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[on:]

I need to connect 200 LEDs to one output, and another 200 LEDs to another output,
Each 200 LEDs needs 500mA and the arduino can support 20mA per output, how do I amplify the current without damaging the arduino board?

I heard about transsitors but I didn't understand how to connect them...

My project is to do siren lights,
It's have 200 red LEDs, and 200 blue LEDs, that blink at 200ms.

[Reply #1 on:]

Need to use a MOSFET transistor.
http://www.digikey.com/product-detail/en/NTD5867NL-1G/NTD5867NL-1GOS-ND/2401422

Arduino pin drives Gate thru a 150 ohm resistor, transistor sinks current from LED cathodes to Gnd.
Power source thru current limit resistor to LED anodes.

What do you have for a voltage supply? If you have a 12 or 15V source you can put the LEDs in strings and cut your current requirements way back, to 20mA per string of 4 or 5 LEDs.

[Reply #2 on:]

Need to use a MOSFET transistor.
http://www.digikey.com/product-detail/en/NTD5867NL-1G/NTD5867NL-1GOS-ND/2401422

Arduino pin drives Gate thru a 150 ohm resistor, transistor sinks current from LED cathodes to Gnd.
Power source thru current limit resistor to LED anodes.

What do you have for a voltage supply? If you have a 12 or 15V source you can put the LEDs in strings and cut your current requirements way back, to 20mA per string of 4 or 5 LEDs.

Tnx for the reply,
My voltage supply is 18v,
Do you have a example circuit how to connect this transistor to an led?
It's in 500mA per 200 LEDs that connected in 8x25 strings.

[Reply #3 on:]

With 200 LEDs only taking 500mA that only leaves 2.5mA per LED.
They are not going to be very bright at that.
You can wire several in seriese, at 18V you could put  9 LEDs in seriese, and boost the current to 20mA through the LEDs, is that what you want to do?

[Reply #4 on:]

Like this

[Reply #5 on:]

With 200 LEDs only taking 500mA that only leaves 2.5mA per LED.
They are not going to be very bright at that.
You can wire several in seriese, at 18V you could put  9 LEDs in seriese, and boost the current to 20mA through the LEDs, is that what you want to do?

Yes this i what i want to do,
And how i increase the current that leaves the arduino without damage the board?

and if i need to use a transistor how do i connect its to the circuit?

[Reply #6 on:]

What is the forward voltage and recommended current of each individual LED  ?

[Reply #7 on:]

and if i need to use a transistor how do i connect its to the circuit?

That is what that diagram from Crossraods is showing you how to do.

[Reply #8 on:]

What is the forward voltage and recommended current of each individual LED  ?

2v

and if i need to use a transistor how do i connect its to the circuit?

That is what that diagram from Crossraods is showing you how to do.

Ok i will check this

[Reply #9 on:]

As Crossroads drawing with 100 ohm resistors, thats for red 2v forward LEDs, the blue will be different forward voltage