Atlas DCA User Guide
October 2007 – Rev 7
Bicolour LEDs
Bicolour LEDs are automatically identified. If your LED has 3
leads then ensure they are all connected, in any order.
A two terminal bicolour LED consists of two LED chips which
are connected in inverse parallel within the LED body. Three terminal bicolour
LEDs are made with either common anodes or common cathodes.
Here a two terminal LED
has been detected.
Two terminal
bicolour LED
This message will be
displayed if the unit has
detected a three terminal
LED.
Three terminal
bicolour LED
The details of each LED in the package
will then be displayed in a similar way
to the diode networks detailed earlier.
Pinout for D1...
The pinout for the 1st LED is displayed.
Remember that this is the pinout for just
one of the two LEDs in the package.
RED GREEN BLUE
Anod Cath
Interestingly, the voltage drops for each
LED relate to the different colours
within the bicolour LED. It may
therefore be possible to determine which
lead is connected to each colour LED
within the device. Red LEDs often have
the lowest forward voltage drop,
followed by yellow LEDs, green LEDs
and finally, blue LEDs.
Forward voltage
D1 Vf=1.98V
Test current
D1 If=3.22mA
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