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Wave Viewer - A Mechanical Oscilloscope

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Picture of Wave Viewer - A Mechanical Oscilloscope
What It Is:  This "wave viewer" creates a zoetrope-style effect that lets students see a snapshot of the waves on a vibrating string.

Learning Objectives:  A kid-powered, mechanical oscilloscope helps students explore wave phenomena.  Younger students can get a feel for the concepts of waveforms, frequency, and amplitude.  Older students can gain a greater understanding of the functions of an electronic oscilloscope (such as sample rate and amplification).

Grades:  Kindergarten through high school

Sources:  This project was begun as part of a university's science outreach program to an elementary school.  Inspired by the concept of "The Exploratorium Science Snackbook," which offers instructions on how to create classroom-sized versions of science museum exhibits, and by the amazing artwork of Norman Tuck, we created this project. 

Cost:  $20 - $30

 
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Step 1: Parts and Supplies

For the main assembly:

   - A plastic bucket, 5-gallon size or similar
   - A lid to match that bucket
   - Black spray paint, suitable for use on plastics
   - Black elastic cord, about 24" long, and the thicker the better.  (This is available at most craft stores.)
   - A "lazy Susan" turntable bearing.  (I used a 6" version.)
   - White paint
   - A wide board to use as a base, about 12" x 18"
   - Two small eye hooks
   - A small cleat, such as the kind used for window blinds' sash cords
   - Three lengths of 1" x 2" wood, each about 16" long (or about the same height as your bucket)
   - Two triangles of scrap lumber, or two store-bought angle braces (see step 6)
   - Wood screws, 1" length or similar
   - Various nuts and bolts.  (I heartily recommend grabbing a $2 assortment of machine screws, rather than tracking down each part individually)

For the handle:

     Either Version One:  - One bearing from a skateboard wheel (see step 8)
                                        - One half-inch PVC pipe coupling
     Or, Version Two:  - A length of half-inch dowel (about 4" to 5")
                                  - A length of half-inch PVC pipe (of the same length as the dowel) 

Tools and other equipment:

     - An electric drill
     - Screwdriver
     - Pliers
     - Sandpaper
     - Paintbrush
     - Oven

Extra supplies for lessons:

     - Black electrical tape
     - Scissors
     - A black Slinky (the small kind sold as party favors by dollar stores)


BertieB3 months ago
Thanks so much for posting this! I saw an oscylinderscope at a science museum and have wanted to build something like it ever since. Voila, your project - affordable and simple to build. A few design changes I made: for the stripes, I bought white electrical tape and used a knife to cut the roll to a narrower width, then I taped the stripes on. Much simpler, and I can adjust them if I want. I made mine with three different plucking strings so that people can compare the wavelengths of strings with different pitches. I also purchased a small rotating caster wheel to use for the handle on top, but in the end I found that just pushing it with my finger works well. I think not having the handle will reduce wear and tear by avoiding rocking the bucket back and forth. (It's for kids to use!) Thanks! I am looking forward to using this in my classroom!
schaude2 years ago
very nice project, indeed!

two years ago i've seen something similar but bigger - called "oscylinderscope" and built by norman tuck - and being very expensive - on an education show.

we tried to build our own with a few girls during a day for musical projects at school using an ikea sideboard, some scrappy plywood and a broken guitar. the ball bearings we've used for the drum came from a pair of inline skaters, very close to your solution ;-)

hopefully you can see the images attached here. one is as seen on the show while the other shows our nearly finished product. the girls painted it nicely afterwards and for two years now it's bringing fun to pupils walking along or waiting in front of it while physics teachers can use it for educational purposes with the wave theory.
Musikschulfest 2010 693.jpgOszylinderskop Didacta K��ln 2.JPGOszylinderskop Didacta K��ln 3.JPG
ChrisMentrek (author)  schaude2 years ago
Wow! Your guitar-based oscilloscope looks great!

I think that you should consider posting an Instructable on how to make your creation. I'm especially curious about how you attached the large drum to the skate bearings.

How easily does the drum turn? Have you tried varying the width and spacing of the lines on the drum?

Thanks for your pictures, and "Viel Erfolg!"
hey chris,
thanks!

after painting a large circle on the plywood we cut the circled shape with a milling cutter. with the same tool we cut a bigger hole in the center - up to half of the plywood's thickness. that's where the bearings found their new home.
close to the outer circle, around 5 cm away, the milling cutter cut out a notch, circa 6 mm deep. that's where later on a thin plywood will form the cylinder drum's bent tube wall.

we put a threaded rod into the center of the bearings and fixed both sides with big washers and  screw-nuts. the rod was inserted through the big drum into the other side's bearings. the fixing procedure was the same here.

between all that it was tricky putting the thin, white-striped and spray-painted plywood (as we use it in the back side of some cupboards) into the small notch and putting the whole thing into the ikea shelf type "ivar, 50 cm". during this process we had to fix all the screw nuts on the threaded bolt - also the ones inside the drum that should later fix the bearings from the inside. the strings are more or less tuned in major thirds.

you can now easily turn the drum with one hand while the other is pulling the strings. the "oscylinderscope" has three nylon strings of different lengths and a foot pedal (where the strings are fixed) to enlarge the string length while enhancing the string tension. pulling the strings while pressing down the pedal makes you easily play the intro of deep purple's "smoke on the water" (as i heard it once when a girl played it on the oscylinderscope).

unfortunately i don't now a lot about american and international copyright and related rights. so i wouldn't like to violate the owner's rights. as written above tuck norman has built the version i had seen first. but if you like i could send you some more detailed pictures of our finished product.

please excuse my bad english - being an english learning pupil for me is a long time ago now!
best wishes,
schaude
ChrisMentrek (author)  schaude2 years ago
Hi, Schaude:

This sounds like it would be a lot of fun to build! I'd love to see more photos and hear more about how you built it.

Have you considered making an Instructable for your creation?

Thanks again!
almateus2 years ago
Very nice project. We did a smaller version using a soda bottle. You can see it here http://pontociencia.org.br/experimentos-interna.php?experimento=38 (instructions are in Portuguese only, but there are lots of images) or just look at the video (http://www.youtube.com/watch?v=XQQFP2Eq3Rc).
ChrisMentrek (author)  almateus2 years ago
Obrigado, almateus!

Maravilhoso! I love the soda bottle version! The wide stripes and ease with which it can be rotated look to be real improvements. I'll try to make one of these this weekend.

Now I'm hooked on this cool ("legal"?) Pontociencia website -- it's going to take me a long time to learn all of these projects.

(P.S. -- "Ghost Riders" was an outstanding choice of muical accompaniment.)
I am really glad you liked it! Pontociencia has the same idea as Instructables, even though it is just about experiments. Step by step instructions, videos, images. I should post some of our projects here, to get more american visitors (at least those that don´t mind the portuguese, like you!)
ChrisMentrek (author)  almateus2 years ago
Hey, almateus:

Pontociencia is a great site! I've already found a bunch of experiments I'd like to try. It'd be appreciated if you made some posts to help English-speakers find more experiments.

And thankfully, all the handy photographs make the experiments easy to understand for those of us who can't read Portuguese.

(I mean, the only Portuguese I know is... um... "moqueca de peixe," and... "Anderson Varejao.")

Ralphxyz2 years ago
Hey Chris, that http://www.instructables.com/files/orig/FP4/D3WC/GZ6T0ION/FP4D3WCGZ6T0ION.avi video shows the Wave nicely, thank you it really adds to the project!!

Ralph
jolshefsky2 years ago
This is a really cool project. I thought I'd mention that I believe the inside diameter of skate bearings is 8mm. a 5/16" screw is 7.94 mm, so it fits a bit better than 1/4" (6.35 mm).
ChrisMentrek (author)  jolshefsky2 years ago
Hey, jolshefsky:

Thanks! There WAS a bit of wiggle room while tightening the screw-bearing-nut parts in Step Eight. The slightly-wider 5/16" screw would probably help correct that!

(If fact, if you look closely at the photos, you can see me struggling to keep the screw properly aligned with the inside sleeve of the bearing!)

Thanks again!
I used that 5/16 trick in the past ... the other handy fractional-inch-to-metric conversions are:

5/64 = 1.984375mm
5/32 = 3.96875mm
15/64 = 5.953125mm
5/16 = 7.9375mm
25/64 = 9.921875mm
15/32 = 11.90625mm

I find 5/16 is the most convenient because it's the lowest denominator ...
ajoyraman2 years ago
I saw the video , Great Teaching concept ! Best Wishes for many more such ideas.
ChrisMentrek (author)  ajoyraman2 years ago
Hey, ajoyraman:

Thanks for your comment! I'm intrigued by your "sound card oscilloscope / function generator" project -- I'm going to get a colleague with more technical expertise to help me try it out.
Ralphxyz2 years ago
Nice project,

But I cannot believe you did not included a video!

Or would your cell phone or camera not catch the effect?

Any way great idea, I'd love to see it working.

Ralph
ChrisMentrek (author)  Ralphxyz2 years ago
Hey, Ralphxyz:

The illusion is not nearly so pronounced in my cellphone-grade video as it is to the human eye, but I've still included a video of the oscilloscope effect.

It's posted above as "WaveViewer3.avi"

I'll see if I can get a friend with a niftier camera to help make more video for the future.

rusty01012 years ago
A tip for doing this on your own.

Get four pieces of string, the diamater of the bucket lid should be long enough.

Tie one end of each string to the thread of one each of the machine screws.

thread the other end of the string through it's respective hole in the lid for the bucket. (Optionally tie the ends together once through the lid, not necessary, but may be helpful.

Now use the string to guide the screw through the hole in the bucket lid.

Remove the string and attach the nuts.


Separate tip if you have the time. To make it easier to tighten the nuts,

- Before putting the machine screws in the turntable bearing to begin with, put one or more of the nuts on the machine screw
- mount the screw in a vice.
- Using a hacksaw cut a clot in the end of the screw so that you can provide leverage for tightening with a flat head screwdriver.
- Remove the machine screw from the vice
- remove the nut from the machine screw - This will do some repairs to the threads you cut with the hack saw, reducing the chances you will cross thread the nut onto the screw when assembiling the turntable.


Hope someone finds these tips helpful.
another option for getting the machine screws to mount into the holes in the lid easier would be to tighten them to the turntable bearing with a second set of nuts, make sure that they are positioned correctly, and adjust as needed, then mount the turntable bearing to the wood base. This may also reduce the need for a way to hold the bolt fast when tightening the lid down to it.

Obviously if you have a welder, and the steel of the bearing and the machine screw are compatible enough, you could just spot weld them in place, though adjusting that would be a bit more difficult.

Over all I like the project. Thanks for sharing the instructable.
ChrisMentrek (author)  rusty01012 years ago
Hey, rusty0101:

Thanks for the tips! They sound like they'd make for some seriously sturdy wave viewers!
Royski2 years ago
I used to show my pupils the wave form produced when "twanging" a piece of elastic band. I put up a white page on my computer monitor, held the taught band in front and plucked it.
Whilst being assessed by the headteacher I used this teaching aid but as he was in a completely different part of the room, he couldn't see the effect. When I showed him after the lesson he had to amend his notes which had said I was wasting time!
You can get the same effect with a CRT television.
ChrisMentrek (author)  Royski2 years ago
Hey, Royski:

Holding an elastic string in front of a CRT television or monitor sounds like an awesome start to another project:

Could we get the monitor to display "flashing" videos at different frequencies, and then use these as backgrounds for a vibrating, elastic string?

Thanks for the tips -- I'm glad you got credit for Not Wasting Time!
wilgubeast2 years ago
This is great. I love the stuff that's coming out of the Exploratorium. It was a great field trip destination, and the summer PD is awesome. Looking forward to more great stuff!
heathbar642 years ago
very cool! I was wondering, just cuz i probably will play with this by myself, Why not add some weight to the bucket to act as a flyweel. then it would spin more steadily and longer. Also wondered about wrapping a rope around it to pull and spin it.
ChrisMentrek (author)  heathbar642 years ago
Hey, heathbar64 and ilpug:

These are great ideas! If we made another one and didn't paint on the stripes, we could always change the stripe width/spacing by applying new stripes from some kind of tape.

My first instinct is to use a combination of that narrow, white typist-correction tape for some narrow stripes. For wider stripes, we might try that white, labeling tape made by Post-It...

The flywheel is another good suggestion; right now, the bucket won't "coast" through more than about half a turn or so. (Though the kids always seem ready to keep it moving with some vigorous turning.)

Maybe if we added a denser layer to the inside of the bucket lid? Perhaps a circle cut from thick MDF or plywood?
ilpug2 years ago
Oh wow, ingenuity at it's best. I approve, with one question: could you widen the white stripes slightly, to make the "image" appear a little better? or make a way so that you could substitute in various sizes of white stripe to see how it affects viewing?
sdallesasse2 years ago
Did you think about or perhaps try cutting slots in the bucket? I'm thinking that with a light source inside the bucket you could project an image of the waveform. I'm not sure how far of a projection or how clear it would be, but it seems like it's possible.

Nice project, my son and I saw something similar and larger at a local museum in Milwaukee, WI. It's called Discovery World.
ChrisMentrek (author)  sdallesasse2 years ago
Hey, sdallesasse:

Ooooooh! A shadow show! That sounds like it'd be a lot of fun to try!

I think I'll try out your idea on a smaller model -- probably one made from one of those cylindrical oatmeal containers.

(In a side note, on my first version of this wave viewer, the stripes were just lengths of string that I'd glued to the bucket, since I was too impatient to paint on the lines. These still produce the intended effect, but they're nowhere near as durable, and don't stand up well to being obscured with black tape.)

Discovery world sounds like a great place! Time for a road trip!
kelseymh2 years ago
This is a very cool project, but I'm having some trouble visually what you'd see in real life. Have you tried making a video of it in action? I know there are going to be nasty aliasing effects from the different frequencies of the video framing vs. bucket rotation, so it may not work.
ChrisMentrek (author)  kelseymh2 years ago
Hey, kelseymh:

I took your advice and tried to include a video of the oscilloscope in action.

The effect is nowhere near as pronounced in the video as it is to the human eye, but it still gives you an indication of what you'd see with the wave viewer.

We'll see how it goes!
rimar20002 years ago
Any video, may be? This seems very interesting.
Dr.Bill2 years ago
Next Step: Radio !
That's very clever! I like this project! Thanks for sharing!
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