tams
elektronik
FD-R Basic 2
English
possibly leading to a modification of the data signal and thus to
disturbances in digital operation.
Always determine the necessary series resistor´s value for the peak
value of the available operating voltage. With regulated boosters this
corresponds to the specified boosters´ output (= track) voltage. With
not regulated boosters or analogue driving transformers the peak
value is approx. 1,4 fold the nominal voltage specified on the
transformer.
Serial connection of LEDs
When you want to connect several LEDs to one output you can switch them
in series via a common series resistor. The current consumption is max. 20
mA for all LEDs, depending on the series resistor´s value. The maximum
number of LEDs to be connected in series results from
Peak value of the operating voltage
-
sum of the forward voltages of all LEDs
> 0
The advantage of this solution is the low current consumption.
In order to determine the necessary series resistor for a serial LED´s
connection first add the forward voltages of all LEDs. The forward
voltages depend on the lighting colour and should be given in the
technical specifications. In case there is no manufacturer information
available, you can take as a basis 4 V for white and blue LEDs and 2 V
for yellow, orange, red and green LEDs.
The remaining voltage has to be "eliminated" by a resistor. The formula
for the calculation of the resistor is:
required R
V
[Ohm] = ( U
B
[V] – ∑ U
F
[V] ) / (I
F
[mA] x 0.001)
U
B
= operating voltage (peak value) | ∑ U
F
= sum of the forward voltages of all LEDs
I
F
= current with max. luminosity
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