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I want to be able to sense the distance to a car driving in front of me, what kind of sensor would be best? Answered

I am trying to modify my cruise control with an arduino clone, and want to find a sensor which will give me the ability to sense the distance between my car and one directly in front of me. This will help me to let the arduino control the cruise control to adjust the speed to keep a safe distance without manually adjusting the cruise control. Any suggestions?


Have you considered exploring a system that works similar to the xBox Kinect? I'm not sure of the DIY practicality or how easily the technology is translated, but it is worth throwing in the idea mill.

Here is one explanation of that system if interested.

Depends on the conditions. SONAR will give a wide sweep of what is in front of you (on a 10 lane highway, five of them going in your direction, you may have difficulties determining which car is which). Radar can be aimed a little better, but is expensive and still can lead to false readings. Sadly, LADAR (or LIDAR) is probably the best & most accurate, but will also be the most expensive.

I thought there were games you could play with sonar to cancel side noise...maybe not afterall. My experience is limited to a couple of small robotics projects and a bit of reading but thought it would be the more practical than either Radar or Lidar. You make a good point...I should have considered the divergence

It would definitely be more accessible than Lidar :-) If there is a way to eliminate the divergence of the sound traveling out and back, I haven't heard of it, but then, that doesn't mean it doesn't exist ;-)

Yeah. I figure money is part of the issue... RE S/N: Nor have I...It's not so much to eliminate, but overcome. I just don't remember and am not terribly invested...(no offense kikiclint) I'm glad you reminded me though of its fundamental limitation. My gears were beginning to spin.

btw, if it were a static measurement, a parabolic reflector could be used to narrow the field, but at 50+ mph, I don't think that would be such a good idea...

ultrasonic detector, imo

Yebbut, how is the fact you are moving fast affect sonar response. ?

Ding...was waiting for that objection...I realized it as soon as I posted but didn't want to complicate the discussion, since I was simply asked to suggest a "best" sensing technology rather than hired to design and implement. My first thought was, like Goodhart, Lidar or Radar, but I immediately canned those due to cost for a DIY game. ....honestly, I would be more worried about air currents between the two than a doppler issue. If any, I believe that could be calibrated out with some ease. run the numbers...I think you'll see that iff V<< speed of sound, and vehicle A and B are moving at the same rate of speed, there is little difference between moving and static measurement. Can't say for sure without pushing equations more than I want to for this "light-hearted" discussion, but if anyone would like to pay my consulting fee I'd be glad to grind it out. :) !!! As Goodhart soundly noted, the big problem is intrusion by UN-desired objects into the sensing field via divergence, or said more plainly, S/N --> 0 I probably could even make a case for it with all the noise, using multiple transceivers, trackers and auto-correlation techniques, but I'm not going there. First because it would end up being expensive (see Lidar/Radar) and second, because it's way to dull for DIY

BTW, shrewd mind to see that. Most would have missed it

Its called a doppler sensor. If you look on the late model Mercedes cars, you'll see 1/2" sized dots on the rear bumper, these are the doppler sensors. You might be able to order some as replacements, then make your own controller using an Arduino board.

Does you car have a reversing sensor? One of those things that makes a beeping noise which gets progressively faster the closer you back-up to something? That's probably your best practical bet. You can surely buy them. L