Friday, 3 May 2013

Electrical theory 1.3g - Parallel LED connections

So what happens if LEDs are directly connected in parallel as shown below?

The constant voltage behaviour of LEDs will cause a problem:
 
If you use 2 different colours, the lower voltage LED prevents the voltage rising to a value for the second LED to turn on, eg a red LED and a white LED are connected in parallel.
 
Result: Only the red LED will give light because the voltage is limited to 2.0V across the white LED. This is shown in the photo – look carefully because the white LED is unlit! (LHS of photo)
If you really want more light, use a brighter LED, larger size LED (eg 10mm) or connect the LEDs in series.

 
If the 2 LEDs are the same colour, the common problem is the LEDs don't share current equally and it can look terrible. So use above advice!
 
END

1 comment:

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