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Making 100 leds flash?

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¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
25,510
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25,510
I was assuming 20mA for the LEDs, and 20 strings of 2 LEDs, so 400mA per mosfet.

If you're running 50 at 30mA, then that's 25 strings at 30mA which is 750mA. So it's still fine.

At 1.2A (40 leds all running in parallel with their own resistors?) the mosfets may get a little warm, but as long as the flash rate is low, I can't see it being a huge problem.

If they get too warm to comfortably hold between your fingers then I'd say something is wrong.
 

Sinpy

Nov 10, 2013
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I still don't fully know the terms but I was looking at this type of wiring for the leds (photo below) and I was wantting power 50x2 leds but dropped it to 40x2 leds
 

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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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25,510
OK, in your example you have 40 LEDs, each running at 30mA, arranged in 10 strings of 4 LEDs.

The 10 strings are in parallel and the total current is 300mA

HOWEVER, that calculation has the resistors only dropping 0.3V. This is unlikely to be a great idea. You suggest you're using strings of 2 LEDs, and I assume your resistor is around 180 ohms.

This still has a total of 300mA.

Another option is to have 3 LEDs in each string. The resistor would be around 68 ohms.

In both of these cases the resistors drop sufficient voltage that the current to the LEDs is regulated to an acceptable degree. In the example you gave, it is not -- this is a common failing with these calculators.
 

Sinpy

Nov 10, 2013
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Righto, think I have a good understanding of this now and guessing nothing much is changed in the whole circuit/schematics other than the mosfets, Think I may be able to do this soon as I buy the parts.
 
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