Arduino Support high Amps??

Forum 2005-2010 (read only) General Exhibition
1

I have a project for my Arduino Diecimila, i have about 200-350 leds
each led is a 3.3v and uses 20mA, thats about 7 amps.

since im plaining on using more then 500mA in total, would this still be okay?

If i make the digital pins all ground (LOW) would this destroy the chip when it grounds out led? because of the high amps?

There are lots of example on youtube if you type in LED Strobe light
Thanks in advance for info and thanks for all the help.

2

You're limited to 40mA per IO line, the 500mA is what the arduino board can supply.

You'll need an external power supply to get the 7 amps and driver circuitry to switch that kind of power without frying the Arduino.

3

Thanks for the reply Oracle, i did a drawing (mind my artist skill) just to a get a better picture, this is how i want to set it up,

1024×768 72.6 KB

my arduino will still be safe and could still operate the LEDs in the sequence that i would like to be in correct?

Thanks for any info and help

4

That won't work because you're still trying to sink the 7 amps of current with the arduino and you're limited to 40mA. In electronics, there's very little difference between supplying "sourcing" or taking "sinking" current. It's so similar, the early electronics engineers guessed backwards, so physically, the electricity flows from ground to positive (they had a 50-50 chance and got it wrong when they set up the labelling conventions).

You still need the current to flow back to the battery, and it simply can't go through the chip. You need something else to handle the current, and what you'd use is a transistor. But you still need to be careful because 7 amps is such a large amount of power you'd need a big power transistor.

There's also a huge amount of heat involved. 7 amps at 5 volts is 35 watts. That's a lot of heat. Standard resistors are usually 1/4 watt or even 1/8 watt.

5

Hold everything, that schematic will make a mess of your Arduino. The full current will be sinked by the Digital IO pins. Those BLACK wires you show connecting the cathodes of the LED's will have the same current trhough them as the RED wires sourceing the LED's. You want a simple transistor switch to sink the LED cathodes to GND.

Someone posted a similar question in another section.
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1223957838

check out the first reply on that page.

-=KG2