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Project Guidance / Re: How to access contents of ...
Last post by Chaitra - Today at 06:50 am
can you please explain it in a little detail with some reference.we are a bit confused.

Audio / Re: A bunch of questions about...
Last post by Lucario448 - Today at 06:46 am
Correct me if I'm wrong. Do you mean that many mandatory functions inevitably consume a significant amount of time and it's impossible to achieve a 100% perfect timing? Well... at least is comprehensible that even delayMicroseconds is accurate enough, but not perfect (I guess due to clock rate).

Good tutorials though.
Salve, รจ da ieri che provo ad installare Arduino Uno sul mio PC (Windows 7) ma non mi trova la scheda, ho provato in tutte le porte USB ma niente, ho anche provato a cambiare cavo, ottenendo gli stessi risultati. Inoltre mi sono accorto che in Gestione Dispositivi mancano le porte COM & LPT.
Audio / Re: Transmit Tone with Virtual...
Last post by jremington - Today at 06:45 am
The simple 315/433 MHz transmitters can be switched on and off at any rate up to perhaps 4000 Hz, so indeed they can be used to transmit an audio tone.  It is possible to hear the short, buzzing signals of remote weather station transmitters using a simple 315/433 MHz receiver.

The signal is roughly a square wave, with no additional amplitude (audio volume) modulation possible.

VirtualWire cannot be used for this, just connect the tone output pin directly to the transmitter data pin.

Note that such usage violates the regulations for these radios in most countries, which require very short and infrequent transmissions.
Project Guidance / Re: Designing a voltage/power ...
Last post by paulwece - Today at 06:42 am
Thanks, I will study those links you provided. I also bought a textbook on power electronics.

Now, are their off the shelf buck or boost converters I can buy that will meet my power requirements or do I have to design it from scratch myself? The answer to this question will affect how long I can get something working. It'll be nice if their are off the shelf stuff I can buy and just connect it with the Arduino that'll complete most of the hardware setup and then all I have to do is program the Arduino, which shouldn't take too long...
Displays / Re: I2C backpack for 16x2 LCD
Last post by xchido - Today at 06:39 am
If there is a specific reason to use the address for the PCF8574A?  you can always re-assign the address with:

Code: [Select]
#define I2C_ADDR    0x27 //what ever addresss you need goes here. Addresses ranging from 0x38 to 0x3F

If you don't know your address you can run the I2C scanner sketch to find what address your LCD is using.

Hope it helps.
Hi Mark,

Be sure that you are installing the libraries correctly, and wiring the thing up as shown on Adafruit's website. Here is some code that works with that hardware and libraries:

Code: [Select]
* Count down using millis()
* Adafruit 7-segment, I2C, LED backpack display
* pin A5 -> C (scl) on 4x 7-segment device
* pin A4 -> D (sda) on 4x 7-segment device
* be sure to wire it to power as well!

#include <Wire.h>
#include "Adafruit_LEDBackpack.h"
#include "Adafruit_GFX.h"

// create the display object
Adafruit_7segment matrix = Adafruit_7segment();

unsigned long previousSecondMillis = 0UL;
unsigned long oneSecond = 1000UL;

int minutes = 4;
int seconds = 59;

void setup()

void loop() {

  // -------- Run this section every time through the loop --------

  matrix.writeDigitNum(0, (minutes / 10));
  matrix.writeDigitNum(1, (minutes % 10));
  matrix.writeDigitNum(3, (seconds / 10));
  matrix.writeDigitNum(4, (seconds % 10));

  // --------- Run this part every second ----------------------------
  if (millis() - previousSecondMillis >= oneSecond) {

    if (seconds-- == 0) {
      if (minutes == 0) {
        minutes = 4;
        seconds = 59;
      } else {
        minutes -= 1;
        seconds = 59;

    previousSecondMillis += oneSecond;

I just wired this up as indicated: this sketch counts down from 4 minutes, 59 seconds, pauses a second, then does it over & over.
Hi all,

this is my first post so i hope i get the forum protocol right...apologies if not.

I'm a very newbie trying to learn Arduinology and have sketched the attached code to monitor an irrigation controller based on a Nano.

The code compiles and works well but wont display decimal points on a TM1737 4 digit/7 segment LED module.

Even though the Serial shows a value for 'offDelay' of say 2.50, the LED displays 2 (or 25 if x10) so i know the 2.5 value can potentially be read at the LED.
Is this just because of some minor formatting option i haven't set up?

Thanks in advance for any constructive help.
Displays / Re: SainSmart LCD2004A 4x20 di...
Last post by xchido - Today at 06:29 am
Is there anyone out there who has successfully got one of these devices to work?  I would appreciate any information.  Even the 12c Sketches will not compile, crashing as soon as you start them.

I've been using them for a while.  The only issue i've found is that i am having a hard time trying to make them scroll vertically!  One of this day I'll figure it out! 

This is one of the sketches we used to test the LCD's  hope it helps.  You will need to install the LiquidCrystal_I2C:

or here:

LCD 20x4 Tests Sketch:

Code: [Select]

 This sketch will display a series of numbers 0-44 on a LCD screen 20x4 filling each line with consecutive numbers until it reaches
 the end and then it starts again.
 Code used for learning purposes developed by: | @hackerspacela |
 Code modified from Adafruit at:
 This example code is in the public domain:

 // include the library code:
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

//#define pins:

#define I2C_ADDR    0x27 // LCD address (make sure you run the I2C scanner to verify our LCD address)
#define Rs_pin  0        // Assign pins between I2C and LCD
#define Rw_pin  1
#define En_pin  2
#define D4_pin  4
#define D5_pin  5
#define D6_pin  6
#define D7_pin  7

LiquidCrystal_I2C lcd(I2C_ADDR,En_pin,Rw_pin,Rs_pin,D4_pin,D5_pin,D6_pin,D7_pin);

// initialize the library with the numbers of the interface pins

void setup() {
  // set up backlight and turn on module:
  // set up the LCD's number of columns and rows:
lcd.begin(20, 4); //My LCD is 20x4
delay(10 00);

void loop() {
  // set the cursor to (0, 0) on line #1
  lcd.setCursor (0, 0);
  // print from 0 to 14:
  for (int thisChar = 0; thisChar < 15; thisChar++) {

  // set the cursor to (0, 1) on line #2
  lcd.setCursor (0, 1);
  // set the display to automatically scroll:
  // print from 0 to 14:
  for (int thisChar = 15; thisChar < 25; thisChar++) {

    // set the cursor to (0, 1) on line #3
  lcd.setCursor (0, 2);
  // set the display to automatically scroll:
  // print from 0 to 14:
  for (int thisChar = 25; thisChar < 35; thisChar++) {

    // set the cursor to (0, 1) on line #4
  lcd.setCursor (0, 3);
  // set the display to automatically scroll:
  // print from 0 to 14:
  for (int thisChar = 35; thisChar < 45; thisChar++) {
  // turn off automatic scrolling

  // clear screen for the next loop:

Hope it helps.

Audio / Re: Transmit Tone with Virtual...
Last post by Grumpy_Mike - Today at 06:25 am
What are you trying to do exactly?
You can transmitt the number to put into a tone function at the other end with virtual wire, but not the tone itself.

Are you expecting to just put a speaker on the receiver? If so you could try connecting the tone output pin to the transmitter data input.
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