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Cheap wireless (RF) receiver/transmitter solution?

Discussion in 'Electronic Basics' started by Phantoz, Dec 14, 2004.

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  1. Phantoz

    Phantoz Guest


    I'm in a situation where I would like to buy (or build, prefferably the
    former since I have little to no skills in electronics) a large number
    (perhaps few to start with, but scaling up to 100 or so) rf
    receiver/transmitters. I would like to use these in an academic setting,
    where each student in a classroom has the device and can use it to indicate
    a choice in a multiple choice quiz (live, during the class). The only
    requirements are that the devices have some sort of unique signature to map
    to a particular student (though simple attacks to this like giving their
    device to another student are not an issue atm), as well as that the device
    allow the student to choose one of four options, and work at an acceptable
    range (say, 20-25 meters). I would like to translate the results real time
    to some comodity pc hardware.

    The key, of course, on an academic budget is cheap. Similar experiments
    have been done with things like pocket pcs, but we have no where near the
    budget for that.

    Any suggestions on a place to look for this, or pointers on how to build?

    Thanks in advance,

  2. Rich Grise

    Rich Grise Guest

    Get some undergrads to wire a pushbutton array to all the seats, like they
    do on those TV shows where everybody votes. Better yet, call one of the TV
    show production outfits and find out how they do it.

    Good Luck!
  3. Why do you need radio communication for distances of 25 m ?
    A network of computers and a simple program is a lot easier, and the
    students already have laptops, I presume. (The pupils get free laptops
    to use in the schoolwork when then begin school at 6 years age in my
    country, and all classrooms have networks built in already)

    The simple function you described can be realized with a simple directly
    wired circuit, if the students have no laptops. Hardware cost is
    something like 100 dollars.

    In short, forget the radio communication, it is extremely unnecessary for
    the purpose you describe. We are trying to minimize non-important radio
    communication, because there is too much pollution of the radio frequency
  4. John smith

    John smith Guest

    Try this. not a very cheap solution, but it
    works. we've used it succesfully.
    Last I heard, years ago, they were testing a low cost/low tech/simple to use
    unit for K-9, maybe HS students.
    Their signature system is used by large corporations for voting by their
    board. We used it on classrooms.

    BTW, The Fleetwood Co. is better known for making furniture, go figure!

    Also, google for "response system".
  5. Phantoz

    Phantoz Guest

    Great link. Looks exactly what I would like, but the cost is a bit pricey
    ($130US per unit for the cheapest unit type).

    Will keep poking their site though, see what else they might have around...

  6. Phantoz

    Phantoz Guest

    So, the fallback is to create a wired circuit. It requires signifigantly
    more prep time for each class, and makes demonstrations of the technology a
    bit more painful. This is likely how I will go, but thought it wouldn't
    hurt to hit usenet first for some opinions.
    As far as I know, we don't give our 6 year olds laptops yet, but one day
    perhaps (though I hope not). Truthfully, I doubt more than 50% of the
    students would use them at once during the class anyways, due to the size.
    Something of a smaller form factor like a remote control or a car alarm
    remote is what I would be aiming at instead. Pocket pc sized would be
    acceptable but kind of the largest I would be looking at...

  7. Gary Schafer

    Gary Schafer Guest

    Try garage door openers. You can program multiple codes in them and
    they are available with multiple functions.

    Gary K4FMX
  8. CWatters

    CWatters Guest

    One student with a finger on the button would probably block all the other
  9. CWatters

    CWatters Guest

    Mobile phones? Text 1,2,3,or 4 to this free number etc...

    Do a deal with the phone company for special rates to that phone number.
  10. mark thomas

    mark thomas Guest

    The artist formerly known as Phantoz wrote:

    | So, the fallback is to create a wired circuit. It requires signifigantly
    | more prep time for each class, and makes demonstrations of the technology
    | bit more painful. This is likely how I will go, but thought it wouldn't
    | hurt to hit usenet first for some opinions.

    The ultimate logic behind a wired versus wireless system can be identical,
    meaning there would be no increase in prep time required for each class.
    The added pain of demonstrating the wired technology is of little
    consequence compared to the actual functionality of the system, in my

    | Pocket pc sized would be
    | acceptable but kind of the largest I would be looking at...

    I have friends currently developing an in-house solution to a similar
    problem in a corporate environment. Their solution involves a simple
    program running on Blackberries, that parses data into XML format and emails
    it, all transparent to the user.

    A program that uses this email technique running on a similar pocket pc is
    very easy to implement, but of course the cost of the wireless pocket pcs
    and wireless 802.11 router would be too expensive for your budget.

    Your 3 main options are to either go with the wired approach, seek
    additional funding, or scrap the idea altogether.
  11. Rich Grise

    Rich Grise Guest

    I don't understand this at all. What's "prep time"? Why does it take
    longer to tell kids, "with the pushbuttons in the little box on your desk,
    select ..." than to tell them, "get out your laptops, start your wireless
    network, log into our system and download the software,..."

    I apparently don't know what "prep time" means in this context.

    And that "demonstrations of the technology" is a complete non-sequitur.
    What is the goal here? To have a multiple-station voting/quiz answer
    thing, or to demonstrate the technology of a multiple-station voting/quiz
    answer thing?

  12. John smith

    John smith Guest

    Yes. they are pricey - now I remember, this was years ago.
    Talk to them, I believe they have special pricing for schools.
    The system works, and they had good customer service (directly from them,
    not the many resellers they had).
    There might still be competition, I kinda remember a British offering or
    some other low tech device.
    I wish I had their names for you. I remember we went through a lot to get
    alternate sources,and there were some, but we went with fleetwood --- their
    furniture is so comfy:)
  13. John smith

    John smith Guest

    A similar problem is Hot/dead spots.
    We had that problem with a system in two adjacent classroms operating in the
    same band.
    You have to make sure you are not in close proximity to a garage opener
    testing ground.
  14. John smith

    John smith Guest

    I'm not a teacher. I'm an engineer who researched the technology at the
    request of teachers,
    many, MANY, teachers that teach for a very LARGE corporation.
    These teachers said they needed a system like the OP requests, I found one
    solution for them - the company also makes furniture.

    The logic behind it is, AFAI remember, similar to what hapened when I went
    to school; the teacher asks
    a question and points to a studnet to answer it - now he knows one student
    got it right/wrong - but what about the rest of the class?
    Nowadays, specially adult learning, you get many people in one room and not
    enough time to querry and interact with everyone.

    This system allows the teacher to prepare a test - project it on big
    screen - querry the class - and immediately see the results for each student
    (honor system). The teacher can analyze the data and find which students did
    not understood the material (concentrate on them) or if the teacher sucks
    and have to explain the concept all over again.

    soap box: Every classroom should have overhead projectors, PC and software
    for presentations, and one such reponse systems, along with the best
    trained/paid profesionals, along with a few other tools... (slide rule and
    yard stick:)
  15. Mike

    Mike Guest

    Since you'd want to do your data capturing on a PC, perhaps an electronic
    unit on each unit equipped with an 802.11 interface that has a unique
    assigned address. Not sure how you'd go about that, but I know that option
    is there.

  16. Wim Ton

    Wim Ton Guest

    Does it have to be RF? When inside one room, IR may be an option as well
    (cheaper and more common)
    The protocol may be complicated: imagine the following situation:
    the first 2 students answer at exactly the same time, so the signal is
    garbled and rejected, the answer of number three comes in on its own, and
    he wins, how unfair ;-)
    This may be solved by sending a timestamp. Desiging such a protocol and
    proving its correctness would be a nice academic assignment.

  17. Wim Ton

    Wim Ton Guest

    We had that problem with a system in two adjacent classroms operating in
    Use IR ?

  18. Mike

    Mike Guest

    As a professional software developer, I can say that a client/server
    environment would be ideal. On the server side, assigning a "test unit" to
    each student is as easy as keying in the serial number of the unit (which
    typically would map the IP). Data capture could be done in just about any
    language supporting socket IO operations. If you (or anyone in the group)
    can figure out how to make such a unit with an 802.11x module, this is
    probably a good candidate.

  19. CWatters

    CWatters Guest

    There are several companies that make this type of system. Speak to
    companies that make "audience response systems" or "quiz show systems".

    You can even rent them if you want.

    Probably too expensive for schools though.

  20. d.wills

    d.wills Guest

    Since you didn't indicate that this was based on some "game" "quick
    response" type situation, I would go the route of IR. A simple handheld
    device for each student, with the output configured to send a serial #
    (uniquely assigned to each student) and then the response (A, B, C ... etc.)
    You could easily place a couple of receivers around the room and have them
    all tied into one PC. A simple display board that gives feedback to the
    students that their response was received would allow them to know whether
    or not their answer has been registered (I am thinking a grid of lights, one
    per student that gets reset with every question, assuming that all students
    are answering every question.) The PC could give immediate feedback to the
    teacher to indicate whether they understood the material, or, if this is a
    true testing situation, would give immediate scores. You would also know
    each student has answered before moving on to the next question.

    I see it as a bunch of IR remotes transmitting to 4 or 5 carefully placed
    receivers, attached to a pc running a fairly simple VB program to tally the

    Now if you are thinking a gaming system of some sort, most of this doesn't
    work (ir is too prone to interference), but since you didn't indicate that,
    I think this will work. The great thing about this layout is you can always
    add remotes and basically have an unlimited supply of unique serial numbers
    or number of answers (10 to 16 with most standard keypads), and can cover a
    larger area by simply adding ir receivers. Each student can keep their own,
    and you can probably build (buy?) them for $3 to $6 each (small board, PIC,
    ir led, crystal, a few discreet components) and write the software in a day
    (or have someone do it for you.)

    Just an opinion

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