.5mm audio jack, like the kind used in the previous synthesizer how-to article and a SPDT (three way) switch. Solder a wire to the signal lug and a wire to the ground lug on the jack. Then, solder the signal wire (the blue wire) to the left hand pad of the .01 uF capacitor, which is outlined above in red. Our solder joints look like a warzone, but it all works. We swear.

There are two places the ground wire can be soldered, and each has a different sound; we installed a switch so that both could be used. Solder the ground wire to the center lug on the SPDT switch. Solder one of the outside lugs to the board’s ground, and another to the other pin of the .01 uF capacitor, as outlined in red above.

To use the audio input, flip the SPDT switch to either outside position, then patch some audio to the input. Music, drum machines, other synthesizers and more all work to make an interesting sound.

Adding a waveshaper knob

In its default configuration, the ThingamaKIT only has a switch to select between triangle and square wave main oscillators. By replacing this knob with a potentiometer, you can transition smoothly between the two waveforms. However, there will be a significant attenuation (decrease in volume) when the potentiometer is near its center, as both outputs will have increased impedance. This is not easily corrected, except with active amplification, or a dual potentiometer with two different tapers, which we have been unable to find.

To do this mod, you first need to remove the waveshape switch if you have already attached it. The easiest way to remove it is with a desoldering iron. Simply squeeze the bulb, place the hot iron over each pad (pads to remove are outlined in red on the image above), and release the bulb. Do this for each pad until all solder is removed, then remove the switch. Keep the switch, as it will be useful if you want to do the sine wave hack.

Next, solder three wires to a 10K potentiometer, such as the one pictured above. The red wire goes to the middle lug, and the other two go to either end on the board.

The waveshaper knob is complete, and you can now easily fade between square and triangle waves.

Adding a sine wave switch

While reading the datasheet (PDF) for the XR2206, the signal generator that the ThingamaKIT uses, we noticed a very easy way to change the triangle wave output into a sine wave, which has a softer sound.

If you are doing this with the waveshaper hack above, start by taking the old switch, and removing one lug from its side. Then bend the other two down slightly, as shown. This will allow the switch to fit where the old one did on the panel, without being in contact with the board. Solder two short wires to the remaining lugs. Then, stick a piece of electrical tape over the top of the pads on the board where the potentiometer is now wired, and put the switch there, using a bit of hot glue to hold it in place.

To one wire, solder a 220 ohm resistor inline; an extra is helpfully provided in the kit. Wrap the resistor in electrical tape to cover the exposed leads, then solder the two wire ends to pins 13 and 14 of the XR2206 as outlined in red above. The sine wave mod is complete!

Adding a spike wave switch

Another bend we found while poking around in the unit caused the main oscillator to create a “spike” waveform. It produces a nice lo-fi, glitchy sound. To add this bend, take any normal SPST (two way on-off switch) and solder a wire to each lug.

Then, connect it to pins 8 and 6 on the XR2206, as outlined in red. The spike wave mod is done.

Packaging it all up

To finish up our ThingamaKIT, we followed the instructions provided with the kit, but with a few modifications. A couple of extra holes had to be drilled for the new potentiometer (5/16”), the spike wave switch (5/16”), and the audio input (1/4”).

We had some difficulty getting all of the new components fitted into the case, but with some rearranging we managed. Be sure not to push the photoresistors up higher on the face then is shown on the drill jig, or you will have trouble fitting them around the LEDacles. The volume potentiometer was also mounted a little low, and we had to put the speaker toward the controls side rather then the LEDacle side of the case to fit it in.

Check out the demo video below to see our glorious leader in action.

Further hacks

To hack your ThingamaKIT further, Dr. Bleep has some recommendations in the manual: using the extra oscillators on the board to add effects, replacing the variable photocells with resistors and buttons to make a keyboard, making a patchbay, and getting complete control over LEDacle 1 with potentiometers.

That concludes our ThingamaKIT hacking. Have any of you built one? To see other custom ThingamaKITs, check out the Flickr group.