How do you calculate the control resistance for A3D/M2D Push Buttons LED lamps?
Set the control resistance within the range for the LED lamp characteristics.
Use the following formula to find the external resistance.
Control Resistance (Recommended Values)
|5 VDC||165 Ω||140 Ω||145 Ω|
|12 VDC||515 Ω||490 Ω||495 Ω|
|24 VDC||1,100 Ω||1,090 Ω||1,095 Ω|
Calculation Example: A3D
LED lamp illuminating color: Red
E = 24V
IF = 20mA
Ta = 25℃
Therefore, inserting the values into the formula above (R = E - VF/IF(Ω)):
R = (24 (V) - 1.7 (V))/0.02 (A) 1100 (Ω).
The recommended resistance is 1.1 kΩ at 1 W (2 x IF2R).
Note:Approximately twice this value is appropriate to provide a margin in the capacity of the resistor.
LED Characteristics (VF-IF Characteristics)
Forward Current Reduction Curve
Applicable models: A3D Push Buttons, A3A Push Buttons, etc.