Below this section, all the resistors in E series and Renard’s numbers compatible to the entered value are listed. The closest match given in this set would be highlighted with green font. In the above example it is the E series resistor E12: 180Ω.
Now, if you click on the arrow near each colour given for each band, it opens a drop-down menu which lists all the colours as in the standard code.
Suppose we select first band—orange, second band—white, fourth band—red, fifth band—blue and sixth band—black. The resistor value changes to 3900, tolerance to ±0.25 per cent and temperature coefficient to 200 ppm (parts per million). The closest standard resistance value is E192 = 3.92kΩ.
Note. Preferred numbers/values are standard guidelines used by manufacturers to choose exact product dimensions for given constraints.
Renard’s numbers/values are a set of preferred values defined by the French army engineer, Colonel Charles Renard, and is used within the SI system.
E series is another set of preferred numbers proposed by international standard IEC 60063 for electronic components such as resistors, inductors, capacitors and Zener diodes.
Calculation of LED resistance
Every LED circuit should have a resistor connected in series in order to work properly. The second tab in the window, Calculate LED resistors, is where you can calculate the resistor value required for an LED circuit. When the user enters the supply voltage (in volts), voltage drop across LED (in volts) and the current of the LED (in milliamperes), the value of resistor to be connected to this circuit and the power dissipation is calculated and displayed by the program.
If two or more LEDs are connected in a series or parallel, the resistor value for that circuit can also be found out by entering the number of LEDs in series/parallel under its corresponding sections LEDs in series connection/LEDs in parallel connection.
By clicking on the Show resistor button, the calculated value is shown in Resistors tab where you can determine its colour code.
Example. Suppose you want to calculate the value of resistor for a single LED where supply voltage is 24V, drop across the LED is 3V and LED current is 25mA. Enter these values in their respective fields, and the Resistor value is calculated by the program as 840Ω. Power dissipation is also calculated automatically, which is 525mW in this case.
Now consider another case where the parameters are the same but five LEDs are connected in a series. Under the subheading LEDs in series connection, enter the corresponding values. So the Resistor value and Power dissipation will be displayed as 360Ω and 225mW, respectively. By clicking on the Show resistor button, you are taken to the Resistors tab, where the resistance and colour coding of the calculated resistor value of LED(s) is given.