黑暗激活LED或灯闪光电路--Dark-activatedLEDorLampFlasher

黑暗激活LED或灯闪光电路--Dark-activated LED or Lamp Flasher
  Simple photo-sensitive circuit
  3V battery supply
  
  Parts:
  R1_________________Photo resistor (any type)
  R2________________100K 1/2W Trimmer Cermet
  R3,R4______________10K 1/4W Resistors
  R5________________470R 1/4W Resistor
  R6_________________47R 1/4W Resistor
  C1________________220?F 25V Electrolytic Capacitor
  D1______________1N414875V 150mA Diode
  D2_________________LEDAny type and color (See Notes)
  Q1,Q2____________BC33745V 800mA NPN Transistors
  SW1_______________SPST Switch
  B1__________________3V (Two 1.5V AA or AAA cells in series, etc.)
  Circuit operation:
  This circuit adopts the rather unusual Bowes/White emitter coupled multivibrator circuit. The oscillation frequency is about 1Hz and is set by C1 value. The LED starts flashing when the photo resistor is scarcely illuminated. The onset of flashing can be set by trimming R2.
  Notes:
  Best results in flashing frequency can be obtained using for C1 a value in the 100 to 1000?F range.
  To drive a filament lamp the following changes must be made:
  
  Use a 2.2 to 3V, 250-300mA lamp in place of the LED
  R2 = 10K 1/2W Trimmer Cermet
  R3, R4 = 1K 1/4W Resistors
  R6 = 1R 1/4W Resistor
  C1 = 470 to 1000?F 25V Electrolytic Capacitor
  In LED-mode operation the stand-by current consumption is less than 400?A.
  In Lamp-mode operation the stand-by current consumption is about 3mA.