Science Buddies: "Ask an Expert"

Hi, I'v been trying to make an alarm using IR so far I have succeeded in making the project but I'm stuck with the relay part. The alarm needs to beep continuously....which doesn't happen it simply goes off when the beam reaches the sensor once again.

rohit_gxr wrote:Hi, I'v been trying to make an alarm using IR so far I have succeeded in making the project but I'm stuck with the relay part. The alarm needs to beep continuously....which doesn't happen it simply goes off when the beam reaches the sensor once again.

Hi, rohit_gxr!

So it sounds like you have part of the circuit working - the IR detector seems to be doing the right thing. From your description, I'd say that when the IR beam is broken, the alarm sounds, but as soon as the object obstructing the beam moves away, the alarm shuts off. It also sounds like what you want is an alarm that sounds as soon as the beam is broken and won't quit until you reset it somehow. Is that right?

It sounds like you need some kind of circuit to drive the alarm that provides a set/reset function. When the IR detector trips the alarm, it sounds until you press a button to reset the circuit.

Have you done any web searching for set/reset circuits or devices?

Hi rohit_gxr!

Elaborating on the previous response, you can provide "How do I design a burgular alarm reset device?" to answers.com.

Two notes in using answers.com:

1. Generally, the "Sponsored Links" are commercials. So, it's best to skip them and use only the "Web Results." (this time, there don't appear to be any "Sponsored Links.") There are several sites to skip, however, since they're just trying to sell something.

2. With answers.com, you may need to tweak your wording for best results.

thank you sir........