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shdharsha

The flashing Heart(i have some doughts)

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I think he means this one:

http://www.electronics-lab.com/projects/games/001/

You build the project and give it your partner, batteries included! Hopefully they will appreciate your effort and think that you love them. You can then take it from there ;)

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It seems silly to run the thing off 12V and connect all those LEDs in parallel.

LEDs shouldn't be connected in parrallel anyway because they all have slightly different forward voltages.

The LEDs should be connected as several series strings in parallel to save power.


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I just counted the number of LEDs in that piece of junk. There are 42 red LEDs (forming the heart) , 84 yellow LEDs (forming the frame) and 16 green LEDs (for the letters "I" and "U" (btw. wrong English: You starts with "Y"  ;) ).

Considering that half of the 84 yellow LEDs are on at a time the total current flow in the circuit will be exactly 2A!!!.

(Can you afford installing a nuclear power plant in your backyard just to tell your beloved one that you love her? Try out your charm before wasting electric energy! Mine has been overwhelming throughout my life so far.  ;) )

The small transistors will be happy if the clock rate allows cooling phases between switching them on.  ;D (The current flow for the red and yellow LEDs is 840mA with standard 20mA LEDs!)

A better and power preserving way would be to wire the LEDs for least power (current) consumption and multiplex well planned groups of LEDs to reduce current flow to max 200mA.

Multiplexing at frequencies higher than 100Hz will appear as steady light for human eyes. (They're damn slow!)

HtG

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You is often shortened to U in an informal message, e.g. text speak, cards or instant messaging.

I'd reduce the LED current to 10mA because they won't be much brighter at 20mA.

The yellow LEDs can be connected in 21 strings of four in series, cutting the current again by a quarter.

Assuming the red LEDs have a forward voltage of 1.8V they can be connected as seven strings of six in series or if that's too much eight strings of five and one of two.

The green LEDs could be connected as four strings of four in series.

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