Reconnect pin 21 and ground. The console displays text similar to the following: (05/10/2022 16:00:25) READY ✅ If you enjoyed making this project, then you can find many more GPIO Zero guides in our GPIO Zero Essentials book! Laser receiver sensor module is the generic name applied to a common module found at many internet retailers. The device may vary in name or manufacturer, but should resemble this image. Unless you’re working in a darkened room, you’ll probably notice little difference between the measured light level when the laser pointer is directed onto the LDR and when it’s not. This can be fixed by reducing the amount of light that the LDR receives from other light sources in the room, which will be essential for our laser tripwire device to work effectively. We’ll achieve this by cutting off a short section – between 2cm and 5cm – of an opaque drinking straw, and inserting the head of the LDR into one end. Now try the test code again and see how the measured light level changes when you shine the laser pointer into the other end of the straw. You should notice a larger difference in values. Wire up the buzzer NOTE: Laser pens can still be dangerous and should never be directed toward anybody’s eyes! The laser trip wire build

As noted earlier, when the laser is shining on the resistor it reads about 620, so in the sketch I’ve set the buzzer to sound only if the value is more than 850. This value is between our laser value and our nonlaser value, so we know the laser beam to the resistor has been broken if the value reaches 850. One 200k resistor Really any large resistor will do. I tested it with a 1M resistor and it worked fine. FYI 10k was too small. An LDR (also known as a photocell) is a special type of electrical resistor whose resistance is very high when it’s dark, but reduced when light is shining on it. With the Raspberry Pi turned off, place your LDR into the breadboard, then add the capacitor. Now connect this column (with a leg of both components) to GPIO 4. Connect the other leg of the LDR to a 3V3 pin, and the other leg of the capacitor to a GND pin. Your circuit should now resemble the circuit diagram below. Test all is working by running cd /directory where you put the file/ chmod 777 read_pin_with_mail.py sudo python3 read_pin_with_mail.pyUnless you’re working in a darkened room, you’ll probably notice little difference between the measured light level when the laser pointer is directed onto the LDR and when it’s not. Using the mirror to reflect the laser allows you to keep all the wires and power connectors on one side of the door. It is possible to put the laser and sensor on either side of the door, but this requires powering both. This solution solves for that issue and keeps the project simpler. Summary This laser tripwire project is a great introduction to digital making with a Raspberry Pi and breadboard circuit. Once you have changed these variables at the beginning of the script run the program by entering the following in the terminal. cd /folder where you put the script/ sudo python3 send_mail.py In IDLE, create a new file, enter the final code below, and save it: from gpiozero import LightSensor, Buzzer

Now try the test code again and see how the measured light level changes when you shine the laser pointer into the other end of the straw. You should notice a larger difference in values. Originally posted by Out Of Bubblegum:Here is a screen of what i am trying to do. I need something that is timed for about 30-60 seconds. The wiki is no help to say what can be timed. I can use the logic gates if I get something with a timed delay. The diagram depicts a breadboard and GPIO breakout for illustrative purposes, but feel free to just connect a ground pin and pin 21 with a jumper wire on the Raspberry Pi.

Now shine the laser on the resistor’s cell, and also note this number; my reading is 620. This might seem counterintuitive, as you would expect more light to provide a higher number, but the figure is actually translating the resistance – more light, less resistance. You can change this number to adjust the sensitivity; a higher value will make it more sensitive. Try running the code. If you break the laser beam, the buzzer should beep for eight seconds. You can adjust this by altering the buzzer.beep parameters and sleep time.

When the light beam is interrupted, the resistance of the photoresistor increases dramatically. As a result, the voltage at pin 6 also increases and goes above the reference threshold. This causes the output pin 3 to go LOW and activates the alarm. The batteries are mounted in individual AA battery holders. The three battery holders are soldered together in series and the end leads are soldered to the circuit board.A using declaration creates an instance of GpioController. The using declaration ensures the object is disposed and hardware resources are released properly. An analogue input can have a range of voltages from 0V up to 3.3V, however, and the Raspberry Pi is unable to detect exactly what that voltage is. Some sort of breakout kit for the raspberry pi so you can have easy access to the pins on the processor. Laser beams that are visible in daylight or even in the dark are very powerful and can be extremely dangerous. In this project we’ll use a low-powered laser pen instead.

Lasers are not toys. Ensure that you know how to handle a laser safely by reading the information on laser safety . This will give you precautions on different classes of lasers. We then assign the variable ldr to the LDR input on the GPIO 4 pin. Finally, we use a never-ending while True: loop to continually display the current value of the light sensed by the LDR, which ranges from 0 to 1. Try running the code and then shining your laser pointer on it to vary the light level. Enclose the LDR Once everything is working well, you can enclose your Raspberry Pi and breadboard in a plastic box (such as an old ice cream tub), with the drinking straw poking through a hole in the side. The main power buses on the breadboard are regulated. Unregulated power from the power adapter goes into the power regulator on the Arduino It’s essential to get the correct polarity for the latter component: its longer (positive) leg should be in the same breadboard column as one leg of the LDR. Now connect this column (with a leg of both components) to GPIO 4. Connect the other leg of the LDR to a 3V3 pin, and the other leg of the capacitor to a GND pin. Your circuit should now resemble the diagram above. Test the LDR circuitIn this tutorial, you will learn how to set up a laser tripwire sensor and trigger an actuator, in this case an LED, upon the beam being broken. You will learn how to use an if/else loop, laser diodes, and a photoresistor. With the Raspberry Pi turned off, place your LDR into the breadboard, then add the capacitor. It’s essential to get the correct polarity for the latter component: its longer (positive) leg should be in the same breadboard column as one leg of the LDR. There is also a Delayed Switch that you can connect a Terminal to (after hooking it up to what you want to affect) and set it for 1/8s up to 10s. Since you want something that 'fires' after about 60secs, then you will have to set up six of these in series, so that each one 'waits 10s then fires, passing on the current to the next' - six times. At the end, set the Gate to toggle (along with the Laser Tripwire), then it will also 'reset itself'. This tutorial describes how to create laser tripwire with an Arduino Uno. If you are unfamiliar with the Arduino platform please refer to the “Setting Up Arduino Tutorial.”