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Step 2Circuit Design
Standard USB output is 5VDC and can draw up to 100mA. We only need ~2VDC for each LED@30mA. Your mileage may vary depending on the LEDs you choose. Lucky for us there is a wizard we can plug numbers into that will help design the circuit for us. Use this LED wizard to help with your design - LED Wizard. I Chose a 2x4 array with 1 extra LED.
each 27 ohm resistor dissipates 24.3 mW
the wizard says the color code for 27 is red violet black
the wizard thinks 1/4W resistors are fine for your application
the 100 ohm resistor dissipates 90 mW
the wizard says the color code for 100 is brown black brown
the wizard thinks 1/4W resistors are fine for your application
together, all resistors dissipate 187.2 mW
together, the diodes dissipate 567 mW
total power dissipated by the array is 754.2 mW
the array draws current of 150 mA from the source
each 27 ohm resistor dissipates 24.3 mW
the wizard says the color code for 27 is red violet black
the wizard thinks 1/4W resistors are fine for your application
the 100 ohm resistor dissipates 90 mW
the wizard says the color code for 100 is brown black brown
the wizard thinks 1/4W resistors are fine for your application
together, all resistors dissipate 187.2 mW
together, the diodes dissipate 567 mW
total power dissipated by the array is 754.2 mW
the array draws current of 150 mA from the source
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