I needed a foot switch for my DSLR camera so that I could take hands-free pictures. On a long-shot, I went down to the local Radioshack to see if they had one. As expected, they didn’t have any camera foot switches, but I did luck out that they had all the parts necessary to build my own. Here is how to throw together a 5-minute camera foot switch with easily obtainable parts from Radioshack.
What is an IR detection sensor?
IR detectors are little microchips with a photocell that are tuned to listen to infrared light. They are almost always used for remote control detection – every TV and DVD player has one of these in the front to listen for the IR signal from the clicker. Inside the remote control is a matching IR LED, which emits IR pulses to tell the TV to turn on, off or change channels. IR light is not visible to the human eye, which means it takes a little more work to test a setup.
There are a few difference between these and say a CdS Photocells:
- IR detectors are specially filtered for Infrared light, they are not good at detecting visible light. On the other hand, photocells are good at detecting yellow/green visible light, not good at IR light
- IR detectors have a demodulator inside that looks for modulated IR at 38 KHz. Just shining an IR LED wont be detected, it has to be PWM blinking at 38KHz. Photocells do not have any sort of demodulator and can detect any frequency (including DC) within the response speed of the photocell (which is about 1KHz)
- IR detectors are digital out – either they detect 38KHz IR signal and output low (0V) or they do not detect any and output high (5V). Photocells act like resistors, the resistance changes depending on how much light they are exposed to
In this tutorial we will show how to
- Test your IR sensor to make sure its working
- Read raw IR codes into a microcontroller
- Create a camera intervalometer
- Listen for ‘commands’ from a remote control on your microcontroller
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