Long-wavelength infrared diodes

Thread Starter


Joined Apr 18, 2009
Has anyone seen retailers selling these types of diodes. I'm making a passive infrared detector as part of a indoor security system. Human peak infrared emission is at around 12 micrometer wavelengths.
Almost all diodes i come across are peaking at around 950nm with upper half bandwidth at 1050 nm which is far from the spectrum i'm seeking.

I would like to do this passively. If i can't find proper passive infrared diodes for 12um i assume i'll have to change my system to an active system with pinging infrared radiation. But that's slightly more complicated.

Anyone run across these types of diodes capable of pointing me in the right direction ?


Joined Sep 26, 2009
You need to look for PIR sensors or Passive Infrared Sensor,

Quote from Wikipedia:

A Passive InfraRed sensor (PIR sensor) is an electronic device that measures infrared (IR) light radiating from objects in its field of view. PIR sensors are often used in the construction of PIR-based motion detectors (see below). Apparent motion is detected when an infrared source with one temperature, such as a human, passes in front of an infrared source with another temperature, such as a wall.[1]
All objects emit what is known as black body radiation. It is usually infrared radiation that is invisible to the human eye but can be detected by electronic devices designed for such a purpose. The term passive in this instance means that the PIR device does not emit an infrared beam but merely passively accepts incoming infrared radiation. “Infra” meaning below our ability to detect it visually, and “Red” because this color represents the lowest energy level that our eyes can sense before it becomes invisible. Thus, infrared means below the energy level of the color red, and applies to many sources of invisible energy.[2]
B. Morse


Joined Nov 6, 2005
These are available, but it is often cheaper to buy a ready built PIR module than just a sensor.

PIR elements detect body heat. They must have a matching infra-red lens so the infrared patterns from people etc. appear as focussed spots on the sensor surface. It's the focussed patterns moving across the sensor segments that allow the movement detection to occur.

If you look closely at the front body of a commercial PIR module, you will see it's a fresnel lens.

PIR device:

This is a lens to suit.


Joined Sep 26, 2009
there are some available at sparkfun, and even radio shack that are perfect to include in your own project....

There is even one from sparkfun with a built in uc based on a Zilog mpu, and another based on the MSP430F2013 uc.

B. Morse