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It's science fair time at Nick and Ro's house again as our young scientist comes to visit from Chicago. One project I hope to do with him is the LED flasher circuit, also known as the blinkie thing. I had one in Jr. High that was the fascination of the school. I told people it was a Geiger counter, missile guidance system, radar detector, a "bug" - heh heh heh. Electronics is such a mystery to most people. Of course this was the mid-seventies and LED's were a big deal back then.
This is the symbol for a resistor - 
Resistors impede the flow of electrons. With more resistance, less electrons can flow; With less resistance, more electrons can flow. Resistance is measured in units called ohms. The resistance in ohms is usually marked on the resistor by color coded bands. The colored bands can be decoded using the table below.
Resistor Color Code:
| Zero | One | Two | Three | Four | Five | Six | Seven | Eight | Nine | |
| First Digit | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
| Second Digit | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
| Multiplier | 1 | 10 | 100 | 1,000 | 10,000 | 100,000 | 1,000,000 | 10,000,000 | 100,000,000 | 1,000,000,000 |
Examples:
| 4 | 7 | x10 |
A resistor with the color code shown above is a 470 ohm resistor. (47 X 10 = 470)
| 3 | 9 | x10,000 |
A resistor with the color code shown above is a 390,000 ohm resistor. (39 X 10,000 = 390,000)
This is the symbol for a capacitor -
Capacitors can hold and release a charge of electrons very quickly. Bigger capacitors hold more charge than small capacitors. Capacitance is measured in units called Farads.
This is just one of the symbols for a transistor -
(There are many different types of transistors, this is only one of them. A
bipolar-junction NPN transistor.)
Transistors can control a large flow of electrons with a smaller flow of electrons. This is called "amplification." Transistors have three terminals, the one on top is called the collector, the one on the left is called the base and the one on the bottom (with the arrow) is called the emitter. A small flow of electrons taken from the base will make a proportionally larger flow of electrons to go from the emitter to the collector.
This is the symbol for a diode -
Diodes only let electrons flow through them in one direction. They are like one-way valves for electricity. Light emitting diodes (LEDs) are a special breed of diode. When electrons flow through an LED, the electrons make the diode emit photons. Depending on how they are made, LEDs can emit light in many different colors; Red, Green, Yellow, Blue, Orange - even colors that humans can't see - infra-red.
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The schematic diagram for the LED blinker. |
The circuit is an electronic version of the buzzer we made a few years ago. When one side is on it turns the other side off until the capacitor charges up and then the side that was on now turns off and the side that was off now turns on , and it goes back and forth like that as long as there is power. This guy explains it quite well.
I helped the young scientist make a blinkie thing the other day. It is such a pleasure to teach someone who is so willing to learn. Brett has a natural knack for stuff like this and he did all the work. He trimmed the board to size and then chamfered the edges using a power miter saw. Brett used a nail gun for the first time and I was nothing less than amazed. I marked the board with dots where the nails should go. Brett missed the first mark by about one-eighth of an inch and then bulls-eye, bulls-eye, bulls-eye. Day-yum, that's better than I can do! It must be all those video games. Next he soldered all the components on to the nails and connected them up. When the battery was connected, the lights flashed as expected. The experiment was a success!
The young scientist at work.
Saturday May 23, 2009
