This instructable will aid in the construction of a RFID controlled door light, which will assist only the right people in opening your door.
The goal of this prototype is helping the user in opening the door when it is dark outside by providing a light from above, showing the door handle and key hole.
Benefit of using RFID (Radio Frequency Identification) is that the tag (in this case a simple keychain) does not need an external power source, but can be passive and therefore always be used.
The use of RFID in common household object is definitely emerging, as the technology becomes cheaper and more widely available.
Disclaimer: this instructable concerns the construction of a working prototype which can be tested on location. However, for a permanent installation in a more harsh, outside, environment, extra protective measurements have to be taken.
Another disclaimer: think about the safety of your home before installing such a prototype to your frontdoor. We are not responsible for any negative aspects caused by this idea, we just want to inspire.
Step 1: Collecting the Parts
In order to be able to replicate this RFID door light, the following parts are needed:
- An Arduino board (this instrucatble uses an UNO. However, other variants may be used)
- RC522 RFID board
- RFID tag
- male USB A to male USB B connector
- Male to Male cables
- 10 Watt Power LED
- 2N5088 transistor (NPN)
- Pins for the RFID board
- D44H8G transistor (NPN)
- 0.5 Ohm, 5 Watt resistor
- 10K resistor
- 230V/12V converter plug
- (Also not shown in the image) 9 Volt battery (only for testing)
- Computer with the Arduino IDE installed.
- Soldering Iron and tin
- Pliers / Wire strippers.
Step 2: Soldering the Pins on the RFID Board
Our RFID board did not come with male connectors, so these have to be soldered on. If your board does have male connectors already, you can skip this step.
Connect the connectors using a soldering iron and soldering tin as shown in the image above to properly connect each of the pins to a separate hole on the RFID board.
Step 3: Construction of a Test Board.
In order to ensure that the final product will function properly, first a test board was constructed using all of the components. Instead of immediately hooking up the 12 Volt power supply, the 9 Volt battery was used.
Both the physical board as well as a schematic are shown above.
The schematic displays the total circuit. In the top left corner the RC522 circuit board is located. Take care when hooking up, since the pins used on the Arduino are in a different order than on the RC522. In the upper right corner, the power plug for the 12V connection is located. The components on the breadboard form the circuit to ensure a constant current flows through the LED. Be aware that the same current that flows through the LED will also flow through the 0.5 Ohm resistor, meaning that it should be capable of handling quite some power. We used a 5W resistor, since we had these lying around. Also be aware that the circuit shows a normal LED instead of a power-LED.
Step 4: Construction of the Code
Due to the newness of the RC522, we struggled quite a bit getting the board to work properly. We ended up using an RC522 library, which can be downloaded from here:
Also, we used an online tutorial to get to know the basics of the board and the code, the tutorial can be found here:
Using these two links, we managed to construct a proper code. First, the code does some set-up and tries to find the RC522-board. When this is done, the code will loop until a tag is presented. It will then read the tag information and control the serial number. According to this number, the LED will be actuated. When the correct tag is presented, it will slowly turn on and dim to darkness again after 10 seconds. If a non-correct tag is presented, the LED will blink three times.
When using this code, make sure to change the RFID serial number in the code to your own tag's number, as the code will otherwise not function properly.
Step 5: Soldering the Power LED
In order to be able to position the power LED above the door and be functional, long wires have to be connected to both the LED and the rest of the circuit.
With the rest of the circuit (the Arduino, breadboard and RFID scanner) being positioned on the side of the door, two cables (a positive and negative) of approximately 1.5 metres were soldered onto the LED.
When soldering, be careful about connecting which cable to which end of the LED. As the LED is a diode, polarity is an issue and it will only function when the positive side of the LED and the positive outlet of the circuit are connected and vice versa.
Step 6: Constructing the Final Product
Using tape the final product was positioned in its correct place. Most of the circuitry (the breadboard, RFID scanner and Arduino) are located left on the door, easy to reach and therefore easy to modify. The power-LED is located on the ceiling above the door in order to sufficiently aid the user in opening the door. The RFID scanner is located on a comfortable using height, allowing a quick and smooth functioning of the product.
When positioning the circuitry, be careful as connections may be fragile. It is smart to check all of the components and their connections when sufficiently positioned, ensuring a correct functioning before further testing.
Step 7: Finalising and Testing the Final Product
The clip shown above shows the final functioning of the product.
The prototype shows what can be done using an RFID reader. In this case, we decided to only lighten the door to enable easy opening (imagine never having to enter your key in pitch black darkness again thanks to a proper door lighting, wouldn’t that be amazing?). However, it leaves enough room for future development or adding other components. After setting up the RFID reader, there are plenty of options to add. One could think of using a solenoid to lock the door, only being opened by the correct RFID tag. Or how about adding multiple tags, one for each family member? One could add a unique greeting for each tag. Also, one could use this prototype to track who is in the building, which could increase safety in case of emergency situations.
As stated in the description, the prototype in its current form cannot withstand harsh conditions, for example rain. If the prototype was to be used in an outdoor environment, we would recommend to construct proper casing for all components.