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Prototype an Electronic Coin-toss Step 2: Connect LEDs to Resistors

An electronic coin toss doesn’t literally toss a coin, but it does make a good first project for the aspiring electronics hobbyist. Rather than flipping a coin, one of two lights stays lit when the user removes his finger from two metal contacts, indicating whether the result of the coin toss is heads or tails. Which light stays lit will be essentially random.

Before you connect the LEDs and resistors R3 and R4 using these steps, you will need to have your schematic diagram and have connected the integrated circuit (IC) to power. The LEDs will use the terminal strips in rows 19 and 21.

  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.

  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.

  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).

    image0.jpg

These steps identify specific holes in the terminal strip area of the breadboard using numbers and letters. You might encounter a different numbering system. If so, you can use this template to translate the numbers given in the steps for the breadboard you're using.

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