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46  Using Arduino / Sensors / worlds-smallest-sized-radar-system on: December 05, 2012, 09:56:42 am
Hi, I found this link on the WWW.

http://www.gizmag.com/worlds-smallest-sized-radar-system/25152/

Is there anything similar already out there within (the reach of hobby folk like me) that could be use with an Arduino? Maybe with a range of say few a cm to a few metres? Tried some of the robotics sellers' websites, but no joy.

Cheers
47  Using Arduino / Sensors / Re: Keypad.h on: November 09, 2012, 02:23:08 pm
Many thanks again. I'll check it out.

I believe it's a good idea for me understand the stuff I'm using in more depth, now.

I've been using arduino for just over 12 months now.  It's a bit off post, but I just bought this book http://www.amazon.co.uk/Introduction-Embedded-Systems-Development-Environment/dp/1608454983/ref=sr_1_9?s=books&ie=UTF8&qid=1352488796&sr=1-9 to help speed the path to better understanding  smiley

Cheers
48  Using Arduino / Sensors / Re: Keypad.h on: November 09, 2012, 01:57:31 pm
Here's the link:

arduino.cc/playground/uploads/Code/keypad.zip

robtillaart many thanks for the explanation, I think I understand it now.

Although the C files make heavy reading, I can see that they appear to be pulsing and checking row and column pins.

Cheers
49  Using Arduino / Sensors / Keypad.h on: November 09, 2012, 11:52:54 am

Hi,
I’m using a keypad these with the Keypad.h library and, yes it works fine. But I don’t understand how the arduino is handling the input from it. I get that when a key is pressed a connection is made between a row and a column pin, which when read by arduino gives us a particular key as a result.

When I attached my ohm meter to various pins on the keypad I was basically measuring a drop in resistance (probably Megohms down to a few ohms) when a connection was made and the matrix from these tests gave me the data for the library to use. I understand that to calculate ohms (R) you can use V and I.
Does anyone know how the arduiono is handling these inputs?

I already tried looking at the keypad.h file and didn’t get any further either.

Cheers
50  Using Arduino / Sensors / Re: Mouse traps on: October 31, 2012, 03:43:50 pm
Brilliant! Could be very useful for humane pest control too. Although I hate the mess and damage house mice make.

It would be very useful to do this type of project with humane traps for ecological monitoring.

We used these traps in the 80's http://www.nhbs.com/title.php?bkfno=176703&ad_id=813 to monitor populations of wood and yellow-necked mice in the Midlands UK.

It would be great to bring this type of work into the 21st century.

So when a trap becomes occupied you are alerted and can go to investigate / identify the critter. Or better still, with web cams in each trap, you could ID the critter remotely and then release it automatically via your link. How about biometric sensors for length and weight etc...= total armchair ecology  smiley

51  Using Arduino / Sensors / Old UK TV satellite dish to Boost RF signal on: October 04, 2012, 08:10:20 am
Hi,

I've got an old concave UK BskyB dish and I would like to use it to "boost" a signal from my RF module attached to arduino. The RF module is a Jeenode type RF12, but my setup is not Jeenode it's attached to an Arduino Uno.

After a bit of research, I think I have to position the receiver module an exact multiple of wavelengths from the center of the dish to get it to work as a collector of "waves" and reflect them towards the RF module efficiently (ie so they mostly add up instead of cancel out).

Using the equation
Code:
wavelength = C / f

(C is velocity of light and f is freq of radiation) I get

 
Code:
3*10^8 / 868 MHz = 34.56 cm

I would appreciate an experienced look at my logic and Maths and some comment on it.

Am I on the right track?

Cheers
52  Community / Products and Services / Surplus 28pin DIL Sockets - Make your own boards! on: September 27, 2012, 08:21:29 am
Brand new, unused 28pin DIL Sockets Narrow (7.62mm with Central Support). Ideal for ATmega328 in DIP package.

I have 25 of these. Will ship to UK addresses in minimum batches of 5. Ideal for Arduino embedded projects.

Open to offers.

Please make me an offer by forum message. Will sort out payments via paypal.

Cheers

PS also available 25 of 18 pin DILs, brand new for DIP package (eg PIC 16F84a)
53  Using Arduino / General Electronics / Impedance and reactance on: September 10, 2012, 04:22:00 am
Hi,

I've looked on the WWW. with Google for a "newbie" tutorial or explanation of the above terms, but haven't been able to to grasp it easily - loads of maths and equations  smiley-roll-sweat

I kinda get that it's like resistance but applied to AC, and that extends to digital circuits with ON / OFF states and clocks, crystals etc..

I find the fluid analogy of resistance in DC circuits useful for understanding resistance - anything similar for the Impedance and reactance?

cheers

PS My education is in Biology. Been using Arduino for about a year now.
54  Topics / Robotics / Re: Looking for Linear Actuators for small 10W solar panels on: September 05, 2012, 10:30:59 am
Hi, have a look at these low cost ones, for schools projects

£5
http://www.mindsetsonline.co.uk/product_info.php?products_id=204

£10
http://www.mindsetsonline.co.uk/product_info.php?products_id=937

Cheers
55  Topics / Science and Measurement / Re: processing code? on: September 05, 2012, 04:50:30 am
Hi,

 I have also not been able to get this to work
Code:
myPort = new Serial(this, Serial.list()[2], 9600);


Try it wihout the [2].


If again no joy try this:
When I tried the same code on one of my projects a while ago, I had to use this instead:

Code:
import processing.serial.*;
Serial myPort;


void setup()
{
  size(800, 800); // pane size
 
myPort = new Serial(this, "COMn", 9600);



wher "n" is the port number. Use whatever you are using for port eg 2.



56  Using Arduino / General Electronics / Re: Lower than notmal serial monitor numbers from photocell on: August 14, 2012, 06:37:40 am
HI,

could you post a links to the tutorial and other pages you mention?

thanks
57  Using Arduino / General Electronics / Re: Timed action help on: August 14, 2012, 06:32:46 am
Hi,

Delay() will work, but you will be wasting a lot of power whilst your device is waiting to do it's task. That may mean a flat battery if battery powered. You could put your Arduino to sleep for much of the waiting time and save power.

See http://arduino.cc/playground/Learning/ArduinoSleepCode

and Nick Gammon's page http://www.gammon.com.au/forum/?id=11497

I managed to get current  down to a few uA in sleep using these techniques.

Cheers


58  Using Arduino / General Electronics / Re: small speaker for arduino projects on: August 11, 2012, 01:27:04 pm
Hi,

if you need a low power loud alarm why not try using a 3v magnetic buzzer. These are pretty loud and use very little power.

http://uk.rs-online.com/web/c/?searchTerm=buzzer&sra=oss

Cheers
59  Using Arduino / General Electronics / Re: Reverse polarity protection? on: August 11, 2012, 04:59:08 am
Thanks people for the input. I feel more confident now and I'll stick with the Mosfet as it is very efficient for my project.

Could this be a suggestion for enhancing arduino shields and allied boards, ie to add a simple low power circuit that protects it from reverse polarity mistakes? MOSFETs only cost a few cents, which seems a good investment to save maybe tens of dollars.

Cheers

PS really liked the You-tube tutorials
60  Using Arduino / General Electronics / Reverse polarity protection? on: August 10, 2012, 05:33:28 am
I recently blew up a motor shield made by a third party because I attached the power leads the wrong way around. Lots of heat, smoke then a nice pop! Ok it was a cheap shield from HK, maybe it's karma. I since bought the kosher rev 3.0 board which is much better anyway.

I decided to put a reverse polarity protection circuit between the battery and the my project. I'm not sure whether it's absolutely necessary, but for a quid it's worth it I think.

Not sure if most Arduino hardware already has this. I guess (maybe wrongly) that if the hardware has a voltage regulator, it is protected, but I also note that many shields and other pieces rely on the regulator on the Main board, so if you power it directly (as in a motor shield) you can possibly fry it!

My circuit works, but not sure if it is a good circuit. Could someone with please offer advice?

Many thanks
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