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571  Using Arduino / Programming Questions / Re: LM 35 Temperature sensor accuracy on: August 10, 2012, 03:48:41 pm
How is your Arduino Uno powered ? I hope not only the USB bus.
If you use the +5V reference, the value changes if the voltage changes.
If you have selected 1.1V reference, it is no problem.
http://arduino.cc/it/Reference/AnalogReference
http://arduino.cc/playground/Main/LM35HigherResolution

You should take the average of 10 to 20 samples. There is always some ADC noise, and noise from the circuit. You could even add a delay of about 100ms between the samples. If your power supply is good, taking the average should make a smooth line !

How is your hardware ? If you have long wires to the sensor, there must be a decoupling capaciter of 100nF.

There are many other things that could cause this: a draft by opening a door; electric noise; a bad switching adapter;  and so on.
572  Using Arduino / Project Guidance / Re: interfacing a display with arduino on: August 08, 2012, 04:22:04 pm
Give it a try !
573  Using Arduino / Project Guidance / Re: Timing Issues To Make Arduino RC Car Realistic on: August 08, 2012, 01:06:14 pm
I was assuming that you use 5V servo motors.
If you do use 5V servo motors, the voltage regulator (on the Arduino board or an other voltage regulator) could get hot. A DC-DC converter would convert the voltage without loss, so your battery is will last longer.

574  Using Arduino / Project Guidance / Re: interfacing a display with arduino on: August 08, 2012, 12:39:53 pm
You are right, but I can't find what kind of controller is used.

There is also an original datasheet. Download it here: http://www.datasheetarchive.com/CU209SCPB-T20A-datasheet.html (click on the PDF thumbnail for the 484.77 Kb, and then click on the image of the first page).

You could check that datasheet against a datasheet of an LCD with the HD44780, to see if it is the same.
575  Using Arduino / Storage / Re: Webduino, getting data from SD card on: August 08, 2012, 06:34:34 am
I have this code:
Code:
if (error404)
{
      // The file didn't exist, or it was not a file after all.
      Serial.println(F("Error 404 !"));
     
      pClient->println(F("HTTP/1.1 404 Not Found"));
      pClient->println(F("Content-Type: text/html"));
      pClient->println();
      pClient->println(F("<h2>File Not Found !</h2>"));
}

The pClient is a pointer: EthernetClient *pClient;
The error404 is an error flag: boolean error404;
So an error is returned and a message is displayed.
576  Using Arduino / Networking, Protocols, and Devices / Re: Serial Communication Problem on: August 08, 2012, 04:18:38 am
Well, that might be the problem.
The level shifter receives a the higher level correctly.
But it transmit only a 5V level, it does not create the higher levels for output.
You need a board with the MAX232, that's what everyone is using.
577  Using Arduino / Networking, Protocols, and Devices / Re: Serial Communication Problem on: August 08, 2012, 03:24:19 am
According to the document at page 34 : "Signaling levels: RS232".
So it does need the higher levels of the original RS232.
So first make sure the level converter is working.
Can you upload a schematic of the level converter ? The RX of the Arduino is also influenced by its own serial-to-usb-converter. The level converter has to override that.
578  Using Arduino / Project Guidance / Re: interfacing a display with arduino on: August 07, 2012, 09:18:18 pm
The 'C' code is for another microcontroller. You can see how it is done, but you can't just copy it.
The pins can be any of the 13 digital pins.

If you are new to Arduino, you should try something easy first. A few leds and switches and so.
Arduino has code for displays with a HD44780 controller : http://arduino.cc/en/Tutorial/LiquidCrystal
If your display is different, it can be hard to make it work.
You need an example of someone who has used this display with the Arduino.

Your first stop is the playground section about VFDs: http://arduino.cc/playground/Main/InterfacingWithHardware#VFD
This looks also very interesting : http://www.neilhannah.com/arduino-vfd/
579  Using Arduino / Networking, Protocols, and Devices / Re: Ethernet Shield + Pro Mini 3.3 v on: August 07, 2012, 09:06:52 pm
You can send a 3.3V signal to a +5V Arduino. The 3.3V is seen as "HIGH".
But you can not send a 5V signal to a 3.3V Arduino.

If you look at the schematic of the Ethernet Shield, the main chip, the W5100, is at 3.3V
http://arduino.cc/en/Main/ArduinoEthernetShield
The ethernet board contains logical level shifters to be able to connect it to an Arduino at +5V.
But to change the ethernet board, to make it run at 3.3V... perhaps that is possible, but I doubt it.
580  Using Arduino / Project Guidance / Re: Timing Issues To Make Arduino RC Car Realistic on: August 07, 2012, 08:49:45 pm
That 500ms is easy. It would take perhaps a few milliseconds.

If you use a RF link, it has to be reliable. The cheapest modules are not very reliable.

I think that measuring time is not needed. The main thing is the smoothing of the accelerometer. The accelerometer will have strong output changes for little vibrations. So you have to average or smooth it, and that will need a number of readings and will take some time.

You also need a driver module for the motor. And perhaps a DC-DC converter for the 5V of the servo.

The RC car has to stop if it is out of range. You could send keep-alive commands twice a second. If the RC car doesn't receive those anymore, it could stop.
581  Using Arduino / Project Guidance / Re: interfacing a display with arduino on: August 07, 2012, 08:38:52 pm
If you go to the website on that datasheet : http://www.noritake-itron.com/
And choose "software examples", you will see some code. Choose 'C' code.
Also check the "application notes"
582  Using Arduino / Motors, Mechanics, and Power / Re: Sharing Base Transistor fries H-Bridge! Why? on: August 07, 2012, 07:40:47 pm
It can work, but you have to connect all four bases with a resistor to Arduino outputs.
Most of the time, it is used like this:
- One of the PNP-transistors is switched on.
- The opposite NPN-transistor (on the other side) is a PWM signal to regulate the speed of the motor.

If you want to turn the motor left and right, and control it with PWM, you have to use 4 Arduino pins, or use a special ic (that ic might also need 4 pins of the Arduino).
If you want to turn the motor left and right, without PWM, just two Arduino pins are needed, but the H-bridge needs 8 transistors, or 4 transistors with the emitter connected to the motor, to make it safer.

Here is such a 'safe' version with the emitter connected to the motor: http://amitraj.webs.com/roboticsfordummies.htm
583  Using Arduino / Programming Questions / Re: Data sending and receiving through serial port on: August 07, 2012, 05:20:47 pm
I'm not sure what you write.
You use a PHP webpage, and you use the Serial library for commands and so ?

I'm new to this, but you can request (a GET request) a file from the Arduino webserver. For example request data.txt.
Instead of retrieving that from the SD card, the Arduino detects "data.txt" and generates on the fly that file (or actually a fake file) and fills it with data.
In the PHP script you have to extract the data from the file.

There must be other ways, since I'm just learning this.
I was trying to make an HTML5 live update code of Arduino webserver, but it is not working yet.
584  Using Arduino / Networking, Protocols, and Devices / Re: Serial Communication Problem on: August 07, 2012, 05:09:39 pm
Can you give a link to that sms-module ?
Is it expecting ttl-level signals, or rs232 level (normal, or low voltage).
What is the baudrate ?
The TX of the Arduino should probably be connected to the RX of the sms-module.

Can you check everything once more: baud rate, no parity, 8 bits. No handshake (not hardware, and not software).

If you send something to the serial monitor, that should be the same as using the TX/RX pins, and via adapter to the computer. Can you try to make that work. Do you have an old PC with a serial port perhaps. Or try a different program.

If everything fails, you could try SoftwareSerial. That emulates a serial port on any pin. That way you can use the serial monitor of the Arduino (with normal RX/TX pins), and send messages to the sms device (with SoftwareSerial) at the same time.
The SoftwareSerial is a standard library.
http://arduino.cc/hu/Reference/SoftwareSerial
585  Using Arduino / Motors, Mechanics, and Power / Re: Varying Voltage to a Pump on: August 07, 2012, 02:35:35 pm
Yes, that's okay. It is the same.
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