Building a PIR Motion Sensor Circuit on a Breadboard

The purpose of this video is to demonstrate how to design and build two PIR motion sensor circuits that illuminate an LED when an object passes in front of the sensor.
Every object that has a temperature above absolute zero (-273.15°C or zero on the Kelvin scale) emits some heat energy in the form of electromagnetic radiation. The hotter the object, the more radiation it emits. This is invisible to the naked eye because it radiates at infrared wavelengths, which we can’t see, but it can be detected by purpose-built electronic devices. So, if an object passes in front of one of these devices, the device is able to identify that there has been a change in the radiation detected.
A Passive Infrared (PIR) sensor is able to detect movement that takes place within a certain range of the sensor (typically within a few meters).
A PIR sensor consists of two main parts: a Pyroelectrical sensor and a Fresnel lens, which is a special type of lens that focuses infrared signals onto the sensor.
The pyroelectrical sensor has two rectangular slots in it that allow infrared radiation to pass through. Behind each slot is an infrared sensor electrode; one electrode produces a positive output and one produces a negative output. The way that the electrodes are wired up is such that they cancel each other out. If one electrode detects more or less infrared radiation than the other, which is what happens when an object passes through the detection area, the output signal swings either high or low. When there is no movement, the same amount of infrared radiation passes through both slots and there is no output signal.

[@captainprototype187]

I cannot be the only one who discovered these great tutorials.

[@alessandrog5261]

Thanks. It would be very interesting a circuit about how to build a timer for this kind of sensor. Keeping the lights on for a certain amount of time like 2-5 minutes

[@quickstartworkbook1532]

Some motion sensors enable you to set the amount of time the signal stays high for. I've got one set up in my shed so that the LEDs stay on for about 3 minutes. I used a 12v battery with 4 LEDs and no resistor.

[@tscherer1982]

I don’t understand the transistor…doesn’t the PIR already act as a switch like in the first circuit?

[@quickstartworkbook1532]

The problem with the first circuit is that the output from the pir sensor wasn't really powerful enough to properly illuminate the LED. If I remember correctly, it was only about 3mA, and you need something more in the region of 10mA at least. So what I decided to do was to use the 3mA is switch on a transistor which then allows current to flow directly to the LED without going through the sensor. Basically, the sensor isn't capable of driving a device itself, but is perfect for providing a small current to switch on a transistor.

[@hello2803]

My circuit isn’t working and I can’t figure out why

[@quickstartworkbook1532]

Which of the two circuits are you trying to build?

[@hello2803]

@@quickstartworkbook1532 Ive tried both, think it’s my sensors that aren’t working