hey there

[bryanperito]

i am having problem on how to make that stupid automatic door to close and open whenever a person or thing entered how is that....i saw some of its appllications at the city...

 

[Nigel Goodwin]

i am having problem on how to make that stupid automatic door to close and open whenever a person or thing entered how is that....i saw some of its appllications at the city...

They usually use microwave radar to detect a body approaching, you could use ultrasonics to make a less reliable version.