Connecting Leds To The Function Outputs - tams elektronik FD-R Extended Series Manual

English

6.4. Connecting LEDs to the function outputs

The decoder´s function outputs switch respective to the decoder
ground. For that reason you must connect the cathodes (-) of the LEDs
to the function outputs and the anodes (+) to the decoder´s common
return conductor for all function outputs.
Caution:
!
If you use light-emitting diodes (LEDs) you must always operate them via
a series resistor, otherwise they will be damaged when put into operation
or their duration of life will be reduced considerably!
When doing without a series resistor, other components undertake the
series resistor´s function (e.g. rails, wheels, current connectors), 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
Page 22
FD-R Extended