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1  Using Arduino / Project Guidance / Re: proximity sensor only activated by certain things on: Today at 12:59:09 pm
did you try this:-
  int readTag;
  int readTagTwo;

void loop() {
readTag = (readerOne.uid.uidByte[0] << 8) | (readerOne.uid.uidByte[1]);
readTagTwo = (readerTwo.uid.uidByte[0] << 8) | (readerTwo.uid.uidByte[1]);

It is what I said.
2  Development / Other Software Development / Re: pcb design schematic on: September 30, 2014, 03:34:38 pm
Really better..??
Yes.  smiley The antenna bit now looks like one. If you post the Gerber files it will allow people to look more closely.

Can't do too much this week as I am in Rome for the Maker Fair.
3  Development / Other Software Development / Re: pcb design schematic on: September 29, 2014, 04:34:40 pm
Better  smiley
How about the ground plane?
4  Using Arduino / Project Guidance / Re: Analog Multiplexing on: September 28, 2014, 03:55:22 pm
it says 0,4 to 4 Ma

I hope not 4 Mega amps is a lot of current.

My data sheet says +/-25 mA.

Do your sensors take less than this.
5  Using Arduino / General Electronics / Re: Resistor value on: September 28, 2014, 07:57:16 am
Btw how do you know the voltage drop is 2V? voltage drop is Vbe(sat) right?
No it is the Vce(sat) + 1.2V ( two transistor's Vbe)

So what should I do?
Follow the component values on the schematic.
6  Development / Other Software Development / Re: pcb design schematic on: September 28, 2014, 07:55:05 am
The antenna is the up an down PCB track at the top of the board on this link:-
Note how there is no ground plane over this section of the circuit.

That is what you have to copy exactly, unless you know how to design it better. A proper design will require you to know the dielectric proprieties of the PCB substrate, which I suspect you don't.
Try and copy the placement of components around this antenna as close as you possibly can.
7  Development / Other Software Development / Re: pcb design schematic on: September 28, 2014, 07:31:54 am
so the antenna used in that board I have used the same antenna...
You just posted a schematic not a PCB layout. That is not an antenna.

Remember when I said earlier that you have a lot to learn?
Part of learning is not ignoring what people say.
8  Using Arduino / General Electronics / Re: Resistor value on: September 28, 2014, 07:27:14 am
I cant find the current gain on the datasheet.
No nether can I.

Note this is not a very good circuit. Q1 will have a voltage drop of 2V and so will Q2 so therefore with 24 V on the input the motor will only ever see 20V.

Remember when calculating resistors like this you are calculating the maximum possible resistor value. It is normal practice to take this value and half or quarter it, or even more, to give you some margin.
9  Using Arduino / General Electronics / Re: Resistor value on: September 28, 2014, 05:30:29 am
R4 is a pull down resistor designed to turn off transistor when there is no signal connected to the input. It's effect is to reduce the impedance on the gate so that interference does not turn it on. The voltage developed across it must be less than 0.7V when an interfering voltage is present. So you need to know the maximum interference voltage you will get and also the impedance of that interfering voltage. Then the calculation is similar to R3.

However, the impedance of the interference voltage is a difficult thing to measure and requires a specific environment to measure it in ( an EM shielded chamber ). So in practice 10K will cover virtually all interference situations you will ever encounter.

The maximum value of R1 could be calculated if you know the current gain of Q1 and the collector / emitter current current being passed by the transistor. For this you would need to know the supply voltage and the current draw of the motor. So R1 would be:-
the base current into Q1 = current gain of Q1 / collector to emitter current of Q1.
10  Using Arduino / Sensors / Re: sensor selection on: September 28, 2014, 05:16:26 am
that i could perfectly monitor the motion of human.
Nothing perfectly monitors the motion of human.

The simplest would perhaps be a PIR sensor but it is not very directional. You would have to do things to make it more directional, like putting it down a long tube.
11  Using Arduino / Sensors / Re: I want to use the Ping))) sensor to measure the speed of sound through water on: September 28, 2014, 05:14:12 am
Is it possible to use the ping sensor to measure the speed of sound through water?

I want the sound to be able to cross an interface and bounce back towards the microphone to record results.
How would that measure the speed of sound in water?
You would need to know the distance from the sensor to the water and the depth of the water, assuming it is bouncing back off the bottom.
However there will be so little sound even entering the water and less still bouncing off the bottom and even less crossing the water / air boundary that it will be impossible to detect any secondary return echo from the water.

Also 40KHz is not a good frequency for propagation through water, most systems use something higher in the KHz region.
12  Using Arduino / Programming Questions / Re: sending a train of data through digital I/O pins on: September 28, 2014, 04:16:54 am
Your problem is not that you are taking too long to send that bit stream but you are sending it too quickly. The transmit module will only be able to cope with slowly changing signals because the transmitter does not have the bandwith for fast ones.

Anyway you can't just transmit that and expect to be able to sort it out at the other end.

You need something like this:-
13  Using Arduino / Sensors / Re: Ultrasonic on: September 28, 2014, 04:10:38 am
This is the code I have for making the PWM go at the sorts of frequencies you want.
Just do an analogWrite to pin 3 with a value of 128.

/* Code to pulse pin 3 with a modulated signal
* By Mike Cook Nov 2011 - Released under the Open Source license

void setIrModOutput(){  // sets pin 3 going at the IR modulation rate
  pinMode(3, OUTPUT);
  TCCR2A = _BV(COM2B1) | _BV(WGM21) | _BV(WGM20); // Just enable output on Pin 3 and disable it on Pin 11
  TCCR2B = _BV(WGM22) | _BV(CS22);
  OCR2A = 51; // defines the frequency 51 = 38.4 KHz, 54 = 36.2 KHz, 58 = 34 KHz, 62 = 32 KHz
  OCR2B = 26;  // deines the duty cycle - Half the OCR2A value for 50%
  TCCR2B = TCCR2B & 0b00111000 | 0x2; // select a prescale value of 8:1 of the system clock

void setup(){

void loop(){
// do something here

OCR2A controls the PWM frequency, it looks like something in the order of a value of 49 should give you what you want.
14  Using Arduino / Motors, Mechanics, and Power / Re: motor wheel stops when placed on ground on: September 28, 2014, 04:01:47 am
you need a 6-pack of AA rechargable batteries which can
push out amps and hold up their voltage under load.   
Not quite the same thing.

I am suggesting that for a 9V motor he needs to power it with 12V if he has any hope for the motor to actually receive 9V.
15  Using Arduino / Programming Questions / Re: digitalwrite has opposite effect on: September 28, 2014, 03:36:48 am
I have this same problem with the built in led on my nano. Any ideas?
I think you do not.

According to the schematic I have of the nano the internal LED ( and resistor ) is directly connected between Pin 13 and the ground. Check the schematic for the revision of the nano that you have.
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