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[SOLVED] Switching 2 Amp using AT89S52

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wicus

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I'm busy designing my own christmas lights using the AT89S52. it works 100% using 32 LED's , one connected to each I/O port via a 220Ohm resistor. I need to expand ths now by adding 20 LED's to each port, but is struggling to calculate all resistor values to be able to use a transistor. What transistors can be used to switch a max of 2A on each IO Port from a 12V Supply, with 5V/oV from the I/O Ports ?

I'm really clueless should I use PNP or NPN transistors, and what values of resistors to use for a 12V supply, and the AT89S52 which switches out 5V

I've posted the schematic I'm using here

**broken link removed**

But now I need to add lots of LED's in parallel and add a transistor in each Leg

Any asistance will be mush appreciated
 

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    wicus

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Thanks wp100 - Just the pointer I was looking for. I assume using a few LED's in parallel will require 'n high wattage resistor i.e 5W between the +12V and the LED's . As I have it, on the AT89S52 the 32I/O ports is active when switching to 0V and off when it have +5 V. Should I not then use a PNP rather ?
 

Hi,

For resistor wattage see this calculator - you will be surprised how small they really need to be. **broken link removed**

For transistor types again just search on npn v pnp - lots of explanations heres one Difference Between NPN and PNP? - Page 1

Out of interest that eevblog forum has some very, very interesting stuff on his main site - for beginners and experienced users.
EEVblog
 
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