Hello engineers, In this article I am going to share an LDR operated laser light security Alarm system. This circuit having LDR as the light-sensing component. This circuit discussed here has a relay that simply changes whenever the laser falling over LDR is interrupted and then Buzzer turns ON.So let’s get started with understanding in detail. with our Laser light security alarm circuit or Burglar alarm.
Materials:
- Laser Light
- RL1-Relay 12V dc
- Q1 -Transistor TIP122
- R1-470K
- LDR1-LDR
- BUZ1-BUZZER 12V
- PCB
- BATTERY /POWER SUPPLY -12V dc
- D1-LED
The Circuit for laser light security alarm
In the circuit above the Laser light is falling over the LDR. An LDR is a photoresistor whose resistance is least when the incident light is at the high intensity and highest when kept in dark. So, when the laser is falling over the LDR, its resistance is least approx.100ohms which makes the transistor base to be shorted by ground and transistor is kept turned off and the relay is also turned off and the buzzer is also not getting supply.
When Laser is interrupted
When Laser is interrupted, Light is not falling over LDR and LDR’s resistance is maximum, up to 1M ohm which is higher than R1 which is just 470Kohm and lesser than the LDR’s resistance 1Mohm. So, now the transistor’s base is connected to +12v via 470k resistor (because current follows the easiest path) to travel through. The active state transistor turns the TIP122 which turns ON the relay and then com is connected to the NO. This condition connects the Buzzer +ve and -ve both terminals.
Applications Of circuit
These kinds of circuits are employed in various security systems,
- Theft alarm systems,
- Field security
- Cattle herd protection system
- Burglar alarms,
It can be employed in field boundaries to automatically turn on fence gates at night to protect crops, etc.
I hope you guys liked it. Comment below to share your views.and ideas. Below is a full simulation video check that too.
Watch full simulation video and do subscribe to that channel for getting updated about new circuit diagrams ,simulations and gadgets because there are somethings i only upload there
Check a much More advanced smart automatic Intruder detector Burglar alarm with 400metres loud sound and motion detection feature. Circuit here. Also having additional functionality of auto power on and off during night and day.
That nice post though my students get help
What size laser and how long does the laser stay on without burning out?
It can be a normal laser light, just like the one here https://quartzcomponents.com/products/laser-diode-laser-led-light?sca_ref=124121.iBaVABJvPr
And yes, it will not burn out, you can turn on the circuit manually at night or just use another circuit to turn on the alarm and the laser at night only.
Even though, you leave the laser turned on then too it will not burn and will serve long.
Is that a transformer between TIP122 and R1?
Hello, thanks for visiting. It is a relay and not a transformer.
Hmm is anyone else experiencing problems with the images on this blog loading?
I’m trying to determine if its a problem on my end
or if it’s the blog. Any feed-back would be greatly appreciated.
Hello, Sorry for the inconvenience but everything on the website’s end looks fine. It can be either your internet connection or maybe some technical issue on the website, a lot of users come so sometimes it can be a server problem too.
If images are loading after you are scrolling that part and not already load when you aren’t viewing that part of the page, then that’s a lazy loading plugin feature. to decrease page load time and also it saves your internet data too.
If my users are facing problems then I am going to remove that. Please update if anyone else is also facing any problems.
Thanks for visiting.
Very good info. Lucky me I recently found your site by accident (stumbleupon). I’ve book-marked it for later!| а
hi,thanks for visiting.
Great job man!
Hello,Thanks pranath. stay tuned.
ok sir
very good ,please also upload pcb print.
hello,thanks for visiting creta ,i will upload it soon.
hello ,very nice aabhishek
hello dibya ,thanks for visiting.
Osm you are intelligent
Thanks for visiting anjali.