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46  Using Arduino / Installation & Troubleshooting / Re: Arduino Unknown Device on: April 16, 2014, 12:20:24 pm
Unknown Device probably means that you do not have the proper driver installed. What model Arduino?
47  Development / Other Hardware Development / Re: How to lower power output on laser diode? on: April 16, 2014, 12:17:26 pm
I think the laser diode package usually includes a photodiode that measures the light output so the control circuitry can adjust current to the desired output. Perhaps you should specify which laser diode you are using and what driver circuit you are using.
48  Using Arduino / Sensors / Re: Problems with Ultrasonic Range Finder - Maxbotix LV-EZ1 on: April 16, 2014, 09:09:31 am
If you are trying to avoid problems with overlapping beams you should probably run then sequentially instead of simultaneously:

When they say "Then the micro controller will have to return it's pin to a high impedance state " they mean set the pinMode() to INPUT.

In both cases you only need one output pin as shown in the schematic diagrams.
49  Using Arduino / Installation & Troubleshooting / Re: Cannot upload application to a UNO-board from Mac Pro on: April 15, 2014, 06:32:42 pm
Bad USB cable or port?
Have you tried the loopback test (stickied) to see if round-trip communications is possible.
Do the Receive and Transmit lights on the Arduino blink when you try the upload?
50  Using Arduino / Project Guidance / Re: Two power systems, reading voltage off both without magic smoke. on: April 15, 2014, 06:24:06 pm
Question 1: Will tying the ground of both power systems together cause any system destroying issues?

Question 2: Should I be slapping a diode from ground to the voltage reading analog inputs for protection?
That would only provide protection against reverse voltage by shorting out the battery.  The diode would then die, followed by the Arduino.  A diode in series would protect against a reversed battery but  it would offset any voltage reading by the voltage drop of the diode.  Use a voltage dividers to get the voltages being read down to a safe voltage (typically 5V or less).
51  Using Arduino / Networking, Protocols, and Devices / Re: SainSmart W5100 Network Module (not shield) pinout needed on: April 15, 2014, 06:15:10 pm
I wonder if it is a clone of the ermicro board:
52  Using Arduino / Project Guidance / Re: help please on: April 15, 2014, 06:04:08 pm
The pin is fixed because it uses the Input Capture Pin of a hardware Timer/Counter.  On the Arduino UNO there is only one ICP and that is Pin 8: ICP1.  On the Arduino MEGA you can also use Pin 48 (ICP5) or Pin 49 (ICP4) because Timer4 and Timer5 have that feature.
53  Using Arduino / Project Guidance / Re: How to run a loop only once while having constant update on a sensor? on: April 15, 2014, 05:53:45 pm
Instead of:
     x= analogRead(2);

you mean:
    while((x = analogRead(2)) > 300)


    x = analogRead(2);
    while(x > 300)
       x = analogRead(2);


    while(analogRead(2) > 300)
54  Using Arduino / Programming Questions / Re: icmp_ping library not compiling on: April 15, 2014, 05:48:41 pm
Looks like standard network library functions that are not being included.  They appear to be part of the Ethernet library.  Are you including <Ethernet.h>?  If so you might also have to include <Ethernet/util.h>.
55  Topics / Science and Measurement / Re: Pulse generation using atmega 328 on arduino uno board. on: April 15, 2014, 05:41:20 pm
Don't forget to add code tags by selecting your code an clicking on the '#' icon above the text box.

Of course your blinking repeats...  Nothing turns off "state=1" so every time through loop() it repeats the pattern.

const int pin = 13;
volatile int state = 0;
int i;

void setup() {
  pinMode(pin, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);
  pinMode(7, OUTPUT);
  attachInterrupt(0, Comparator, RISING);

void loop() {
  if(state==1) {
    for(i=0; i<=2 ; i++) {
      digitalWrite(pin, HIGH);
      digitalWrite(5, HIGH);
      digitalWrite(pin, LOW);
      digitalWrite(5, LOW);


    for(i=0; i<=2 ; i++){
      digitalWrite(6, HIGH);
      digitalWrite(7, HIGH);
      digitalWrite(6, LOW);
      digitalWrite(7, LOW);


void Comparator() {
56  Using Arduino / Sensors / Re: Optical Guitar Pickup on: April 15, 2014, 05:25:46 pm
I expect the tone decoder uses a modulated IR source and the comparator just compares agains a fixed analog level.  Either one could work.  Have you done a literature search?  Maybe you aren't the first person to want to detect vibrations in tuned strings.

These folks use piezo-film elements to detect plucking of strings:

This unit uses lasers to (somehow) detect finger positions.  It is not clear to me how they detect plucking or strumming:

Rowland apparently makes a magnetic pickup with individual coils:
57  Using Arduino / Sensors / Re: Problems with Ultrasonic Range Finder - Maxbotix LV-EZ1 on: April 15, 2014, 02:41:00 pm
Start by disconnecting two of the the RX pins from Pin 11 and connecting then to two other digital output pins.
Wait, so do I need 3 RX wires? If so, can they all branch out from one?
My understanding is that you have three ultrasonic sensors, each with an RX pin.  If you want to control them separately you would need to connect each to a separate output pin.
58  Using Arduino / Project Guidance / Re: Possible to use photoresistors as digital in? on: April 15, 2014, 07:48:40 am
You can use a digital input.  The switching might not be clean since there is a undefined state between 0V and 5V where the input isn't guaranteed to be 0 and isn't guaranteed to be 1.  As your variable resistor changes and the voltage passws through that region you may get random switching.  I think you can use a Schmidt Trigger inverter to clean up the input.  It provides solid switching on a slowly changing signal.  Each 74HC14 chip will do 6 channels.
59  Using Arduino / Project Guidance / Re: 4 to 20mA Current Source using PWM on: April 15, 2014, 07:42:20 am
Are you sure it is 1-5V and not 0-5V?  The 0-5V would be easy, just connect to any PWM pin and use analogWrite().

Perhaps you should specify the part number of the converter you are using or, better yet, provide a link to the datasheet.
60  Using Arduino / Sensors / Re: Optical Guitar Pickup on: April 15, 2014, 07:05:45 am
I just need an indication that the string is vibrating. No audio. So will this type of modulated IR reflection sensor be the right sensor for the job?

I would worry about ambient light and sensitivity.  The optical difference between a steady string and a vibrating string is very minor.  Have you thought about using a magnetic pickup?  You would have to use separate coils for each string to tell the strings apart.  To detect vibration you would amplify the signal and filter for the audio range.
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