Available shields and shield ideas

You may want to include this one as well:

RG (dual color) 8x8 LED matrix shield

Yep, any that you can think of should be included...

:smiley:

Mowcius

I think the Arduino Mega would be a nice and cheap platform for WSN research. What it lacks is a good radio shield however. The xbees are relatively expensive, especially as you buy a separate shield for it. They're also not really interesting for researchers as they already have all the routing built-in.

I'd like to see something like an nRF905, CC24xx or CC25xx on a shield with both a trace antenna and a connector for an external one. Adding a few extra leds, buttons, and maybe screw terminals or headers for sensors wouldn't hurt either.

If you can add a few more details on your idea then I can have a look and maybe do a first production run of a few. I have also been looking for a cheaper alternative to the Xbee...

Mowcius

I know of a CC2500 shield that works much like the xbee shield in that it is designed to carry separate board which has the actual radio chip on it (in Dutch):

http://static.knutsel.org/kits/CC2500_Arduino_Shield_v03/

I would rather have a shield which doesn't rely on a separate board. A temperature sensor and a few leds/buttons would be nice as well. Apart from that I'm not sure what kind of details you're after - I'm not an electrical engineer :3

Ok, I have been having a look and I am wondering what you are wanting on the other end. Say there was an arduino shield with a transmitter/receiver on it, what would you want for the 'other end of the link.

A 5v serial board? A USB (serial) transmitter/receiver?
An option of another arduino board/boards so data from one can be ttransmitted to more than one other arduino?

Also what kind of range would be good? I think that 100m max with only a few kb (5-10) data transfer speed would be satisfactory for most uses. But I presume that from your recommendations you were wanting something more substantial say 100kbs correct?

Have you got a site/sites that the modules can be purchased from at a competetive price for a small order?

Mowcius

Ah, I'm getting your point now. I'm looking mostly for arduino<->arduino communication. I want to build a network of several arduino mega based sensor nodes that form an ad-hoc, multi-hop wireless network. For integration with other networks I would probably either hook an arduino with said radio shield up to a PC via serial or use an ethernet/wifi/bluetooth shield.

Applications are mostly research, such as development of routing protocols and WSN middleware. The typical WSN application is the gathering of sensor information (temperature, humidity, soil moisture, wind speed, that type of thing) and send it over some ad-hoc, multi-hop network to a base station. There exist several hardware platforms that allow for this, using mostly CC1000, CC2420, or nRF905 packet radios in combination with either an MSP430 or AVR MCU, some leds/buttons and maybe a temperature sensor. These are quite expensive however, often around 100 USD for a single node. Since arduino mega's are cheap to buy a shield for WSN research would allow for larger testbeds at constant cost. There exists a node that integrates an arduino (328) with an xbee called 'squidbee': http://www.libelium.com/squidbee/index.php?index.php. I want something that's cheaper and with a bigger MCU (32kB program flash is not enough for our purposes).

As for the chips, mouser carries the cc2500 at a unit price of $3.33, $2.67 and $2.08 USD for 1, 25, and 100 units respectively. Atm they have 800+ in stock.

Mouser link: http://nl.mouser.com/ProductDetail/Texas-Instruments/CC2500RTK/?qs=sGAEpiMZZMvQdkNSkjJ8MkrqFaehF5L4
CC2500 datasheet: http://focus.ti.com/lit/ds/symlink/cc2520.pdf

edit: the CC2500 has an 400m line-of-sight range according to the datasheet, bandwidth isn't important for my application (in fact, I'd be in the business of efficiently supporting ultra-low data rates, as in a few packets per minute).

edit2: fyi, the CC2500 uses 3.3v, and communicates over SPI.

I found this:
http://www.quasaruk.co.uk/acatalog/DSQFM-TRX-2.pdf
which is the module used on the board you commented on. It is £5.50 but would be considerably easier to implement on a small scale basis than soldering all the surface mount chips. It would then be 'on board' - permanently soldered on (removing the current connector on it) but would not all be built in to the main board.

From what you have been saying, you seem to know how all this stuff works. I have not done a lot of stuff with wireless networks so if you know what components you are wanting and if you have a vague idea of how you want them implemented together (multiplexing sensors on minimal pins or on seperate pins etc) then I will have a play on EAGLE and see what I can come up with...

I'll reply to anything else you say in a bit - i'm just going to have lunch!

Mowcius

Also, are you looking to log data to the shield? MicroSD/EEPROM on board (256kbit EEPROM would be easy to add)

Mowcius

Right, the cafe's a bit full so I'll have lunch later...

Ok, looking at that CC2500 chip, I will need to add a logic level converter on board because it is 3.3v rather than the Mega/duemilanove's 5v. I am taking a closer look at the shield page you linkied to...

Mowcius

I guess that if I wanted one of these shields I would simply have 100+ made and populated. In your experience, could this be done for a unit price of <20 USD including parts (CC2500 chip, headers, resistors, etc) ?

And storage? Well a microSD card slot wouldn't add too much to the unit price I suppose.

I see the Arduino Mega has a 3.3v pin, reading the specs it says it's coming from the FTDI chip. Is that only under power when the USB is connected?

Again, I'm just a computer scientist, so I'm just guessing here :wink:

In my experience, boards can be produced for about $5 for arduino sized board. (much less for a second run from ourpcb - but that's another topic completely). Deal with board pricing when you get there in my experience.

Are you including somone populating the board or are you thinking that you would solder them yourself?

The components end everything obviously depend on how cheap you can get them. I would have thought that with that wireless module and a microSD slot, EEPROM, headers, resistors and all that other stuff, you could easily build the board for less than $20 if you are making 100. I would have thought that you could do about 25 for less than $20 per board also...

Mowcius

I see the Arduino Mega has a 3.3v pin, reading the specs it says it's coming from the FTDI chip. Is that only under power when the USB is connected?

Again, I'm just a computer scientist, so I'm just guessing here

As far as I understand it, it is just a 3.3v power pin, not a 3.3v data pin. For those wireless chips you need 3.3v digital data rather than the 5v digital data that the arduino gives out. So you then need a logic level converter...

Mowcius

I would like to have the boards populated in the factory, and I'm still talking about having the CC2500 on the shield itself, so i'm supposing you'd need a machine to do that?

$20 usd is fine, that's roughly 12 pounds uk or 13.5 euro. At that price point you could have a operational sensor node for 45+20 usd, or ~44 euro.

edit:

As far as I understand it, it is just a 3.3v power pin, not a 3.3v data pin. For those wireless chips you need 3.3v digital data rather than the 5v digital data that the arduino gives out. So you then need a logic level converter...

makes sense, thanks.

I would like to have the boards populated in the factory, and I'm still talking about having the CC2500 on the shield itself, so i'm supposing you'd need a machine to do that?

If you have a company in mind then they would normally do eveything, surface mount and all. You don't necessarily need a machine to do it...

$20 usd is fine, that's roughly 12 pounds uk or 13.5 euro. At that price point you could have a operational sensor node for 45+20 usd, or ~44 euro.

If you are interested in getting the cheapest sensor node you can then you could add the atmega1280 chip to the board and have it all in one...

Assembly is obviously much more expensive than just getting the boards made...

If you have the board design and parts list then you can contact ourpcb to get a quote. I have no experience of their assembly service but their production service and quality is pretty good...

You may have difficulties getting a board made and assembled for less than $20 but i'm not sure. If you did an all in one board then you could do it cheaper than $65...

Mowcius

If you are interested in getting the cheapest sensor node you can then you could add the atmega1280 chip to the board and have it all in one...

That's always an option, but I would like to still be able to use all the shields available for the arduino platform. It's really nice to be able to walk around with a node and have a little screen with debugging information about the routing tables in the neighbourhood for instance.

I'll have a talk with a couple of my EE buddies and see what they think. I'd probably be interested in an initial run of 25 boards. If they solder all the components for me all I have to do is send them a BOM and eagle drawing? Or should I source the CC2500 chips myself and have it shipped to them? What other steps besides designing the pcb would I need to take to get the final product sitting on my desk?

That's always an option, but I would like to still be able to use all the shields available for the arduino platform. It's really nice to be able to walk around with a node and have a little screen with debugging information about the routing tables in the neighbourhood for instance.

Ok, I see your point, but overall it will probably cost more...

I'll have a talk with a couple of my EE buddies and see what they think. I'd probably be interested in an initial run of 25 boards. If they solder all the components for me all I have to do is send them a BOM and eagle drawing? Or should I source the CC2500 chips myself and have it shipped to them? What other steps besides designing the pcb would I need to take to get the final product sitting on my desk?

You send them gerber files, from eagle and they will send you a quote, it is less for not having lead-free etc. I'm not sure about components and everything. They have a stock of parts and I think that they would buy the CC2500 chips and other components and include it in the final cost...

If you are not sure as to how to get the gerber files then just search it in google. I'm afraid that I will not be able to reply again for about another hour, then I could help...

If you can tell me what components and everything you want then I can probably do a board design for you...

Mowcius

Thanks for all the information! I'll go have a think about what the best option would be.