I'm very new to Arduino, but not to electronics (which I've been doing for 30+ years). I've been working from the book Beginning Arduino by Michael McRoberts and I've had very few problems so far. I've just started the chapter on LCD displays and I'm trying the Basic LCD Control project. I am using a brand new display that I bought from Rapid Electronics (UK):
I had to solder a header to it to use it on a breadboard. I took ESD precautions and I've tested that there are no shorts and that all pins are connected OK. The thing is, when I try out the program, absolutely nothing happens - the backlight doesn't even come on. I am aware of errors both in the book diagram (where R/W is not connected to GND) and in the program which showed a compile error initially, but I found a fix on this forum. I have checked the connections and code over and over again, but with no mistakes found. I've checked that everything that should be at 0V/+5V actually is. I've even checked that all of my Arduino digital pins are still working using a simple LED flash program.
FYI, pin connections used are:
Arduino LCD Display
Digital pin 11 Pin 6 (Enable)
Digital pin 12 Pin 4 (RS)
Digital pin 5 Pin 11 (DB4)
Digital pin 4 Pin 12 (DB5)
Digital pin 3 Pin 13 (DB6)
Digital pin 2 Pin 14 (DB7)
Pin 1 (Vss), Pin 5 (R/W) & Pin 16 (Backlight K) to GND
Pin 2 (Vdd) to +5V
Pin 3 (VO) via 10K to +5V
Pin 15 (Backlight A) via 220R to +5V
After all this, I can only assume that my new LCD is dead :0
First things first, let's get the backlight lit.
You have a 220 Ohms resistor, i'm guessing because you want to reduce LED current and know a 220 will do in most cases.
But that's for a standard LED, and this isn't one of those.
The datasheet tells this about the LED backlight:
Supply current: Min 104 mA, Typical 130 mA, Max 150 mA
Supply Voltage: Min 4.0 V, Typical 4.2 V , Max 4.4 V
These are the numbers you should use to calculate the resistor for your LED.
You are powering it from 5 volts
You can use help available from internet to calculate the correct resistor.
Google for "LED calculator", and you;ll be offered a bunch of tools to use.
You'll find out that that 220 Ohms resistor might be a bit too much.
After you have the backlight going, we'll have an other look at getting that display to show some characters that can actually be seen.
Well you have your contrast pin (pin3 of the lcd) tied to the +5 thru a 10k resistor. Should have a pot (5-10k ) connected to the +5 and ground with the wiper(middle pin) going to pin3. For a get around just tie pin3 to ground which will give maximum contrast (black boxes before the program tries to initialize it).
Unfortunately, I followed the book instructions without really thinking about it (or reading the datasheet properly ). I know how to calculate the value for an LED series resistor, but I didn't do it for the reasons above. I've now decided on 6R8 (but it's possibly not necessary at all...). This gave me a backlight, but no display. I added the contrast pot (also shown on the datasheet) and hey presto! I have a display.
The reports of my LCD's demise were a bit premature.
Glad to see you solved it.
Saves you a buck or two and some time because you don't need to go and get yourself a new one.
Few lessons to learn from this:
Don't give up too fast (ask for help instead).
There's a whole lot of crappy tutorials.
"Make" sites are notorious for screwing enthusiasts that are eager to learn with tutorials that are just plain wrong and will never work, complete with replies of people telling how well it works for them.
If a tutorial tells you how to do something (because that's the way the author did it), but not why and how it works, it has a bad smell.
If there is an explanation that doesn't seem to make sense, some checking would be a good idea.
My electronics experience is mainly music related (analogue synths, guitar pedals etc.). I know a reasonable amount about CMOS/TTL logic circuits, but this is my first foray into the world of microcontrollers (apart from a couple that I've bought pre-programmed) and I'd never used an LCD display before. I knew how they worked at the most basic level, but it was still a bit of a 'black box' to me. I shall do a bit more in-depth reading about them to get a proper understanding.
I've found quite a lot of mistakes in that book (many of which are not listed on the publisher's errata page) so that should have rung alarm bells...
). I know how to calculate the value for an LED series resistor, but I didn't do it for the reasons above. I've now decided on 6R8 (but it's possibly not necessary at all...). This gave me a backlight, but no display. I added the contrast pot (also shown on the datasheet) and hey presto! I have a display.