I had that idea for the first crystal radio I tried to make. When it failed to produce any sound I assumed the microwave piezo speaker crystal was to big or something. Now that I've made some more advanced crystal radios and seen this, I'll probably dig those old microwave parts out of a box and give it a go again. Thanks for sharing!
Yes. In fact I used one of those greeting card crystals in my "Piezoelectric generator LED lit by rain water" video. But I think more and more these days the greeting cards contain electromagnetic speakers. It's a little difficult but if you go to the card store looking for them and want to know which type is in the card without tearing it apart, the electromagnetic speaker ones have a Neodymium magnet in them, so test the cards with something ferromagnetic, some keys for example.
Yeah, I keep finding new things in this microwave oven. It really is a treasure trove. Took from capacitors from the board too while I was at it. Glad to hear you enjoyed the video.
+Avichai Marcovitch I give two links in the video description to where you can buy crystal earpieces (piezoelectric speakers) online. PS There's no Reply button under your comment because of your Google+ settings. - go to your Google+ page, - in the top, right corner click on your thumbnail icon, - in the popup that appears, click on "Settings". - for the 2nd question down "Who can comment on your public posts?" set it to "Anyone".
RimstarOrg Thanks for the quick reply ,fixed the reply ability as well. I've been having some difficulty finding a site that can ship a crystal earphone to my country without insane costs, so i wanted to make one from a piezoelectric buzzer like in your video therefore it would be greatly appreciated if you could recommend a buzzer to use (im assuming those would be more common and easier to find a site that delivers to Israel :)
Avichai Marcovitch I don't have any specific recommendation. This is the one I have and that works www.thesource.ca/estore/product.aspx?language=en-CA&catalog=Online&category=CLRBatteries_Cables&product=2730060 Probably a lot of others work too. You should be able to find one in an electronics or hardware store in Israel.
That's very creative Steve :) I built a radio just like that about 3 years ago and had great success hooking the antenna to my drain pipe on the side of the house. Would a longer antenna make the signal stronger for you?
Thanks. And yup, been there done that. Of course you need something to tap or flex the crystal in order to get it to light the LED. I've even used water drops, dropping from a 4 foot height to tap on the crystal.
Hey, try this.... use a resistor and short out the piezo's terminals. The value varies, but 10k to 12K seems to work best. Easiest way to determine the correct resistance is to use a low-step resistance substitution box, or a variable resistor to find the best value. Depending on your method, you may then want to read the resistance you use with the VOM. Bet you'll be surprised by the improved audio.
I love how you re-use found objects. Especially since Radio Shacks are harder to find these days. I'd love to see a video on where and how to collect electronic components from found objects. Also a video on how to make a morse code practicing sound generator. Thanks
Yup, I showed it in my "Crystal Radio Troubleshooting and Tips" video. Of course the other issue is, is the ground hole in the wall socket connected to ground? It is in only one socket in my whole apartment. To check, I use my voltmeter on the AC scale to test voltage between neutral (the taller of the two) and ground holes. In North America there should be close to 0 volts between them.
I watched another video of yours before and it was about the headphone speakers and the transformers, I just wanted to let you know next time you take the small transformer off a circuit board the solder side on the bottom of the board tells you which coil is which where it solders in most mocrowaves
The component you salvaged from the microwave is called passive buzzer. You can buy these for next to nothing at any electronics supply store. You can even get ones with 40-50mm diameter for louder sound
A timer that you spin/dial. That does sound like an old design. As you say, it's probably a mechanical bell. There's no harm in opening it up and checking for the fun of it. Just be careful not to touch the high voltage capacitor. I'd say the capacitor is usually in the bottom, rear on the side with the electronics but with your microwave oven it may not be.
Cool! Have fun making it and let us know how it goes. And if your Ma is talking only about the capacitor then I guess she just volunteered to make that part of it! :)
Those elements ( unmounted ) are called "piezo benders", you can buy them separately lots of places, including digikey, quite cheap. They are used for all sorts of things including ignition generators in trigger operated barbecue starters, stove top igniters, butane cigarette lighters, air humidifiers ( they are used to boil the water with explosive sound waves ) and the Webb telescope where they are used to "nudge" the individual mirrors just a tiny fraction of an inch, to align them all perfectly.
Thanks Grant. Drain pipe? I'll have to try that. A longer antenna should help. I use three 15' wires in parallel and have tried one 50' length but I guess they were equivalent since there was no improvement.
Just spent ages looking for the board from the microwave I took apart...but got tons of regular piezo's. Always wondered about a casing and here it is ! lol. Could do with finding that board though. Enjoyed that, completely practical and useful as always :)
+Dev TheHam What does your plain old piezo element look like? Can you be more specific? PS There's no Reply button under your comment because of your Google+ settings. - go to your Google+ page, - in the top, right corner click on your thumbnail icon, - in the popup that appears, click on "Settings". - for the 2nd question down "Who can comment on your public posts?" set it to "Anyone".
By the way if you put a choke across Diode input to ground , something like 25mH, it will also greatly increase the performance of the crystal set. It gives a DC return path for the diode while blocking the RF frequencies and forcing them to go through the diode. So what I mean is you put a choke just before the diode, across to ground, a nice high value one that has a high impedance at AM frequencies. 25mH should do fine. To the RF it looks like a giant resistor so it doesn't load things down. But for the diode it's like a DC path to "complete the circuit" that doesn't have to go through the earphone - you will get much better signal with less distortion
I tried that. The crystal radio didn't put out enough power to make it work. I did get that to work with a clock radio though, but that has an amplifier. If you're curious, see my video "How to Make Piezoelectric Crystal Speaker" (you can find it on my channel page.)
Try using those small cheap piezoelectric tweeters. Although they're used with 8 ohm speakers, their impedance is actually in the kilo-ohms (and highest below 15khz).... they're just really efficient.
Nifty! Me and pa are gonna make a similar radio like you showed. My ma ain't listnin to me 'bout how to make it. She just talks about the capacitor! Still, thanks for the step by step jazz. It was real helpful!
Thanks for these great videos! I was looking for a cheap source of piezo speakers and found the easiest for me was to buy a window alarm from Dollar Tree. This works great because it also provides the housing.
I don't know the substance. It looks like the same type of material as in piezo disks you find in commercially available crystal earpieces, gift card speakers and piezo buzzers, in case that helps you find out. The use in a microwave oven is for the speaker that beeps when something is cooked.
I've used piezoelectric elements too for crystal radio work, but I always have to wire a resistor of 10k-12k across the piezo leads to get any volume. Dunno, maybe the radio or the piezo has a resistance built in. It's a good cheap way you describe, but in case you don't have an old microwave sitting in the corner, an even louder piezo is the Mallory FT-417 --- a very large device. You can use a single one with the resistor wired across the red and black leads. Or, for true headphones use two elements ---- simply tie the red wire of one piezo to the black wire of the other. You are left then with one red and one black lead. Wire the above mentioned resistor across the remaining leads, then apply the crystal radio's audio to the red lead with the black one going to ground. I've found these elements rival the old military sound-powered elements even when they are well adjusted. Many hobbyists mount the elements inside a pair of soundproof earmuffs after removing the foam.
+mnpd3 My understanding is that at least one reason a resistor across the piezo leads helps is if your diode doesn't have enough leakage for each reverse cycle. It hasn't made a noticeable difference for me in the past, probably because my diodes have enough leakage. A google search for Mallory FT-417 and variations didn't turn up anything relevant. Is that a speaker or just the piezo crystal? I've always wanted to try making headphones. Just a question of too much on the todo list. :)
Yeah, it's pretty time consuming to do subtitles so only a few of my videos have them so far. Meanwhile, the automatically generated ones are good if you ever need a laugh. :)
Warning. Discharge big capacitor with a high insulation screwdriver before touching inside the electronic side of a microwave owen. Even if the plug is not conected to the wall. Voltages about 3000 volts can be present before discharging.
Back in the days people did this a lot, but nowadays most hobbyists, including me, just order ready imtes on Ebay for 0.12$ or something. I liked it this old way though, of harvesting electronics. I'd figure it would be piece of cake to use some opamps to amplify it to speaker level...
What about a piezoelectric disk or piezo buzzer? I was working on a wireless telegraph project for physics class and then I realized that we can transmit sound just by changing the resistance/voltage. I've tried making a microphone by changing the length of the circuit using the force of a sound wave (like a phonograph) but it only makes noise. I gusse it can work as a speaker as well
Yes, a piezoelectric disk will for it too. That's what's inside this one from the microwave oven and that's what's in the regular piezo earpieces. As for a piezo buzzer, it depends on if there's any other circuitry in the buzzer that might interfere. I've used one as a speaker in this other video ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-b4vr1aE0zzw.html
Very nice. I was thinking about buying very cheap 100 piezo elements from aliexpress. But i just wonder how much impact does the impedance have? though they moastly are arround 300 ohm on this elements, and a crystal earpiece use to have 20k impedance. Any idea about that?. Would be very easy to make perfect earpieces with a 3d printer and blender i think.
With a normal crystal radio, you need high impedance, as you say 20k. For low impedance you can add a transformer. For example, normal earbuds are low impedance, tens of ohms, but with a transformer, they work, though there are more losses. I did that here in this video ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-GCh2LVHUavQ.html . And great idea about using a 3D printer to make the case! I didn't have a 3D printer back then but that should work well.
@@RimstarOrg Thanks for response. Yes i tried to find these elements with higher impedance, but no luck so far. But same time in this video it seems like it works well to use this traditional piezo elements for a crystal receiver. Very nice idea to use a transformer then to get higher impedance. Will make some experiments with this and buy the one labeled 300 ohms impedance to check it. I can not use a crystal receiver here in Sweden then, though to far from a transmitter, but i have small low voltage receivers i have made that needs these crystal earpieces to. Yeah same with me, i had my first printer 2 weeks ago.
I guess youtube's algorithm wrongly decided it was spam. I don't see it in my list of comments for review so the algorithm must have rejected it completely.
Paul Crissman One dollar in 1960 would be $8.42 today. Also supply and demand, with transistor radios just emerging, the the supply kept up with the demand. Now with decreased production they have become commodities since less people value them and vice versa.
That would have been cheating. It's not homemade. But you're right, it didn't even cross my mind. I have that big a mental separation between homemade things and commercially manufactured things.
easy fir most to achive I thought I would see a rochelke salt crystal grown, crystal then sandwiched between two pieces of silver foil with wires atached, now difficult part, which way does it deflect most? largest deflection direction is determined by some neans. now crystal is connected to a beam armature so max deflection is achieved, end of beam then linked to a transducer membrane (usually aluminium foil). then something like the enclosure you made is fitted. This us nice though, relatively easy to do with care it can be dobe without a soldering iron by cutting away the circuitboard around the solder holding the transducer carefully
I use my rochelle salt crystal in this video ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-0-PParSmwtE.html , mostly as a speaker though I create a small earpiece sized one at around seven minutes and twenty seconds into the video. I tested the polarity of that crystal in this other video ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-R9m79oWdOZI.html
+RimstarOrg Yep, output is constant depending on station strength. One tip though --- if any crystal element stops working altogether, try a moderate tap or drop against a hard surface to get it going again. Sometimes these crystals will develop a charged polarity and have to be moved to discharge it (my theory anyway ---- in any case the thump or drop works).
Ha Ha! I'm not surprised your mom won't let you do that! :) Often people throw them out and I take them when I see them. You can also use piezo buzzers available at electronics stores. You can buy crystal earpieces online (I put some links in the description below this video.) You can use earbuds, like iPod earbuds for example, by adding a transformer. It's harder to do. You can see how in my "Use Earbuds/Earphones with Crystal Radio" which you can find on my channel page.
oh, i got a microwave and it dings (ding is produced by bell or something) when it's cooked, also, it has no buttons, you have to spin the timer. soo my microwave is probably old designed.
I suspect not. There isn't a lot of power coming from the crystal radio and so it has to be one that can give good vibrations for the sound waves while still being given lower power.
I was just curious. Whenever the current enters the diode, it looses voltage and the negative portion of the wave is stripped off. Then it goes back into the earpiece. What makes the crystal sense it then? What exactly does the diode cut off? Does it make the audio wave more positive by cutting off electrons so the earpiece only pickups the protons?
Lucas Wootten Rather than type out a long answer, I'll refer you to my video on how a crystal radio works ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-0-PParSmwtE.html. 2:02 has stuff about the diode and crystal. 8:55 starts talking about the radio and audio waves.
I understand the majority of it, I actually did a presentation on it. But my professor wants every possible detail. But mostly how exactly the piezoelectric crystal picks up the waves after it exits the diode?
Lucas Wootten Hmm... I don't know what more I could say besides what I explain starting around 2:02 into the video. Did you watch all of the video? There's even more about the waves starting at 6:54 that then leads into the stuff I pointed out at 8:55.
I haven't opened on up for I can't say for sure. The ones I've heard were all quick "ding!" sounds which I suspect is a bell mechanism of some sort and not a piezoelectric component.
Cameron Cooper The answer is yes, it's both. A transducer is something that converts energy from one form to another. So a piezo crystal acts as a transducer when converting mechanical energy into electrical energy and when converting electrical energy into mechanical energy. A piezo buzzer does the latter, converting electrical energy into mechanical energy which produces sound waves in the air. But the one in this video isn't quite the same as the piezo buzzer you get from radio shack. The one from radio shack is like this but with the addition of some extra circuitry for converting DC electricity into something that pulses the piezo crystal.
Ok thank you! Also I'm not sure what my inductance should be for my coil. I'm using a short piece of bamboo with a diameter of 2.75. The wire I decided to use Is thermostat wire which I believe is 18 gauge. Now rather than wrapping it and then sanding the insulation off I made 7 individual taps by raising that piece of wire and stripping the insulation and twisting it that way my alligator clip can clip onto that wire.. What is your opinion on my construction/calculations... My calculated inductance is 148.5uH
Cameron Cooper I'm assuming that's 2.75 centimeters. 2.75 inches would be a pretty thick piece of bamboo. To calculate inductance I'd also need to know how many turns you have on your coil and how long the coil is. My coil tops out at 369uH.
RimstarOrg Yes it is 2.75 inches in diameter. Length of coil in inches is 3.5 and number of turns is 61 with a tap every 7 turns giving me 7 taps total.
Cameron Cooper Cameron Cooper At full length I calculate an inductance of 789uH. If your variable capacitor is the same as mine with a top capacitance of around 600pF then you should be able to tune up to 1.7MHz, so that includes the full range a normal AM radio can tune into. That's using only the formula for parallel coil and capacitor resonance (LC tank circuit.) The inductance formula I'm using isL = (permeability x number of turns x number of turns x area) / lengthwhere the permeability of air or bamboo is around 1. This is using the metric system, so the dimensions use meters.
It's still possible that your antenna is too short if there are no radio stations nearby. I have a few radio stations near me. But there are other possible reasons too: bad connections in your wiring, not making good contact between the wiper blade and the tuning coil, not a good enough ground.
Chris Maness That'll probably work just as well. They're harder to find these days but I did make use of one in the opposite way for my rain powered LED here ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-laSQ6yd7jaE.html
+Chris Maness All piezo elements will work, but the smaller ones suffer from reduced volume. With piezos pressed into service as sound producers, bigger is better. I've experimented with these for years and have never seen a case where the larger elements don't give louder volume over smaller ones. There are some really large piezos out there. Another source for an even bigger piezo "speaker" is an old smoke alarm. These things have to be loud and the ones I've take apart always had a large pieze inside. The best piezo I've found is the Mallory part number FT-417 which can have several different letters/numbers after the "7". I've seen a "W"; also "5WQ." Other than different colors they all seem to work the same.
HI!! I know it’s probably weird to get a comment on a 10yr old video, BUT your process on making a crystal radio and this video might help me recreate something of my own. I’d like to reference your videos if that’s okay! I’m not sure when I’ll have time to work on this BUT IK I MUST DO IT THIS SUMMER. This comment is probably confusing and out of the blue, but that’s okay, all of science is at first!
Hi! Some of my video which are older than this still get plenty of comments so it's not weird at all. A sure, you can reference my videos, as long as you don't reupload them to your own channel, which judging by your channel, you wouldn't. Good luck with your project!
I'm glad you asked it that way! I have a tips and tricks section on my website that addresses the usual problems rimstar.org/science_electronics_projects/crystal_radio_tips_and_tricks.htm.
USE TO SELL 2000 OHM EARPHONES THAT WORK GOOD AND DON'T LOAD DOWN THE CIRCUIT...WITH CRYSTAL DIODE...ON THE OLD ROCKET RADIO'S AM RECEPTION....JP RADIO SHACK OR SUCH MIGHT HAVE THEM...
That's not unusual for it to not work at first. Rather than repeat all the suggestions, I've put together this tips and tricks page here rimstar.org/science_electronics_projects/crystal_radio_tips_and_tricks.htm
I just subscribed. I made a similar radio but I used the NTE 109 diode and placed the antenna coil inside my tunning coil by doing this it makes it easier to tune by being able to move the antenna coil side to side inside the tunning coil. Instead of a capacitor i wired in a ferrite rod with coil from an old radio before the incoming side of diode to the antenna. This may give it a boost. if you would like to see it check out my channel. the video quality isn't to good but its all i had.
It's surprising they don't make the fuse more easily accessible and put in microwave oven manuals that it should be checked the the microwave stops working.
I bought a standalone plug, ones for making your own chords, and hooked up only the ground prong. Basically a one-wire extension chord. I plug that into the wall socket.
