My doubts are, how to know if the USB is able to provide enough power for my current setup?
generally speaking, you'll need external power to power stuffs that requires more than 5V, I can say motor or light bulbs and heaps other things.What happen if you didn't feed enough power? Well, the targeted thing just won't run. Don't think it'll damage your Arduino though
I think a USB port device is limited to 0.5 A at 5 VDC.
You need to know in advance what the voltage and current requirements are for anything you connect to the Arduino
Quote from: rweber95 on Dec 10, 2012, 02:01 pmI think a USB port device is limited to 0.5 A at 5 VDC.0.5 for USB 2.0 and 0.9 for 3.0Quote from: PeterH on Dec 10, 2012, 02:04 pmYou need to know in advance what the voltage and current requirements are for anything you connect to the ArduinoActually the .5amp 5vdc limit is enforced with a on-board 500ma thermofuse on the arduino board, so the limit applies to both USB 1,2, or 3. Note that if you are powering the board via the arduino external power connector then you can draw a little more current then the 500ma USB limit, depending on the actual voltage applied to the external power connector or Vin pin.LeftyI guess so, I could also use an Amperemeter connected in series with the +5v line of the USB cable, right?
Ok thank you.Please help me understanding this:Lets say I want to connect some simple leds like these:http://www.ebay.com/itm/100pcs-Purple-5mm-2000mcd-Lamp-Ultra-LED-Free-Shipping-UV-/110980369904?pt=LH_DefaultDomain_0&hash=item19d6f20df0specs says: Max Peak Forward Current : 75mAYes but it's the max average forward current that will determine what you run your leds at. 20ma is the current limit you should use for these leds set by the size of a series current limiting resistor between each output pin and the led.Does this means that with 6 or 7 leds I would be reaching the limit of the board? Also the Mega documentation says each port delivers only 40ma so I don't get it. Each pins has an absolute max 40ma rating, and 30ma pin output current or less is safer valueto run the output pins at. So 7 leds running at 20ma is 140ma total, which is well within the boards +5vdc current capacity and each output pins rating.The key is it is up to you to manage the total current requirement for the complete project. If driving standard 20ma leds you do that by proper sizing of the current limiting resistors you have to have between the output pins and the leds.Lefty
Again thanks,So, according ohm's law and as i'm using 1K resistors..I = V/R5/1000 = 0.005Are my leds using 5ma each?Am I right?
I guess so, I could also use an Amperemeter connected in series with the +5v line of the USB cable, right?
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