Today light-emitting diodes are applied everywhere: as indicators, illumination elements, in pocket torches and even traffic lights. There are thousands of models of these devices. On their base in house conditions it is possible to assemble entertaining devices easily. Light-emitting diodes freely are on sale in shops of radio components. Unlike glow lamps, they cannot be connected directly to a current source - light-emitting diodes fail. The restrictive resistor is necessary. Therefore the question of how to calculate resistance to a light-emitting diode rises at once before its use.
It is required to you
- The reference book on light-emitting semiconductor devices, knowledge of standard face values of resistance of resistors (ranks E6, E12, E24, E48), or Internet access for obtaining necessary data. The sheet of paper with the handle or the calculator.
Instruction
1. Learn electrotechnical parameters of the used light-emitting diode. For calculation of resistance of the resistor, it is necessary to learn the direct tension and rated current of the device. Knowing model, or on the Internet find the required parameters in the reference book. Remember or write down their values.
2. Determine tension sourceof food from which the light-emitting diode will be powered. If as the power supply use of galvanic cells or accumulators is supposed, learn their rated voltage. If the light-emitting diode has to eat from chains with wide spacing of tension (for example, the car power supply network), determine the greatest possible tension of a chain.
3. Calculate resistance to a light-emitting diode. Make calculation on formula R = (Vs - Vd) / I where Vs - tension of the power supply, Vd - the direct tension of a light-emitting diode, and I - its rated current. Pick up the closest bigger value of resistance in one of nominal ranks of resistance. It makes sense to use row E12. Admission in face values of resistance of this row makes 10%. So, if a calculated value of resistance of R = 1011 Ohms, as actual resistance it is necessary to choose value of 1200 Ohms.
4. Calculate the minimum necessary power of the extinguishing resistor. Calculate value on formula P = (Vs - Vd)²/R. Values of the Vs and Vd variables are similar to values of the previous step. The value R is resistance calculated earlier.