Introduction: Music Channel Difference Signal Blinking LED
In this Instructable you will be making a "Music Channel Difference Signal Blinking LED".
You will need: a dozen general-purpose NPN BJT transistors, a dozen general-purpose PNP BJT transistors, 6 LEDs, two small matrix boards, 1 kohm resistors (10 pack), 10 kohm resistors (5 pack), 100 kohm resistors (5 pack), screw driver, three 470 uF bipolar capacitors, three 100 nF pillow capacitors, nuts, bolts, washers, three 2 Megohm variable resistors (might work with 1 Megohm variable resistors), wire stripper, wires, thin 1 mm metal wire, two encasements (optional), - soldering iron (optional), solder (optional).
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Step 1: Make the Amplifier
If you are going to connect external amplifiers then make sure the negative terminal from the amplifier output is grounded. Otherwise, there could be over 100 V potential difference between input and your device ground.
Alternatively, you can use a battery-operated device mobile phone that is completely isolated from the mains power supply. The best option is to connect a battery instead of a 12 V mains power supply to this device.
The voltages in the amplifier and the LED driver must be the same. The range could be 4 V to 12 V. In the video the device is working with 4 V. However, the minimum power supply also depends on the input signal amplitude. The higher supply voltage will increase the amplifier gain.
Use bipolar 470 uF capacitors for input.
The 2 Megohm resistor can have one terminal connected to power supply instead of transit collector (do not use more than two terminals of the variable resistor because some have three terminals). However, the feedback bias shown in the circuit provides better stability due to collector voltage fluctuations caused DC current gain changes with ambient tempareture. You might have to play a bit with the three potentiometers until the circuit starts working. You need to wait for the capacitors to settle.
Step 2: Make the Differential LED Driver
The input Vin1 is the output of the three-channel amplifier.
The voltage across each LED must be 2 V. Try increasing the power supply if the LED light is to dim. However, do not increase above 12 V.
Step 3: Make Encasement
Use an electric drill to drill holes in enhancement and connect the bolts, nuts and washers.
You are now done.