Introduction: Free Sources for Infrared LEDs and Photo Transistors
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The project described in this article requires basic electronics skills and is provided for information purposes. Do not attempt to replicate it or use it for any purpose unless you've got the proper knowledge and skills.
It’s easy to recover infrared LEDs and photo transistors from junk electronics you can obtain for free. Old remote controls, VCRs, and broken DVD players are excellent sources.
I keep two boxes of remote controls, one box with the original remotes from each of my current electronics (normally I use a multi-function remote on a day-to-day basis) and a junk box with old remotes after I’ve tossed out broken electronics. Why do I keep the old remotes? Just in case they are useful in the future. For example, one of my junk box remotes was for an old Panasonic VCR and would also control a TV set. I recently found a Panasonic TV set for $5 in a thrift store and realized it was the right size for my guest bedroom. It turns out that the junk remote operates all of the functions I need for that television, saving the cost of getting a universal remote for that TV.
But there are plenty of remotes in the junk box that I’m extremely unlikely to ever use again.
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Step 1: Recovering Infrared LEDs
Most of the time the remote is held together with a couple of tiny screws, but in some cases the halves of the remote’s case are glued together. Make sure you check inside the battery compartment for hidden screws. Since you’re just harvesting parts to recycle you don’t have to worry about damaging the remote.
Use a small soldering iron to remove the infrared LED. I’ve found that in most cases I don’t need a desoldering sucker or wick and it’s easy enough to just melt the solder and pull the LED out with pliers. In most case the leads will be bent 90 degrees to mount the LED on the PC board and that’s easy enough to unbend.
I was rather surprised that one remote I disassembled had actual mechanical microswitches inside. Occasionally you will find two LEDs inside the remote. If the remote is a “learning remote” (one which can be pointed at another remote to learn its commands) then there will be a photo transistor (the infrared receiver) in addition to the normal transmitting LED and that’s also a good part to recycle.
Step 2: Recovering Infrared Photo Transistors
In the case of VCRs, DVD players, and other devices which are operated by infrared remotes it’s normally pretty obvious where the infrared receiver is located on the unit. First and most important make sure the power cord is disconnected and the power supply is discharged. Capacitors can hold power for a long time and the high voltage circuits inside most inexpensive electronics is not inside any protective enclosure.
Disassemble the unit (taking extreme care if it’s a television set with a cathode ray tube – both for high voltages and to avoid breaking the tube) and remove the circuit board with the infrared receiver.
The receiver may just be a photo transistor or a small module. It should be easy to desolder.
Step 3: Conclusions
Infrared remotes are extremely common and even if you have to purchase them pretty inexpensive. The infrared LEDs can be used for night vision illumination projects or infrared control projects. Paired with an infrared photo transistor you can control devices or even use them for wireless communications.