FLASHER - 2 LED

INSTRUCTION SHEET

 

 

 

Price - Stock No 90

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Schematic Diagram

PCB Layout

CONSTRUCTION

  1. Determine  the  values of the resistors by their colour bands.  Bend the legs with long-nose pliers and fit them to their positions.   The  two  10K  resistors  should  be mounted vertically; the 390R can be put in  flat on the board.  Solder in position by applying heat to the pad  beside  the leg until the solder flows.  Apply more solder to form a small cone of  molten  solder  with  its  apex  on  the component leg.  Heat the leg only   enough to make a bond.  Do not overheat any component.
  2. Bend the legs of the diode IN4002 to match  the  holes.   Check  the  polarity  by  locating  the  band  on  the  body at the end marked K.  Solder.
  3. Determine the polarity of the two 220uF electrolytic capacitors   by finding the arrow printed on the body.  This arrow points  down  the  K   (negative)  leg.  Position the capacitors in their correct polarity as the drawing shows.
  4. Place the two transistors in position with  the  flats  on  the bodies as shown.  This will locate C,B,and E legs correctly.
  5. The  LEDs are also polarised.  Find a small flat on the flange  below the globe.  This is above the K  (negative)  leg.   This  K  leg  is  usually  shorter  than the A leg.  The A and K positions are etched in the PCBoard, and also shown on the drawing.
  6. Connect the red lead of the battery snap to the  9v+  location, and the black to the 9v-.  Connect a 9 battery and test. 

Trouble  shooting  will  consist of checking locations and polarity carefully, and also checking soldering.   Any  suspect  joints  should  be re-soldered.   Ensure  also  that  no  bridging  of tracks has occurred by solder. This circuit is the original "flip-flop".  It is a  binary  counter around  which  the  computer  was  designed.   These and much more complex circuits are miniaturised to pin-point  size  and  built  into  Integrated Circuit "Chips". Speed  of  flashing  can be varied by changing the value of the two 10K resistors and the values of the 220uF Capacitors.

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