How well do IR Distance Sensors see smaller objects?

I’m working on a soccer-bot solution. Wondering how well the Sharp distance sensors ‘see’ smaller objects such as:

a) another 3pi - perhaps with a white cardboard collar or skirt to make more visible
b) even smaller objects - in my case a ‘ball’ or ‘puck’ about 1.5 inches in diameter - could also be painted or coated to maximize reflectivity.

I’ve seen projects (e.g. where the Sharp Analog Distance Sensor 10-80cm is used to guide the 3pi away from walls and other larger obstacles. But does anyone have experience using any of the Sharp sensors (10-80cm, 4-30cm, etc.) to locate smaller objects around 3 or even 1.5 inches in diameter from a distance of say 1-2+ feet (30-60cm or more) away?

Or is there a different sensor someone might suggest for this?



The Sharp distance sensors have a fairly narrow detection angle, which can be both a blessing and a curse for detecting small objects. It means that it’s not necessarily relying on reflection from a large area, so it should be able to detect “small” objects up to a point, but it also means that there’s only a very narrow window where it will detect a small object. Also, the sensors have a worst-case update rate of around 25 Hz, which means that they might not catch a small object that moves by quickly. I think they will work over some range, but I really don’t know what that range will be. I’m sorry I can’t be more helpful. If you try them out, we’d love to hear your results!

- Ben

Okay, I’ll probably order a couple of the Sharp sensors and experiment a bit to see how well they detect various small objects - static and moving. If/when I do, I’ll be sure to post what I find out.

Another thought: If I mounted an IR LED on top of the 3pi or ‘puck’ or whatever remote object I wanted the 3pi to ‘see’, is there a simple IR photosensor with a narrow ‘view’ that would see the IR LED at a distance of 2-3 feet?

I read about the Pololu IR Beacon pair. I assume it’s advantage is that looks in 4 directions at once and gives the 3pi a direction to head. I was wondering if there’s a solution that used less expensive electronics if I’m willing to have the robot spin once in a while to scan 360 degrees to locate the remote object.

I think IR detectors are generally intended to be rather wide-angle, but you could always mount something like a tube to create a narrower viewing angle. You could try building something simple with a bright IR LED (or maybe a ring of IR LEDs) and a Vishay IR detector module. Note that the sensor is looking for IR modulated at 56 KHz, so you would have to pulse your IR LEDs at this frequency.

- Ben