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

[Explorer]

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:

MediaFire

MediaFire is a simple to use free service that lets you put all your photos, documents, music, and video in a single place so you can access them anywhere and share them everywhere.

www.mediafire.com

(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!

 

[danadak]

Do you have a scope ? If so is it a DSO ? Model # ?

A schematic you can post ?

Regards, Dana.

 

[Alec_t]

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]

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:

 

[Explorer]

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]

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!

 

[Explorer]

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]

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]

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]

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]

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.

 

[Explorer]

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

But, THANKS!

 

[bertus]

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:


This is the effect of changing the voltage on pin 5:


More info can be found in the attached datasheet.

Bertus

 

[Explorer]

Yup! I figured all that out, Bertus. Thanks!

 

[Explorer]

My electronic bagpipe adventures continue. I’ve devised 2 new circuits on breadboard and I’ve built a new extended keyboard.

It’s played with 2 finger-worn contact devices, and the ability to slide them across the aluminum foil tape-keys actually works really well, when there’s a succession of adjacent notes in a tune.



I’ve got a new PDF on my mediafire page with the new schematics and build photos of the new keyboard. Is there some place else on this website that I might post the project, where it might be more likely to be found, by anyone who might possibly be interested? Or is it not worthy?

 

[Explorer]

It’s just as well that no one answered my last question about where I might post my finished project(s). I’m having trouble with the my new chanter circuit/keyboard.

I had no idea a power supply, or wall wart, could impact an audio circuit in such a huge way! I’m now getting a sort of warbling sound (vibrato? tremolo?) across my whole new keyboard—all 23 notes—with most of the power supplies that I‘m trying. When I go back to a 9V battery (that is probably partly run down), the problem goes away. Also, the wall wart that I switched over to, to power the Chanter circuit in my first device, works nicely. And provides really nice sound. (It’s a switching power supply, 6V, 100mA.) But, I don’t want to remove it from the first device. And I don’t know yet how hard it would be to find a duplicate. It says Intertek on it, but I don’t think that’s a brand name...

I’ve got 2 decoupling caps in parallel in the new circuit, a 100uF and a .1uF; the .1 uF is soldered under the board, right across pins 1 & 8 of the 555 timer in my new chanter circuit. Should I experiment, up and down, with the value of the .1uF cap?

I came home this afternoon with another pile of wall warts from a salvage place and one of them puts out AC output. I looked up the datasheet of an LM555CN timer chip and there’s nothing about AC or DC, with regards to voltage input. If I try this power adapter in my circuit, will I be making a huge mistake?

Does anyone have suggestions for how to go about solving audio problems in circuits powered with wall warts? Thanks!

 

[Alec_t]

I looked up the datasheet of an LM555CN timer chip and there’s nothing about AC or DC

I'm surprised. The IC needs a DC supply, shown on the datasheet as +Vcc at pin 8. AC will almost certainly kill it.
Edit:
A wall-wart rectifies the input mains supply, which creates many harmonics of the mains frequency, well into the audio range. Depending on the quality/construction of the wall-wart those harmonics could be leaking through to your circuit and causing interference., particularly as you have the wall-wart in the same box as the circuit.

 

[Explorer]

Ahhh... one of those acronyms that I will probably have to look up, every single time I see it. I have trouble with much of the language of electronics. Most of it seems highly, and possibly intentionally, obfuscating to me. Thanks, Alec!

 

[Alec_t]

The Vcc notation applies to bipolar transistor circuits and means "the (positive) Voltage at the Collectors". For circuits with field-effect transistors the notation is Vdd, meaning "the (positive) Voltage at the Drains".

 

[bertus]

hello

this wiki page will tell you more about ic powerpin naming

IC power-supply pin - Wikipedia

en.m.wikipedia.org

bertus