wireless video transfer - how?

[The_UnforgiveN]

I'm working on a mobile robot which will go on a mixed terrain.

Just tell me how can I stream a video from robot to a nearby pc which in a range of about 100m ... RF? BTW, I will send some commands back to the robot on pc.

Thanks for help

 

[The_UnforgiveN]

By the way, it doesn't necesseraly have to be a video stream. With a color image sensor I can use a few fps to send to the pc

 

[ericwertz]

From what I can tell, the overwhelming majority of wireless video is transferred using "analog" (NTSC) rather than "digital" data formats. The reason for this is pretty much the legacy one where you just take the received signal and plug it into a video monitor. From what I've seen, about 99% of what I've found off-the-shelf fits this model.

If you really need this to go into your PC, then it would seem that you basically need some sort of NTSC video (capture) card/dongle for your PC.

I've seen very little in the way of digital video capture and wireless digital frame transfer.

good luck,
-e

 

[RadioRon]

Why not just use a PC at the robot, equipped with a Wifi card and do the wireless through wifi file transfer or streaming. 100m distance will require directive antennas, but otherwise should be feasible.

 

[The_UnforgiveN]

The robot will not be such big and powered to equip with a laptop.

It doesn't have to be a video transfer, I can transfer still images at 4-5 fps to a laptop. Suggestions?

 

[ericwertz]

Maybe a cheap digital camera with a servo to press the shutter button and an Eye-Fi card.

I think that's the closest you're going to get off-the-shelf. If you want to make your own, you could probably put together something with a wireless module from Digi and an AVRCam (or CMUCam).

You haven't specified either how much you're willing to spend or if you have any skills to put anything together. You should at least do that much when asking for help. If you have $1000, I'm sure someone will do it for you.

-e

 

[ericwertz]

Some examples of people selling things in this space:

https://www.rangevideo.com/
**broken link removed**
**broken link removed**
https://www.superdroidrobots.com/shop/

 

[The_UnforgiveN]

No, I'm not willing to buy a complete set or make someone do it for me.

I'm planning to do some image processing on chip later on, because of that, the circuit should be mine.

With something similar to AVRcam or CMUcam, how can I transmit the images to a computer which will be in a 100m range?

 

[ericwertz]

AVRCam has an accompanying program that runs on the PC that connects to the board with a standard RS-232 cable. The CMUCam probably does too. All you really need to do is to swap out the wired connection for a wireless one. There are a number of products that claim to do this fairly transparently. For example, Digi, as I mentioned earlier.

If you check out their products, you'll find all the keywords you should need to find (a.k.a. Google) other like products. Or alternatively, solutions for building your own. There are a bunch of pretty cheap transmitter/receiver or transceiver pairs that claim to behave like a "virtual wire", sometimes just one-way. With two pairs of these you'd have what you need to roll your own Tx/Rx RS-232 pair. There may/should even be a way to make it one-way only with no handshaking, if you only care about the image data, and don't need/want the return channel for controlling the mobile unit. What you're really looking for is a serial-to-anything-wireless translator. They can be as simple as 315MHx ASK encoded up to standard 802.11 Wi-Fi, depending on your money and power budget.

 

[The_UnforgiveN]

I see, thank you. Then, I all need to do is finding a wireless replacement for RS232 connection, right?
For example, Zigbee productions can be suitable for this? Say that I'm transferring images in 352x288 @ 15 fps, then I will need at least 1.5Mbs bandwidth, right? And the range issue. about 100m.
I'm a newbie in wireless issues as mention in my profile infos sorry for that

 

[ericwertz]

I think you need to think about something more like 5fps. 1.5Mbps is a lot of data. No way you're doing that with ZigBee/802.15.4 either. There's no way the processor in the AVRCam can push out that kind of data either.

It says that in snapshot mode it's only putting out 176x144. At 15fps, that's still 380kbps. I doubt that the AVRCam is capable of pushing around even that much data either. Most RS-232 links aren't driven nearly that fast either. I'm not sure if you can safely do that over Zigbee either -- that's not what it was designed for. I think that you need to be thinking Wi-Fi or perhaps something vendor-specific. Read the datasheets for the radios for the throughput and distance info, and assume maybe you'll get 1/2 to 1/4 what they say.

Unless you reset your thinking to 2-4 fps, the AVRCam probably can't do it, and you need to think about the CMUCam.

Regardless of which camera you pick, I'd get the camera before you invest in the wireless stuff, to make sure that they meet your minimum requirements, wired.

 

[The_UnforgiveN]

Thank you ericwertz..
Could you take a look at this : **broken link removed**

it works at 2.4Ghz, and says that it has 1to2Mbps air data transfer rate. Can smt. like this handle my communication?

Btw, nothing mentioned about its range, any predictions?

 

[ericwertz]

I've heard good things about the Nordic chips. Since they do not specify range, I'd worry about it though. I do know that you can get modules from https://www.olimex.com, and they're somewhat close to you (in Bulgaria).

Because your application is mobile with difficult terrain (and a moderate to high data rate), you are going to need a good antenna and relatively high transmit power (probably 50-100mW).

If you still really want to do be able to do > 250kbps, you're probably looking at something more like these for your RF:
https://www.acroname.com/robotics/parts/R195-CONNEXLINX.html

and this for your camera/interface
https://www.acroname.com/robotics/parts/R245-CMUCAM2-PLUS.html

Most already-made video modules that use RS-232 to get out data don't go any faster than 115kbps. If you need something higher than that, you might need to go up to a security camera, which will be larger and need more power.

If you can live with 115kbps, either the CMU or AVR cams should be ok. You might be able to use this for your RF:
https://www.electro-tech-online.com/custompdfs/2008/09/ds-xbee-pro_pkg-rf-modems.pdf
but it'll be very close because the maximum is 250kbps.

That's pretty much all I know. Good luck.
-e

 

[The_UnforgiveN]

I got the idea. Thank you. If there are any other suggestions, I will welcome them