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Looking for more help with my electronic ‘bagpipe’ project...

Explorer

Mar 28, 2014
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I abandoned my chanter circuit based on the 40106 IC and now have a 555 timer circuit in my ‘bagpipe’ box. I’ve done extensive documentation of the project, in the form of something like a 24-page PDF, complete with bagpipe tuning info, notes on my process and mistakes, schematics, circuit board layout, build photos, keyboard tuning values, and 4 musical arrangements for the device. If anybody wants to take a look, it’s here:


(However, I made a modification to the 555 circuit this morning that is not yet reflected in the document. No matter. The modification didn’t help.)

I also have a decent, 24-second, audio sample, via the camera/video app on my iPad. When I email that file, it appears to be 2.4MB. But, when I try to upload it to the mediafire folder, or a format converting web service, it appears to be 43.8MB—which seems like really bad news. If anyone wants to hear it (a verse of “House of the Rising Sun,” which it took me forever to play decently), I think I can email it safely. But, I don’t know if something is trying to go along with it, when I attempt to upload it.

Anyway, the final problem I’m trying to solve with this iteration of the project is a very pronounced vibrato or tremolo or ripple or warble sound, when I hit one of my keys—B, which is currently tuned to 384 Hz. The key next to it does the same thing ever so slightly. That’s my C note, currently tuned to 427 Hz.

I have a 100uF cap between the positive and negative rails of the 555 circuit. And, I’ve been learning more about decoupling/bypass caps the last couple of days and just added a .1uF ceramic right beside the 555 IC this morning, between pins 1 & 8. It didn’t help.

It does help if I remove the little switching adapter that is powering the circuit and use a battery instead.

Below is a photo of the inside of the box and how I’m powering it. I’d like to know if there’s a way to solve my problem without putting a battery in the box.

THANKS!


6D6FEB86-805B-4106-8B35-C1C8A11CDAA5.jpeg

86064EC9-38BB-4179-95FD-09C5CB43F4F0.jpeg
 

danadak

Feb 19, 2021
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Do you have a scope ? If so is it a DSO ? Model # ?

A schematic you can post ?

Regards, Dana.
 

Alec_t

Jul 7, 2015
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Anyway, the final problem I’m trying to solve with this iteration of the project is a very pronounced vibrato or tremolo or ripple or warble sound, when I hit one of my keys—B, which is currently tuned to 384 Hz. The key next to it does the same thing ever so slightly.
This is a long shot, but as there seem to be two switch-mode power supplies in the box it's just possible they have slightly different switching frequencies resulting in a low interference beat frequency somewhere in your circuit.
Try using screened wiring, e.g to/from the pots, for all signal wires if possible.
 

Explorer

Mar 28, 2014
47
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Mar 28, 2014
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I don’t have a scope.

At one point, when I had the device tuned differently than I do now, the really pronounced ‘vibrato’ was on my C note. So, it has shifted, with my current tuning. Although the C note wavers ever so slightly, too. I’m trying to replicate bagpipes, which is a pretty unique instrument, so perhaps some ‘breathiness’ on a note or two just adds to the thing. But, I’d love to figure out how to eliminate it.

“For ALL signal wires...“ I might need help with that suggestion.

Thanks! And sorry I didn’t see the replies yesterday. I’m in Vermont, awaiting another big snowstorm, on top of a big one on Monday, with power and wifi outages. The storm tonight is likely to be worse...

Here’s the page from my PDF on my chanter circuit:

DD9E3E21-6CCB-467B-B8AD-CD1918DE82B4.jpeg
 

Explorer

Mar 28, 2014
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I had the thought to try a different power adapter, too. But, that might have to wait until the weekend, when I can go poking around in a couple of not-so-local junk shops, one of which I know has 3 milk crates full of power adapters that I can dig through.
 

Explorer

Mar 28, 2014
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Mar 28, 2014
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YES! I totally spaced! (I struggle a lot with insomnia.) I spent so much time playing around with ‘voltage starve’ with my previous 40106 circuit, that it just fell out of my brain that I could put a wall wart in there with higher voltage, and that I had even said above that a 9V battery seemed to get rid of the problem. I just put a 6V, 100mA adapter into the box, powering the chanter circuit and 100mA is surprisingly enough and the ‘warble’ is gone!

I’m going to revise my PDF and upload again. See if I can record another decent audio sample. See if I can convert a MOV file to an MP3 file and upload it, as well, to my mediafire page. And then I look forward to sharing it far and wide. I think it’s pretty fun. And I’ve spent a lot of time on it...

I’m already working on another keyboard, with aluminum foil tape, that will be played marimba- or xylophone-style and tuned to piano key frequencies, from middle C to A5, and hoping I can expand the bagpipe sound to a larger scale.

BTW, I’ve got one page in my PDF on a simple way I thought of to add a string of diodes to a circuit board and play with ‘voltage starve,’ without needing or having to use a rotary switch. (By later today or sometime tomorrow, power and wifi permitting, I’ll have a revised PDF uploaded, with mention of the wall wart problem.)

THANKS EVERYONE!

E8DC4264-0457-44B0-B5E0-87CB6350E7C1.jpeg
 

Explorer

Mar 28, 2014
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YES! I totally spaced! I spent so much time playing around with ‘voltage starve’ with my previous 40106 circuit, that it just fell out of my brain that I could put a wall wart in there with higher voltage, and that I had said above that a 9V battery seemed to get rid of the problem. I just put a 6V, 100mA adapter into the box, powering the chanter circuit and 100mA is enough and the ‘warble’ is gone!

I’m going to revise my PDF and upload again. See if I can record another decent audio sample. See if I can convert a MOV file to an MP3 file and upload it to my mediafire page. And I look forward to sharing it.
 

Explorer

Mar 28, 2014
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This morning I’ve been able to convert my MOV file to MP3, without any of the problems I was having the other day, and upload it to my mediafire page (see above). It’s there with the PDF documentation of the project that I revised last night.

The audio sample is from before the last modification that I made yesterday, and it was recorded with my iPad, which, please keep in mind, doesn’t do the greatest recordings.

Hmmm... I thought I could upload it here, too. But, the file is grayed-out when I try to select it for upload.
 

Alec_t

Jul 7, 2015
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I thought I could upload it here, too.
This site doesn't accept uploading of an MP3 file, but if you change the file extension to .txt the file will upload ok and the extension can be changed back again by users.
 

Explorer

Mar 28, 2014
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Thanks, Alec. But, I’m still not sure how to do that on my iPad. The file is in my “Files” folder. And when I click on the name, it allows me to rename the file, but it doesn’t show me the file extension. There’s no “MP3” after the file name. So, if I add .MP3.txt to the file, I’m not sure what I’ll be doing to it.
 

Alec_t

Jul 7, 2015
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Doesn't the iPad have a "save as" option? If not, you need a proper computer :) .
For those interested, I'm attaching the MP3 file with the .txt extension added. Delete the .txt extension to play the file.
 

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Explorer

Mar 28, 2014
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Alec, did you do it for me??? I'm on my desktop computer, and realized I could do it here...

But, THANKS!
 

bertus

Moderator
Nov 8, 2019
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Hello,

In post #4 you have a potentiometer on pin 5.
Be carefull with the setting of that potentiometer.
On the end stops, the 555 will stop working.
Pin 5 is the control voltage of the threshold:
NE555_functional_diagram.png

This is the effect of changing the voltage on pin 5:
NE555 Pulse Position Modulation.png

More info can be found in the attached datasheet.

Bertus
 

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