motion sensor

[mahinda jayasinghe]

Could you please help me to find motion sensor circuit to connect swith ON/OFF light bulbs.
I have a circuit (Light activated with LDR) and I want to connect a motion sensor part to it.

Many thanks.

 

[Russlk]

You can buy a motion detect light for less than the cost to build, so why do you want to build it?

 

[mahinda jayasinghe]

As a hoby and for my personal interest. I have one installed at my home. But still I want to find the circuit

Many thanks.

 

[dingo]

Motion sensors are just an op amp with filter. There are 2 types - active ones, ultra sonic and micro wave or passive thats infra red. I would stay away from infra red because the layout is critical. Where you place the pyro and how you divide what it sees in order to sense motion.

Ultra sonic would be the best for a hobby. Do a search on ultra sonic transducers and look at the aplication notes. The basic idea is you feed a wave in one tranducer and use the filter circuit to detect changes in the received wave form. The ultra sonics will bounce around room, off the pot plant, ceiling and fish tank, as the is no movement the recieved signal will be constant. In practice these sensors are only good if you move directly towards or away from them, slow movement across them is hard to detect without it being so sensitive it will fasle alarm every 5 minutes.