Fading LEDs

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This circuit operates two LED strips in pulsing mode, i.e. one LED strip goes from off state, lights up gradually, then dims gradually, while the other LED strip does the contrary. Each strip can be made up from 2 to 5 LEDs at 9V supply.

Notes:

For those whishing to avoid the use of trimmers, suggested values for 9V supply are: R4=3M9, R9 & R13=47K and trimmers replaced by a short.
Whishing to use a wall-plug adapter instead of a 9V battery, you can supply the circuit at 12V, allowing the use of up to 6 LEDs per strip, or at 15V, allowing the use of up to 7 LEDs per strip.
In this case, the value of the trimmers R7 & R8 should be changed to 100K.

R1,R2_______________4K7  1/4W Resistors

R3_________________22K   1/4W Resistor

R4__________________1M   1/4W Resistor (See Notes)

R5__________________2M2  1/4W Carbon Trimmer (See Notes)

R6,R10,R11,R14,R15_10K   1/4W Resistors

R7,R8______________47K   1/4W Carbon Trimmers (See Notes)

R9,R13_____________27K   1/4W Resistors

R12,R16____________56R   1/4W Resistors

C1__________________1µF   63V Polyester Capacitor

C2________________100µF   25V Electrolytic Capacitor

D1-D4 etc._________5 or 3mm. LEDs (any type and color) (See Notes)

IC1_______________LM358  Low Power Dual Op-amp

Q1,Q2,Q4__________BC327   45V 800mA PNP Transistors

Q3,Q5,Q6__________BC337   45V 800mA NPN Transistors

SW1________________SPST  miniature Slider Switch

B1___________________9V  PP3 Battery