There are times when we do not need a full microcontroller or processor for a project. Sometimes we just need a simple switch that will bring our project to life. Well, for £3 we have found such a switch. In fact, there are three of them! Let’s take a look at a pack of three LED lights which are controlled via an infrared remote. Can we use them in the project? Well, there is only one way to find out: we need to tear it apart!
The LED lights are constructed in sections from easily worked plastic. These sections are all held together by three cross-head screws. When the screws are removed, the unit will naturally fall apart as it has no physical retention tabs. Inside the light, we see a silver plate that fits over the LED board. While it may look like metal, it is not and merely silver-coloured plastic. Removing the plate requires the use of side cutters to remove two plastic ‘stakes’ that hold both together. Once you’ve snipped these, we have access to the electronics. Remember the orientation of the stakes and where the screw holes and standoffs are, as they all need to connect to hold the light as a solid unit.
The remote control unit is made from the same plastic, and for such a small remote it has five cross-head screws holding it together.
Once removed, the top layer containing the buttons will come away to reveal a plastic sprue, similar to model kits, that could be easily reproduced using CAD software, enabling your own custom buttons and layout.
The electronics for the LED lights are obviously built to cost, and that is evident with the soldering and general neatness of the board. The infrared receiver is the most obvious example in that the legs of the IR receiver have not been snipped off and sit rather too close together. So get your snips and trim the legs! On the board, we have a no-name eight-pin chip, but we can see that the output of the IR receiver connects to pin five of the chip, and that means we can read the signal if we so wished. Pin three connects to the momentary switch on the reverse, and by pulling pin three to GND, we can toggle the LEDs on and off. Power for the LEDs is provided by the AA batteries via a 10 kΩ resistor.
The remote control uses a KXD6122-S1 which, according to its datasheet, is an IR remote-control transmitter circuit. And this is directly connected to the momentary switches via specific pins. The chip will constantly ‘scan’ the inputs to see if any have been pressed; if that is so, then the pin will receive ~76 mV and this change of state triggers the chip to send a code via the IR emitter. There are four buttons on the remote, but the chip can detect up to 16 inputs.
For a £3 piece of kit, we can hack this in a number of ways. Let’s start with the remote control. We can easily remove the PCB and use it with a board such as an Arduino. The button presses can be replaced with sensors that when triggered will pull the correct pin on the KXD6122-S1 high and trigger the IR emitter to send a signal to the LEDs. 3D-printing new buttons and a case for the board is also a fun activity and means that the board can be easily integrated into cosplay – a remote-controlled arc reactor for an Iron Man costume perhaps?
The LEDs are the easiest part of this product to hack. But the first question to ask is: do we still want the LEDs? If not, then the best option is to desolder them from the board, and this will require a hot-air rework station if you mean to keep the LEDs; if not, brute force and a soldering iron will do the job. The outermost track of the PCB is our GND connection, and the next inner track is VCC which receives power when the chip is triggered by the IR receiver. So we can either integrate the LEDs into a project, or remove them and use their tracks to trigger other devices. We scraped away a little of the tracks and soldered an L298N motor controller along with a simple geared motor which we triggered to life when we turned on the ‘LEDs’. So this means we have a simple and cheap remote trigger for projects, including using it with Arduino and other boards.
For £3, we have an IR transmitter capable of sending up to 16 codes, and three receivers that can be hacked into projects with great ease. The PCB for both devices is easy to work with and will only take a few minutes to decipher and hack into something much grander than lighting your cupboards.
SOURCING THE LIGHTS
This project used Hyundai 3 × LED Remote Control Lights (£3). Chances are that, unless you live in the UK, you are unlikely to find this exact product. But despite being sold under a Hyundai brand, it will be made by an original equipment manufacturer (OEM) which will produce similar products for different companies and markets. But no matter the brand on the box, the electronics will be similar enough to hack. Our top tip is to use your multimeter to first trace where the VCC (+) and GND (-) connections are around the board.
This also requires us to find VCC and GND on the chip; for that, you’ll need to use the continuity test function of your multimeter. To do so, put one probe of your multimeter on a GND connection, and the other is gently dragged across the pins until you hear a beep from your meter. Make a note of the pin and its use. Do the same for VCC. Then, trace the connections from the IR receiver to the chip. To test the buttons, set your multimeter to DC voltage, and connect a probe from your multimeter to a button leg, and the other to a leg on the chip. Press the button. Does the voltage change? If so, that means the chip to which it is connected is waiting for a HIGH / LOW signal to trigger an action. If there is no change, move to the next leg until you see a change. Your multimeter is an essential tool that can help diagnose faults and trace paths around any circuit board.