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 Forum index » DIY Hardware and Software » Musical Interfaces
Help with basic squre wave generator
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omonoid



Joined: Jan 11, 2011
Posts: 4
Location: spokane

PostPosted: Tue Jan 11, 2011 11:30 pm    Post subject: Help with basic squre wave generator
Subject description: Ap physics Extra Credit...not much electrical experience
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OK i have to build a waveform generator with adgujtable amp and freq. I have lots of soldering expericne, but no schematic reading experience.

I found this helpful guide to achieve what i want
[URL="http://www.instructables.com/id/Build-a-Square-Wave-Oscillator-Part-1-of-DIY-Mod/"]http://www.instructables.com/id/Build-a-Square-Wave-Oscillator-Part-1-of-DIY-Mod/[/URL]
Here is the shematics (hard to read kinda)

Posted Image, might have been reduced in size. Click Image to view fullscreen.

My basic questions so far are...

First, in the parts list it calls for 5x 1kΩ Resistors and no 10k ones, but the schematics show 10k ohm ones instead...I bought 5x 1kΩ ones so hopefully i can use them.

Second, I have plenty of 4.7k and 10k pots. It calls for 500k ones. I have 2 of these http://www.radioshack.com/product/index.jsp?productId=3012598, but they onoly have 2 pins instead of the standard 3 pins. Am i out of luck, or can i use a combonation of what i have?

Last, how would you recommend soldering it all? I have a perfboard but none of the holes are connected. Should i use solder to make the leads between two things?

Thanks a ton in advance

Any suggestions help!!!
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richardc64



Joined: Jun 01, 2006
Posts: 611
Location: NYC
Audio files: 25

PostPosted: Sat Jan 15, 2011 5:42 am    Post subject: Reply with quote  Mark this post and the followings unread

OMG, I scarecly know where to begin! How about
FUCK INSTRUCTABLES! Fuck 'em! With their crappy instructions that you have to register to see in more detail, only to find out the project wasn't worth even that little bit of effort. And the oh-so-helpful Commenters who don't know their collective asses from a hole in the ground.

"This next step requires the most skill out of the others, namely the ability to read a schematic..."

No shit. Especially one drawn as badly as that one. Lazy bastard should have put more effort into something intended for people with little or no electronics experience. But this is typical of Instructables: as long as there's pretty pictures -- or OH BOY! A Vid! -- it doesn't matter how crappy the "documentation" is.

It might help if Instructables had someone competent to evaluate submissions like this. I wouldn't hold my breath waiting for that.

All of which explains your confusion. God DAMN! Something so simple -- not to mention LAME! -- shouldn't be hard to understand. And it wouldn't be, if the Submitter had put half as much work into documenting the electronics as he did in the making of the box to put it in!

Now that I got that off my chest, you're right. The parts list is not in agreement with the so-called schematic, which shows 5x 10k resistors, not 1k. The submitter left out the zero in the list. It also shows 3x 1Meg resistors, not 2 in the parts list. So the parts list is wrong on two counts. I suggest you purchase a total of seven 10ks because two of the 1Ms are just plain WRONG where they are in the circuit.

The resistor in series with the frequency pot should be 10k. That will allow a wider frequency range. The 500k frequency pot only needs 2 terminals, so you're good there.

The resistor in series with the output level pot should also be 10k, NOT 1M. THERE you need 3 terminals. Maybe you can solder to the eyelet where the missing terminal should be? (Edit: It occurs to me that the eyelet might not connect to anything inside the pot, in which case you would be out of luck.)

Also, the polarity of the 100uF at the output isn't shown. + should go to the pot and - to the jack. 100uF seems excessive. 10uF should be enough.

Ugh. What a mess this thing is.

Quote:
Last, how would you recommend soldering it all? I have a perfboard but none of the holes are connected. Should i use solder to make the leads between two things?


The usual procedure with perfboard that doesn't have conductors is to let the leads of the various components form the connections.


In closing: FUCK RADIOSHACK, TOO!

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"I am endeavoring, ma'am, to create a mnemonic memory circuit... using stone
knives and bearskins." -- Spock to Edith Keeler
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omonoid



Joined: Jan 11, 2011
Posts: 4
Location: spokane

PostPosted: Sun Jan 16, 2011 10:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ill open with: FUCK RADIOSHACK

$1 for 5 resistors???

I ended up getting help from a guy on physicsforums. He modified the shitty schematics to something that should work

Posted Image, might have been reduced in size. Click Image to view fullscreen.

I'm too new at this to recognize a bad instructible so thanks.

Ill be putting it all together tomorrow. hopefully it works

The above shcematic is modified so i can use a 10k pot for the amplitude change insteasd of 500k. It also has different resistors that should be better according to the guy who helped me.

Let me know if you have any further suggestions
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bod



Joined: Apr 28, 2009
Posts: 148
Location: Glasgow

PostPosted: Mon Jan 17, 2011 3:43 am    Post subject: Reply with quote  Mark this post and the followings unread

richardc64 wrote:
OMG, I scarecly know where to begin! How about
FUCK INSTRUCTABLES! Fuck 'em! With their crappy instructions that you have to register to see in more detail, only to find out the project wasn't worth even that little bit of effort. And the oh-so-helpful Commenters who don't know their collective asses from a hole in the ground.



Laughing

anyway, this seems a little too involved for a squarewave generator, what about CMOS and a lunetta style oscillator?

unless of course you want it slightly more complicated for the extra credit aspect?
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omonoid



Joined: Jan 11, 2011
Posts: 4
Location: spokane

PostPosted: Mon Jan 17, 2011 12:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

well i already have all the parts
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richardc64



Joined: Jun 01, 2006
Posts: 611
Location: NYC
Audio files: 25

PostPosted: Mon Jan 17, 2011 3:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Physicsforum Guy added an unnecessary connection, the 33K to +4.5V. Splitting the 9Volts eliminates the need for that. I found this by Googling "741 square."

http://www.circuitstoday.com/square-wave-generator-using-ua-741

It even explains how it works, which you could include for extra extra credit.

Another good example of the same circuit is here
http://www.play-hookey.com/analog/square_wave_generator.html

Including the formula in the second link will either dazzle your professor or make him suspicious. It might be best to not push your luck.


Involved? Naw, but Instructables Guy should've realized it might appear that way to some and made an effort to make the most important part clearer.

Good Luck, omonoid.

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knives and bearskins." -- Spock to Edith Keeler
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omonoid



Joined: Jan 11, 2011
Posts: 4
Location: spokane

PostPosted: Mon Jan 17, 2011 7:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

So with the first one does R1 have to be a 2.5M pot? i have a 4.7k 10k and 500k and would rather not buy another one

If i wanted to throw in an amplitude pot would i just wire in a pot on the output?
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richardc64



Joined: Jun 01, 2006
Posts: 611
Location: NYC
Audio files: 25

PostPosted: Mon Jan 17, 2011 10:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

omonoid wrote:
So with the first one does R1 have to be a 2.5M pot? i have a 4.7k 10k and 500k and would rather not buy another one

If i wanted to throw in an amplitude pot would i just wire in a pot on the output?


No, the 500k pot is good for the frequency pot, and wire a 10k at the output.

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knives and bearskins." -- Spock to Edith Keeler
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droffset



Joined: Feb 02, 2009
Posts: 486
Location: new zealand
Audio files: 2

PostPosted: Mon Jan 31, 2011 2:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

richardc64 wrote:
OMG, I scarecly know where to begin! How about
FUCK INSTRUCTABLES! Fuck 'em! With their crappy instructions that you have to register to see in more detail, only to find out the project wasn't worth even that little bit of effort. And the oh-so-helpful Commenters who don't know their collective asses from a hole in the ground.

(etc...)

In closing: FUCK RADIOSHACK, TOO!


This made me burst out laughing and my coworkers looked at me like i'm crazy. But it's true, Instructables was already messy but ruined itself with that signup thing.

Omonoid, best of luck with your project.

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Edit: Spelling mistakes.
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