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Bangladesh Distributor
Question
How do you calculate the control resistance for A3D/M2D Push Buttons LED lamps?
Answer
Set the control resistance within the range for the LED lamp characteristics.
(Set the forward current for the LED lamp to 8 mA min.)
Use the following formula to find the external resistance.
R = (E - VF)/IF (Ω)
E: Operating voltage (V)
VF: LED forward voltage (V)
IF: LED forward current (A)
Control Resistance (Recommended Values)
| Voltage | Red | Yellow (White) | Green |
| 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℃
Based on the VF-IF characteristics in the diagram below (red):
VF = 1.7 V when IF = 20 mA.
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)
A3D Series
A3A Series
Applicable models: A3D Push Buttons, A3A Push Buttons, etc.
61F-G[]N
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