Cheap serial radio

Whats the cheapest method of transmitting serial data over the air? i need 10-15 meter range.

Cheers Guys

You might want to consider VirtualWire--it's been discussed on the forums before.

--Phil.

what are the options for bluetooth? Ive not got a bluetooth arduino, and i only really use it for prototyping anyways. Plan to do a PCB, and code a tiny24 using avr studio4. or maybe IAR

where can i order thoes livewire babys pref in the UK, and how much they gona set me back?

Bluetooth will not be cheap.

You want to search the usual stockists for 433MHz transmitter/receiver modules. I'm guessing this is compatible but YMMV: http://www.maplin.co.uk/Module.aspx?ModuleNo=22965

--Phil.

Cool cheers. just one more question. what have i got to do about the antenna? will just a length of wire do, or is it a bit more complicated? i was looking at the rd3001 transiever.

A length of wire will be more than enough for that short of range.

From memory I think the suggestion is a 17cm piece of wire for the antenna.

--Phil.

Yeah, just wanted to check that. If anybody is intrested you can get the rd3001 tranciever for £6 here: http://cgi.ebay.co.uk/RF-Monolithics-DR3001-433MHz-Data-Transceiver-Module_W0QQitemZ120341284294QQcmdZViewItemQQptZUK_BOI_Industrial_Automation_Control_ET?hash=item120341284294&_trksid=p3286.c0.m14&_trkparms=72%3A1301|66%3A2|65%3A12|39%3A1|240%3A1318

Ive got my self 8, got all sort or ideas for projects, hopefully i'll get the time!

A rule of thumb for a starting point is 1/4 of the wavelength, and the wavelength is the inverse of the frequency divided by the speed of light. So, for a 434MHz module, 1 / (434x106Hz / 3x108m/s)=0.69m. 1/4 of that is indeed ~17cm.

Technically you need to multiply that by the velocity factor of the wire, but for this application that's probably an unnecessary refinement. :slight_smile:

Just in case you ever use, say, a 315MHz module or a 900MHz module, this formula will get you to an appropriate 1/4 wave antenna.

Hams (ARRL) have a handy little formula and a constant that reduces the math a bit (and gives an answer in inches for us Americans), but since I'd already cluttered my brain remembering the speed of light, I didn't bother memorizing it. I just do the math when I need to...

-j

lol totally, i'm doing electronics at college, but they also feel the need to teach us things like how to work out how long it will take a falling item to hit the ground. Not completly usless i must admin, but when the same letters are used in mechanical engineering and electronics, it is a tad confusing!

Have a choice of 121 different systems.

or sorted by price:-

All much too complicated. For reliable communication up to 30 meters use Xbee. Cheap, easy and reliable. Code for Xbee communication can be found on the Arduino site.

Cheap, easy and reliable.

Not quite - pick two.

The cheapest Xbee I turned up in 27 seconds worth of searching is a 1mW model at Sparkfun for US$30, so US$60 for a complete com link.

If you can live with a one way link, a TX/RX pair of the modules in question can be had for US$9 (sparkfun again). Even two pairs for a complete bidirectional link are only US$18, 30% the price of a minimal Xbee solution.

Xbee looks easy and reliable, but does not take first place in the "cheap" category.

-j