Does anyone know a reference design with bill of materials of less than 30US$ for collecting weather data from the Internet eg. Yahoo's and show it on a LCD?

I found many design and dev kits but most of them are too expensive and mainly target tablet, photo frame, internet radio and the like. I just need a slow CPU 50-200Mhz, wifi, and LCD (up to 5", QVGA) or multi-line characters.

I really appreciated any of your feedback.

  • \$\begingroup\$ Using an Arduino with a ethernet shield that get RSS feeds and a simple lcd. Not sure how much total cost and how easy it would be. Obvoisly wireless boosts the price. Maybe somebody else has a good suggestion \$\endgroup\$ – Piotr Kula Jun 8 '11 at 19:51
  • \$\begingroup\$ Thanks ppumkin, I'm google for the Arduino wifi option, looks like element14 has a tutorial about it, but not sure about the price. \$\endgroup\$ – Liam Jun 8 '11 at 20:39
  • \$\begingroup\$ hmm async_labs offer WiShield 2.0 for 60US$ which is not affordable for my project. Any other alternatives, please \$\endgroup\$ – Liam Jun 8 '11 at 20:45
  • \$\begingroup\$ For $30 wifi in low quantities, you may have to buy a chip rather than a module, then you'll need to do the RF circuitry and the drivers. \$\endgroup\$ – Toby Jaffey Jun 8 '11 at 20:48
  • \$\begingroup\$ You can try the cheap 433mhz radio tranciever versions but it will require allot of codding and mucking around. Also depend on the range you want. \$\endgroup\$ – Piotr Kula Jun 8 '11 at 20:50

Your desired spec is a little overpowered and certainly you're not going to get it for less than $30. A 50MHz CPU is waay over the top for a weather readout given that you can connect a 16MHz chip up to Ethernet just as easily. Similarly, a 5" LCD is probably going to run you at least $20 anyway.

If you want 'WiFi', you could cut corners and use a base device plugged in via Ethernet. This would then talk to another module connected to the screen (wherever you want to place it). Ethernet and 2.4GHz transcievers (e.g. Nordic nrf24l01+) are comparatively cheap compared to fully fledged Wifi modules if you build all the circuits from scratch.

You can use a cheap Ethernet chip like the ENC28J60 to connect to the router, you'd then need to either find code or write your own TCP/IP stack. Google yields some application notes, and here is a web server written for an Atmega168. http://en.klinkerstein.m-faq.de/index.php/MicroWebServer. Personally I think you'd be best off just building it from scratch using a bare AVR and an Ethernet controller rather than paying for an Arduino which will negate the point of saving money.

For the receiving end, you'd need another wireless transciever (2.4GHz or radio, your pick), another microcontroller - say an Atmega168 for arguments' sake - which recieves the weather information and displays it. Using a bog standard HD44780 16x4 LCD you could display more than enough information. If you need graphics, pick up a KS108 based screen. Plenty of code and drivers on the web for LCDs.

I would hard code the format into the display micro and when you recieve a weather update, store it in EEPROM. All you'd need is, say for 5 days, 5 values for temp, wind, weather type, etc. 1kB is more than enough space. EEPROM does have a finite r/w limit, but realistically if you update the weather 24 times a day you could still go for years.

You'll probably need to go surface mount to be seriously cheap, and as for a BOM, it's hard to list one without an exact design spec. I would say you'd be looking at around $40 maximum - bear in mind that's less than the cost of some Wifi modules anyway.

NRF2401L (QFN) - $5 each
ATMega168 - $3 each
16x2 LCD - $5 on eBay
ENC28J60 $3

Other components like resistors, caps and so on are negligible compared to the above. You might have to pay a dollar or two for the Ethernet plug and the antennae for the transceivers. Prices were checked on Farnell UK, converted roughly into dollars.

  • 1
    \$\begingroup\$ I found solutions from La Crosse Technology that look really like what you described, Josh. smarthome.com/19417/…. The most important parts are it doesn't need for PC and is low-cost! This is really what I want. Now I need to learn how to build the hardware or searching for one. Thanks for the detailed hardware components' information, Josh. Tried to vote UP for all you guys but it said I don't have enough reputation yet :). Really helpful answers. \$\endgroup\$ – Liam Jun 10 '11 at 10:34
  • \$\begingroup\$ Yea that is really the best answer as its the cheapest way. Allot of debugging and codding.. but yea - that's the world of prototyping....the 2.4ghz can be replaced with cheap radio stuff. \$\endgroup\$ – Piotr Kula Jun 10 '11 at 10:52

The Twatch is the right kind of device. But, it's wired ethernet only.

The firmware will need some tweaks - currently it connects to twitter's API over TCP/HTTP and parses JSON.

The parts list doesn't include prices, but the BOM should easily be under $30 in quantity.

Part    Value   Package
IC1     PIC 18F67J60    TQFP-64
C1-3    10uF tantalum capacitor, 10volts+   SMC_A
C4,5    33pF capacitor  0805
C10,11,C14-23   0.1uF capacitor     0805
ICSP    5x 0.1″ male pin header     
J1  2.1mm SMD power jack    SMD
J2  HR911105A ethernet jack     RJ-45
L1, L2  Ferrite bead, 200ma+    0805
NPN1    NPN transistor, 250hfe+, 800ma+     SOT-23
Q1  25MHz SMD crystal   HC49UP
R2(A)   10K single turn trim resistor   3mm SMD or through hole (cheapest)
R3  240 ohms resistor   0805
R4-6    390 ohms resistor   0805
R7  2,260 ohms resistor, 1%     0805
R10-21  10,000 ohms resistor    0805
R30-33  49.9 ohms resistor, 1%  0805
VR1     LDO 3.3volt regulator (LD1117)  TO-220
VR2     7805T 5volt regulator   TO-220
HD44780-LCD     20×4 HD44780 character LCD
  • \$\begingroup\$ That's a really great stuff, Joby, thanks. I'm making an order. This would be exactly what I'm looking for if it has wifi instead and not be limited to 100 times programmed only. \$\endgroup\$ – Liam Jun 8 '11 at 20:13
  • \$\begingroup\$ @Glorindel - it's understandable why you are wanting to do batch fixes, but a lot of these old question you touch would not be allowed on the site if posted today, and calling undeserved attention to them is likely to get them closed. \$\endgroup\$ – Chris Stratton Apr 8 at 19:02

Try this - Broken out from my comments on your question for communications. Dirt cheap and allot of options

Cheap solution using Radio waves (needs something to communicate with on a pc?)

RF Link Transmitter - 434MHz

List of Radio Trancievers

2Kilometre Radio Reciever :)

More expensive but directly connects to your router, gets an IP and you can issue real http GET commands - but will need to be able to parse headers and body.

WIFI b/g 2.4Ghz

Using the 434Mhz Module at 2400bps you could potentially send 300bytes of data per second. So that's roughly 300 ASCII Characters.

I think I calculated it correctly (2400bps / 8 (bits in a byte)) = 300bytes

  • \$\begingroup\$ Cheers ppumkin, the radio solution has great price but doesn't fit my needs regarding the speed. \$\endgroup\$ – Liam Jun 9 '11 at 14:53
  • \$\begingroup\$ Cheers ppumkin, the radio solution has great price but doesn't fit my needs regarding the speed. I looked at the wifi module but it seems to use it I need to build a base board or buy an Arduino as you mentioned which is over my budget, and I really don't know how to make one. So I'm still looking for reference design, with LCD, board, and dev kit, something I can start coding. Thanks! \$\endgroup\$ – Liam Jun 9 '11 at 15:03
  • \$\begingroup\$ I found this one and emailed them but got no feedback yet.cambridgeconsultants.com/news_pr181.html \$\endgroup\$ – Liam Jun 9 '11 at 15:11
  • \$\begingroup\$ What speed do you need? Using these modules all the processing gets done on a pc and sent via serial as text. which at 4800bits per second is almost instant :) The arudino program using one of these is simple and the arudino community has tons of examples \$\endgroup\$ – Piotr Kula Jun 9 '11 at 15:11
  • \$\begingroup\$ Is that not just a radio reciver DAB or something? \$\endgroup\$ – Piotr Kula Jun 9 '11 at 15:12

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