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jdlogicman

Member Since 17 Jan 2013
Offline Last Active Jan 04 2017 07:43 PM
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Posts I've Made

In Topic: Eliminating noise from the Netduino 2 plus - optocoupler?

16 March 2014 - 07:33 PM

I was about to suggest that it forms some sort of lowpass filter on the input, but the resistor is in the wrong place. Maybe I'll flip it tonight and see if that is equivalent.


In Topic: Eliminating noise from the Netduino 2 plus - optocoupler?

16 March 2014 - 03:53 PM

It's to the negative terminal of the battery. Sorry, I don't have it diagrammed out, but parts of it that show the issue are straight out of the typical applications section of the data sheet, "Amplifier with gain=200" here http://www.ti.com/li...mlink/lm386.pdf


In Topic: Eliminating noise from the Netduino 2 plus - optocoupler?

15 March 2014 - 11:50 PM

may have figured this out. If so, this may be of use to others. 

 

Short version: use a resistor when referencing your signal to ground.

 

Long version: I am using the LM386 audio op-amp, which like many others, amplifies the differential between two inputs. When you reference one of them to ground, you create a path for signals to flow from your power supply into the op-amp. 

 

I remedied this by using a 100K resistor instead of a wire. Perhaps obvious to some, but not a noob like me.


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