Distance sensor

[jcb344]

I am working on a project that would measure the distance between the car you are driving and the car in front of you. So I am looking for some sort of distance sensor with a range between 10 and 40 feet with and accuracy within a half a foot or so. I know ultra sonic has a limited range. Any ideas?

 

[crutschow]

I believe most commercial adaptive cruise controls use high frequency radar (77GHz) to detect the car in front and determine its distance. Those are probably very specialized and not easy to buy.

You might check out ultrasonic tape measures. They are good to 50-60'.

Edit: You might also look up "short range laser range finder".

 

[birdman0_o]

I would suppose that the Doppler effect would come into play when the car is moving which is why ultrasonic would be a mess (along with the nasty acoustics of the rushing air).

 

[BrownOut]

I like the laser idea. Microwave is not easy for a home brew project.

 

[jpanhalt]

I believe most commercial adaptive cruise controls use high frequency radar (77GHz) to detect the car in front and determine its distance. Those are probably very specialized and not easy to buy.

Yea, the Ford Fusion at about $24K is a good example. Just a little too expensive for hacking right now. It is only a matter of time...

However, Stanley Tool makes a FatMax that is laser time of flight, not Doppler or triangulation. I got a new, low-end one for about $50 on eBay a couple of years ago. Current retail is about $100. Some other brands also available.

John

 

[Mr RB]

I would suppose that the Doppler effect would come into play when the car is moving which is why ultrasonic would be a mess (along with the nasty acoustics of the rushing air).

I think doppler requires relative movement between the two objects? However you are totally right about the ultrasonics. They are useless in high wind conditions and cars at speed have additional pressure turbulence etc on top of the high wind conditons.

 

[birdman0_o]

Example of Doppler: Car zooming by you: as it gets closer you hear the frequency go up, as it goes away, it goes back down again. Just think of standing beside a highway.

 

[Mr RB]

Yep I knew that.

But that requires a change in relative distance between the 2 cars. If you used doppler radar between 2 cars traveling forward at the same speed there is no relative movement. You need a time of flight radar.