So i'm working on an autonomous hexapod and I need a gps, an ultrasound or a camera and some module to ensure communication between the hexapod and the laptop.
I'm working using and arduino. I'd really appreciate your suggestions on the matter.
The cost plays a major role but I won't go too cheap
What kind of communication? Telemetry? Video? Commands? What interface are you using to connect to Arduino and laptop currently? Also what terrain? You could achieve everything with a simple 2.4GHz WIFI or RF link.
Well I have about 100$ but I'm not spending all of it on that because I still have other parts to purchase.
I'm wondering can I make the robot navigate an unknown terrain using ultrasound only ? or do I need a camera too.
My first thought was about specifying the end point using a GPS and then the robot has to find a way to get there.
Well then that's a no-go, because you either process the data to transmit through a single, bi-directional interface (I'd suggest 2.4GHz wifi for this purpose), or you have to use several independent pre-made interfaces.
You could transmit the video separately and bother with the data only, which could actually work.
For that you would need all the sensors and a GPS unit for the Arduino, either a wireless camera (a small one could be had for some $30) or a normal camera and wireless transmitter modules. Then you'd need a wifi module for Arduino and a fair bit of programming to get it all working.
If you managed to tote around an actual wifi access point, you could have both the video and telemetry/commands transmitted via WIFI.
There's that, but you wouldn't have to get any special HW on the laptop side. And in open terrain, with a reasonable antenna, wifi's gonna give you close to 100m.
You could also use something like 433MHz transceivers, but then you'd need to get the corresponding laptop-compatible part as well, and you still wouldn't be able to skip any of the programming.
Ultrasound is much, much, much simpler and cheaper. But it won't be 100% reliable in open terrain (it won't see smaller obstacles or wood/vegetation). Try to come up with a backup sensor (motor input? accelerometer? GPS) to sense your hexapod getting stuck.
If you aren't experienced in video processing and/or don't have a good library handy, don't even think of using a camera for autonomous navigation. It's only good for manual driving.
Try sourcing from China - http://www.dx.com/c/electrical-tools-499/arduino-scm-supplies-436/boards-shields-472
Either get a cheap Arduino-compatible one, and do the interface programming yourself (easy, you'll just be sending pics over wifi very quickly), or get a wifi camera for drones - like this one:
http://www.banggood.com/Syma-X5SW-X5SC-WiFi-2MP-Camera-p-987145.html There are probably some cheaper ones as well...