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1  Using Arduino / Displays / Connecting to a Computer LCD on: March 03, 2013, 09:39:22 pm
I just took apart an old laptop (I always had wanted to see what one looked like on the inside), and noticed how nice and shiny the LCD looked. smiley-wink

So, I'm wondering if it is possible to connect my Arduino (Uno) to the LCD screen.  Somewhere I read something about needing a driver board (or something similar) to make it work.  Not exactly sure what that means, though.

If someone could point me in the right direction on where to learn how to connect my LCD to my Arduino, that would be great. smiley  (I'm not afraid of spending time researching/learning, but more afraid of breaking my Arduino.)

If it helps, my LCD screen is an LP141WX1 (TL)(A2) by LG Philips.
2  Using Arduino / General Electronics / Re: Using an Unknown LED on: January 06, 2013, 09:54:44 pm
Thank you very much for all your help (to those who responded)!

I now have my LEDs up and running, and my multimeter correlates that I'm under 10mA (and boy is it bright) with ~2V drop across LED. smiley

//Andrew
3  Using Arduino / General Electronics / Re: Using an Unknown LED on: January 06, 2013, 09:09:56 pm
Forward voltage: calculate the resistance using 2 volts. Then measure the actual forward voltage with a meter.
oh.  I should have thought of that... smiley-red  Thanks!

//Andrew
4  Using Arduino / General Electronics / Re: Using an Unknown LED on: January 06, 2013, 08:50:35 pm
Compute your resistor for 10mA forward current and go from there... adjust if it's too bright or too dim.
What do I do about forward voltage?
5  Using Arduino / General Electronics / Using an Unknown LED on: January 06, 2013, 08:26:47 pm
Ok... I have another question. smiley

I purchased a "Sidekick" kit from Amazon with my Arduino.  (link: http://www.amazon.com/gp/product/B007B14HM8/ref=ox_sc_act_title_1?ie=UTF8&smid=A1LHQ5G6ONPXVT)  I figured that, because I don't have a lot of components (e.g. resistors, etc.), it would be a good start for electrical components as I experiment.

HOWEVER... It doesn't come with documentation.  I can figure out the resistors (those are obvious), the mini servo that comes with it has a manufacturer and part # on it, but the LEDs are unmarked.  I know they're 2mm (from measuring), but don't know where to find a datasheet on them.  There's also an RGB LED that is unmarked.

My question:
What do you do to determine the specs for a component with no documentation?  (Or, if there isn't a cut/dry way, what do you do when you're in that situation?)

Thanks!

//Andrew
6  Using Arduino / General Electronics / Re: A noob resistance question on: January 03, 2013, 09:44:45 am
JimboZA's post really cleared it up for me--I needed that background information that is probably really basic to a lot of people here... smiley

Thanks, everyone, for all your help!

//Andrew
7  Using Arduino / General Electronics / Re: A noob resistance question on: January 02, 2013, 10:21:02 pm
Quote
When performing Ohm's Law calculations, what specifies the values for V and I?
V, to me, should be the supply voltage (3.3V or 5V would be what I'm using in this case).

No, V is actually the voltage "drop" across the resistor. Eg, if 1K is tied between 5V and
3.3V, the current I = Vdrop / R = (5V - 3.3V) / 1K = 1.7 mA, and not 5 mA or 3.3 mA.
In your example, you mean a 1K(ohm) resistor, right?  (just making sure--I'm really new, if you haven't figured it out yet.  smiley-red)

So, in this LED (for example), it says "forward voltage drop" is 1.8V-2.2V (DC).  Let's say I have a circuit that has 5V---LED---1K(ohm)---Gnd.  I want to find the current.  I = Vdrop / R = 2.2V / 1K = 2.2mA.

Right?  Or am I still confused... :/
8  Using Arduino / General Electronics / Re: A noob resistance question on: January 02, 2013, 09:46:03 pm
40ma is absolute maximum, but 20-30 ma is a better maximum limit standard to stick to. Keep in mind due to internal resistance of the output pins the output voltage will sag as current draw from the output pin is increased. Just shows that there is a difference from fundamental principal and electrical reality of real world components. That is why the datasheet for devices are so important to study and understand a chip limits and capabilities.
Ok.

Quote
Because there is no exact answer. If the board is being powered via USB then there is a 500ma thermofuse that sets a maximum limit for the board and anything you wire up to it. But if powered from an external DC voltage source then there might be somewhat more but it depends on the exact DC voltage input as there is a heat dissipation limit for the on-board 5vdc voltage regulator. So hard answers are desirable but often allusive in the real world.
Hmmm... Ok.  Where do I find the information for the on-board 5vdc regulator?

Quote
No, totally different components, and a switch doesn't share all the characteristic of a switch and visa versa.
:-\  Just when I thought I found a shortcut... smiley-wink  Ok. 
9  Using Arduino / General Electronics / Re: A noob resistance question on: January 02, 2013, 09:23:08 pm
I was about to start a thread on this very topic, but apparently it has been asked before! smiley

After reading through the thread (and the links posted therein), I have a couple of questions:

1. When performing Ohm's Law calculations, what specifies the values for V and I?
V, to me, should be the supply voltage (3.3V or 5V would be what I'm using in this case).  And should I be the maximum allowable current to pull from the pin?  Just wanting to make sure... smiley

2. What is the maximum allowable current draw for the 5V pin on an Arduino Uno?  From this page, I see 50mA for the 3.3V pin, but nothing is listed for the 5V pin.

3. Can one model a switch/pushbutton similarly to an LED?  I ask this because a switch also has "infinite" resistance when not activated, but near 0 resistance when pressed.
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