Please recommend transmitters/receivers

Discussion in 'General Electronics Chat' started by wannaBinventor, Jun 9, 2010.

  1. wannaBinventor

    Thread Starter Member

    Apr 8, 2010
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    I feel like I am at the point that I could start tinkering with wireless control of my projects. The problem is, I have no idea where to start. I have a very basic idea of how I want it to work. I've glanced over serial/parralel conversion, so from what I understand I'm going to use a PIC or some other device to send something like "1..0..1..1..0..1..0..0", to the transmitter, then receiver receives 1 bit at a time, and then the receiver (by wire) sends it into a PIC on the other receiving end where the info is consolodated into 1 byte that I can then use to perform some function (turning on different LEDs, controlling H-bridge, whatever)

    Is this roughly correct?

    Googling just brings up a bunch of mixed junk. A search of my electronics components distributor of choice takes me to line drivers/transmitters and line receivers, which by looking at the datasheet I'm not sure is what I'm looking for.


    Can some1 suggest some particular transmitter, receiver, and/or transciever IC's/modules for me to read up on? Specifically I'm looking for radio, but I'd like some suggestions on IR too.

    Thanks
     
  2. SgtWookie

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    Jul 17, 2007
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  3. nickelflipper

    Active Member

    Jun 2, 2010
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    If you want to hide from all the gruesome details of installing a stack, then use something like the 2.4Ghz Digi XBee or XBee Pro. Simple, and transparent, serial communication is all that is required. Kinda spendy if you dude it up with a 0.1" spaced breakout board (the Xbee has a 2mm pin spacing).

    Saw that a Chinese company has married a cloned 2.4Ghz Microchip transceiver module, with a 24F series PIC, to supposedly do the same. A review for the 2.4Ghz model, and a different but more powerful, distance wise, 915Mhz model. In any case a 2.4Ghz tx/rx will give you high baud rates for short distances, while a 433-915Mhz tx/rx will give low baud rates for longer distances.

    If this is going to be for a rc controlled robot?, then consider a ground based RC transmitter, receiver combo. An example would be a Vex transmitter receiver add on kit, "sometimes" reasonably priced (<$30) on auction sites. Read less time spent on control hardware, more time on microcontroller software.
     
  4. wannaBinventor

    Thread Starter Member

    Apr 8, 2010
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    Thanks Sgt - it seems like they spell out how to interface with other PICs. I may have to look into the 12F675, seems like it could be usefull.

    I'm wondering why they don't have anything in a DIP package on the MC website. That's the only package I've ever worked with, and it's of course just right of the breadboard. The website seems to show a bunch of SSOP, QFN, etc.
     
  5. BMorse

    Senior Member

    Sep 26, 2009
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  6. wannaBinventor

    Thread Starter Member

    Apr 8, 2010
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  7. SgtWookie

    Expert

    Jul 17, 2007
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    The MAX232 simply converts between EIA/TIA-232 (RS-232) signal levels (-12v to 12v) and TTL (0v-5v) signal levels. It is not designed to be an RF transmitter.
     
  8. FastEddie

    Active Member

    Jul 14, 2007
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  9. coldpenguin

    Active Member

    Apr 18, 2010
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    I got a couple of those, and just ordered another 3.
    Was extremely simple to use, the PIC I had just uses it like a 9600 baud UART, and the data drips off the other end into another PIC as a 9600 baud UART.
    I am trying, slowly, to get my project to work, which is running into other problems. The range however, with one unit attached to a PIC and UART at my computer, and the other 15m away in greenhouse, I had to be careful of the orientation of the device, but this might be more to do with the metal in the greenhouse rather than anything else. Up to 10m the range seems AOK

    However, if you are not thinking about serial digital communications, then the lower frequency analog transmitters/receivers are possibly cheaper and longer range.


    BTW. Ebay, from sure electronics, is often cheaper than buying from the sure electronics shop.
    Not entirely sure why.
     
  10. SgtWookie

    Expert

    Jul 17, 2007
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    If the transceivers will be in relatively fixed locations, you could use a simple and cheap corner reflector made from aluminum foil and a couple of boxes. Just put aluminum foil on two sides of the boxes, and then position them like this:

    [​IMG]

    Looking down from the top of it, the "L" shapes are the aluminum foil covered sides of the box, and the dots are the vertical antennas. Each reflector will give roughly 10dB gain.
     
  11. nickelflipper

    Active Member

    Jun 2, 2010
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    Good insights to those modules, Thanks for sharing!

    Questions, can the baud rate be changed?, is there a desktop interface?

    I am jealous, and stuck trying to make the bare MRF24J40MA modules that I have work. What a pain:(.
     
  12. wannaBinventor

    Thread Starter Member

    Apr 8, 2010
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    Thanks for all the further advice guys - it is much appreciated.

    Sgt. Wookie - Can that be scaled down to say a couple inches of surface area with a small antenna an still give me some worthwile gain?

    Also, is really the advantage of the module over the stand-alone chip really there other than getting a few passives pre-placed and it all being soldered up on a PCB?

    The SURE does seem like it has some relative bang for buck, and I would probably just buy it if I was building a robot to play with, but my long term goal is to market this little invention - which means I don't mind taking the long road as long as it leads to a lower cost unit later. With that said, it may be beneficial for me to buy it so I can crawl before I walk with this RF stuff. (The walk being a stand-alone RF IC).

    From looking @ the datasheets provided by MicroChip, the MRF89XA and the MRF49XA's do not look like they are THAT difficult to wire up and interface to the PIC - just a bit tedious. It seems like one of those things that I could get going with some deligence and perhaps the help of a few gurus here. My biggest limitation is that in terms of prototyping, I'm not confident that I can solder a TSSOP or QFN package (the only packages those come in). I've found a few adapters that are just PCBs that let me solder on the IC and then use it as DIP for my breadboard, but as I said before I'm certain I'd be accidently soldering 4 leads at once and/or burning the chips up.
     
  13. coldpenguin

    Active Member

    Apr 18, 2010
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    Microchip used to do a daughter card for the mrf24j40, which had the chip onboard, and antenna, and it came out with two single-in-line connections (one pin one socket).
    This might be a suitable way for you to go. No need to be doing the hard soldering so long as you can get suitable connectors, and you can program direct to the chip.
    However, when I got mine ~4 years ago, they were $14 a piece.
    But, once you have a working design, and have practiced your soldering, you could easily create your own design around it (as your code would already be interfacing with the chip directly).
    These are the same chips that the SURE pcbs use.

    The baud rate is maximum of 9600 unfortunately, according to the sure site. I am not sure why though, unless they couldn't get higher without also including a crystal
    It looks like all of their product have this limitation. In theory you can re-program the chip on-board, it has an icd pinout
     
  14. coldpenguin

    Active Member

    Apr 18, 2010
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