Author Topic: head for walking robot (Read 6705 times)

toastman · « **on:** August 12, 2006, 02:58:59 AM »

hi... I'm new here n also quite new to robotics... I'm currently doing my final year thesis project on the head for a medium size walking robot. So the main thing that I need to do is:
1. to use sensor to detect objects within 1-2 m,
2. then if object is detected, turn on camera and capture an image, send wirelessly to a PC
3. write some software to process the image and determine the object's height
4. based on the height, send some feedbacks to the robot on what to do next

As I said before, I'm kinda new to robotics, and I have a limited budget for my project, so now I'm kinda stuck on what components should I use. I've been doing some researches and plan to use sharp gp2y0a02yk for the sensor. As for the camera, I initially plan to use wireless webcam but the cost certainly not desirable by my supervisor. So I need to find some other alternatives. I read somewhere on using gameboy camera for robotics, but not sure whether I can make use of it and how can I build the wireless communication. I'm really kinda desperate and since it's my final year project. Hope anyone can give me some suggestion.... thanks in advance.

JedOs86 · « **Reply #1 on:** August 12, 2006, 07:06:14 AM »

You meantioned using the camera from a gameboy. Well I think you might be in luck, sites such as www.hackaday.com (they also give links to other mod sites) offer some in depth discussions of using peripheal devices from commercial products such as gameboy. I seem to remember them talking about using a gameboy cam, but not totally sure.

Admin · « **Reply #2 on:** August 12, 2006, 10:37:55 AM »

Wireless cameras + the reciever are going to be expensive. Try E-Bay, I often see a load of them on it for cheap.

toastman · « **Reply #3 on:** August 13, 2006, 05:29:45 AM »

I find this wireless camera on e-bay: http://www.ebay.com.my/viItem?ItemId=140018069600

What do u guyz think bout this one? Can it be used in my project? In my understanding, this camera will transmit wirelessly via usb so image can be viewed on pc. is it correct?

If let say this camera really can be used for my project, I think I still need another wireless connection for feedback from pc to the robot. any suggestion on the circuit to be used?

Oh n thanks for the replies ^^

Admin · « **Reply #4 on:** August 13, 2006, 09:37:50 AM »

What kind of feedback do you need?

toastman · « **Reply #5 on:** August 13, 2006, 10:33:16 AM »

well for initial stage, let say I only need to turn on some leds based on the different height of object detected. Later on, my supervisor kinda want to make it able to control the robot action based on the height of object.

Admin · « **Reply #6 on:** August 13, 2006, 11:23:56 AM »

What is your budget? What you are asking to do will cost you a good $300+

toastman · « **Reply #7 on:** August 13, 2006, 05:54:02 PM »

It's not fixed yet but we're trying to make it as low as possible. So do u think the wireless camera that I found before usable?

Admin · « **Reply #8 on:** August 13, 2006, 09:03:52 PM »

Why do you need a wireless camera? Perhaps you can use a CMUcam2 instead?

Anyway the camera will work, but you would then need to write software to interface with the camera.
And dont ask cause I dont know how! Ive only done it once, and I used source code given to me . . .

To interface with a microcontroller and computer you should use bluetooth wireless modules.

toastman · « **Reply #9 on:** August 18, 2006, 09:27:25 AM »

CMUcam not desirable by my supervisor. Is it possible to use usb webcam instead, and connect it to usb connector on pcb, which will then be connected to microcontroller, then transmitted wirelessly thru a wireless circuit to PC? A lot of programming needed for image acquisition, if do this way, is it? bluetooth should be quite expensive rite compared to rf modules?

Admin · « **Reply #10 on:** August 18, 2006, 09:54:59 AM »

Yes, it is possible. USB has 4 wires: tx, rx, power, and ground. Use a rf transciever to transmit this. Then at the recieving end have another transceiver reconnected to a usb that goes to your computer.

I recommend the easy radio transceiver:
http://www.easy-radio.co.uk/about/index.php?language_id=1

This wireless transmission method requires no software and is very simple, but you still need software to interpret the webcam data into useful information . . .

Quote

bluetooth should be quite expensive rite compared to rf modules?

And bluetooth is a rf module . . .

dunk · « **Reply #11 on:** August 18, 2006, 05:18:06 PM »

sorry to be the bearer of bad news but the easy radio transceivers Admin is talking about will not work carry a USB signal.
they are meant for RS232 serial ports which are quite different from USB.
i have used them successfully for controlling a robot (over the RS232 serial port) but they will not carry anything like the sort of transmission rate you would require for live video.

in a project similar to yours i used a wirless video camera connected to a PC TV tuner card. the picture quality was ok for my purposes (displaying on the robot's controll web page) but you would have to do quite a lot of filtering to get rid of the noise caused by any radio interference if you are going to use it for machine vision.

the wirless USB camera looks like a winner to me.
you are essentially doing the same thing i did with the TV card and wirless camera but with one less component.
i wish they had been on the market when i was building my bot.

dunk.

Admin · « **Reply #12 on:** August 18, 2006, 06:55:45 PM »

But the easy radio takes TTL right? My understanding is that an rs232 signal would fry it, no?

I am clueless of what is transferred with usb tho . . . I guess a bad assumption . . .

dunk · « **Reply #13 on:** August 19, 2006, 06:13:29 AM »

umm, yes.
sorry, i should have been clearer.
if you are going to attach one of the easy radio modules to a PCs (RS232) serial port you will need to use a MAX232 level shifter (or something similar) to convert between the RS232 voltages on the PCs port and the TTL levels on the easy radio module.
it's a fairly simple circuit at the PC end. there is an example of how to do this on the easy radio datasheet.

USB is quite a lot more complicated.
i'm only learning about interfacing to USB devices so can't really be much help here but as a basic overview:
USB equipment is separated into "HOST" and "DEVICE" categories.
the HOSTs controll the USB connection and require a lot of programming. you only really find HOST ports on full-blown computers.
the DEVICEs are anything you can attach to a USB HOST port. these require far less programming and hardware. there are microcontrollers out there with USB DEVICE ports built in. all the USB equipment you plug into your PC (mice, keyboards, webcams, memory sticks, etc) are USB DEVICEs.

there are 2 common USB standards in use on modern computing equipment. USB1.1 and USB2.0.
USB1.1 is an older, low speed implementation.
USB2.0 is newer, high speed.
because USB is backwards compatable you can plug a 1.1 or 2.0 DEVICE into a 2.0 HOST port.
all new PCs ship with 2.0 HOST ports so unless you have a really old computer on your desk, chances are you have USB2.0 on it.
most low speed USB peripherals (like keyboards and mice) use USB1.0 as it's cheaper to manufacture.
things that require high data through put (like webcams and USB hard disks) will use USB2.0.

it is possible for the hobbyist to build USB1.1 devices at home.
here's a very good starting point: http://www.obdev.at/products/avrusb/index.html

i haven't seen anyone out there who has successfully built USB2.0 DEVICEs or any sort of HOST without access to a lab that can produce surface mount boards and a huge amount of work.

dunk.

toastman · « **Reply #14 on:** August 19, 2006, 06:49:36 PM »

thanks a lot for the replies... it's been a lot of help to me ^^ So I'm a bit confuse now... basicallly using usb webcam and build wireless transceiver won't work because the signals of usb and rs232 are different? is there any possiblity to convert the usb signals into rs232?

Quote from: dunk on August 18, 2006, 05:18:06 PM

the wireless USB camera looks like a winner to me.

are u referrring to the wireless camera on e-bay (http://www.ebay.com.my/viItem?ItemId=140018069600) i talked about last time? but with this one i'm confused on how i'm going to control the shutter to open when sensor detects object.

dunk · « **Reply #15 on:** August 19, 2006, 07:40:01 PM »

there is no easy way to send output from a USB webcam to a RS232 port.
like i said, building anything yourself that could read information form a high speed USB device like a camera would be a huge undertaking.

i am indeed talking about the wireless USB camera you saw on ebay.
i know on the Linux operating system there is no shortage of applications that will grab a single jpeg image from a USB camera when you run them.
i have no idea how you intend to decide when to capture an image. presumably you are going to need some sort of wireless sensor feedback to your PC as well as the webcam.

dunk.

toastman · « **Reply #16 on:** August 23, 2006, 11:24:53 AM »

Thank you again for all the helps... I'm still trying to find other possible design for this, but for now I think I'll stick with this idea of using wireless webcam first. So if using the wireless usb webcam, i think i still need wireless transceiver, since the wireless webcam take picture by software means, so i think i need the sensor to send signal to pc when object detected so that the software would start taking picture, process, then send feedback back to the robot. so i find this wireless transceiver circuit... just want to know whether this kind of circuit would be enough to be used in here (http://www.semifluid.com/PIC18LF2550_RF24G_serial.php). And will it be a problem to have one 2.4 GHz wireless link and also one 1.2 GHz wireless link for the webcam?

dunk · « **Reply #17 on:** August 24, 2006, 04:13:12 AM »

yes, the wireless transceiver circuit you link to there would work fine.
it's far more complicated than it needs to be in my opinion though.
i don't understand why he needs a PC serial port link on both modules rather than just a PC at one end and a microcontroller at the other.
the link that site references is far simpler but less well documented:
http://www.istop.com/~micro/electronics/rf.htm

to get that sort of link working, the first thing you want to do is get a microcontroller communicating with a PC's serial port using the microcontroller's UART using a MAX232 buffer to convert between the PC's serial ports (higher) voltages and the micro controller's (lower) voltages.
do a web search for help on this part. there is lots out there. (also search this forum. i've replied to this sort of thing before.)
once you are able to pass information over this link, insert a pair of transceiver modules between the micro controller and the MAX232 chip.
it's fairly straight forward once you have the PC->microcontroller link working.

i really must write an article on this for Admin to post on his site as lots of people ask about this.

as for your question about 2 different radio links on the one project,
yes, that will work fine.
you will need 2 different aerials but as long as both circuits use different frequencies they should play together.

dunk.

Admin · « **Reply #18 on:** August 24, 2006, 07:08:01 AM »

Quote

i really must write an article on this for Admin to post on his site as lots of people ask about this.

I encourage you! I am currently working on a bluetooth tutorial, but I wont go into very much detail on the UART/serial thing.

This is it so far:
http://www.societyofrobots.com/electronics_bluetooth_robot.shtml
But as of this post its like only 20% completed . . . I will also do another tutorial on the transceiver in maybe like 2-3 months from now . . . but if you do a UART/serial/rs232 tutorial that should really help as I can just link to it in future tutorials.

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Author Topic: head for walking robot (Read 6705 times)

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