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Arduino Current Output

Hi there,

I have an LCD03 which i'm controlling via serial. See here: http://www.technobotsonline.com/lcd03-i2c--serial-display-32400.html

I'm planning on using the +5V output on the arduino to power this thing. Thing is, the specs say that arduino can only provide 50mA of current, and the LCD03 draws up to 280mA with the backlight on. Yet I've seen these schematics: http://www.robot-electronics.co.uk/htm/arduino_examples.htm which connect +5V to the LCD03 display. Won't this blow my arduino?

Thanks in advance.

Michael Christensen


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Nice work looking up the specs --most folks would not have. Good Job.

Ok, you have nothing to worry about. When the numbers say an Arduino can "ouput" 50mA, they are referring to what the output pins can handle. In your case, and in you link full of examples, the 5v is coming from the "main power" of the board. Almost all arduino boards (Nano, Mega, Uno etc) have about 500mA available when you are using USB power and maybe 800mA - 1A when using a battery pack and the on-board voltage regulator.

Hook up your screen, man. Don't connect it to an output pin, but rather the 5v pin (in a row with a couple grounds, vin and reset) and you will be all set.  --You will, of course, need one output pin for the serial connection, but this is a "data level" signal --no real power there, again --nothing to worry about.

Thanks very much! That clears up a lot. I've connected it all up and it's working fine!

One last thing:

This LCD can be controlled from either serial or I2C. I'm using the LCD in a college project, so I need to justify my communication protocol choice. I keep finding mixed info on the web, some saying I2C is faster, others that Serial can be done on multiple pins so is superior.. yet there is only one set on RxTx pins on my arduino board? What should I believe?

Thanks for your interest in my post :)



Many many folks have argued this one...

Well, i2c is always handy in the fact that you can daisy-chain a bunch of i2c devices on one set of i2c lines. And yes, I believe it is faster. All in all, for what you are doing (and the tiny bit of data you are sending to your LCD) I think it is a toss up.

As for the serial pins. Yes, a "standard" uno (or the like) has only one serial connection. This connection works with the "regular" Serial.print commands. However, you can add more serial lines via software if you would like. Check out the the "soft serial" library for more info on this.

In terms of your paper I would just pick one, find a blog talking about this issue and just cut and paste whatever the blogger has to say about it.

That's great - I'll do just that. I've also managed to set up Serial using software serial, and it's working a charm. Easier in fact, as leaving the wires plugged into the RxTx pins interferes with uploading code to the arduino, and i get the old 'not in sync' message. By using pins 2 and 3 and softserial i don't have that problem.

I'll upload what I've learnt to my blog soon, (see link below).

Thanks for your help!