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How can I make a siren chime for a few seconds when a laser hits a photo resistor using a 555 timer chip? Answered

I am trying to make a target for my laser for camping trips. I don't know how to create my own arduino codes to program an ATtiny so I was hoping to create a monostable circuit using a 555 timer chip instead (If monostable is the correct circuit). Basically I have a 6-14V siren and want it to chime for at least a second when the laser beam hits a photoresistor during day or night. I have tried but to no avail, since I have not been able to understand the ways of the 555. Any suggestions with or without a 555 timer chip are completely welcome. 


Really you don't even need the 555 timer to do it. Are you wanting the circuit to activate when the laser hits or if the laser beam is broken?

Either way you can make either a light detecting or a dark detecting circuit with an NPN transistor, Photoresistor, 10K pot and a few other resistors. The 555 timer will make it easier to generate a sound from a small speaker.

Just do some searches for terms like '555 light detector', '555 laser tripwire', '555 dark detector'. All sorts of projects and diagrams will come up.

He wanted the 555 as a means to make it sound an alarm longer than the contact.

I think the ATtiny is probably going to end up easier, but the 555 is magic. There is an MIT instructable on programming the ATtiny.

google suggests http://www.kpsec.freeuk.com/projects/lalarm.htm would that work?

Thanks for your input! I was looking over the diagrams but noticed that the chip being used was a "7555" I have several Texas Instrument 555's so I would like to use those and not buy a different chip since I have several of them laying around. My only concern is if the resistance or overall functionality differentiates between each chip.

The safest plan would be to compare datasheets. Chances are that they are identical in function, but slightly different in terms of tuning with a specific R and C value.

There's lots of general info about 555's floating about as you can do all sorts of things with them. https://www.instructables.com/id/learn-about-the-555/

I have done several *dim* sensing circuits, kind of like the solar powered lights people place outside in they're yards, but the system is either on, or off. quatch is right when he says the 555 timer is meant to allow the system to run about a second when the laser beam hits the target. I'm trying to move toward using an IC to get used to them so I can use them again in later projects.