It is a simple circuit of optical index of level of sound signals, adapted in various needs of user. It can be adapted in various levels of entry, regulated from trimmer TR1 Level – TR2 Gain, then it is rectified by the D1-2 cutting off of negative periods of signal-rectification and drived to the main circuit of index, that it is constituted by D3…D13 , the transistors Q2-Q13 and the materials that exist around them.
The optical index him we take from the line of LED LD1-13. The each led turns on when the level is altered at 0,65V roughly. The requirements in current are 100 ma with complete index. We can add all units LED we want, always calculating the current where they will need the news LED.
R2-3 =1Mohm TR1=100Kohm Trimmer LD1-7=LED Green
R4-R7=1Kohm TR2=4.7Kohm Trimmer LD8-10=LED Yellow
R5=100ohm C1=10uF/25V LD11-13=LED Red
R6=18Kohm C2=100nF/100V MKT D1-13=1N4148
R9-11-13-15-17=560ohm C3=4.7uF/25V Q1 ….Q13=BC550C – BC549B
R19-21-23-25-27=560ohm C4=4.7uF/25V IC1=TL071
R29-31=560ohm C5=10uF/25V IC2=7812 [With Heatsink]
R16-18-20-22=4.7Kohm C7-8=100nF/100V All Resistors is 1/4W 1 -5%
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