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Author Topic: Cheap Wifi/Bluetooth  (Read 4187 times)

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Offline Rand alThorTopic starter

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Cheap Wifi/Bluetooth
« on: June 12, 2008, 12:58:48 AM »
Hello. I'm planning on doing my own robot. It will have a claw or two, deferential drive wheels (or tracks if I can find them cheap), a microphone, a speaker, and a video camera. I also want to be able to program it (i guess I'm going to have to make a circuit board to control the api... I have a floppy drive already salvaged and ready to go), and maybe upload/download files. And of course I want it to all be wireless. Bluetooth looks really/pretty cool, but the prices look like they'd eat me alive. Is there any way I could find a cheap bluetooth transceiver and USB adapter? Alternately, how can I just receive/transmit signals to and from my robot (wirelessly), like as a "send to" type of deal? and how would I make it so I can control it with the computer? I'm ready to program, being pretty experienced in that area.

Also, couldn't i use IREDs and detectors to transmit signals? would they go through walls?

Offline airman00

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Re: Cheap Wifi/Bluetooth
« Reply #1 on: June 12, 2008, 06:45:02 AM »
how big of a robot , because you could use an old laptop with wifi

IR is a wavelength of light , so they cannot go through drywall walls
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Offline krich

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Re: Cheap Wifi/Bluetooth
« Reply #2 on: June 12, 2008, 12:14:24 PM »
Cheap is relative.

If you have a few hundred bucks to blow, then a $50 module from Sparkfun is cheap.

If you are scrounging motors from free printers and VCRs you found on Craigslist, anything over "free" is not cheap.

Most of us are somewhere in the middle, scrounging where we can and spending cash on those things that "just need to work".  Any RF circuit, I've found, is in the "it just needs to work" category for me.  Home built RF solutions can plagued with all kinds of problems that will suck up all your resources and time.  Why deal with that, when you can spend $50 and get something that you know will work and, as is the case with most Sparkfun wireless modules, is very well documented.

I've done a lot of research into what wireless modules I want to work with.  I haven't pulled the trigger yet, but here's my short list:

The most simple wireless connections are those that just extend a serial port from your computer to the device:
*  RF Link at Sparkfun runs at either 2400 or 4800 baud.  Super easy to use.  Come in transmitter/receiver pairs, so buy two for duplex communication.  $10 a pair.  You'll have to build a board to hook the computer to it's radios.
*  The Nordic based devices, also at Sparkfun, run at a higher rate (~1Mbps in bursts).  ~$20-30 for one transceiver.  You'll need two and you'll have to figure out how to hook it up to your computer (probably just a MAX233 or something).
*  BlueSMiRF, at Sparkfun, are bluetooth devices that have a serial port profile (among others, I think...).  Super easy on the PC side, not too hard on the robot side.  They run about $50-65.  You'll only need one.

There are more advanced, higher bandwidth modules out there, namely:
*  Any of the ZigBee, 802.15.4 modules, there are several vendors.  The one at Sparkfun is ~$25 for the robot side, but I'm unclear on what (and how much) you need on the PC side of things.  There are development kits availble for a few hundred bucks.   :o
*  Lantronix has a line of 802.11b/g Wireless LAN adapters called MatchPort b/g.  These are serial to WLAN modules.  I think they have some capabilities to serve up custom web pages, so you could potentially do a web interface on the robot.  They are about $90-100 though.  Avoid the Matchport AR, it's an Ethernet module with the same pinout and footprint as the wireless ones.  Allows you to develop your solution wired before going wireless by simply swapping the module.
*  I have yet to find a good WLAN module with raw packet capabilities but, to be honest, I haven't looked to hard at that...yet...  I'm still trying to figure out how to work my voltmeter.  :-\


Offline Rand alThorTopic starter

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Re: Cheap Wifi/Bluetooth
« Reply #3 on: June 13, 2008, 06:46:01 PM »
I guess I'm near (or at ) the bottom of the "middle" of the scale. I like to and try to scavenge for everything I can... right now, all that I own parts-wise are from a dissected tv and printer. $10 wouldn't be too bad, but how/would I be able to tranmitt files, esp. audio and video, and what protocols do I need to use?

Offline Admin

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Re: Cheap Wifi/Bluetooth
« Reply #4 on: June 18, 2008, 09:27:27 AM »
hmmm why would your robot need to transmit files? what type of files?

Offline Rand alThorTopic starter

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Re: Cheap Wifi/Bluetooth
« Reply #5 on: June 18, 2008, 10:29:36 PM »
Well, as I (apparently didn't mention in this thread), I am an experienced programmer (in computers, not robots), and so I'm planning on making a program from which I can remotely control the robot. Ideally, I would like have it play a wave file for sound, stream record sound and video to my hard drive, etc. I did find a schematic for a "remote loudspeaker via ir link" in a library book I checked out, but that brings back my problems with IR. I thought about a device that will transmit signals from my bedroom through the walls to a transceiver in the family room that will transceiver IR signals to my robots. I have noticed that remotes can work from upstairs, so I don't think there is any problem with that idea. I plan to do it using inductors, since i don't think Mom would appreciate me drilling holes in the walls :P.

But the problem is, I don't really how inductors work/how to use them/this is possible. I understand the theory of it, how they temporarily store energy as magnetism, but I don't understand any applications for them in real-world time.

But I suppose if it came down to transmitting actuall files, I guess I could program it to just stream audio/video, but I need a pretty good bandwith to do that, don't I? Unless i use flash memory or something like that.

Offline Admin

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Re: Cheap Wifi/Bluetooth
« Reply #6 on: June 21, 2008, 04:58:23 PM »
Just to take this from a different angle, how about low-tech analog techniques? Wireless sound transfer has been around for over a century, and wireless video transfer has been around more than half a century. ;D

Of course its neat to do it to do it all from your laptop over one datastream . . . but is it neccessary for your goals?

Anyway, it almost sounds like my robot . . .
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Offline izua

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Re: Cheap Wifi/Bluetooth
« Reply #7 on: June 21, 2008, 06:57:31 PM »
You can't get so much data (like video, or sound) in real time over an IR link. You'll have to either trade time (send 1 sec of 200x200 video in 5 seconds) or quality (send 4x4 pixels per second, every second).
As admin says, analog modulation of analog signals is a very common technique (TV, radio :P). And analog cameras are cheaper than their digital coutnerparts. you will need some kind of decoder at the computer (like those tv-tuner things). Or you can watch your robot, live, on TV (over a short distance, of course)

On the other hand, I'd like to know if there is some chip for wi-fi 802.11b/g communication. Like ENC28J60 is out there for ethernet. Or a module. Or maybe a bluetooth thingy.
« Last Edit: June 21, 2008, 06:58:37 PM by izua »
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Offline Rand alThorTopic starter

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Re: Cheap Wifi/Bluetooth
« Reply #8 on: June 21, 2008, 07:10:53 PM »
Quote
Wireless sound transfer has been around for over a century, and wireless video transfer has been around more than half a century.

Well, yeah, I guess so.

But how exactly would I make a radio transciver? I have no clue as to with regular ol' components. Of course, I could get the chip antenna from sparkfun, but I'm kinda pressed for cash rigth now.

Offline izua

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Re: Cheap Wifi/Bluetooth
« Reply #9 on: June 21, 2008, 07:18:19 PM »
you don't. analog radio emitters are cheap enough that everybody can afford one. just get one of those that emits your mp3 player signal for the car radio. this way, you can listen to your robot on the radio.

a beter idea is to use a wireless analog camera (some even have mikes) and get the singal on your tv/computer.
i think there are some modules on sparkfun. it's really the cheapest way.
this is what you're looking for. you can't go cheaper than this. come on, ask your parents, go take round the plate, sell lemonade. 50 bucks is not that much.

also, you need to understand one thing. a transceiver works both way. this way, the main software can reside on your computer. this is expensive. with radio, i mean. i've been planning to do this with infrared, using wireless hubs spread around the house, and use a directional protocol, similar to UDP broadcasting, but with ingress filtering ('cause packets would bounce around the room). you can get transceiver modules from sparkfun, but you would need to decode the data and send that to your computer (a base station). you'd also need to decode data and send it to your robot (mobile platform). and since it's radio, you'd need some error correction.

admin is preparing an IR transceiving tutorial. maybe he'll add some ideas about broadcasting packets using "hubs" between rooms.
« Last Edit: June 21, 2008, 07:21:16 PM by izua »
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Offline Rand alThorTopic starter

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Re: Cheap Wifi/Bluetooth
« Reply #10 on: June 21, 2008, 09:23:09 PM »
Wow. I remember seeing that there but I don't remember it having an antenna and receiver as well. Maybe it is worth the price.

But what the heck does "go take the plate" mean?  ??? ??? ??? ??? ???

Offline izua

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Re: Cheap Wifi/Bluetooth
« Reply #11 on: June 21, 2008, 11:34:48 PM »
we call it "chetă" around here.
like, when you're stuck in a remote city where you arrived moneyless just for a concert, have no place to stay and nothing to eat, what do you do to get a train ticket? do that to get a transceiver or a wireless camera :P
« Last Edit: June 21, 2008, 11:37:19 PM by izua »
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Offline Rand alThorTopic starter

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Re: Cheap Wifi/Bluetooth
« Reply #12 on: June 24, 2008, 12:49:20 AM »
So I'm supposed to hop on a freight train to get a wireless camera? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ( :P :P)

Offline izua

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Re: Cheap Wifi/Bluetooth
« Reply #13 on: June 24, 2008, 01:03:05 AM »
well, you can, if it carries wireless cameras :P
its just asking for stuff, you know.

get some carton paper, and write something about robotics on it :P that, of course, if you don't want to get a job :P
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Offline Rand alThorTopic starter

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Re: Cheap Wifi/Bluetooth
« Reply #14 on: June 24, 2008, 01:10:55 AM »
Ahh... asking..I'm good at that. My family and I are going to see the relatives in  Utah for about a month, so I'm going to take Admin's advice and "beg beg beg" around.

Offline Admin

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Re: Cheap Wifi/Bluetooth
« Reply #15 on: July 05, 2008, 07:38:24 AM »
Quote
admin is preparing an IR transceiving tutorial. maybe he'll add some ideas about broadcasting packets using "hubs" between rooms.
It can only do 115.2kbps, with a range of only 2-3 meters, so I wouldn't recommend it for audio or video . . .

 


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