|
|
|
 |
|
|
| When you look at your computer, radio or television and wonder how they work you can easily become confused. One of the traditional starting points used when first teaching electronics is the old demonstration of rubbing something until static electricity is produced and showing how that object picks up a few bits of paper and then telling the experimenter that they have just seen electricity charge something. I don't know about you, but, as a child, I walked away from this demonstration wondering what it had to do with the way my television worked. The only real connection that I can think of is the fact that if the air is dry enough in your house (to help charged objects along) you may notice dust or very light objects on the order of burned paper ashes sticking to the front of your television screen because of the charge on it. Still doesn't help you to understand how it works, does it? |
|
| You can start learning about electronics with the help of a flashlight. Go to the store and buy a flashlight that you can easily take apart, like a plastic one that unscrews on both ends, rather than a solid metal one. Make it a large flashlight that uses two of the large "D" size batteries and you don't have to spend a fortune on it. |
|
| Also needed are some wire and wire cutters to cut and strip some wires for your experimenting. With this minimal investment in materials you can start learning more about electronics than you will ever get from a book without getting your hands on anything. |
|
| Put your batteries (actually, two cells) into the flashlight and make sure that it works. If the light doesn't go on, you're not going to learn anything. Unscrew the top of the flashlight and notice how, with the use of the top section of the flashlight, you can handle the bulb easily and have access to it's two contacts, the side of the bulb and the little button on the bottom of the bulb, just like the cells inside your flashlight do. That can be your first lesson, observing how that bulb needs to be connected to electricity through those two points (the side and bottom of the bulb) to work. |
|
| Now take out the two "D" cells and stack them on top of each other with the bulb sitting on top like it's arranged inside the flashlight. What's missing? A connection from the bottom of the "D" cells to the side of the bulb, that's what! Notice how, when you switch the flashlight on it slides forward a little metal strip that contacts the bulb on it's side to complete the circuit. Do this with a length of wire taking the place of the contact inside the flashlight. If everything is touching (it may be tough to balance everything together) the bulb lights! |
|
| Now take away one of the two cells and repeat the connections to the bulb. If everything touches again the bulb lights! However, if the "D" cells are not absolutely new you will notice that the bulb lights dimmer with one cell than it did with two. Now what did you learn from this simple experiment? |
|
| Aside from the fact that you learned that there is not enough voltage in two flashlight batteries to shock you (notice, I didn't warn you to keep your hands away from anything) you got a look inside your flashlight and saw the different components that are inside it and needed to make the flashlight work. These components were the bulb, the battery (two "D" cells) and some kind of conductor to connect them properly and light the bulb. What do you think would happen if you accidentally shorted the wire to the wrong side of the bulb and instead of the bulb across the battery you had only a wire across the battery? Don't try it. What would happen would be a "short circuit" and the "D" cells would soon be drained of their energy. In fact, if the wire was small enough (thinner than one strand of the wire) it would actually get hot and maybe even burn open. (This is what a fuse does when it "blows".) |
|
| Now you know the concept of a "circuit", that is, a path for electricity to flow out and back to a source in the hope that the circuit does what you want it to do. In the case of lighting the bulb with the single cell, the cell is your source of electricity. The button on top of the battery is your positive side, and the bottom of the battery is the negative side. When your circuit goes out of the "D" cell, into the bulb, out of the bulb and back to the other end of the battery your circuit lights the bulb. If you had the wire going just across the cell you would still have a circuit, but we would call it a "short circuit" because the electricity in the cell isn't going where you want it to go (through the bulb) and unless the wire is small enough to burn open you won't see anything to prove to you that any electrical action is going on while you "burn out" your flashlight cell. |
|
| Another thing you can do at this point is to buy a few small resistors of low value, such as 1 OHM (don't worry if you don't understand "OHM"- you will later) or 5 OHM in value and place them in series with your skeleton of a flashlight. To place them in series means, for instance, taking one side of the resistor and touching it to the positive top of the cell instead of the bulb and then touching the bulb with the other side of the resistor so that all the electricity that goes through the bulb passes through the resistor. You will notice that the bulb gets dimmer with a resistor in series with it and very soon, with a certain number of resistors placed in series with the bulb, it won't light at all. At that point electricity will still be flowing in a circuit, but not enough to light the bulb. Again, you'll have a complete circuit, but without the bulb lighting you won't have anything to indicate to you electrical activity is going on. Meanwhile you're wasting the energy in the "D" cell. |
|
| What does this all have to do with how your computer or TV works? Quite a bit, actually. You need to have the concept of a complete circuit running from a power source to its intended point and having everything connected up properly before electricity can flow in the way you were hoping it would. Did you ever have an electronic device that "blew" a fuse? That indicated to you that inside the device a short circuit had occurred. |
|
| Now would be a good time to go out and buy a VOM (Volt-Ohmmeter) to measure voltage, current and resistance. (Resistance is measured in OHMs.) You can use your VOM to measure the voltage on each of the "D" cells and anywhere across two points in your flashlight circuit. One word of caution when you use a VOM for the first time: Make sure you have it set up to measure voltage when you connect it across your cells or anywhere in your circuit. If you have it set up to measure current or resistance and you put the probes across a source of voltage you may end up "blowing" a fuse in the meter and wondering why these functions won't work in the future. Just set up the VOM to measure voltage according to the instructions that came with it and have fun measuring away. |
|
| Another word of caution: Don't be so free about touching things electrical other than the low-voltage flashlight cells that you're using here. Although by itself a flashlight cell or two or even three cannot cause you any harm they are a source of energy. You can actually make up a circuit with a few certain components that will give you quite a wallop from a single "D" cell! I'm not about to tell you how to do that, either. The point is that using a couple of flashlight cells is a great way to start getting your hands on things but don't let it go beyond that. I shouldn't have to warn you that anything which is plugged into the wall or running on a gigantic battery can easily kill you if you touch the wrong spot and put yourself in the circuit. There was a man who managed to get himself electrocuted with two military vehicle batteries while standing up to his ankles in mud. This poor fellow found a way to die from the misapplication of 42 volts! Don't make yourself one for the record books and make sure to play safe and keep away from the circuits you're working on if there is anything more than a few volts around. |
|
| The biggest point that you can learn now and keep in mind for the rest of your electronics career is that a flashlight is a DC device. The "D" cells are a source of DC voltage. (These Ds have nothing to do with each other.) The current flowing through the bulb is DC current. |
|
| All things electrical are either working on DC (Direct Current) or AC (Alternating Current) or a combination of both. When you plug your computer into the wall the voltage at the wall outlet is AC. By the time the electricity gets applied to your computer circuits it is DC. Inside the computer circuits themselves the applied DC is changed to AC and back to DC. This is exactly why, when you start with a simple, basic item like a flashlight you have trouble relating what you learn about it to other electronic devices. If you don't learn about simple DC devices such as that flashlight and study up on the differences between the nature of DC and AC you'll be forever lost. |
|
| I have had the unfortunate experience of meeting practicing technicians who never grasped certain fundamental differences between the nature of DC and AC. For now, just realize that you are going to start your learning experience in electronics by studying DC devices, such as a flashlight, before you can get a "feel" for things more complicated such as your computer, radio or TV. |
|
| Now that you've got your hands on something electrical, go on to the next subject in "Electronics Basics". |
|
| |
|
| |
|
