Switch for Quiz Game From Plastic Bottles

This pair of switches mounted inside a plastic Bottle uses a very simple circuit to control the LED Lights. After one button is pushed, it's lights will turn on, thus disabling the the other set of lights.

All the pictures after the zoom image are larger pictures of the steps, take a look if you need to see the details.

Step 1: Step 1 - What You Will Need.

Materials:

- 2 Small plastic bottles.
- 2 Medium plastic bottles.
- 16 Screws.
- 2 X 6.5cm long - 20mm diameter PVC pipe.
- 2 X 6.5cm long - 25mm diameter PVC pipe.
- Double layer fiber glass PCB
- 2 Springs (Made of a weldable metal)
- 2 Normally open push buttons
- 5 Green LEDs
- 5 Red LEDs
- Cable with 4 wires
- 2 NPN Low power transistors (I used BC337)
- 2 X 330ohms resistors
- 2 X 10Kohms resistors
- 9V Battery and clip

And Also:
Soldering iron, scissors, screw driver, saw, tape, glue gun.

Step 2: Base

Assembly of the base now.

Step 3: Switch

Note: If you're going to use the plastic spring, you won't need a double layer PCB.

Step 4: Top

Make a hole on the bottle, pass the cable through it, connect two of the wires to switch and two of the wires to the LEDs. Write down the connections on a paper.
Mine is:
Orange - Green LEDs positive terminal.
White - Green LEDs negative terminal.
Green - Switch Terminal A.
Blue - Switch Terminal B.

Step 5: Circuit

Step 6: Wiring

If you're not a beginner in electronics, you can skip this step.

Before soldering the circuit let's do the connections and test the device.

Now, that the emitters are connected i'm going to label the transistor marked by the green arrow as green transistor and the red arrow as red transistor.(The same for the switches)

Step 7: Twist, Solder, Tape

Solder all connections and pass the tape around them, except on the transistors bases.
If you can't find the base, just turn on the circuit touch the battery "+" terminal with one finger, and when you touch the transistor base, the LEDs will show a weak bright. Do it with the two terminal you labeled as switch, one of the them must be the base.

Step 8: Play

Find some good questions and test your knowledges.

Step 9: Appendix - Expanding the Circuit.

Before trying to expand the circuit, and adding another switch i'll explain how it works.

When S1 is pressed, Q1 is polarized and the current flows through D1(LED1). If S2 is pressed now, there won't be enough current to polarize Q2, because the current is being drained by Q1 and D1(LED1).
That's why only one LED can be turned on, one disables the other.

To add another set of lights, every single switch would have to disable the other two. See figure 2.

In the second circuit, pressing one switch, two LEDs will turn on, and nothing changes if the other switches are pressed.So the output would be:

Press: - Lights ON:
S1 - 1,2
S2 - 1,3
S3 - 2,3

I'm not sure if it's the best way of doing it, because it would later need decoding with AND gates.

If someone got a better idea please comment.

PS: Please rate this instructable if you like it. Thanks