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building a remote control — Parallax Forums

building a remote control

Lord VaderLord Vader Posts: 24
edited 2007-01-14 03:10 in General Discussion
For a project I am working on I want to build a remote control similar to the ones used in hobby RC stuff.
I would like the remote to have channel mixing so it can control multiple servos.
Does any one know of were I could find information on this kind of thing, ex. Books, internet articles.
Right now I am in the process of getting my amateur radio license so thats not a problem.
Any help on the subject would be great.

Thanks,
Joshua Terrasas

Comments

  • GadgetmanGadgetman Posts: 2,436
    edited 2007-01-12 10:49
    Essentially, instead of buying an of-the-shelf RC set, you want to build one yourself?

    Why?

    I can't imagine that anything you build is more compact or cheaper than a pre-made one.
    Pre-made ones also comes with the nifty funtion that you won't be carried off the field to be tarred and feathered because interference caused someone else's materwork to take a nosedive into tarmac...

    So, you want to control a couple of servos, even do a bit of mixing.
    What's the range you'll be operating this on, and how many servos?
    (Tell us a bit more about your project)

    You may be able to use a couple of EB500 (BlueTooth) modules to work as transmitters and receivers, and have a microcontroller in the transmitter read off the stick positions using AD-conversion, and send them over the link to another microcontroller which then calculates the servo-responses and effects them.

    No need to do all that messy Analog RF stuff...
    It'll also give as many 'channels' as you could dream off...

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  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2007-01-12 17:12
    A year or so ago, there was a thread here that discussed this topic. Everything about this technology has been really reduced to one or two chips that care the six channels. Joysticks have nearly disappeared as separate components, so you might find those to be quite expensive or poor quality.

    R/F can be quite troublesome to get right. Circuits must be tuned. In a factory, it is a quite routine chore, but if you don't have the frequency counter and oscilloscope; it can be quite costly to get started.

    If you want to really save money, it would be easier to buy an R/C packaged deal with Transmitter and Airplane.

    And the newer R/C Transmitters will interface with your computer to practise flying on bad weather days.

    If you cannot afford new -- try EBay for used. I am sure you will find yourself much happier with the factory made devices. Or try your local R/C club for a hand-me-down.

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    "If you want more fiber, eat the package.· Not enough?· Eat the manual."········
    ···················· Tropical regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan
  • Lord VaderLord Vader Posts: 24
    edited 2007-01-12 19:21
    The reason I want to make my own is mainly for educational purposes, I want to know radio and remote controls work. I realize that I wont be able to make my own remote that is better than the ones made commercially, but I still would like to know how they work. Thanks for all the replies.

    Joshua Terrasas
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2007-01-12 20:17
    Lord Vader,
    ·
    The first thing you need to do is find or build a reliable transmitter/ receiver pair.· From there, you can cook up just about any data transmission
    scheme you want.· There are several to choose from, or you can implement a derivative of your own.· One of my favorites is MFM (Modified
    Frequency Modulation) which is a method used to store information on floppy drives for PC's.· Another is PSK (Phase Shift Keying) which usually
    refers to Phase Shifting a sine wave.... when applied to a digital signal it looks more·like PWK (Pulse Width Keying).· In this case you modulate
    both the top and bottom·portions of your wave to transmit data.· Another form of this would be Fractional Bit Period Serial Communication.
    ·
    First things first though... find a reliable transmitter and receiver pair and·expand from there.
    ·
    ·


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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • Lord VaderLord Vader Posts: 24
    edited 2007-01-13 04:11
    So if I get a transmitter and receiver I can apply channel mixing to the signal to control multiple servos?
    Any suggestions on transmitters and receivers to buy?
    One more question guys (once again, thanks for all your help so far).
    I have book with a bunch projects for RF transmitters that mainly talks about video transmitters,
    can I use a transmitter from the book for data transmission? I am assuming it should work fine but I just wanted to make sure.

    Thanks,
    Joshua Terrasas
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2007-01-13 05:47
    Lord Vader,
    you said...
    So if I get a transmitter and receiver I can apply channel mixing to the signal to control multiple servos?

    Essentially yes, the channels will need to be converted from analog to digital, and then sent by your method of choice. Any "mixing" between channels can be done within software.


    you said...
    Any suggestions on transmitters and receivers to buy?

    Here is a link to some of our digital RF Transmitter/Receiver modules. These are essentially "raw" devices, meaning that you send a logic HIGH in the transmitter and you "see" a logic HIGH on the receiver. Likewise with a logic LOW. Any signal conditioning or error checking must be done by you. This leaves them open to numerous transmission techniques that you can apply.

    www.parallax.com/detail.asp?product_id=27980 - Transmitter
    www.parallax.com/detail.asp?product_id=27981 - Receiver
    www.parallax.com/detail.asp?product_id=28180 - Transmitter/Receiver package


    you said...
    One more question guys (once again, thanks for all your help so far). I have book with a bunch projects for RF transmitters that mainly talks about video transmitters, can I use a transmitter from the book for data transmission? I am assuming it should work fine but I just wanted to make sure.

    It probably would, but I can't answer that for sure without more information about the design. If the circuit is designed for video, then you would be wasting allot of bandwidth if you were just using it for RC communication.

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • Lord VaderLord Vader Posts: 24
    edited 2007-01-13 06:19
    The remote is for an RC application that would act as a manual override to the autonomous flight. As long the basic concept of the circuits in the book I have will work, that should be a good enough start for me to design one for my application.
    What I'll probably do is use the Parallax transmitters and receivers for now until I can design my own long range one.

    Thanks for all the help,
    Joshua Terrasas
  • BobalouBobalou Posts: 7
    edited 2007-01-13 22:58
    Beau said...
    Here is a link to some of our digital RF Transmitter/Receiver modules.

    I'm new to this, but am a long time Ham. I notice these things operate within the 70cm Ham Band. Is a license required to use them, or is there some exception that allows them to operate without a license. i.e., maybe the limited range?

    Bob
    KK6QQ
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2007-01-14 03:10
    Bobalou,

    Page 8 of the Transmitter's pdf document....

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
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