mogix wrote:Hi,
I'm trying to design a simple circuit.
I do think I should add some resistors and connect everything in parallel however, the led calculator showed me a diagram I didn't understand... it seems there are 11 leds in series and 10 equal series in parallel.
Which would be the best to connect 102 infrared lights (1,6 V - 10 mA) fed by 18.5V ??
They will be assembled in a square shape, sending light to the inside of the square.
Thank you!
Each led has a pedestal voltage. You have to exceed that voltage by a small amount
before *any* current at all will flow in the led. So each led's pedestal voltage
*subtracts* from the total PS voltage...do that enough times and you have zero volts
left, which is what you want. To be honest, I would place 50% of the leds in series
(like six leds per chain) and then use a resistor to drop the other part of the
voltage based in the 10ma current in the chain. This way I could fine tune, maybe
balance the brightness of a particular chain. The resistor would also save the
PC board traces in case all of leds in a chain were shorted for some reason
like manufacturing or test problems. You know; those "real world" problems.
You would pay the price in doubling the heat output comming from the array.
But for a maximally cost sensitive device they can probably be run without any
resistors in the above configuration case, by trusting in modern led manufacturing
techniques.
:mscoffman
