Homemade LED lamp circuit diagram

Also known as the electric-free lamp (commonly known as the Burmese lamp by online sellers), because it uses the incoming line voltage of an ordinary household fixed-line telephone as the power supply, without the need for batteries or AC mains power. The crystal head at the end can be inserted into the telephone extension interface to illuminate, without the need for another Pay the electricity bill and don’t worry about power outages. It also doubles as a flashing light for incoming phone calls. Remind the elderly with poor hearing to answer the phone in time, because the LED light will go out when the phone is off-hook. It can also help you detect in time whether the phone has been stolen by others. It also has a certain protection against lightning strikes. However, since this product uses the feed power supply of the telecommunications equipment room where the phone belongs, if the current required is too high during use, it will inevitably affect telephone dialing and fax sending and receiving, especially when ADSL broadband users dial up to access the Internet, it is easy to cause frequent disconnections. Figure 3 is the working principle diagram of the telephone line LED lamp circuit. The 36V or 48V telephone line DC voltage passes through the 10kΩ current limiting resistor and is polarized by 4 diodes (or rectifier bridges) before being added to the LED. When the telephone feed voltage When it is 36V, the measured working current is about 1.2mA, and the brightness is low. When the current limiting resistor is changed to 5.6kΩ, the working current rises to 2.1mA: the brightness is slightly increased.

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Considering that the telephone line LED lamp has a negative impact on the Internet and cannot be frequently connected to the telephone line, the author has made some modifications to the lamp. The modified circuit schematic is shown in Figure 4. The six LEDs in the middle have been modified. In parallel connection, a 3.6V mobile phone lithium-ion battery is added at the same time. Normally, the built-in new lithium battery is used to work. When the current limiting resistor is 5.6Ω, the operating current is about 120mA, and the brightness is quite satisfactory. In an emergency, you can still use the plug-in telephone extension interface for lighting. After the modification, the operating current is about 4.6mA, and the brightness is reasonable.

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