Measuring distance

Without going into too much depth of my project, I will need to measure a how close my hand is to the ground and hopefully get an analog reading from that. I need them to work in a poorly lit area and I have the liberty to mount them on the ceiling or floor or both.

Is there anything out there that can do this?

I am placing a Sparkfun order soon with other stuff I need. If it can be bought there, it would be best.

You can use use and ultrasonic speaker and an ultrasonic transducer in order to compute the distance between an object and the speaker.

What you have to do is compute the time among a ultrasonic pulse comes out the speaker and it is bounced again through the transducer. Maybe there would be simpler solutions, but that's a suggestion if you haven't any more ideas.

Rubén ;)

The distance between your hand and the ground, at a specific place on the ground, or anywhere on the ground ?

At a certain place on the ground would be preferred however I would need a little more than 10 of them. What would I be looking at in terms of cost?

If I did anywhere on the ground, would it be cheaper? I can sacrifice functionality for cost if need be.

The point is, do you want the sensor on you hand, or on the ground ?

If you carry the sensor in your hand, you can measure the distance from your hand to the ground, anywhere.

Otherwise, you would have to cover the ground with sensors.

You could use of the small ultrasonic sensors which people stick on the front of their little robots.

Or if you wanted to try something completely different, you could read up on how a theremin works, although I doubt that that principle would work well with the ground.

I will need to cover the ground with sensors. I do not want to hold anything.

I think the ultrasonic is more what I'm getting at. I'm not entirely sure how they work though. Do I need an emitter and receiver?

Funny you mentioned the theremin. Really similar to what I'm trying to do.

Ultra sonic modules have a transmitter and receiver they work by measuring the time of flight between sending a signal and getting a reflected signal.

Something along the lines of this ?

https://www.sparkfun.com/products/639

Yes that should work.

Anybody know if a smoke machine would effect these sensors? I probably should have mentioned it earlier.

In what way? Smoke will not affect the ultrasonic signal.

Okay awesome, yeah I will be turning on a smoke machine. I just wanted to make sure the smoke didn't obscure the reading.

If cost is a concern it might be worthwhile looking on ebay

I have a couple of these (from that guy)

Which seem to work fine for my purposes (basic robot navigation)

Cheap and they turned up to NZ in about 14 days