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Assuming you do the right thing and use current limiting resistors for them all then the resistor has to drop 8.6 volts at 16mA. This is a resistor value of about 537 ohms. However, you could wire 3 in series to produce a combined LED voltage of 10.2 volts then use a resistor of 112 ohms. It will be a more efficient way of driving the LEDs .If you pick a resistor form the SMD power rating chart that can dissipate 0.025W then dissipating 0.0025W will obviously not be a problem. Regarding your question about your circuit with R2,R3 and high current you calculated: R2 and R3 are current sense resistors (hence their low value). And yes, the power dissipated will be large.
As per the datasheet of the 5mm White LED, the Forward Voltage of the LED is 3.6V and the Forward Current of the LED is 30mA. Therefore, VS = 12V, VLED = 3.6V and ILED = 30mA. Substituting these values in the above equation, we can calculate the value of Series Resistance as. RSERIES = (12 – 3.6) / 0.03 = 280Ω.D1 is a visible LED that indicates when the input is pressed. R1 and R2 are 1/4 of a 8-resistor SOIC-16 SMD package (Bourns 4816P-1). Since there are three of these circuits, two of the resistors in the package are left unconnected. Question 1: Is there any reason why this circuit would need two 2 kΩ resistors, instead of one 4 kΩ resistor? NXtlhDr.