# I need to step down 12V to 3.2V to power 512 LED's in a parallel circuit, 256 in each. How can I do this?

My power source has 12V, 6A. Each LED draws 10-20ma and is powered on 3.2 V. Ive tried looking up how to do this already but havent really found anything like what im trying to do. The LED's will not all be on at the same time, im building an LED cube that pulses to music.

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iceng6 years ago
If it is an LED micro controller it will run on 5 volts or lower.
You said the LEDs are 3.2 volts I have to assume that your system is 5 volts.
You will be using a 7805 12v to 5v regulator which can only supply 0.5A ..

Assume 15ma LED current each that can only supply 33 LEDs per regulator.
That is 8 regulators for 256 LED at once.
Each LED will need a 120 ohm  resistor in series with it.

There are a lot of things unanswered here,  what micro is it you are using
what POV scheme are using in your musical cube which decides the
real current ??

A
rbeck_v (author)  iceng6 years ago
Im not using any micro controllers, Im going to be using a TIP41 transistor to operate the LED's. The Tip 41 will recieve signals (weak or strong) from the audio line on the collector, and the transistor allows electricity to flow to the lights through the emitter.
6 years ago
Emitter follower configuration is acceptable LED drive but through the base
the collector gets tied to +V because the tip41 is a 6A NPN with a marginal
gain of 15 at 3A say 4A which is 256 LEDs @ 0.015A each and the
base current needs to be 1/4 Amp which will certainly not going to
come out of an audio signal.

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rbeck_v (author)  iceng6 years ago
Well, Ive used a tip31 transistor in this same application just lower voltage, current and less LED's and it worked beautifully. But if the TIP41 requires a stronger current from the audio signal can't i just simply amplify it.
6 years ago
Every tip41 can be different, the spec sheet lists gain minimum = 15 and
gain maximum = 60   this means a randomly selected tip41 could have a
gain of 50 or 60 or 20.

In engineering, one designs to handle the minimum semiconductor capabilities, unless  you test the components before use.

The tip31 has an even poorer hfe ( DC gain ) then the tip41 but you
say it worked for you.

Every time I suggest something, you suddenly produce more factoids.
I help best with a thorough circuit schematic.

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rbeck_v (author)  iceng6 years ago
Sorry for the randomness on my part, I appreciate the help youve given me. Ill do a little more research then see if the tip41 will work or not.

Thanks again, I appreciate it
--Richard
Re-design6 years ago
Google "voltage regulator". It a 78' number or something like that. I only remember it when I need it. You can adjust it to what ever voltage you need. You may have to add some transistors like a 2n3533 or something like that. Still can't remember the number unless I'm building something but there are plans all over the internet for these.

Is'nt the internet great.  You can get ANY answer you need just by googling if you know the correct keywords to use.  Yes I said ANY ANSWER!