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Topic: LED array controlled by an Android phone? (Read 652 times) previous topic - next topic


I would really like some guidance on a project I'm working on if that's possible.
The project basically involves lighting my computer case up like a Christmas tree.
I'll have three or four different colored LED arrays, each array is wired in parallel.
The LEDs I was thinking about ordering are these:




Each array will be wired to a port on a self powered USB HUB.
Each port will output about 5v and will be able to support max 25 LEDs.
Each LED has a forward voltage of 3.3v and a forward current of 20 mA (max value).

Basically I will "run" the LEDs at 16 mA each, I want to be able to control the LED arrays with an arduino.
What kind of Transistor should I use for each array, and is it possible to control the output to the transistors using bluetooth?


The idea of powering them via a USB hub does not make sense to me.

Firstly, you'd need to consider the total power available for the hub as a whole, which is most likely not enough to run all the ports at the full current in high power mode. Since the hub would merely be acting as an electrical distribution box, and not a very good one, it would make more sense to connect your circuits directly to a suitable power supply.

In any case, the hardware you're using is not already connected to a USB plug  so using a USB format plug to connect to your power supply doesn't save you any work. It would make far more sense IMO to design your LED circuits so that they can be powered efficiently from one of the outputs from your PC power supply. By 'efficiently' I mean that you design the series/parallel circuit to maximise the voltage drop across the LEDs and minimise the voltage drop across the current limiting resisters.


Powering them to a self powered USB hub should work, although I need to find a reliable one.
It's also much more of a hassle to power them with a power supply.
Power supplies as I've understood require feedback.

How would I wire my circuit if I used my PSU?
A series of three LEDs connected in parallel, and a resistor on each series to drop the remaining voltage?

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