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How to add LED's to circuit?
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Project_2501



Joined: Jan 31, 2018
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PostPosted: Sat Jun 09, 2018 11:23 am    Post subject: How to add LED's to circuit? Reply with quote  Mark this post and the followings unread

Just curious if there is a simple way to describe adding LED's to a known circuit to indicate if there is a signal present(incoming or outgoing) in the module.

Is adding an LED rudiment as adding an LED onto an INPUT of the CV or signal[main]output of an module with an added 1n4148's or 100k resistor for protection? Would that work for these purpose?
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PHOBoS



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PostPosted: Sat Jun 09, 2018 7:34 pm    Post subject: Re: How to add LED's to circuit? Reply with quote  Mark this post and the followings unread

You might get away with it in some cases if you use blue or white LEDs as I have noticed those can still be quite bright and work
fine with such a large resistor value (maybe some high efficiency LEDs for other colors could work too). But usually you will need
a much smaller resistor value (somewhere between 1K..10K) and then you get in trouble with the current consumption. And because
a lot of circuits use 1K resistors on the output you could also get a very noticable voltage drop. So you will need some kind of buffer
like a transistor or opamp. It might require some experimentation to get a nice response depending on the LEDs and the voltage level.
Outputs can already have a buffer which could drive a LED directly.

duo-color LEDs are nice to indicate both positive and negative CVs btw.

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gabbagabi



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PostPosted: Sun Jun 10, 2018 12:53 am    Post subject: Reply with quote  Mark this post and the followings unread

as usual Yves already has prepared something for us Wink


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JovianPyx



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PostPosted: Sun Jun 10, 2018 10:08 am    Post subject: Reply with quote  Mark this post and the followings unread

Be careful about things that switch fast in an audio circuit - it can cause clicks or pops in the audio. Using some kind of lowpass filter to slow the switching helps.
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cslammy



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PostPosted: Fri Jul 19, 2019 1:50 pm    Post subject: Reply with quote  Mark this post and the followings unread

I recently put up a blog post with a small SMT op amp PCB I use for bi color LEDs. Not sure if that's what you're after, but it follows the same ideas already posted here--you want to buffer your signal before feeding it into the LED, and a bi color LED can give you an idea which way your current is flowing.

https://audiodiwhy.blogspot.com/2019/07/getting-started-with-smt.html

Scroll about halfway down the post.

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Grumble



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PostPosted: Sat Jul 20, 2019 11:07 am    Post subject: Re: How to add LED's to circuit? Reply with quote  Mark this post and the followings unread

PHOBoS wrote:
duo-color LEDs are nice to indicate both positive and negative CVs btw.

I use those in combination with a simple comparator, green for in range and red for out of range.

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