damenace

First off. I know it would be much easier for me to just go and buy all this in a kit but my challenge from this project is actually building it from scratch.

The laser transmitting portion of this circuit I beleive i won't have trouble with this portion. I intend on using a IR LED with about 850nm and a variation of a laser driving circuit i found on the net.......unless somone has a better version i can study.

However, im not sure how to do the recieving part. I intend to build it so that once the light is interupted it sets off a relay. There is actually other parts of the alarm system but im just having problems comming out with a schematic for the beam reciever.

Here's what my plan is. I was going to use a PIN Photo diode since i've read that its sensitivty is the best detector with a peak range at around the same frequency of the laser. I CAN put the reciever in a pvc pipe or something to block out ambient light and external sources however i wan't to build this with some filters in it as well.

Diod-amp-filter-*****-relay

when theres a sudden voltage drop from the beam dissapearing it sets of the relay?

Anyone have suggestions on basicly anyhting i have said?

mrkedar_kyk

i know your prblem.
but i have solution on it.
i am giving here a ckt diagram of such systembeam_alarm1.gif

ericgibbs

hi,
Have you seen the date on the post.?

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

Torben

Hi Eric!

I think that's some kind of record for dead thread resurrection.

Now, if the OP actually responds--that should *definitely* be a record.


Torben