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 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
(Noob Alert!) Noise Toaster LFO questions
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altern8



Joined: May 25, 2012
Posts: 29
Location: chicago

PostPosted: Fri Nov 02, 2012 7:30 pm    Post subject: (Noob Alert!) Noise Toaster LFO questions Reply with quote  Mark this post and the followings unread

Humbly seeking knowledge...

My first foray out of CMOS land and into op-amp circuits. Starting with some stuff from the Noise Toaster.

I'm wondering why certain components are on the schematic. I breadboarded this up as it is and got nothing until I eliminated C13 and C14 from the LM324 power pins and wired them straight in. I also don't quite understand the ground connection shown between said caps or how to include this in the breadboard layout.

Happy to have achieved oscillation I was still getting no LED rate indication until I ran R65 straight to negative, eliminating C26 and R70. Would this be an issue with the LED? What's the purpose of the whole R65, C26 and R70 section?

While I'm asking silly questions -- I don't understand how the power schematic shown at the lower right (lifted from Page 1 of the Noise Toaster schematic) relates to anything on the circuits.


toaster_LFO_power.jpg
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Noise Toster LFO with power supplies
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toaster_LFO_power.jpg



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ashleym



Joined: Aug 20, 2009
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PostPosted: Sat Nov 03, 2012 3:19 am    Post subject: Reply with quote  Mark this post and the followings unread

I can try to answer the power supply part of your question.

The 2 caps you are talking about (C13&14) are power supply by-pass capacitors. They by-pass the effect the local chip can have on the power supply. When the local chip needs some extra power it can draw this from the bypass caps without draining too much from the main supply because if it did other parts of the circuit could be effected. THere are other uses but that is for another day.

The earths on the circuit diagram are virtual earths. Ray has made these to be half way between +9 and 0V, the local virtual earth for this part of the circuit is section with R37 and R42. Wire back to that earth point.

Without testing the LED section my tip is to check the cap polarity and spin it round to check.

I hope this helps and I hope I have aimed my advice at the right level.

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altern8



Joined: May 25, 2012
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PostPosted: Sun Nov 04, 2012 10:10 am    Post subject: Reply with quote  Mark this post and the followings unread

That's how I thought C13 and 14 were supposed to function. Will they work as supply bypass if I connect them as shown but also connect the pins directly to the supply rails? I got the impression that the caps were the only connection to the power pins.

I suspected that the R37 and 42 assembly was a virtual ground. Thanks for clarifying that.

For the LED section -- is R70 to positive and C26 to negative intended to minimize the LED's effect on the circuit? It's kinda hard to miss the polarity markings on a massive 470uf cap but I tried reversing it anyway. Even connected correctly it just seems to be creating too much resistance to the negative rail for the LED.

Thanks again for your help!

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ashleym



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PostPosted: Tue Nov 06, 2012 12:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

You dont NEED the bypass caps and if you arent sure what to do with them then leave them out.

If the LED isnt lighting properly make sure you have the right LED type or resistor value. Look at something like this

http://led.linear1.org/1led.wiz

Click the ? and you will see that different coloured LEDs have different forward voltages.

Always happy to help the trouble is I am not always right!! We all live and learn Exclamation

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