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1  Using Arduino / General Electronics / Audio Amplifier with multiple outputs on: December 16, 2013, 08:43:21 pm

I have been doing streaming on and use an audio mixer to pull together a number of audio sources.  The problem I am running into is I need a number of the input sources, as well as a number of the outputs from the mixer, to each split off to other devices (headphones, SD audio recorder, speakers, PC audio input, PC audio output, Mac audio input and output).

I can look up the schematics for an audio amplifier online no problem, but my question is about where the amplifier IC should be when it comes to multiple outputs.  should there be a single amp IC between the input and multiple outputs, or should there be an IC for each output?
2  Using Arduino / Motors, Mechanics, and Power / 5V USB Batteries in Parallel? on: September 18, 2013, 01:44:32 pm
Everyone has probably seen these USB-based battery packs at their local shops.

They tend to have a capacity between 2000 and 3000 mAh each, and provide 5V via the USB-A connector.

My question is, has anyone attempted to build a circuit that would connect up multiple batteries of this nature in parallel or even in series to either boost the capacity or the voltage respectively?  I am not sure of the wiring between the port itself and the battery, so I am unsure of the it would work the same as connecting pure batteries in series/parallel.  Figured i'd ask.
3  Using Arduino / General Electronics / Re: Resistor Color Code Finder App on: August 29, 2012, 05:54:44 pm
No idea but I would be surprised if there was:-
1) It is so hard to identify colour from an image
2) The colours on real resistors do vary wildly
3) It is so stupidly easy to do yourself.

True, though i do find those online converters slow to deal with at times, especially if i have a lot of mixed resistors to sort thru.  I bet we will see one as camera color sensors or near-object focus get better in the future.
4  Using Arduino / General Electronics / Resistor Color Code Finder App on: August 29, 2012, 04:07:13 pm
Does anyone know if there is an iOS or Android app that lets you take a picture of a resistor and then it does a look up based on the color code and returns the resistance value?
5  Using Arduino / Motors, Mechanics, and Power / Re: MOSFET IRF510 (radio shack purchase) issues and testing question on: August 19, 2012, 01:25:44 pm
awesome, everything is working perfectly now, thanks.
6  Using Arduino / Motors, Mechanics, and Power / MOSFET IRF510 (radio shack purchase) issues and testing question on: August 19, 2012, 12:13:46 pm
I just picked up a IRF510 MOSFET from Radio Shack in my out of town trip this yesterday (closest radio shacks are about 45min-1 hour away).  After I got home, i went to test it out.  My question is, should i be able to test out the source-drain with just the +5V from my arduino (+ resistor + LED), or do I need to have a higher power source?

the way I hooked it up to test was like this...

Arduino Pin 7 to Gate, with 10K resistor pulling to ground.
Arduino 5V to Source
1K resistor from Drain to LED, and LED to ground

in that configuration, no matter if Pin 7 is HIGH or LOW, the LED stays on
7  Using Arduino / Networking, Protocols, and Devices / Re: Ethernet Shield, RFID Scanner, PHP Server with MySql on: July 03, 2012, 07:28:24 pm
basically, in the setup() block I am connecting to the web server (, 80) as most example scripts do, mainly to see if the connection works.  What i haven't put in yet is a boolean or function that will prohibit the rest of the program from running if there is no ethernet connection.  I then stop the connection (mainly because I have been unable to find any information about how long the connection can be kept alive).  This device will be running relatively 24/7.

I am assuming it would be more reasonable to connect to the server ONLY when I need to make a request, as the server never will be sending data back to the Uno unless the Uno requests said data.

As i said before, the code right now is incomplete, since i am stopping the Ethernet connection in setup, and as of yet havent figured the best place in the code to reconnect.
8  Using Arduino / Networking, Protocols, and Devices / Ethernet Shield, RFID Scanner, PHP Server with MySql on: July 03, 2012, 07:08:21 pm
Okay, here is the deal:

Working on an RFID scanner mod that will take the resulting RFID code, send it as a GET request to a PHP script that will process the RFID and the time the RFID was scanned (or roughly the time it is scanned), log it to the MySQL database, do some calculations, send back a few string-based values and display them on a 16x2 LCD module.

I have looked at a bunch of example code, and can get most of this working individually, but not exactly in tandem as i would like.  These are...
   - Display information on the LCD
   - Read the code from an RFID and turn it into a String.
   - Send a GET HTTP request to an Apache2 web server running on a local Raspberry Pi AND get the web server to use the data as it needs
   - Read the returned data from the web server and, via substring, capture data that is enclosed within <> or {} or [] or ()

I do have a few issues, those being...
  - making the UNO wait within a function for a response from the web server
  - disconnecting and reconnecting to the web server only when i need to send and receive data

here is the code i am using on the arduino as of right now.  not complete, obviously, but if anyone could point out in my code the best place to connect and reconnect that would be great.

i dont need help with the PHP side of things, i have been working with PHP and/or MySQL for about 5-10 years now so I can figure out any issues in that area, and as of right now I dont have any issues there.

#include <LiquidCrystal.h>
#include <SPI.h>
#include <Ethernet.h>

boolean debugMode = true;

byte mac[] = { 0x90, 0xA2, 0xDA, 0x0D, 0x14, 0xE8 };
byte ip[] = { 10, 0, 1, 142 };
byte gateway[] = { 10, 0, 1, 1 };
byte dns[] = { 10, 0, 1, 1 };
byte subnet[] = { 255, 255, 255, 0 };
byte localServer[] = { 10, 0, 1, 175 };
EthernetClient client;

boolean waitingForResponse = false;

LiquidCrystal lcd(A0,A1,A2,A3,A4,A5);

String readString, readString1;

void setup() {
  Ethernet.begin(mac,ip,dns,gateway,subnet);  // start up Ethernet
  Serial.begin(9600);                         // enable Serial
  if (debugMode) Serial.println("Starting Time Management System");
  if (debugMode) Serial.println();
  if (debugMode) Serial.println("Analog Pins set to OUTPUT");
  if (debugMode) Serial.println();
  lcd.begin(16,2);                            // start up 16x2 LCD Module
  if (debugMode) Serial.println("LCD Module Enabled");
  if (debugMode) Serial.println();
  // Attempt to make an Ethernet connection
  lcd.print("Testing Ethernet");
  if (debugMode) Serial.print("Testing Ethernet: ");
  if (client.connect(localServer,80)) {
    if (debugMode) Serial.println("Successful!");
    if (debugMode) Serial.println();
  } else {
    if (debugMode) Serial.println("Failed!");
    if (debugMode) Serial.println();

void loop() {

void checkScanner() {
  String txtMsg = "";
  if (Serial.available() == 16) {
    while (Serial.available() > 0) {
      char inChar =;
      if (int(inChar) > 31) {
        txtMsg += inChar;
    lcd.print("Card Scanned!");
    client.print("GET /monarch-time-tracker/test.php?rfid=");
    client.println(" HTTP/1.0");
    waitingForResponse = true;

void awaitScanResponse() {
  while (true) {
    if (client.available()) {
      char c =;
      readString += c;
    if (!client.connected()) {
      int d1 = readString.indexOf('<');
      int d2 = readString.indexOf('>');
      readString1 = (readString.substring(d1+1,d2));
9  Using Arduino / Motors, Mechanics, and Power / Re: Solid State Relay, but in reverse (AC to control DC) on: June 27, 2012, 08:31:54 pm
Why didn't you tell that in the first place?  (:

I come from the "Clue" school of not telling long winded stories.

Butler: "To make a long story short"
Col Mustard: "Too late"
10  Using Arduino / Motors, Mechanics, and Power / Re: Solid State Relay, but in reverse (AC to control DC) on: June 27, 2012, 02:48:00 pm
basically here is the idea.  i own and operate a motel and am putting together an Arduino Mega system that will automate the motel lights and such with solid state relays (going thru a certified electrician to make sure everything is properly rated and can handle the loads).

There is a light switch in the office that turns on and off an outlet that has the ceiling fan + office lights plugged into it.  When I turn off the office lights, I am usually also closing the office either for a few minutes to hours while I go into town shopping.  What I am looking to do is have that disconnection of power send a signal to the Arduino Mega to let it know "the office is closed, shut off any lights and signage that are hooked up to the Solid State Relays.

I am thinking that the easiest, but perhaps not very practical, method would be to just have a low power wall wart that outputs 5V DC connected to a barrel connector, a resistor to lower the current, and then connect the current limited +5V and GND from the barrel connector to GND and a digital input on the arduino.  If the light switch is turned off, the wall wart gets no power.  If turned on, the digital input read high.
11  Using Arduino / Motors, Mechanics, and Power / Solid State Relay, but in reverse (AC to control DC) on: June 27, 2012, 10:52:38 am
Are there any types of Solid State Relays that will send a HIGH or LOW DC logic signal depending on if there is or is not an AC signal/current going thru it?
12  Using Arduino / Project Guidance / Re: Connecting RF transmitter and receiver pair to arduino on: June 11, 2012, 09:59:25 pm
Just wanted to drop in my 2 cents.  I am using RF Transmitter/Receiver pairs much like those, but from

SparkFun Search Results:

I am using the 315MHz versions.

I am using them at my motel to relay signals when a door sensor is tripped (a potential guest or other person opens up one of the two office doors). Once any of the sensors are tripped, the Arduino Mega transmits a specific message via the RF Link Transmitter.  While the SparkFun page states 5V supply, it can handle 1.5V - 12V.  I am feeding the transmitter 9V directly from the VIN port of the arduino.  More power = more range and signal strength.

The receivers are connected to remote boxes along side a Radio Shack 75dB chime and piezo buzzer.  The chime is for when the office/lobby doors are opened, and the piezo is for other status messages.  If the door(s) are open for 3 minutes (guest didn't shut it all the way), it makes an alternating higher pitched buzz.  I have other status messages as well, but as of yet haven't fully implemented them for regular use.

I have only run into one or two instances where one of the remote chimes rang on its own without the door opening, so it could have been that I simply didn't have the transmitted control code/message long enough and some random noise just happened to match the overall message.  I have since increased the size of the control code/message and have not run into an issue since.

The VirtualWire PDF mentioned above helped out greatly.
13  Community / Exhibition / Gallery / Re: AC Light Dimming [success] on: June 07, 2012, 06:27:32 pm
I could have sworn I saw a data sheet for a Solid State Relay (the boxy kind that has the 4 screw terminals that is about the width and length of an Arduino Uno) that supported PWM for dealing specifically with dimming AC voltages.  Wish I could find it again.
14  Using Arduino / Project Guidance / Re: How to send notifications? on: June 02, 2012, 12:56:28 pm
also keep in mind that a laser has pin-point (or, pencil eraser point) precision, and a light sensor is quite small (well, depending on the light sensor i guess), so if you wanted this to be a sniper-style shooting gallery, that would be a good choice.  however, if you want it to be a more "in the vicinity of the target", IR would work a bit better if you can focus the IR light enough to end up being the diameter of a tin can within the "sweet spot / sweet range".

and just like that How Stuff Works podcast mentions, treat the guns as targets like a Television remote control system.  Each gun has a unique IR code/sequence to differentiate each player/gun from one another.
15  Using Arduino / Project Guidance / Re: How to send notifications? on: June 02, 2012, 12:20:43 am
One last post before i go to sleep.

A How Stuff Works podcast episode on Laser Tag.

also, some pages i have check out show that the lasers (actual lasers) used in laser tag or laser storm arenas are just for show and for the visual apparance, and are very low power, which would require a person to look directly into the beam for an extended period of time for any damage to happen, as opposed to a laser pointer which would cause damage after only a few seconds.

If you do plan to use LASER-lasers in some way, BE SURE they are the semi-safe low power ones, and now just some laser pen style module.
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