Hi, i posted some more info on the object tracking robot i’m building if anyone is interested.
I posted about it in this other thread last night, but didn’t want to hijack that thread any more 
I’ve just done another blog post about how to use an ir compound eye to track objects using gadgeteer.
The ir compound eye is quite a useful sensor. It works by shining ir light at whatever is infront of it and then measuring the reflected ir. It has 4 pairs of photo transistors providing 4 seperate analog readings for left, right, up, and down. It’s also relatively cheap.
When combined with a pan and tilt mechanism, it provides an easy way to track objects at short range.
You can get both of these items from either http://www.robotshop.com in the US/Canada/EU, or http://robosavvy.com for people in the UK
Awesome!
Very cool!
I need to be able to track an object from a farther distance (20’-30’). Any recommendations on a sensor?
I’ve seen people using these sensors with good results
http://www.robotshop.com/eu/parallax-ping-ultrasonic-sensor.html
The range looks pretty good. Up to 3m according to the data sheet
http://www.parallax.com/dl/docs/prod/acc/28015-PING-v1.3.pdf
Very cool
Am going to try to build one, as I was charmed by the way its head looked like a puppy ready for you to throw a ball. Already had a pan & tilt mechanism, just ordered the compound eye sensor (and YET ANOTHER extender module - and if I want to drive two wheels as well, would need a fourth too!). Have you tried adding a camera to the pan and tilt head? I’m wondering if the IR LEDs illumination shows up on camera.
I’ve got a ping sensor. The problem is that I need something fairly narrow at 20’-30’. As you mentioned, the pings aren’t very reliable past 3m or so especially in a room with other stuff. I’m probably looking for something more laser-like.
Ahhh sorry i read that as 20-30 inches when i read it originally, rather than feet.
I’ve only really looked into doing stuff like this at short range i’m afraid 
Yeah i had to use a fourth extender to drive 2 motors.
I’ve not tried pointing a camera at the eye when the leds are switched on.
I can give it a try tonight.