LITMIR.BIZ

      1 Insert the 555 timer IC.Take a close look at the 555 timer IC. On the top, notice a small dot in one corner; this dot marks the location of pin 1. Carefully insert the leads of the 555 timer IC into the breadboard near the middle of the board, inserting pin 1 into hole E14 and pin 8 in hole F14. The IC will straddle the groove that runs down the center of the board.

      2 Connect pin 1 of the 555 timer IC to the ground bus.Insert one end of a small jumper wire into hole A14 and the other end into the nearest available hole in the bottommost bus strip.

      3 Connect pin 8 of the 555 timer IC to the +9 V bus.Insert one end of a small jumper wire into hole J14 and the other end into the nearest available hole in the topmost bus strip.

      4 Connect pins 2 and 6 of the 555 timer together.Insert one end of a small jumper wire into hole C15 and the other end in hole H16. The jumper wire will reach over the top of the 555 timer chip.Figure 6-9 shows what the breadboard looks like after these three steps.

      1 Connect pin 3 of the IC to row 19.Insert one end of a short jumper wire in hole C16 and the other end into hole C19.FIGURE 6-9: The breadboard after the IC has been inserted and connected to the power buses.

      2 Connect the two segments of row 19.Insert one end of a short jumper wire into hole E19 and the other end into hole F19. This jumper wire bridges the gap between the two terminal strips in row 19, effectively making them a single terminal strip.

      3 Insert the red LED.If you look carefully at the red LED, you’ll see that one lead is a bit shorter than the other. This short lead is called the cathode. The longer lead is called the anode. Insert the cathode (shorter lead) into hole D21. Then, insert the anode (longer lead) into hole D19.

      4 Insert the green LED.The green LED also has a short cathode lead and a longer anode lead. Insert the anode (long) lead in hole G21 and the cathode (short) lead in hole G19. Note that the leads of the two LEDs are installed reversed from one another: the red LED’s anode and the green LED’s cathode are inserted into row 19, while the red LED’s cathode and the green LED’s anode are inserted into row 21. There’s a very good reason for this, but I wouldn’t expect you to understand it yet even if I tried to explain it. So for now, take it on faith that you must install the two LEDs reversed like this for the circuit to work. (You learn more about LEDs, cathodes, and anodes in Book 2, Chapter 5.)

      5 Insert resistors R3 and R4.Both of these resistors are 470 Ω. You can identify these resistors by looking at the three color strips painted on the resistors — they’re yellow, purple, and brown. Insert one end of the first resistor in hole B21 and the other end in the nearest available hole in the bottommost bus strip (the ground bus). Then, insert one end of the other resistor in hole I21 and the other end in the nearest available hole in the topmost bus strip (the +9 V bus).Figure 6-10 shows what the breadboard looks like after these steps.