Show Posts
Pages: 1 2 [3] 4 5 ... 7
31  Forum 2005-2010 (read only) / Development / Re: Large LED display for temperature. on: October 11, 2009, 05:14:57 pm
Sparkfun do a 6.5" high 7 segment display at:

http://www.sparkfun.com/commerce/product_info.php?products_id=8530

You could always make your own if you want one bigger, you can use normal led's with acrylic or similar over the top making the shape of the display and acting as a diffuser. Easier to build than making a large LED matrix!
32  Forum 2005-2010 (read only) / Development / Re: Minimum hardware requirements 4 running ATMega328 on: March 18, 2010, 06:29:32 pm
Have at look at the two links below, which give details about how to create a standalone Arduino:

http://art364.pbworks.com/Standalone+Arduino

http://www.arduino.cc/playground/Learning/AtmegaStandalone
33  Forum 2005-2010 (read only) / Interfacing / Re: Question about ENC28J60 Ethernet shield on: August 04, 2010, 07:43:59 am
They are used as level shifters between the ENC28J60 which runs at 3.3V, and the Arduino running at 5V
34  Forum 2005-2010 (read only) / Interfacing / Re: Portable Magnetic card Reader with Arduino??? on: March 04, 2010, 08:25:57 pm
5V DC is good, they are likely to be lower current than the high voltage ones, so will be better for being battery powered.

You can't hook a 5V reader to a 9V supply directly, you`ll most likely damage it. You just need a voltage regulator, which will give you 5V from the 9V battery (eg 7805, very cheap). Alternatively, you could use 4 x 1.5 batteries to give you 6V instead of using a 9V battery, and this would give better battery life.
35  Forum 2005-2010 (read only) / Interfacing / Re: Portable Magnetic card Reader with Arduino??? on: March 04, 2010, 08:09:55 pm
Quote
Any thoughts how to let the Arduino save the data on it's memory?

This is actually pretty easy. You have 512 bytes available on the internal EEPROM. See the following for details on how to use it:

http://www.arduino.cc/en/Reference/EEPROM

Alternatively, you can use an external EEPROM which will give you much more storage space (and they are really cheap). Again, see the following for more details:

http://www.arduino.cc/playground/Main/InterfacingWithHardware#Storage

From a battery point of view, have a look at the battery packs for remote control cars etc, or maybe a mobile phone. Both tend to be fairly high current, but still fairly portable.

Do a bit of research, obviously there are portable card readers available, so read up on their specs and see what sort of battery capacity they have. Obviously its going to depend on your card reader though, and you may not have much choice available. New magnetic card readers tend to be fairly expensive, however you can usually pick up cheap ones from electronics surplus stores. Also try ebay, I recently managed to pick up 5 of them for £1 each, keep an eye out and you save a lot of money.

Have a browse round the net for more details about this type of project. Theres a load of info out there, and many different project write ups etc - all the info you`ll need is already out there, it's just a case of finding it and working out how to apply it to your specific application. It's not an overly complicated project though, and totally possible, so if you stick at it you should be able to build a good device.
36  Forum 2005-2010 (read only) / Interfacing / Re: Portable Magnetic card Reader with Arduino??? on: March 04, 2010, 06:16:16 pm
Using an Arduino and read and store the data from a mag card reader is perfectly feasible, and well within it's capabilities.

However, making it portable may cause problems. The arduino can run off a 9v battery as you've seen, but the actual card reader its self may cause a problem. It's going to be down to the specifications of the reader - some work on 24V, others 12V etc, and they tend to need quite a bit of current, as such it may require quite a heavy duty battery rather than a standard PP3 9V one. It's not impossible, but you`ll have to hunt around and find a reader that makes it practical.
37  Forum 2005-2010 (read only) / Interfacing / Re: Problems with 3w Luxeon LED and PWM on: April 13, 2010, 10:10:38 am
You can buy constant current drivers for these led's - have a look ebay.

They aren't normally expensive, only £3 - £4

38  Forum 2005-2010 (read only) / Interfacing / Re: Problems with 3w Luxeon LED and PWM on: April 13, 2010, 06:57:43 am
The resistors are needed to limit the current, which changes as the LED's temperature changes.

To drive one you really need to use a constant current driver. Do a search on Google as there are a number of example circuits out there. It's also a question that comes up regularly in these forums, so theres lots of info here that will help you.

Without using the current limiting resistors in your current setup, you run the risk of damaging both the LED and Arduino.
39  Forum 2005-2010 (read only) / Interfacing / Re: what the symbols that be in the flex datasheets? on: March 31, 2010, 04:45:15 am
It's an operational amplifier (op-amp)

http://en.wikipedia.org/wiki/Operational_amplifier
40  Forum 2005-2010 (read only) / Interfacing / Re: i have a n70 and n82 and was wondering on: March 25, 2010, 09:00:57 am
I`m not sure about the phones, but I`ve seen a lot of Robosapien hacking sites out there. People have interfaced to the Robosapien in lots of different ways, such as adding a web server giving it the ability to be controlled over the net. Do a search in google and you should find a number of sites with robosapien projects.
41  Forum 2005-2010 (read only) / Interfacing / Re: RFID question - 1m range and collision control on: March 19, 2010, 08:43:52 am
Quote
£3.50 - Where from?

http://www.apdanglia.org.uk/shoppingcart2.html#EM4095-IC

They are £3.85 there at the moment (I haven't bought any for a while). You can also get them from China at around £3 each (still in single quantities).

The U2270's are only £1.49, but need more external components.
42  Forum 2005-2010 (read only) / Interfacing / Re: RFID question - 1m range and collision control on: March 19, 2010, 08:17:31 am
Quote
But it is expensive, you can do it for a lot less from a hand full of parts.

They're only £3.50 for single quantities, and they make life a lot easier, especially when handling the manchester decoding. They need very few external parts as well, so you can make a complete reader for very little.
43  Forum 2005-2010 (read only) / Interfacing / Re: RFID question - 1m range and collision control on: March 19, 2010, 07:01:17 am
Quote
1.5 meter range using a 60cm diameter coil operating on a passive tag

Thats a big difference to a 9 metre range though (as the product has)...

Quote
Is it possible to create diy reader solutions?

Yes definately, have a look at the EM4095 chip which is pretty easy to use, I created my own system with this chip and an Arduino. Also there is the U2270B from Atmel. Both are low cost, and work with 125Khz tags
44  Forum 2005-2010 (read only) / Interfacing / Re: RFID question - 1m range and collision control on: March 19, 2010, 04:50:45 am
Quote
Even with the lower frequency ones and the right sort of antenna design you can get this sort of range

Reading the review of the product from the link it says that it can go to 30 feet (9 metres). How can a lower frequency tag achieve this sort of range without being powered?

Thats why I imagined it would have to be UHF to get this sort of range, and you wouldn't find a UHF reader at the price range of the product.
45  Forum 2005-2010 (read only) / Interfacing / Re: RFID question - 1m range and collision control on: March 18, 2010, 06:46:52 pm
That system may not be RFID in the standard sense, ie it may not use the normal frequencies, and is just a cheap transmitter and receiver at 433Mhz (which are available very cheaply compared to RFID readers).

They would have to be active tags for a true RFID system to get that sort of range, and these are more expensive than the passive tags.
Pages: 1 2 [3] 4 5 ... 7