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1  Using Arduino / General Electronics / Advice for RFID reader and fobs? on: March 26, 2014, 04:51:29 pm
I'm looking for an RFID system that has two types of readers:

- one where the user swipes their fob over the reader

- another where they can walk through a "portal" (door) and have their card read.

Does anyone have any advice towards that?

And any advice on the fobs?

Thanks for any help.
2  Using Arduino / Programming Questions / Re: Problem concatenating a string and integer for Serial.println (solved) on: August 07, 2013, 11:00:56 pm
@groundfungus: Ha, I must have been making my edit right when you were typing the reply. And thanks.

And @Nick: thank you so much for the streaming library, looks phenomenal.
3  Using Arduino / Programming Questions / Problem concatenating a string and integer for Serial.println (solved) on: August 07, 2013, 06:28:45 pm
I'm sure I'm missing something obvious, but I've been googling for a good half hour now and I can't figure it out.

I'm trying to print some debug message to the Serial Monitor. Something like this:

Code:
int test1 = 15;
int test2 = 32;

Serial.println("The value of test1 is " + test1 + " and the value of test2 is " + test2).
That should print to Serial Monitor "The value of test1 is 15 and the value of test2 is 32".

Does anyone have any tips on how I would make that happen?

Thanks hugely for any help.

Edit: as usual, posting made me see the answer. To anyone else who comes down this path, use print in combination with println. If anyone else knows a way to do in-line concatenation, please post.

Code:
Serial.print("The value of test1 is ");
Serial.print(test1);
Serialprint(" and the value of test2 is );
Serial.print(test2);
Serial.println("");

4  Using Arduino / General Electronics / High capacity relay or switch? on: July 11, 2013, 02:11:48 pm
I'm working on a project where a switch needs to go between two very high loads, that are about 80 amps @ 12 volts. I considered using a relay, but the problem there is that (I think) the relay consumes power while engaged, and may overheat over time. That's a problem, since the switch will be engaged for weeks at a time.

I'm wondering if anyone has any advice for a way to switch between two very high loads?

Thanks for any advice.
5  Using Arduino / General Electronics / Re: How to control this stepper motor? on: January 31, 2013, 02:17:23 pm
> The wiring, seemingly 

Yup, and any tips on using it. That's why I'm here, because I have no idea how to turn that data sheet into controlling it from the Arduino.

6  Using Arduino / General Electronics / Re: How to control this stepper motor? on: January 31, 2013, 02:41:53 am
Thanks JimboZA! I edited the post to reflect that.
7  Using Arduino / General Electronics / How to control this stepper motor? on: January 31, 2013, 01:49:23 am
So I picked up an "LED disco light" off Ebay:

http://www.ebay.com/itm/280995441549?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

(If that link is broken, try searching for "DMX512 Disco DJ Stage Lighting Digital LED RGB Crystal Ball Effect Light").

Anyway, the light is great, but the programming is awful. For example there's no way to make the lights stay still or even slow down much, so its super frenetic. My solution has been to put a disconnect switch on the stepper motor, which works, but I was thinking the much more interesting and educational route would be to make it all controlled by an Arduino.

Here's 2 pictures of the servo motor that rotates the LEDs:





Edit: here's the data sheet: http://store.kysanelectronics.com/servlet/-strse-70050/39BYG101/Detail (thanks JimboZA!)

As you can see, the stepper motor has 5 wires: 4 grouped together and 1 set apart.

Wondering if anyone has any tips for controlling that?

One interesting feature is it has a clutch on it, so if it turns against the wires it will simply slip instead of putting much pressure on the wires. So even if I had imperfect control of the motor, I'd be unlikely to damage anything.

Or, failing that, a replacement motor? Its pretty beefy, about 3 inches tall, though that's probably overkill as it only holds 6 LEDs and a small heatsink.

And on the subject of those LEDs, if possible I'd also love to control those. They're 3 watts each though. Any tips on controlling those, ideally with a bit of PWM fading?
8  Using Arduino / General Electronics / Re: Grounding problem? on: March 30, 2011, 09:06:06 am
> The sort of thing I was thinking about was a voltage follower

Does that mean there would be one op-amp per sensor?
9  Using Arduino / Project Guidance / How to remotely mount an Arduino? on: March 29, 2011, 06:09:36 pm
I have a project where I'd like to mount an Arduino about 200 feet away from the computer, ideally connected by Cat5 (or Cat6) cable. The computer should still be receiving Serial messages from the Arduino.

Any tips for doing that?
10  Using Arduino / General Electronics / Re: Grounding problem? on: March 29, 2011, 05:04:31 pm
Aha! I found his circuit, which looks like its exactly the sort of thing you (Grumpy Mike) described:

http://www.instructables.com/id/A-position-sensitive-midi-drum-pad/step8/Building-the-circuit/

Here's just the circuit:

http://www.instructables.com/files/orig/F4Q/P3Y1/GHFJXCHX/F4QP3Y1GHFJXCHX.png

Here it is as wired into the arduino:

http://www.instructables.com/files/orig/F0V/A3LJ/G68HEHUH/F0VA3LJG68HEHUH.jpg

I'm going to take a stab at it, feel free to chime in if anything strikes you (anyone) about it.

11  Using Arduino / General Electronics / Re: Grounding problem? on: March 29, 2011, 01:39:58 pm
> You need an op-amp to convert your high input impedance into a lower one.

Thanks for the tip. I was wondering if you had any pointers on which op-amp to use, and how to use it?

I've never used an op-amp before.
12  Using Arduino / General Electronics / Grounding problem? on: March 28, 2011, 11:03:07 pm
I'm trying to build a knock sensor, something like this:

http://www.arduino.cc/en/Tutorial/KnockSensor

Everything is generally working, but sometimes my threshhold (the knock) is randomly triggered, and it appears to be caused by some sort of electrical interference. I posted a video of the problem here:



The LED should only be lighting when a knock is detected.

As far as the circuit, I'm connecting the piezo's negative to ground, and the positive to analog pin 1, and I have a 1 megohm resistor between ground and analog pin 1. This is the piezo I'm using: http://www.radioshack.com/product/index.jsp?productId=2062397

And to describe the problem a bit more, usually everything works well, but seemingly randomly it stops working and the threshhold (the knock) is detected. It usually remains like this until I touch the ground wire, or even put my hand near the ground wire.

Eventually I'd like to have 6 different piezos detecting different "knocks", if possible.

Any tips on how to get rid of the bad readings?

13  Forum 2005-2010 (read only) / Syntax & Programs / problem returning array from function... on: April 15, 2009, 04:12:24 am
I'm trying to use a function to generate an array. Below is a stripped down version of my code. In the loop, the variable named "pattern" should get an array of numbers from the function generatePattern(). Thanks for any help.


Code:
int pattern_local[] = {1, 2};
int pattern[] = {3, 4};


void setup()
{
  Serial.begin(9600);
}

void loop()
{
  pattern = generatePattern();
}



int generatePattern()
{
 int pattern_local[] = {1, 2};
 return pattern_local;
}

This errors out with:
Code:
In function 'void loop()':
error: incompatible types in assignment of 'int' to 'int [2]' In function 'int generatePattern()':

Can anyone point me in the right direction?
14  Forum 2005-2010 (read only) / Interfacing / Re: Arduino + Firmata + Pyduino (Python) on: January 17, 2008, 05:56:36 pm
Links are broken...

http://rafb.net/p/FjOkxU38.html and http://rafb.net/p/u9u2QP86.html are both 404 for me....
15  Forum 2005-2010 (read only) / Interfacing / Re: Arduino-Python bridge on: January 17, 2008, 01:27:24 am
I'm having some trouble with this in Windows XP / Python 2.4 / Arduino NG Rev C.  Can anyone see what I'm doing wrong?

I'm brand new to the Arduino so it's entirely possible I'm doing something very stupid.

I have this sketch successfully loaded onto the Arduino:
http://www.arduino.cc/playground/Code/SimpleMessageSystem

My Arduino is installed as Com4 under Windows, and I set it's buardrate in Device Manager to be 115200 (it installed as 9600, but the change doesn't seem to have affected it).

For simplicity I extracted the relevant parts of the above code:

Code:
import serial, time

baudrate = 115200

comm = serial.Serial(3, baudrate, timeout=0.25)

for i in range(10):
    comm.write("r d\r")
    o = comm.readline()

    if len(o) == 0: print "no response..."
    else: print o

    time.sleep(.5)

With pins GRD and 11 jumpered I get the following output when running the above:

Quote
d 0 0 0 1 1 1 1 1 1 0 0 0
d 0 0 0 1 1 1 1 1 1 0 0 0
d 0 0 0 1 1 1 0 1 0 0 0 0
d 0 0 0 1 1 1 0 1 0 0 0 0
d 0 0 0 1 1 1 0 1 0 0 0 0
no response...
no response...
d 0 0 0 1 1 1 1 1 0 0 0 0
d 0 0 0 1 1 1 1 1 0 0 0 0
no response...

With all pins open (no jumpers) I get the following:

Quote
no response...
d 0 1 0 1 1 1 0 1 1 1 0 0
d 0 1 0 1 1 1 0 1 1 1 0 0
d 0 1 0 1 1 1 0 1 1 1 0 0
d 0 1 0 1 1 1 0 1 1 1 0 0
no response...
no response...
no response...
d 0 0 0 1 1 1 0 1 1 1 0 0
d 0 1 0 1 1 1 1 1 1 1 0 0

Ok, so far so good, the digit 3rd from the right is Pin 11 and it's indicating its status well. However, if I attach a button across the two pins and press and release I get this:

Quote
no response...
d 0 0 0 1 1 1 1 1 0 0 0 0
d 0 0 0 1 1 1 0 1 0 0 0 0
no response...
no response...
d 0 0 0 1 1 1 1 1 0 0 0 0
no response...
d 0 0 0 1 1 1 1 1 0 0 0 0
d 0 0 0 1 1 1 1 1 0 0 0 0
d 0 0 0 1 1 1 1 1 0 0 0 0

Three questions:

1) How do I make it update faster? When I was pressing that button its status never changed. I have a feeling its reading from a buffer. Do I need to clear that buffer when I read from it? If so, how?

2) Is it normal to get no response from the Arduino when querying it? Even when I increased the timeout to 1 I still get the no responses...

3) And on a minor note, why were the other pins fluctuating even when nothing was attached to them?

Thanks for any help.
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