|
|
Table
of Contents It's hard to believe something so small and unimpressive could do so much for your solar path light. Transistors are really two diodes put together. They can act as switches, regulators, or amplifiers. They "switch" a circuit off and on by "sensing" if there is voltage on one lead: the "base". If there is a small amount of voltage on the base lead, it "turns" the circuit "on" by allowing a larger amount voltage to flow from the "collector" lead to the "emitter" lead. Transistors are "linear" devices: the amount of current flowing into the "base" lead directly affects the amount of current flowing from "collector" to "emitter." In other words, it is a direct ratio: if you double the amount of current flowing into the base, you double the amount of current flowing from collector to emitter. The total current flowing out of the emitter is the sum of the current flowing into the base and collector. |
|
 Transistors are not as readily available as resistors, but you can get the MPS2222A NPN at Radio Shack...individually packaged. OR you can purchase them in bulk online at a cost of about 16 cents each. |
|
|
There is a .7 to .8 voltage drop across the transistor used in this circuit. The voltage drop characteristic of transistors must be taken into consideration during circuit design. Be careful to put the transistors into the circuit correctly: it is easy to be confused about which lead goes where...your circuit won't work if the transistors are installed backwards. Anybody learns these things the hard way. Also, transistors have leads that are a little more delicate than resistors or diodes: it is easy to break them off when you are bending them into position on the circuit. Be gentle! For more information about
transistors, check out these web sites: <<< Backwards Table of Contents Onward >>>
|
