Multisim and Ultiboard

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Parallel LED circuit not reading correctly

Good day,



Can anyone tell me if there is something wrong with this circuit or if the software is acting funny?


I have a voltage source positive going into 3 parallel circuits.  Each circuit contains a 30 ohm reisiter connected in series to 3 parallel LED's.  The LED's have a forward operating current of 20mA.  


the first branch is reading 1.9V the second branch is reading 2.2V and the third branch is reading 3.4V across the parallel LED's.  


hoping it is a bug I introduced or maybe I am misunderstanding how to connect the components properly.  


I have a file with a cap screen to show how it is connected

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I figure out what the issue is.  The different colour LED's have different voltage drop characteristics.  


Is there a way to get a RGB component in the simulation?

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1. Please create .png files from your screenshots and insert them directly into the post. The little Tree icon in the toolbar just above the text box where you type your message inserts images. Some people on the Forum will not open attachements in other file formats.


2. Real LEDs have different voltage drops for different colors due to different chemical composition. Also the parallel LEDs (at least real ones) would have slightly different VI characteristics so that each of the three LEDs(of the same color) would have different currents and, thus, different light output.


3. It is not clear what your intention is. Normally LEDs are connected in series so that the same current flows through each (same color). Rather than fixed resistorrs use some king of current regulating circuit to adjust the current in each series string to get your RGB effects. Note that you will have very little "headroom" between the source (V1) and the series string of blue LEDs (~10 V).



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