alert about distance between 2 objects

[Juan Romero]

Hi

I need to develop 2 devices that alert when the distance between both exceed a limit. For example, that's alert (sound) when the distance between both its more than 1 meter.

How could i do that? Which sensors can i use?
Thanks for any idea or comment.

Thanks a lot.

 

[davenn]

hi there
welcome to EP

ultrasonics is probably your best bet

 

[shrtrnd]

davenn's suggestion is the proper one.
What's your application? Is this two bodies in motion, or a fixed reference point?
When I was a kd, I used to use a lot of photo-electric eye (you break a beam of light to trip an alarm) circuits for simple alarms.
In your case, I'd wire the circuit to trip when the distance increased, and the beam of light was made, rather than broken.
Is this something critical that requires precise measurement, or just exactly what are you trying to accomplish.
Is this a quick, cheap and easy job, or something requireing precision?
Could you use something simple like optics, or would the ultrasonic work better for you.
Someone might be able to suggest a better idea, if we know your application.

 

[hevans1944]

The simplest way to do this is with a string (about one meter long) tied to a clothes pin that actuates a NC switch located on one object that has the alarm. Tie the other end of the string to the other object. When the distance between them exceeds the length of the string, the clothes pin is pulled off, allowing the NC switch contacts to close and sound the alarm.

We can provide help wiring up the alarm if this is too high tech.

 

[Externet]

----> https://duckduckgo.com/?q=child+distance+alarm

----> http://www.specialtyalarms.com/site/1313932/product/30-210

 

[Colin Mitchell]

You can buy a simple "child alert" that buzzes when the distance is a set distance.