Parts Required

2 470 Ω resistors
4 Connection wires
2 LEDs

1. Build the circuit below and remember to be very careful about how you attach the wires so that no unsheathed wires touch accidentally.
2. Pay attention to the flat mark on the LED to see that it is closest to the ground.
3. Notice that a single wire going from the ground plane (VSS) to the breadboard will define a complete row as ground so that both LEDs will then be connected to ground.

   ' {$STAMP BS2} “Command line to tell the stamp it is the BS2

   Railroad:                                     'The label at the start of the program. Note ‘The colon after the name railroad.
   
   

   LOW 0                                        'Turn led0 off
   HIGH 1                                       'Turn led1 on

   PAUSE 200                                  'Hold these LEDs in these states for .2 seconds

   HIGH 0                                       'Turn led0 on
   LOW 1                                        'Turn led1 off

   PAUSE 400                                  'Hold LEDs in these states for .4 seconds

   GOTO railroad                             'Start the "railroad" loop over again

 

2 LED on the Board of EDU coming from pins 1 and 2

 

Notice on the schematic how you can attach both wires coming from the LEDs into a single common ground plane. Notice how there is an arrow coming from pin 0 and pin 1 and this indicates you are driving an output from your Basic Stamp 2.

 

Schematic for circuit


Programming the Project

Enter the program below and hit run. Does the program work? If not proceed to the section at the back of this chapter on debugging.

Your turn

4. Change the timing of the lights to change the flashing of the LEDs by changing the pause cycle.
5. Make one flash at twice the rate of the other.
6. Program one LED to flash once for every four flashes of the other LED.
7. Using multiple HIGHs and LOWs, program your LEDs to start flashing slowly and then gradually increase their rate.