Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
I'm building am Infrared trip alarm, so that when the beam is cut it sounds the alarm, I found an image that would be perfect but the alarm sounds when it detects IR not when it no longer detects IR, how can I change it to do what I want?
The instructions in Chemelec's project say to connect the beeper from pin 3 of the 555 to the positive supply. Then the beeper will beep when the beam is broken but will stop beeping if the beam is shining on the photo-transistor again.
You can do the same thing with a transistor replacing the 555.
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