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1  Using Arduino / General Electronics / Re: RFID Reader ID-20 from Sparkfun = Any hope left? on: August 22, 2011, 09:51:35 pm
I might have to explain further: I had setup the wires to the ID-20 before I inserted it onto the breadboard. This means that pin 11 on the ID-20 recieved 5V. The second time i plugged the ID-20 into the breadboard, I might have inserted it with an offset of one pin, resulting in pin 10 recieving 5V or similar...

Is the ID-20 reader gone for good? Or can I test it in some way?
2  Using Arduino / General Electronics / RFID Reader ID-20 from Sparkfun = Any hope left? on: August 22, 2011, 08:29:10 pm
Hey everyone!

An hour ago I finished soldering the breakout board together to the ID-20 (http://www.sparkfun.com/products/8628). I checked all solder joints and did not see any bridges.
I then hooked up the board to a breadboard, and plugged in wires to the arduino. After doing some testing, where I read two different cards, everything was going great.

I then unplugged the RFID-reader and added an LED, to test the possibilities.

This is where I might have screwed the pooch: I then inserted the ID-20 back into the breadboard - BUT - I am not sure that I placed the reader back in to the right sockets (resulting in a short?).
This time, strange readings were seen on the Serial Monitor. I quickly unplugged the reader. Then I put the reader back in, carefully checking the sockets. Again strange writing.

Next try the arduino stopped responding, until I unplugged the reader and reset the arduino.

My question to you guys: Is the RFID-reader dead or do I have a chance? - I am afraid to do any further testing.
3  Using Arduino / Microcontrollers / Re: Using the Phillips PCF8574A I2C as an INPUT? ( = e.g. a button.) on: July 19, 2011, 04:15:35 pm
[Edit]

Now I managed to get the board to register a button. My problem now lies in the coding.
Can someone tell me how to change the Serial.println so it only prints when the button changes?

Code:
#include <Wire.h>
#define expander B0111000  //expander address

volatile byte count = 0;

void setup() {
 Wire.begin();
 Serial.begin(9600);
 expanderWrite(B00100000);
 attachInterrupt(5, expanderInterrupt, CHANGE);
}

void loop() {
  if(count = 1) {
    Serial.println(expanderRead(), BIN);
    count = 0;
    attachInterrupt(5, expanderInterrupt, CHANGE);
  }
}

void expanderInterrupt() {   
  detachInterrupt(5);
  count = 1;
}

void expanderWrite(byte _data ) {
  Wire.beginTransmission(expander);
  Wire.send(_data);
  Wire.endTransmission();
}

byte expanderRead() {
  byte _data;
  Wire.requestFrom(expander, 1);
  if(Wire.available()) {
    _data = Wire.receive();
  }
  return _data;
}
4  Using Arduino / Microcontrollers / Using the Phillips PCF8574A I2C as an INPUT? ( = e.g. a button.) on: July 18, 2011, 08:21:41 am
Hello everyone !

I recieved an I2C chip a few days ago: The Phillips PCF8574A 8bit I/O expander.
http://www.datasheetcatalog.com/datasheets_pdf/P/C/F/8/PCF8574A.shtml

Half an hour later, I had hooked it up and was able to use it as OUTPUT, using the following (Sinking Current) technique :

+5V -----------> (+) Anode of LED --- (-) Cathode of LED ---[¤ R=33O Ohm ¤] ------------> P4 on PCF8574A.

I have since then tried to use one of the I2C-ports as an INPUT. I have now tried for a few days without luck.
Im not sure I understand how to create a sinking current button. Also, when reading through posts on this board, people seem to mention very different facts on how to setup resistors. One person says "Put 10K on SCL and SDA and put 2.2K on INT" and another says "2.2K on SCL and SDA and nothing else".

Does anyone know how to do this? Help is VERY much appreciated.

Quote
Grumpy_Mike: So in short if an input pin changes state this line (INT) goes low. You can then put this into one of the normal arduino pins and monitor that to see if an input has changed. This is a lot quicker than reading the I2C device itself.
- How would I set that up? Do I put the INT directly to a pin on the Arduino? Do I add pull-up resistors?

Posts with info:
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1256915868
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1281290936
5  Using Arduino / Motors, Mechanics, and Power / Re: Best way to insure fool-proof control of a powerful servo? on: July 11, 2011, 11:40:00 pm
levorto, that circuit should be fine for driving your servo.

Thanks smiley - What a great and helpful forum! I am looking very much forward to inventing with you guys  smiley

Your servo will be stronger if you power it with 6v instead of 5v.

Im not worried about the strength of my servo... Let's just say I have that part taken care of smiley
http://www.servocity.com/html/hs-805bb_mega_power.html = 25 kgcm at max smiley-razz - I will let it run at 5V to reduce wear&tear.
6  Using Arduino / Motors, Mechanics, and Power / Re: Best way to insure fool-proof control of a powerful servo? on: July 11, 2011, 08:36:34 pm


Just to clear things up. Did I miss anything? No resistors or anything? Just making sure smiley
7  Using Arduino / Motors, Mechanics, and Power / Re: Best way to insure fool-proof control of a powerful servo? on: July 11, 2011, 08:05:46 pm
I am just trying to protect the Arduino board.

I had the idea that powerful servos had the same risk as gear reduction motors.
Hence the one-way diode. And thought the signal had to be strong, hence the transistor.


So there is no need for extra security when using a servo?

Just Arduino PIN to servo pulse,
Arduino GND to servo GND ,
servo positive to powersource positive,
servo GND to powersource GND,
and powersource GND to Arduino GND.


The website that made me confused: http://itp.nyu.edu/physcomp/Tutorials/HighCurrentLoads


Might as well explain what I am going to use this servo for:
A Combined 12xKeypad & RFID Door Unlocker - possibly with automatic opening.
8  Using Arduino / Motors, Mechanics, and Power / Best way to insure fool-proof control of a powerful servo? on: July 11, 2011, 07:18:50 pm
Hello everyone

This will be my first project on an Arduino, so bear with me if I am asking questions that might have already been answered.

I have been researching the most fool-proof setup for controlling a powerful servo, and I think I have come up with the best solution.
My means are limited in sense of funding, so investing in a motor board should be my last resort - e.g. if this does not work.

My setup will be: Arduino Uno (w/5V AC/DC) connected to a 5V 800mA(!) servo - which has its own power source (5V 1A - AC/DC).


Here is my question:

Would the following schematic provide fool-proof control of a 5V/800mA servo?
- and if yes, how can it be optimized to perfection?  smiley



I have created this schematic based on how I de-ciphered comments around the web.

Looking forward to hearing if I'm on the right track smiley
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