Let's see how the calculation of resistors for LEDs

Calculating resistors for LEDs is a very important operation that must be carried out before you connect the LED to a power source. This will depend on the performance of both the diode itself and the entire circuit. The resistor must be connected in series with the LED in series. This element is designed to limit the current flowing through the diode. If the resistor has a nominal resistance below the required resistance, the LED will fail (burn), and if the value of this indicator is higher than necessary, the light from the semiconductor element will be too dim.

Calculation of resistors for light-emitting diodes should be made by the following formula R = (US - UL) / I, where:

• US - power supply voltage;
• UL - supply voltage diode (usually 2 and 4 volts);
• I is the current of the diode.

Be sure to make sure that the selected value of the electric current will be less than the maximum value of the current of the semiconductor element. Before proceeding to the calculation, it is necessary to translate this value into amperes. Usually it is indicated in passport data in milliamperes. Thus, as a result of the calculations, the value of the nominal resistance of the resistor in Ohms will be obtained. If the obtained value does not coincide with the standard resistor, then the larger nearest value should be selected. Alternatively, several elements smaller in nominal resistance can be connected in series in such a way that the total resistance corresponds to the calculated resistance.

For example, this is how the resistors for LEDs are calculated. Let's say that we have a power supply with an output voltage equal to 12 volts, and one LED (UL = 4 V). The required current is 20 mA. We translate it into amperes and get 0.02 A. Now we can proceed to the calculation of R = (12 - 4) / 0.02 = 400 Ohm.

Now let's look at how it is necessary to perform a calculation when several semiconductor elements are connected in series. This is especially true when working with LED stripes. A serial connection reduces power consumption and allows you to simultaneously connect a large number of elements. However, it should be noted that all the connected LEDs must be of the same type, and the power supply unit is sufficiently powerful. In this way, it is necessary to calculate the resistors for the LEDs in series connection. Suppose that we have 3 elements in the circuit (each voltage is 4 volts) and a 15-volt power supply. Determine the voltage UL. For this, it is necessary to add the values of each of the diodes 4 + 4 + 4 = 12 volts. Passport value of LED current is 0,02 A, we calculate R = (15-12) / 0,02 = 150 Ohm.

It is very important to remember that parallel connection of LEDs, to put it mildly, is a bad idea. The thing is that these elements have a spread of parameters, each of them requires a different voltage. This leads to the fact that the calculation of the LED is a useless occupation. With this connection, each element will shine with its brightness. The situation can save only the limiting resistor for each diode separately.

In conclusion, we add that according to this principle, all LED assemblies, including LED lamps, are calculated. If you want to build this structure yourself, then these calculations will be relevant for you.