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Transistors in LED matrices? Answered


I'm confused about the purpose served by using transistors in an LED matrix.  Why not simply use current limiting resistors and a shift register?  What purpose do the transistors serve?

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user
Re-design (author)2010-06-14

I don't know what circuit you're talking about but in a  circuit like this one, it allows you to control more lights with the ic than you could without the transistors,  The transistor uses a small current to control a large load.

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fwanderwrwr (author)Re-design2011-09-01

Hello, what you say it's clear, but I'm still asking myself: what rules I have to follow to choose the right transistor? I mean, if I want to light up at the same time 5 leds or 20 leds, I can use the same type of transistor?

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Re-design (author)fwanderwrwr2011-09-01

In this case it acts as a switch that can pass more current than the ic can.

You have to calculate how much power you are drawing with the lights and then pick a transistor that has a higher rating than that.

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fwanderwrwr (author)Re-design2011-09-15

Ah ok! That's clear, thank you! :)

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