Introduction: LaserOscope

Picture of LaserOscope

Build a laser oscilloscope using Lego, littleBits, Erector set, and the Kano Computer. In honor of The International Year of Light I’ll demonstrate how use the Kano computer to drive a littleBits motor with an optical coupler, or optocoupler. An optocoupler, according to Wikipedia, "is a component that transfers electrical signals between two isolated circuits by using light." The Kano Computer is one isolated circuit and the littleBits Light Sensor/Motor is the second isolated circuit. I’ll use the Kano Computer to flash an LED (Light Emitting Diode) and these flashes are read by the littleBits Light Sensor to turn the littleBits motor on and off.

While the LED of the Kano is switched on, the light sensor will switch the motor on and when the LED is switched off the light sensor will switch the motor off. The faster the LED is switched on and off, the faster the motor will spin. Conversely, the slower the LED is switched on and off, the slower the motor will spin. To get the Kano Computer to flash an LED, you’ll need to install the scratchgpio5 software on the Kano. For detailed instructions see my review of the Kano computer here. Also, if you’re not familiar with littleBits, see my review here. In my review of the Kano Computer, I demonstrated how to use MIT’s Scratch graphical programming language on the Kano to flash an LED (the “Hello World!” program of hardware hacking). I’ll again demonstrate how to flash an LED, but using a special variable in Scratch called “MotorA”. Scratch automatically handles all of the programming for MotorA to produce a “pulse width modulation” (PWM) signal on Pin 11 of the Raspberry Pi. For a primer on pulse width modulation, see this article. I’ll show you how to write a simple program to increase and decrease the flashing of an LED by pressing keys on the Kano keyboard.

Don't forget to follow me on Twitter @Steve Schuler20!

Step 1: Create the MotorA Variable in Scratch

Picture of Create the MotorA Variable in Scratch

(You can create your own Scratch programs here).

On the Kano, open up the Scratchgpio5 version of Scratch. In the Kano version of Scratch, click on Variables (on the web version click on Data). Click on the “Make a Variable” button and type “MotorA” in the textbox (see picture 1 above). Click the “OK” button and Scratch will create all the motor control variables for you (see picture 2 above).

The third picture above is the Scratch program I created to control the flashing of an LED. The Scratch program is fairly simple:

WHEN THE GREEN FLAG ICON IS CLICKED

DISPLAY MESSAGE: “Press up arrow to increase speed, down arrow to decrease speed, or spacebar to exit.”

SET MOTOR A TO 0 (Stop motor)

REPEAT

WAIT .01 SECS (Slows processing down enough to display one keypress at a time)

DISPLAY THE SPEED SETTING OF MOTOR A

IF UP ARROW KEY PRESSED

INCREASE MOTOR SPEED BY 1

IF DOWN ARROW KEY PRESSED

DECREASE MOTOR SPEED BY 1

IF MOTOR SPEED IS GREATER THAN 100

SET MOTOR SPEED TO 100

IF MOTOR SPEED IS LESS THAN ZERO

SET MOTOR SPEED TO 0

UNTIL SPACEBAR IS PRESSED

SET MOTOR SPEED TO 0

END PROGRAM

Step 2: Build the Laser Mirror Spinner

Picture of Build the Laser Mirror Spinner

To be able to view the sound wave patterns we’ll need to bounce the laser beam off a spinning mirror and then project the beam on to a screen. Here’s how I built my laser mirror spinner out of Lego and littleBits.

Step 3: Test the Kano Computer and Laser Spinner

In the video I have the LED from the Kano computer plugged into the hole in the Lego Technic plate above the LDR (Light Dependent Resistor) on the littleBits light sensor module. When I press the up arrow on the Kano keyboard the LED flashes faster and faster and the light sensor switches the littleBits motor on and off faster and faster—thus the mirror spins faster and faster. When I press the down arrow on the Kano keyboard the LED flashes slower and slower, the light sensor switches the littleBits motor on and off slower, and the mirror spins slower.

Step 4:

Picture of

For the speaker I chose to use the Boom Tunes speaker. The Boom Tunes speaker is described on Amazon as:

"a compact, lightweight device that turns anything into a speaker that lets you play music around the house, outside, or anywhere you go! Simply plug it into any ipod, music player, or computer and stick the Boom Tunes on a box, table, water bottle or any surface that reflects sound! The bigger the object, the louder the sound. You can turn anything into a speaker- from boxes to cups, to cans, coolers and tables, and even sneakers....almost anything you can think of! The secret is the vibration pod that transfers crystal clear sound with treble and bass to any object. Stick it on almost anything and BOOM...it’s a speaker.”

The actual speaker part is rather small and easy to mount so I could bounce a laser beam off of it. It was a simple matter to attach a small mirror to the sticky part of the Boom Tunes speaker.

Step 5: Mount the Laser and the Speaker

Picture of Mount the Laser and the Speaker

Now we’ll have to hang the laser and the speaker at about the same level as the spinning mirror (it’s easier to aim the laser at the mirror on the speaker, then at the spinning mirror, and then at the graph paper screen). I used Erector set parts to build stands for the laser and the speaker.

For directions to build the stand for the laser pointer see my article “Erector Set Magnetic Optical Mount For Laser Pointer"

Then I built a chip clip mount for the speaker (simple build instructions can be found here) and I mounted the speaker with the mirror attached.

Step 6: Build the Graph Paper Screen

Picture of Build the Graph Paper Screen

The graph paper screen is easy to build with a piece of cardboard, graph paper, and a large binder clip.

Step 7: All the Parts of the LaserOscope Together

Picture of All the Parts of the LaserOscope Together

In the first picture you’ll see all the essential parts of the LaserOscope together (starting from the left): The graph paper screen, Kano computer keyboard, Boom Tunes speaker mounted on Erector set stand, laser pointer mounted on Erector set stand, Kano Computer, Boom Tunes speaker case, laser mirror spinner, and iPod with sine wave generator app loaded. The laser pointer is pointed at the mirror on the Boom Tunes speaker which reflects the laser beam onto the laser spinner mirror which reflects the laser beam on to the graph paper screen.

In order to shoot the following video I had to make two modifications to the original design. I had to attach a wall wart power supply to the littleBits power module so I wouldn't wear out the 9 volt battery, and I powered the Kano computer with a mobile phone battery instead of its normal power supply. The second picture is a shot of the Kano powered by the cell phone battery.

To conclude, review the video again that demonstrates how the LaserOscope works. As I sweep through various sine wave frequencies you see their wave forms displayed on the graph paper screen.

Comments

alponso kane (author)2015-06-28

this is awesome, thanks for share

tomatoskins (author)2015-04-08

This made me chuckle! Home made oscilloscope? Heck yes! I love the use of so many building platforms. Erector set, littleBits, Lego, Oh My! Thanks for sharing!

KRA5H (author)tomatoskins2015-04-09

Thanks for the compliment! It was a cool challenge trying to build an oscilloscope out of a pile of toys. I hope I was able to demonstrate the basic elements of an analog O-scope that displays sound wave forms on a screen as they bounce off the vibrating mirror stuck on a speaker. I also hope that it inspires people to come up with their own o-scope designs built from toys or stuff from around the house.

tomatoskins (author)KRA5H2015-04-09

I've tried to make my own a few years ago using an old CRT monitor. It was an interesting build but it turned out to be a little too dangerous and not accurate enough to use on a regular basis.

Rubiks bakon eater (author)2015-04-09

What if lighting hits you? That would be aukward

KRA5H (author)Rubiks bakon eater2015-04-09

That might depend on if you're going in the direction of Aukland when struck by lightning for it to be "aukward." No matter where you are in the world, I'm sure being struck by lightning would be shocking.

russell1 (author)2015-04-08

What bluetooth keyboard is that?

KRA5H (author)russell12015-04-09

That's the keyboard that comes with the Kano Computer. See my review of the Kano on Science 2.0:http://www.science20.com/square_root_of_not/kano_c...

I post how-to guides on several sites such as Science 2.0http://www.science20.com/square_root_not Hackaday.iohttp://hackaday.io/KRA5H and so on (and, of course, here on Instructables) and use my Twitter account to provide links to my how-to guides on these various sites so don't forget to follow me on Twitter @SteveSchuler20 https://twitter.com/steveschuler20

puma560 (author)2015-04-09

This is brilliant! It would be great to have in classrooms etc.

KRA5H (author)puma5602015-04-09

Thanks! See my reply to tomatoskins below--it's my hope that people will come up with their own designs for an O-scope built out of toys or stuff from around the house.

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