I love that the variable resistor is made from a pencil.

@mattw7949

2 жыл бұрын

I was going to comment the same thing. It brought back memories of my sparky youth.

@stevesedio1656

2 жыл бұрын

I used a pencil resistor to control motor speed for a strobe light (combination of this post and one a couple of posts down).

@EXwifeKILLER

2 жыл бұрын

That is pretty genius

@tylermcnally8232

2 жыл бұрын

@@EXwifeKILLER it's really not. It's fairly basic.

@EzeePosseTV

2 жыл бұрын

It's called a Pencistor.

I qualified as an electronic service engineer some 30+ years ago..... And I've NEVER seen such an elegantly simple demonstration of a variable resistor. EVER! Kudos to you.

@maelixdiogen1383

2 жыл бұрын

I saw something like this in a free Wednesday children program The set was a bulb light whose light was dimmed or brightened with the position on the pencil. Title was msybe 1 2 4 something And the introduction video sequence had a mesmerizing drop falling into water and the bouncing wave and maybe a small round drop coming up in the air. There was all sort of science vulgarisation for kids and fun to see to invite to curiosity. French television from late 70's or early 80's. TF1 or Antenne 2 or FR3 by the time

@bobedwards8896

2 жыл бұрын

very cool indeed, but is an inquisitive person for 20+years , iv seen it for quite sometime.

@majorlee9714

2 жыл бұрын

@@bobedwards8896 im sure we are all pleased that you've seen it before, in fact i was about go give you a medal, but then revoked it due to the fact that an inquisitive mind of 20+ should have better grammar. 🤡

@Wingnut353

2 жыл бұрын

@@maelixdiogen1383 You are probably thinking of 3 2 1 Contact... I can't find the exact episode but here is an episode where they demostrate a generator: kzread.info/dash/bejne/mX9qsNCqd9DIYdI.html if you look up episode 1 it shows them recording the theme song. I used a pencistor in a science far project around 3rd grade... we got a bit carried away with it and since we were homeschooled :D

Now that was an excellent home science video. I'm doing my best to be that kind of dad who encourages his kid to try things and who experiments together with them.

This is so cool I'm going to try building one with my son. I love how easy and informative your videos are. Thanks 😊

Seeing a new Bruce Yeany video pop up in my notifications is the best feeling. I love your content! I always learn so much!

The disk with slots is an optical stroboscope. Spin it and look through it to stop motion like a regular strobe.

@blaircox1589

2 жыл бұрын

What I was thinking as well. Some searching didn't reveal one like it, but somewhat close.

@erictheepic5019

2 жыл бұрын

@@1islam1 Sir, this is a Bruce Yeany video.

@YeanyScience

2 жыл бұрын

Thanks Eric, I want people to comment here. I do read through them and overall am extremely happy with what I find but expect it to be appropriate to the channel. When needed I will remove sexual, political, religious, or offensive comments, there are plenty of other places for those types of comments and viewers may seek them out if they so desire.

@akshinbarathi8914

2 жыл бұрын

@@YeanyScience science is beyoond all

@ahmdabdallah5811

2 жыл бұрын

@@YeanyScience My esteemed professor, I've learned a lot from you, and Keep your creations on my computer But Have you ever asked yourself these questions? "What is the purpose of LIFE?" "My life?" "Your Life?"

Finally a use for all of those old AOL CDs. Other than taking them to the range and shooting them.

@davidparker9676

2 жыл бұрын

Perfect drink coasters.

@themadscientest

2 жыл бұрын

I remember taking a few every time I saw the stack in the grocery store as a kid just to use as a frisbee.

@carmelovespa7333

2 жыл бұрын

Still have some left with original Harry Potter promo 😄😄

@ThatRollerCoasterNerd

2 жыл бұрын

What is a AOL?

@carmelovespa7333

2 жыл бұрын

@@ThatRollerCoasterNerd was/is an american internet provider, America Online

Thanks Bruce, always a pleasure watching your videos!

These videos are amazing. Your ideas are definitely a huge source of inspiration for other science youtubers.

This is so cool! Thank you for the information.

I'm 25, but these videos really take me back to being a kid. Simple and effective explanations, fun practical experiments, safe and family friendly.. Move over Bill Nye!

Learned lots in this video! Thanks for sharing your knowledge!

the world is built by men like this. creative, generous, passionate.

Cool stuff Mr Yeany, thanks for the video!

why youtube keeps recommending me videos like this after midnight? this is why i get up late

Two thumbs up! Excellent demonstration.

I can see a synth patch being created in honor of this called "table saw".

I love this. Simple experimentation is a joy. I used to do experiments in the house with my young kids, using food coloring and water. Do something, observe result, change something, do the same thing, observe new result. Now there is only one small step to making it real science: add a hypothesis at the beginning and a conclusion at the end. Yay! The power of human thought.

Never knew I needed something I didn’t existed until 5mins ago.

@klashnacovak47

2 жыл бұрын

Know^ existed.

This seems like a channel that is just right up my alley!

Using the pencil as a potentiometer is honestly so creative! Awesome!

I saw some dogs doing this in my front yard the other day. I thought they would never stop.

Thank you so much, your wonderful video saved my life from my physics teacher.

@YeanyScience

Жыл бұрын

you're welcome, seriously hope it's not as bad as that sounds

For sending signals to neighbors. Fun way to send a message.

@willbill808

2 жыл бұрын

You could send ASCII as FSK encoded binary

Every time i see one of your videos, i wish i had a teacher like you when i was young!!!

Nice man! Love it👊

SIr you are awesome.. thanks for your cool educational videos.

Thank you for making this video.

Great job, as usual. 👍

wow bruce laural is a great teacher

That's a pretty cool trick of using the graphite of the pencil to act like a variable resister.

@blindleader42

2 жыл бұрын

It's a crude slide pot (potentiometer)

@jackkraken3888

2 жыл бұрын

@@blindleader42 yes that's what I meant.

Hi Bruce awesome video. My daughter, husband and myself the wife have done some of your projects especially the dancing static balls in a box. We love that one. Thank you for this video. We will be doing this one.

Thanks Bruce very cool

6:33 made me wince, imagine that deathtrap shattering and blasting you in the face with shrapnel

That is amazing!

Heyyyy! I had forgotten this channel existed, glad this was recommended

Thanks for the video

I love your videos

Nice, I wonder what sounds you would get tracing out patterns generated from the Chladni plate .

great idea

I love how we heard nothing about harmonic series in this, yet I heart harmonic series.

Love the channel! I subbed!!

That pencil trick is such a macgyver i love it

Very interesting!!

This was a cool video that just popped up in my feed. I have a question. What would happen if you had very stable disks? In all of your homemade ones there is much wobble. Would that affect the sound quality and how?

Thomas Seebeck died in 1831. August Seebeck made the tone disk. It's interesting to notice that the design you used looks like fan blades captured by a camera's rolling shutter.

@YeanyScience

2 жыл бұрын

thank you for the correction, most of the information I would find only listed the last name.

@lotsagrapes

2 жыл бұрын

Maybe you had to have been there

Wonderful as always. I think the foam disc sounds nicest.

wow using graphite to change speed is something new for me, i didnt knew that

Your sirens reminded me of those colorful short tube siren whistles you can buy at the dollar stores. Taking one apart revealed a six hole slotted disc with beveled edges, like little ducted fans. They sound in either end of the tube you blow into. If you put two together in-line in the right way they sync up making an interesting jet engine like chorus effect, as they spin up so freely. If you flip one of the discs, or blow from the opposite end of the two in-line sirens they sound but not in phase. I put a 4 inch length of blue PEX tube on the end of the double siren which makes the effect more pronounced. I too thought of your spinning strings, and wondered what other variables could be introduced to confirm the reasoning behind the Mould Effect.

Cool demonstration thanks. Interesting that the balloon pump in both sucking and blowing is a kind of alternating current, an air current in this case.

Excellent video. I like the way your simplicity and the way you explain with a smile on your face. It reminds me of my late grandfather who sowed the seed of science in me :-). I subscribed to your channel.

@YeanyScience

2 жыл бұрын

thank you

Gracias hermano. Disfruto mucho sus videos. No concibo que alguien teniendo acceso a KZread, diga que se siente aburrido😀👌

You should really wear some sort of safety goggles when rapidly spinning cds with holes drilled in them

@dozer1642

2 жыл бұрын

I knew there would be one of you.

@Justin-hg4ef

2 жыл бұрын

I was thinking the same thing! holy moley that was actually kinda scary

@TheAchaicus

2 жыл бұрын

The speed that little motor can achieve is a long way from the failure point even with the holes added. One demonstration I have seen resulted in the cd shattering at 23,000RPM. Yes the holes do reduce the integrity some, but the 3,082.5RPM one of this video's cds rotated at to produce the note obtained is still well below the failure point of ones with holes.

@adrianshawuk

2 жыл бұрын

Famous last words

@veryboringname.

2 жыл бұрын

@@TheAchaicus Holes is one thing, what about slots like at 6:30?

i love it!

That's pretty neat

i dont know how i got here, but i enjoyed the whole video

4:58 you can hear the timbre change ("ooo" and "ahhh" is how I hear it). is this because of the additional disk mass the air stream passes over in between holes? I'm also wondering what the air column "looks" like when traveling through one of these, specifically *after* moving through the disc.

@RijuChatterjee

2 жыл бұрын

Yes! So it's sort of like pulse width modulation. - When the holes are closer to the center, the distance of travel between two holes is similar to the distance across the hole itself. This means the "on" time and the "off" time are comparable, giving you something close(r) to a square wave (the roundness of the holes will round off the waveform somewhat too but let's ignore that for now). - When the holes are far apart, the "on" time is much smaller than the "off" time and so you get a narrow "pulse wave" which has more more high frequency (harmonic overtone) content. "Ooh" formants have less harmonic content than "aah" formants, so this is why you interpret the inside as "ooh" and the outside as "aah". However, this will only work when you compare them. On it's own, neither of them will sound like "ooh" or "aah".

@CrumbleB33

2 жыл бұрын

@@RijuChatterjee This is exactly what I was thinking! I imagine the slotted disk does something similar since as you get further away from the center, the ratio of open to closed would change. While you're still getting the same number of pulses (hence pitch) the length of the pulses changes, giving you a change in timbre as the harmonic structure/distribution changes. Its pretty subtle, but you can almost hear a saw-wavy sound around 6:40 when he is near the outer edge, and less sharp (fewer higher harmonics?) when in the middle. With a cleaner air source you could probably run this through some spectral analysis and see all that. Idea for a follow up video?

@RijuChatterjee

2 жыл бұрын

@@CrumbleB33 I wouldn't say you need a cleaner air source. You could probably get informative results even from just a frequency-domain analysis of the audio in this video. Time-domain analysis might not work out as well because the digital codecs used for audio compression often mess up phase stuff. If you had a good .wav file you could do time-domain as well.

When you used the foam plate, I heard the beginning cords to "Smoke on the Water"

bro this is amazing. im building one tmr

6:27 - you don't get a change in frequency with this design, but you do get a slight change in timbre as you move around the disk. It sounds a lot like changing the pulse width on a synthesiser, where moving towards the outside edge of the disk sounds like a narrower pulse, and the centre sounds like a wider one. This must be to do with how quickly the hole moves past the air on the different edges. Also your 4 - 8 hole design sounds like the harmonic series, which is pretty cool!

@Greg042869

2 жыл бұрын

I was expecting him to lose an eye at that point.

@GhostsniperAus

2 жыл бұрын

Changing the pulse width IS changing the frequency , it’s the same thing

@edonslow1456

2 жыл бұрын

@@GhostsniperAus no, the pulse width can vary, while each pulse occurs at the same regular interval. You're thinking of wave length, which does affect pitch.

@PaulMillard1973

2 жыл бұрын

I may have misinterpreted the design but it almost sounded like a flange effect. The same effect heard when two tone sounds play simultaneously with a slight variance.

@WilliamHostman

2 жыл бұрын

I'd not say "slight"... it's a rather noticible change, most notable as the airflow begins to cross the edge; that adds another,non-harmonic, turbulent airflow, and an undertone.

I recommend that your next video be on how to build a safety enclosure for your spinning disc

Pretty neat. With all those holes drilled into those CDs, maybe a face shield is a good idea lol!

@stereoroid

2 жыл бұрын

Nah - the holes are circular, so no cracks or stress concentration, and it would take a lot more speed too.

@rong4189

2 жыл бұрын

@@stereoroid There could be cracks, the way drill bits like to grab plastic when you break through.

@crf80fdarkdays

2 жыл бұрын

@@rong4189 haha someone that actually knows what there talking about, love it.

This gives me 2000s type youtube videos

I think the brass disk with the slot was used for scanning light beams. The device used two disks, one for horizontal and one for vertical scanning. The light from an object is focussed on the disks and the resulting beam is a serial scan of the object. I've also experimented with a resistance made from pencil lead drawn in a heavy line on paper.

About the slotted disc and the discs with the same number of holes at different radii: You are right that it doesn't change the pitch. But there is a slight change in timbre because the timings of flow/no-flow of air changes relative to each other. That is probably not the purpose of the slotted disc but it is an audible difference. Also a similar technique was heavily used on older sound chips of home computers but with e.g. high/low voltage level timings on square waves to vary the sound.

Wow, I've just found a good channel.

good stuff

old but gold

Thomas Seebeck was a smart guy. He is also the founder of the Seebeck Effect. This is the basis for the thermocouple. Thomas Johann Seebeck, German physicist who discovered (1821) that an electric current flows between different conductive materials that are kept at different temperatures, known as the Seebeck effect. Seebeck studied medicine at Berlin and at the University of Gottingen, where he acquired an M.D. I just wish I was as bright as my ancestors. 😁

The foam one made my favorite sound

The design with slots is the one which I once found on a loud siren - sounded like air raid siren.

@cndbrn7975

2 жыл бұрын

I was thinking something similar. One of the disks sounded like an old Police siren.

Not sure why, but I LIKE it... subscribed 😁

The slotted disk did not chnage pitch because the number of pulses per revolution is the same at any distance from the center. Your other disks have a different number of holes depending on the position of the air stream.

Hi dear brother I'm science teacher really you channel is so nice

@YeanyScience

2 жыл бұрын

thanks Don

Volume change for the radially cut designs. Closer to center, cut portion becomes proportionally smaller relative to circumfrence.

Around 6:00: I intuitively expect that past a certain size, the loudness will decrease again. I’d think the size of the holes influences the resistance that would have to be matched to the energy input regulated by disk speed and the air speed out of the tube. Some form of impedance matching. Louder = better match. Just a thought.

@Bendigo1

2 жыл бұрын

Thickness of the disk is a factor too. Too thin and it will not "chop" the air as much as a thicker disk. But too thick and it will hold too much of the sound back.

I would say that one could add multiple wind sources to the disk with the slots. Or one very wide air nozzle but with a narrow opening like a vacuum cleaner attachment might have.

Bruce, how do you attach the CD to the motor? What attachment do you use?

Typically, a British air raid siren rotates at 2850-2900 revolutions per minute, one end has 10 openings and 10 blades, the other has 12 of each. This creates two tones harmonically related to each other as a minor third. The tone in Hertz can be calculated by multiplying the rotation speed in R.P.M. by the number of openings and dividing by sixty. For example, at 2850 r.p.m. the two tones are 475 Hz and 570 Hz.

The disc with the slits resembles an arcade machine where the objective was to use a ramp to propel a coin through the slits as it was spinning. It also reminds me of an experiment with a laser. You could make a small adjustment to the slits where they're wider near the outer diameter, forming a triangular shape. That might produce different sounds.

Run one of those with radial slits in front of one with holes. Slowing down the one with holes will produce a beat with the differential speed as frequency. Like the first on a half beat the second on fourth. What would this sound like?

So when you said that the number of holes on the cd effected the pitch, did the speed of the disc have anything as well? Because the disc was spinning faster towards the edge, if they had an equal number of holes for each concentric circle around the disc, would the pitch also change? Or not because the further distance between holes cancels out the moving faster..... idk

@zwitshr

2 жыл бұрын

I was confused as well. But when the hole of the inner row is at the top, the corresponding hole of the outer row is at the top as well. When the inner hole is at the bottom, the outer hole is too. So they pass at the air stream in exactly the same intervals.

@zwitshr

2 жыл бұрын

velocity = distance/time In the outer ring, distance, and therefore velocity get bigger, while time stays the same, and time=time interval is all that matters in this case

For the disk with slots as well as the ones with the same number of holes, you can notice a change in the timbre of the tone as you move from the inside to the outside. If you think of the sound wave like a pulse-width-modulated square wave, you can think of the sound as getting "thinner" as the pulses get thinner, and getting "thicker" as the pulses even out.

@YeanyScience

2 жыл бұрын

we have a change in the linear speed going on here, I wonder how the shape of the hole or slot might address this. Round hole towards the center compared to oval shaped or double holes towards the outside. I have some other projects going on but still want to explore this further

7:00, sounds like a filter cutoff control. The outer bands get you brighter tone than the inner bands. Another thing you can try, is do 1 CD vs 3 stacked CDs.

@kelvin0mql

2 жыл бұрын

Bingo. A couple times the OP said “sounds the same” & I disagreed. Same pitch, sure, but different timbre. I think the brass disc with slits is designed to be matched to another just like it as the air supply orifices. I expect you’d get a very loud result, with very fast rise/fall times, i.e. piercing.

@perwestermark8920

2 жыл бұрын

Yes, the experiment should have included varying disk thickness just to complete the possible variables.

@theeastsensation5295

2 жыл бұрын

@@kelvin0mql I wouldn't say timbre but harmonics, it is not a pure tone. But you are still right.

@kelvin0mql

2 жыл бұрын

@@theeastsensation5295 I have my moments… rare though they may be.

For that disc with the slots, and for the disc with 8 holes both at the center and at the edges, the pitch doesn't change, but the "shape" of the sound changes; it gets either buzzier or smoother. If you record the audio and look at the waveforms in eg. Audacity, you'll be able to see the difference; buzzier sounds will have sharper waves (closer to a sawtooth wave), and smoother sounds will have more rounded waves (closer to a sine wave). A similar effect happens when woodwind instruments change the shape of their mouth around the mouthpiece.

The slotted disk creates the same pitch, but the timbre of the tone is altered as you move in and out. For example, a male and female singing the exact same pitch of note will sound very different.

This reminded me of yelling at a fan as a kid.

I played the trumpet in middle school, so sound changing with the passing of air through holes does not surprise me at all. What I did find interesting was the speed variance demonstration using the pensil.

Interesting video, I'm now considering making a musical instrument based on this concept, thank's for bringing it to light. Just speculation but I wonder if the reason for the slots as apposed to holes on the brass wheel is so that the airflow can be spread accross the width of the slot with a nozzle. It's possible a cleaner tone could be produced with a more distributed and less turbulent flow.

On the one with strait lines there was a audible change, further in was more deep and while further out was more high pitch

5:00 Those pitches are different. Near as I can tell the ones closer to the center make a flatter note. The edge set definitely sounds "brighter"

What happens if you vary the size of the holes on the same row?

@YouCrossedMyPath

2 жыл бұрын

A volume based vibrato would be my guess

Similar to the 'Doppler Effect'. A sound gets higher in pitch as it's coming towards you (Shorter compressed sound waves) and lower in pitch when going away from you (Longer stretched out sound waves). That's why kids go 'Neeeoooow' when imitating the sound of a car passing them. High to low pitch. 🤔

cool. never knew those things existed

I'm wondering if that slotted brass wheel was originally used in a kinetoscope.

I had been wondering whether you were going to make videos in retirement....so glad you are. you can take the teacher out of teaching but you can't take the teaching out of the teacher.

I believe the slotted disk is stationary and one with the holes rotates behind it…like De La Tours siren design, and similar in concept to the slots on the outside of a Federal Q design siren.

Saw a project years ago before the internet in a hobbyist magazine where a rotating disk with holes in a spiral and a flickering light behind displayed a TV image

4:36 I can't tell if this was intended to be funny but made me chuckle

While the fundamental pitch remains the same regardless of the radius, (once the number of holes is the same, or with the slotted disc), it sounds to me like the harmonic content changes, with more upper harmonics present farther from the centre of the disc.