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5716  Using Arduino / Installation & Troubleshooting / Re: Connecting Arduino Nano via USB [MAC] on: April 12, 2012, 01:17:03 pm
Did you install the FTDI drivers in Step 3?
5717  Using Arduino / Installation & Troubleshooting / Re: arduino uno red led,s on: April 12, 2012, 01:15:02 pm
On a genuine Arduino UNO the power LED is green and the 'L' LED (connected to pin 13) is yellow.  Sounds like you have an Arduino clone made by a company that doesn't bother to get the colors right.
5718  Using Arduino / Motors, Mechanics, and Power / Re: multiple 12V DC motor with arduino uno and L293 h-bridge on: April 12, 2012, 01:09:31 pm
Is it possible that your motors require more current than the L293 can control?  Check the specs on the chip and the stall current on the motors.
5719  Using Arduino / Microcontrollers / Re: Arduino with 8MHz crystal on: April 12, 2012, 01:07:07 pm
What board do you have selected under Tools->Boards?  You should select an 8 MHz board.  If none of the existing 8 MHz boards matches your breadboard you should write your own boards.txt file to add your breadboard.  Maybe something like this but with setting for a crystal:

############################################################## on a breadboard (8 MHz internal clock)


5720  Using Arduino / Sensors / Re: Voltage, Amperage & Tempearture Sensors for reading 2vDC Batteries on: April 12, 2012, 12:52:34 pm
Typically you would measure the voltage across a known 'shunt' resistor to determine current.  Connect the - side of each cell through a precision shunt resistor (like 1 Ohm or 0.1 Ohm) to Ground on the Arduino.  Connect an analog input to the + side of the shunt to measure current (1 V = 1 A when resistor is 1 Ohm, = 10 A when 0.1 Ohm).  Connect an analog input to the + side of the cell to measure cell voltage.  You might want to provide a precision A/D voltage reference (Vref) of just over 2 V (maybe 2.048V to get analogRead() * 2 = millivolts).  Subtract shunt voltage from the measured cell voltage to get actual cell voltage.
5721  Using Arduino / LEDs and Multiplexing / Re: How many leds can i connect to arduino powered from usb on: April 12, 2012, 12:42:16 pm
USB can supply 500 mA.  Figure 50 mA for the Arduino leaving 450 mA for everything else.  LED's take about 20 mA each so 450/20 = 22.5.  So that means you can have as many as about 22 LED's on at one time.  If your LED's are multiplexed that can extend to hundreds as long as no more than 22 are on at one time.
5722  Using Arduino / Programming Questions / Re: Why the watchdog at Arduino works wrong? on: April 12, 2012, 12:36:51 pm
The watchdog timer works fine on my Arduino UNO R2 with the latest bootloader from Arduino 1.0.  Have you tried burning a fresh bootloader?

//  Watchdog Timer Example
#include <avr/wdt.h>

unsigned long ToggleDelay;  //  When this delay grows to longer than the WDT interval the WDT resets the Arduino

const int LEDpin = 13;

void toggle_led()
  digitalWrite(LEDpin, !digitalRead(LEDpin));

void setup()
  ToggleDelay = 1;   // Start with a very short delay
  pinMode(LEDpin, OUTPUT);
  wdt_enable(WDTO_250MS);  // Set watchdog to 1/4 second

void loop()
  toggle_led();   // Blinking goes slower and slower until the WDT causes reset, then starts over.
  ToggleDelay += 5;   // Increase the delay by 5 milliseconds.
5723  Using Arduino / Installation & Troubleshooting / Re: uploading sketches using an ISP on: April 12, 2012, 11:44:31 am
Sounds like your chip is not set up to use a 16 MHz crystal.  Do you have a 16 MHz crystal attached to it?

Try adding your programming to the IDE by creating a 'programmers.txt' file in the 'hardware' folder of your sketch folder.
5724  Using Arduino / Microcontrollers / Re: requirements and limits of 8Mhz 3.3v on: April 12, 2012, 11:36:31 am
If you burn an 8MHz bootloader on the chip you can upload sketches just like any other Arduino.  The voltage doesn't matter as long as it is high enough for 8 MHz operation.  You can run at 10 MHz on 2.7 V but 1.8V is only good for 4 MHz so something like 2.4V for 8 MHz?  Anything between 2.4 V and 6.0 V should work.

Arduino 1.0 doesn't seem to come with an 8 MHz version of the optiboot bootloader.  You may have to re-compile the optiboot bootloader for 8 MHz if you really need that.
5725  Using Arduino / Motors, Mechanics, and Power / Re: leverage formula?? on: April 10, 2012, 08:14:10 pm
If your servo torque is measured in kilogram centimeters you need 0.126 kg * 100 cm = 12.6

To get ounce-inches you divide by 0.0720077887081 so about 175

You should also account for the mass of the arm.  Figure average lever arm for the arm is 50 cm.

You may need more torque to accelerate the arm at a reasonable rate.
5726  Using Arduino / Networking, Protocols, and Devices / Re: Still struggling to send data over UDP on: April 10, 2012, 08:06:27 pm
If you are using Arduino 1.0 and want to specify the IP address you also have to specify the Default Gateway and DNS Server addresses before you specify the Subnet Mask.

I think you are passing the subnet mask as the DNS Server address.
5727  Using Arduino / Networking, Protocols, and Devices / Re: Problem connecting to TI ADS1212P via SPI on: April 10, 2012, 05:26:39 pm
If you have SDOUT connected to MISO (Master In/Slave Out) you will have to set the SDL bit of the command register to 1.  The default is to use the same pin (SDIO) for Input and output.
5728  Using Arduino / General Electronics / Re: ATtiny13A for controlling a vibrator - Datasheet Question on: April 10, 2012, 08:44:57 am
I agree with your reading of the graph.  When running off 1.8 V the output pins can supply 1.6 V at 3 mA or 1.4 V at 5 mA.

Switching voltage with a transistor might be the solution but it is my understanding that a transistor has a voltage drop across it much like a diode.  If you r power supply is 1.8 V this voltage drop might be significant. Maybe someone with real electronics training can help.
5729  Using Arduino / Sensors / Re: Magnetic sensor by Sure Electronics DC-SS503 on: April 10, 2012, 08:34:53 am
Couldn't find any application notes on the subject.  Perhaps you should hook one up and see what signal you get when you drive a car over it.
5730  Using Arduino / Installation & Troubleshooting / Re: Bootloader installation problems - mega2560 - ARVISP mkII on: April 10, 2012, 08:16:56 am
> I tried whatever comes loaded on the R3 Arduinos (any idea what that is?) and it timed out properly but never came back after the timeout. 

The test code works fine for me on my Arduino UNO R2. smiley-sad

> I have read that this is the main problem with the Arduino and the watchdog circuit.  It seems
> that on reset (by the WDT) the timeout is changed to 15mS and enabled so the bootloader never
> gets a chance to make it to my setup() code before retriggering.  That appeared to be what was
> happening to me.

I had read that the WDT doesn't get disabled after a timeout and that if the bootloader took too long you could get into a WDT loop but I had not read that the WDT interval gets reset to 15ms.  I just burned the Arduino 1.0 UNO bootloader into my UNO R2 and the WDT test sketch still works fine.

> On a related matter, the Arduino IDE ships with several bootloaders (STK500V?, Optiboot, etc). 
> How do you tell it which one to use or does it pick based on the particular microprocessor
> you have selected under "Tools->Board"?

Yes.  The 'boards.txt' files have a pointer to the bootloader for each type of board.  You can put your own 'boards.txt' file in the 'hardware' folder inside your sketch folder and the IDE will pick that up next time you start it.

> Is there anyway to find out which bootloader is programmed in the chip?

Not really.  The only way I know of to be sure is to burn a fresh bootloader.
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