Following the automated rain gauge project that utilised a Reed switch, and plenty of Youtube Short videos, I thought that I could create a magic lightbulb utilising a reed switch. So I did one.
This is a simple circuit with a Reed switch. Making this magic lightbulb is a fun and hands-on activity for young children to learn about simple circuit. I used a CR2032 button battery and a battery holder (with another on/off switch) for easy wiring. CR2032 is rated 3V and so the LED light preferably should use a white or blue or green LED as they are likely also 3V rated. Normal red and yellow and sometimes green LEDs are around 1.8V ~ 2V so if provided with 3V without a proper resistor, the LED may burn off by excessive current. LED stands for Light Emitting Diode and its voltage rating can be measured by using a multimeter. I have also created a dedicated LED voltage meter/tester if you are interested in making one.
The magic lightbulb above is ok to demonstrate how it works. Since I have plenty of magnets (Neodymium strong magnets), I improvised a bit. You can build one with the materials and steps shown below.
Some points to note:
There are different Reed switches. The glass ones are easy broken so I recommend the plastic enclosure ones such as this.
LED has two legs. The longer one is positive and shorter leg is negative. LED will not work if polarities are connected incorrectly. But do not worry, the LED will not be damaged when the polarities (positive and negative) are connected wrong.
The Reed switch may have a more sensitive side. This needs some testing in positioning. But usually there is a good range to work.
To activate the Reed switch, a small 5x2 neodymium magnet is sufficient in this project. However, I need another 4 (2 on lightbulb and 2 on the socket) to attract these two parts together.
CR2032 or CR2025 or other 3V button batteries can all work. CR2032 will last longer than CR2025 as it holds more energy. However, they can both last long on just one LED as LED consumes only little energy.
Do not worry if you cannot get a button battery holder. Good skills on taping battery and wires can be equally good. Here is the battery holder if you want to buy.
There are other conductive materials such as aluminium tape or copper tape. Try to utilise what you have if you do not have wires.
I found that the 3M Magic Tape is good for this project. You could consider using them.
Be safe and careful when using tools.
There are many problem-solving moments when making one. Young children could explore in depth about circuit, electricity, battery, magnetic sensor (reed switch), LEDs, applications with reed switch, and know what is inside a lightbulb. Be aware to provide safety instructions to young children that the real lightbulb runs on 240 volts AC is not to be tempered.
Another other thoughts? Please leave a comments below.