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Cheapest Wireless Communication — Parallax Forums

Cheapest Wireless Communication

alexopricealexoprice Posts: 20
edited 2005-02-15 21:14 in Robotics
I've seen several solutions but all costing well over 300 bucks. Thats a little steep for me. Anybody know of anything cheaper, RS232 replacement is easiest i think. any suggestions?

Comments

  • Robert SchwartzRobert Schwartz Posts: 141
    edited 2005-02-11 04:12
    IR Buddy from parallax is 40 for a pair.
  • mojorizingmojorizing Posts: 241
    edited 2005-02-11 05:01
    Siteplayer for $30 and a Linksys wet11 for $60 will get you a couple hundred feet of 802.11b range.

    http://www.siteplayer.com/

    http://www.linksys.com/products/product.asp?grid=33&scid=36&prid=602

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    There are 10 kinds of people in the world.... those that know binary, and those that don't.
  • alexopricealexoprice Posts: 20
    edited 2005-02-11 05:06
    awesome! thanks a lot, never thought of that approach, definately cost effective. Im jsut curius if anybody has tried the Wifi approach, will i experience any difficulty controlling the robot or running programs from the PC? What problems will i encounter becuase it will not be RS232, but ethernet?

    Post Edited (alexoprice) : 2/11/2005 6:49:56 AM GMT
  • mojorizingmojorizing Posts: 241
    edited 2005-02-11 17:38
    The added benefit of using ehternet is the user interface can be easily generated on HTML. The downside is that the siteplayer has little or no security...anybody will have access to it who can sniff out your wireless connection. There are work around for this problem, but that entails some coding in the co-processor.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    There are 10 kinds of people in the world.... those that know binary, and those that don't.
  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-02-11 18:22
    Zigbee (IEEE 802.15.4) http://www.zigbee.org
    is an emerging wireless protocol that can support data transmissions upto 40kbps @900MHz and 250kbps @ 2.4 GHz, the chips are pretty cheap (Chipcon CC2420 is <$4 at mouser, Freescale MC13192 is $4.30 at Future Electronics), tranceiver comparision chart is here http://blogger.xs4all.nl/ivonoorh/articles/4269.aspx though findchips.com doesn't show any stock of tranceivers with integrated MAC availible (meaning you have to do communication stacks). At this point I think it maybe to nascent of a protocol·for the average hobbyist to use,·but all reports are this is a friendly, easy to use standard, and by using the standard frequencies of 900 MHz and 2.4 GHz you can probably pick up ancillary items (such as an antenna) from surplus for other consumer products like cordless phones. Expect to see some plug and play modules using this standard within a year.

    BTW this protocol supports mesh networks (point to point, masterless communication) there is also Wireless USB thats basically the same thing, but only supports supports star topology (dedicated master, slaves can only communicate with master) Supposedly this is easier to write the MAC for therefore W-USB will typically leave this to the programmer to implement.

    Post Edited (Paul Baker) : 2/11/2005 6:32:07 PM GMT
  • inakiinaki Posts: 262
    edited 2005-02-11 20:50
    Have you taken a look at the Parallax Bluetooth Transceiver: Embedded Blue 500·?
    It is sold by Parallax and made by A7.
    You use serial wireless·communication between your robot and any other Bluetooth device. It can reach 200Kbps and 100 meters·which is more than adequate for mobile robots. Implementation is easy on both sides, the robot and any PC/PDA supporting Bluetooth.
    It works very well with Basic Stamps. The·Embedded Blue is sold in several versions,·and there is one for the·AppMod slot.

    ·
  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-02-11 21:27
    He's looking for an inexpensive solution, bot to bot bluetooth using the eb500 would be $200, bot to computer (not already BT enabled) would be $300 (2 eb500, 1 eb600), thats not much of a savings for him. Plus honestly BT is overkill for a stamp (so is 802.11b for the same reason) why use a protocol designed for Mbps when your only capable of transmitting in Kbps? (believe max practical is 38.4k baud, therefore your wasting 100's Kbps in bandwidth)

    heres a zigbee module http://www.eazix.com/products/zigbee/ez-zbm.htm·(maybe you can con them out of a sample or two) Free is pretty cheap right? Like I said this is on the cusp, it will explode very soon, just a little ahead of the curve right now. Oh and these things can operate off of a couple AA's for years using intermittant communications, most modules will consume less than 20mA in full power transmission.

    Post Edited (Paul Baker) : 2/11/2005 9:42:36 PM GMT
  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-02-11 21:58
    I just went sniffing arround on the net and I just can't find any easy to use modules for any RF protocol availible now for less than the eb500, sorry.

    Wait I ran across·some surplus Ericsson BT modules (ROK·101 007) (or it may have been ROK 101 008), now Im pulling my hair out trying to find it again, they were $13 each min order of 10. DERG NABIT I really hate that

    heres someone who used one http://myhome.spu.edu/leverj/archive.htm

    Post Edited (Paul Baker) : 2/11/2005 10:20:22 PM GMT
  • SPENCESPENCE Posts: 204
    edited 2005-02-11 22:13
    http://www.aircable.net/AIRcable/serial.html

    EACH $69 + $5 FOR WALL WART

    A PAIR, 1 MALE AND ONE FEMALE CONNECTORS AND 2 WALL WARTS
    DB-9. THEY DO RUN BLUETOOTH FREQUENCYS. EASY TO SET UP. TAKE A LOOK AT THEM......

    I USE A PAIR HERE BETWEEN 2 PC'S AND ALSO BEWEEN A LAPTOP AND A PACKET TNC.

    IF IT IS MORE CONVENIENT, YOU CAN USE 2 MALE OR 2 FEMALE DB-9'S

    73
    SPENCE
    K4KEP
  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-02-12 04:27
    HA YES I FOUND SOME (of course its at a site I frequent, but I've never looked for wireless modules)

    www.sparkfun.com

    Wireless Communication Tab, they've got all sorts of modules for cheap too, and usually have a matching breakout board if the pins are not .100" spacing. If you don't need two way communication they have a transmitter and receiver for <$12, hell for that price you can buy two if you need two way communications (id get different two different frequencies to get full baud) If you go that route Id get the better ones for $17.95, those are based on SAW filters which exhibit·much better frequency stability than LC based transmitter/receivers (though they use ASK which isn't as good as FSK, think AM vs FM)

    My personal fav is the "High Speed Low-Cost Tranceivers - 2.4GHz with Built-In Antenna" for $19.95 apiece and the $0.95 adapter board. They don't have any speed requirements for loading/unloading the data, but bursts the info from one unit to the other when the transmit·bit is set. And the range? 280m @250Kbps ; 150m @1Mbps not too shabby!

    Post Edited (Paul Baker) : 2/12/2005 4:42:27 AM GMT
  • alexopricealexoprice Posts: 20
    edited 2005-02-12 20:50
    This is great, now i have many options, and much cheaper than i thought i could get. Both the air cable looks good and spark fun has a bunch of cheap choices, just have to do some reading and purchasing now. Thanks a lot guys.
  • steve_bsteve_b Posts: 1,563
    edited 2005-02-12 21:55
    Paul, have you used any of their RF gear?· or have heard of anyone?!

    The prices are certainly what hobbiests like....but I'm interested in ease of use and how well they work (specs ARE just specs...not real life).



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    ·

    Steve
    http://members.rogers.com/steve.brady
    "Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
  • alexopricealexoprice Posts: 20
    edited 2005-02-12 22:17
    I was thinking that the aircable system looks the easiest but it only has a range of 10m, would be nice to have a little more room to roam. The High speed low cost trancievers from sparkfun.com look great, although it looks like they are only half-duplex. But they do not look as easy to use, has anybody used anything like this or can offer help with setting this up? because the pricing is great - alex
  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-02-13 05:47
    Like I said, I haven't had an application which requires a wireless module as of yet, so I cannot speak of the quality of those products. I am about to purchase thier SD/MMC breakout board, and I was contemplating using thier pcb service. I sent a couple inquiries regarding the pcb service and they were prompt and helpful and even pointed me to another vendor they thought would better suit my needs. While this does not specifically answer your question, it does seem to bode well with the type of service you may expect from them.

    In general if I were to choose a wireless module from them I would probably not choose thier cheapest module for two reasons. First an LC controlled oscillator is subject to frequency drift more than other types of oscillators (mainly the inductor). I found this out the hard way when I picked up a cheapy FM transmitter that used an air coil inductor. Trying to get it to a frequency that was unused and easily findable was difficult, plus its proximity to metal, water and the human body cause the frequency to drift. Additionally the frequency drifted with time and temperature. Second I would choose some modulation other than amplitude (ASK) as you know AM radio is pitifuly and subject to all types of interference, though digital ASK would have better results than analog ASK.

    I would choose a module that does frequency shift keying (FSK) or some varient of phase shift keying (PSK) they are much more robust in the presence of noise. I would also choose a standard frequency (900MHz or 2.4GHz) because there are so many devices which operate on these frequencies, for a given price a much higher quality oscillator can be incorperated (the whole supply and demand thing). While there are a number of devices which operate on these frequencies, both the above frequencies have multiple channels possible in the band (and I would choose a module that permits changing which channel of operation) this enable flexibility in actual operating environment.

    With all that said I would choose one of the first three or the last, the third being my favorite. The only drawback I potentially see with that one is that the antenna is integrated meaning I can't upgrade to a better one if I wanted to, but honestly it wouldn't deter me from choosing seeing as how far they claim the line of sight communication is, I don't think it would be an issue.

    I would stongly suggest reading the literature provided for the various modules. While this isn't a foolproof method for choosing a product, it can give you better insight on the quality of the product and its ease of use. (I have never encountered a situation where the documents were excellently written and the product was sub-standard)

    Paul

    Post Edited (Paul Baker) : 2/13/2005 5:50:07 AM GMT
  • GadgetmanGadgetman Posts: 2,436
    edited 2005-02-14 23:24
    Paul Baker said...
    He's looking for an inexpensive solution, bot to bot bluetooth using the eb500 would be $200, bot to computer (not already BT enabled) would be $300 (2 eb500, 1 eb600), thats not much of a savings for him. Plus honestly BT is overkill for a stamp (so is 802.11b for the same reason) why use a protocol designed for Mbps when your only capable of transmitting in Kbps? (believe max practical is 38.4k baud, therefore your wasting 100's Kbps in bandwidth)

    There's no need to use the eb500/eb600 combo on a PC. Most $25 - $50 USB-BT adapters will also work fine as they usually installs virtual serial ports on the PC.(Note that some of these adapters are short range models)
    The only reason to use the eb500/eb600 is if the PC doesn't have USB ports or if you can't run Windows or another OS with USB and BT support.

    As for wasted capacity...
    That's another way of saying 'prepared for future expansion'...

    smile.gif
  • jonnyhkjonnyhk Posts: 4
    edited 2005-02-15 21:14
    Hello

    I'm try to hang on to this place. I'm new with stamp, want to make some wireless sensor. 5-6 sensor ( temp - current, etc ) then I want to logg this sensor remote-less.
    I also find a lot of compoment, but I'm sure some have don it befor.

    Thank's
    Jonny K
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