Step 3: Wire the Circuit (piezo)

Tape the piezo at the base to something hard, so it can vibrate more freely. A cheap substitute for the piezo element is an old speaker, which also can produce voltage in response to vibrations.

Schematic for wiring to an Arduino is attached.
<p>Video really very useful.</p><p>Thanks..</p>
<p>Enjoyed that video. Thanks.</p>
<p>Very cool.</p>
Hey, great project! Very simple idea but a rich human-computer interaction.<br><br>I am having a big problem using a piezo sensor in a project I am working on. I just cant get it to sense anything practically. If I hold it and flick it I get a big spike of course, but once I tape it to a surface I can knock all I want and I get almost nothing, maybe 5-6 out of the 1023 of the analog sensing range from the arduino.<br><br>Can you explain how you're attaching it a little better. I just dont know what I'm doing wrong. Thanks for your help.<br><br>
Ours is just taped to a hard surface inside. In the Knock Block, we only need to sense whether or not it was knocked, not how hard, so dynamic range doesn't matter much. We set the threshold at 20 and that filtered out false positives.<br><br>Keep in mind that the Arduino's sampling rate may be too low to capture the high-frequency waveform produced by knocking a piezo. Our rich mahogany case probably helped deepen it. You could try smoothing out the sharp waves with a capacitor, if it is just a sampling-rate issue.
My gut tells me that the sampling rate isnt the issue as when I clamped the piezo into some helping hands it managed to get the vibration into the right part of the sensor because it seemed nice and sensitive then. <br><br>The capacitor sounds interesting. What rating would you recommend and how would you recommend I connect it?<br><br>Thanks!
Ok, how many of us <strong>hobbyists</strong> have a CNC router?<br/>
how many have makerbots?
Actually, one of the team is working on a $100 CNC router. But of course, it can be just as fun to experiment with found containers.
Also, how do you set the time?
Ah, you spotted the weakness! Right now, you have to set the starting time in the source code so that when you upload the code, you start at the right time. Not optimal if your battery dies. An improvement would be to write a setup function that's called at power-up to set the hour, and then the minute. With knocking, of course.
or upload at midnight?
knock block rocks all blocky rocks!
&nbsp;Well, the video is nice and dramatic.
You may be interested in <a href="https://www.instructables.com/id/Piecax-the-Poltergeist-A-Troublesome-Spirit-in-a/">my take</a> on the Knock Block.<br /> (PLEASE&nbsp;don't call it a schlock mock knock block ;&not;)<br /> <br />
if you hit it with a sword, will it say "boing boing" then tell you the time?
lol!<br />
This is such an awesome project.&nbsp; <br /><br />How long does the battery last in it? I can't imagine it would drain them too quickly. Also, would it be possible make a plug on it to plug it into say a USB port for charging only?<br /><br />
This is a great idea! The only suggestion I can make is that you may want to put a reverse-biased diode across the solenoid, to keep the back EMF from destroying the transistor. Apparently the particular transistor that you are using can handle it, but a less robust one might not.
Good point! I didn't put one in while prototyping, and forgot it after that.
This is great. I got it to work with a servo too. Use the servo library to attach it and use two settings for on and off. Increase the delay between "high" and "low" to let the servo swing into position.
I love all of the tongue twisters in the video.
Your block seems to be from 'rubberwood', not mahogany. Rubberwood is a very nice hardwood cut from rubber trees. Natural rubber is not much in demand anymore, so the plantations are being cut down, mostly for oil palms
Thats awesome! A knocking block, lol Now you have something to "talk" morse code to.
That video was epic win. 5 stars!
Video Win! Embed it on the first page!
I have no intentions of making this item, due only to my lack of skill Having watched the video I love the knock block but alas my knocks will have to go unused until i acquire the skills required to harness their true potential
it'd be nice to have a parts list and a video...i could see adding a bunch of these together and having an automated xylophone
There's a Vimeo link on the intro page. I've added a parts list to step 1.
I really like this. Novel, well built, attractive and a total time-waster. BRILLIANT! I can't see any amplification on the piezo. What sort of voltage peaks do you get from it?
Thank you. Our piezo has peaks of 20+V if you really flick it. We tempered this with a 1M ohm resistor. (I've added schematics to steps 3 and 4.)
The shape maybe too foppish, sophisticated...
The wood block is awesome!! I want one. I think this could be extended to have phantom knocks to confuse your friends and co-workers.
or just don't put it in a block...and hook it all up to the door of your house...that way when someone knocks...it knocks back

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