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Laser alarm project
fixit7:
I put this together on my breadboard. The author said that R1 was probably not needed, so I did not use it.
https://makezine.com/projects/laser-tripwire-alarm/
I do not have a potentiometer, but tried a 110 and 530 ohn resistor for R2.
With no power to the circuit, laser shining on the LDR, the reading was around 195 ohms.
I shined laser at the LDR and used the switch in both positions.
Piezo buzzer did not sound.
What can I try next?
ebastler:
Could you post a photo of your breadboard setup? One picture showing the breadboard large enough to see all the wiring, and one showing the complete setup (including the power supply, switch, and speaker) would be best.
fixit7:
https://www.dropbox.com/s/edy9xs8p5rfm15q/Project1.jpg?dl=0
https://www.dropbox.com/s/leak8ty4dsmw88e/Project2.jpg?dl=0
I found out that the power rail is broken up into 2 separate sections.
When I put 2 jumpers between the sections, the piezo buzzer started chirping.
It did so no matter if the laser hit the LDR or not.
I think the problem is in determining what to use for R2.
Specs for my LDR
Features:
Maximum voltage rating @ 25°C: 350VDC
Maximum allowable power dissipation @ 25°C: 400mW
Resistance (Dark): 1MΩ
Resistance (Light): 12kΩ
Lead length: 1.44"
Operating temperature: -30°C to +70°C
Able to withstand soldering at 230°C for 3 seconds
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