Build a Square Wave Oscillator - Part 1 of DIY Modular Synths

Synthesizers have become an incredibly prominent instrument in modern music; it's difficult to hear a track without one anymore! Unfortunately, many synthesizers are incredibly expensive and hard to acquire, making it rather difficult for the hobbyist or budget musician to get any of those sounds. This instructable won't teach you how to build one of those feature-rich, user friendly synths, but it will start you off with a very simple device that can be used with other units to create interesting and unique sounds.

The following is the simplest and most fundamental piece of a synthesizer - an oscillator. This particular oscillator is a "Square Wave" oscillator, and has limited functions, but can still be used every now and then for fun sounds.

Let's get started!

Step 1: Gather Your Parts

The square wave oscillator is a rather simple device, so not much is needed to construct it. Most of these parts have some sort of alternative that can be found at radioshack, but I prefer this website for all of my electronics projects:
http://www.pedalpartsplus.com/

If you can't find all of these on that website, I would also suggest digikey.

Here's a list of everything you'll need:

-Project Enclosure
-2x 500kΩ Potentiometers
-Radioshack Perfboard
-Resistors:
   -1x 4.7kΩ
   -5x 1kΩ
   -2x 1MΩ
Capacitors
   -1x 100µF
   -1x .001µF
-LED, any color
-741 Op Amp
-1/4" Audio Jack
-9v Power Adapter Jack


You will also need a few tools:
-Drill Press
-Drill Bits of Varying Sizes
-Drill Bit Index
-Sharpie
-Breadboard
-Safety Goggles
-Soldering Iron
-Solder

Comments

[pquadros]

Can you use an USB cable instead of the 9V power adapter?

[dnhushak]

Theoretically, one could try it. Note that you'd only be getting 5V instead of 9V, so your op amp rails will only be ±2.5V, which doesn't give you much swing (and therefore not much output), but it's certainly worth a try. Let me know what results you get!

[bengoza]

The ones in step four where you show the circuit laid out on a breadboard. Maybe they're not jumper cables, the thicker black and red wires going off screen. Thanks for the quick reply!

[dnhushak]

Oh, two of those are going to a power supply to give the circuit the +9V it needs to operate - these are replaced by the power jack later on. The other two are going to an oscilloscope just to test output - these are replaced by the audio output jack later on. Hope that helps!

[bengoza]

Where are those jumper cables connected to? What is their purpose? Thanks for your patience, and thank you for this instructable!

[dnhushak]

Which jumper cables are you referring to?

[jatinbatra]

what is peak voltage?

[jin_yeugh]

I'm wondering where the other end of the 500k pot, from pin 2, goes. Do I take it to ground? it already goes to ground through the cap/resistor.

[Skelpolu]

Hey there.
I'm a pretty much newbie in things like this. You will probably tell me to start of by soldering a working LED, but I've done that before. Anyway ...
I am not quite sure, but can't I also use a 12V Power Jack and a 12V LED-Power-Switch? ( It's just a switch with an LED indicating that its "on" ) I'd like to know. And also, another thing: The Schematic doesn't help me at all, I don't say its badly made, it's probably pretty good, but I don't know where what who is... If somebody can help me a bit more with that, I'd appreciate it a lot. See you then guys.

[dnhushak]

Yep, a 12v switch with the LED will do just fine. The 12 supply can be the supply for the rails for the oscillator circuit as well, no problem.

Part of the problem with the schematic is that Instructables doesn't immediately show the image at full size. If you open the image, click on the little "I" in the top left corner of the image, and then click "view original file." This will let you see it in it's full size.

Past that, is the schematic unclear, or is it just an experience reading schematics issue? Let me know, I'd love to help!

[Gray3287]

Hi friend, could you tell me what voltage the capacitors are rated at?

[dnhushak]

Actually, sorry, the little i doesn't exist anymore for some reason.

http://www.instructables.com/files/orig/FG9/MG8C/GFRWMNFA/FG9MG8CGFRWMNFA.png

That'll get you where you want to go.

[Skelpolu]

Well, I've saved the full-sized-schematic btw, but my problem is that I don't understand it. I don't quite understand how those pieces form a Square-Wave for example. Nor do I know how to sold them now, the schematic looks complex for me. And like I said, I have no experience beside soldering an LED, which is pretty much pathetically-easy, eh? Anyway, perhaps we should talk about that using the PM-function to not spam this post?

[jgierczak]

Is there an option to connect this little synth to sequencer?

[oweng4000]

Where's part 2?

[dnhushak]

Haha, I'm working on getting something else up. I'm a EE student, so busy all the time!

[gavox]

Any chance of getting a clearer schematic? can't see a blind thing on this one...

[dnhushak]

http://www.instructables.com/files/orig/FG9/MG8C/GFRWMNFA/FG9MG8CGFRWMNFA.png

That should work.

[gavox]

http://www.banzaimusic.com/ICL7621.html would this op amp work? getting hold of the parts is quite difficult here in france, any way if this one doesn't work that you could find one that does on this website? thanks!

[gavox]

Also it's impossible as far as I can see to get perfboards in france, breadboards are usually to big, or too expensive to lock in an enclosure never to be seen again... so do you have any suggestions? I don't have the meansof etching anything myself.

[dnhushak]

Something from this page should work:

http://www.banzaimusic.com/PC-Boards/

[dnhushak]

That one should work; it's a dual op amp. The model I used is a 741, which I found on that website as well: http://www.banzaimusic.com/JRC741D.html

Both should work at pretty much the same conditions, but I'd go with the 741 just to be safe. Looks like it's about a third of the price

Merci pour examiner, et bon chance!

[gavox]

Great! thank you very much! I hope to do this project real soon!
Merci beaucoup!

and good french by the way!

[-T.]

Thanks for a great post! I notice your parts list calls for 5x 1k resistors, but on your schematic they are marked 10k. I'm going to trust the schem and build with 10k's. This will be my first project on a breadboard so it won't be hard to swap if I got it wrong.

[amruth]

HI, i like ur circuit and i would like to know the minimum and maximum frequency it can create. Thx in advance

[cbien-stephen]

@dnhushak, this cool and something i'm interested in building, have you built any more you could post (filters, other osc's, etc)? i'm putting together my own modular synth

[dnhushak]

That was the intent, to begin building more things, but I'm a EE student, so you know, time time time time time suck like nobody's business. If I do get around to more, I will definitely post it here.

[elijah_rippington]

could you replaced the frequency pot with a resistance based keyboard to get a simple square wave keyboard? or is the frequency range too limited to get a decent two octave keyboard?

[dnhushak]

It definitely wouldn't work like you think it'd work; when no key is pressed the circuit would see infinite resistance (open circuit) in that area of the oscillator, and would oscillate at an asymptotically low (or high, been a while since I've looked at the schematic) frequency, until a key is pressed, when it would go to a different pitch. There'd be no gating/enveloping to "note on" or "note off," to use midi terms, so there would always be a constant tone.

[kkraft2]

Hey I have a bit of a different question. I'm trying to make a light pulse on and off slowly (like in an old horror film) if I connected the light terminals instead of the the 1/4 jack, would I achieve this? Thanks so much. Great DIY

[dnhushak]

You'd have to mess with the component values a lot to get it down to where it's a visible flashing; the frequency that this outputs is around 100-500Hz, much too fast for the naked eye to catch flashing lights. Normal lights operate by flashing at 60Hz, yet it still appears to be always on. Again, messing with the component values could yield an incredibly low frequency that could work. I'd be interested to see if it does!

[allnighterco.]

I'm confused; my friend and I went by the image not the schematic (as we are 13 and have no prior training in PCB), how do you connect the potentiometer/ LED/ 9v/ input? also we wanted to add an output, how would we do that?

[allnighterco.]

I meant connect output; add input

[dnhushak]

Not really sure how to answer your question; do you want to add an input that goes straight to the output, or have it altered in some way? Also, to attach the Potentiometer/LED/9v, you just use longer leads to go from the component/jack to the right spot on the PCB.

[A.Kahn]

Hi! I got a little newbie question. Im using a electrolytic capacitor, for the 100uF, and they need to be placed in the right way according to + and -. I confuse myself everytime i try to figure out which way it should be placed... So if you could tell me how the capacitor should be connected i would be very happy!

[dnhushak]

It shouldn't matter too much, but place the positive end (the longer lead) towards the 500Kohm potentiometer, and that should work.

[Gizah]

Hey, sorry, complete electronics noob here, could I make a guitar pedal out of this with and added jack and dpdt switch, or is that idea just plain stupid?

[dnhushak]

Depends on what you'd want to do with it, would it just pass the guitar signal through and then add the square wave signal to it?

It's very possible to do anything with electronics, it's just a matter of what you want to do =D

[Gizah]

yes, exactly that, can you give me some brief instructions in what would I have to do? I've never built a pedal before, I'm gonna make a distortion one and I'd like to do this after that

[superrust]

This looks pretty cool I'm thinking about giving it a shot.