Wireless-Powered LED

Wireless power is transferred from transmitter to receiver coil using inductive coupling principle. For wireless power transfer to work efficiently, frequency of the transmitter and the receiver must be tuned to the same frequency. LC tank of transmitter side produces an oscillating magnetic field of the tuned frequency. LC tank of receiver side is same as the frequency of transmitter side, thus achieving high efficiency. Let us construct a wireless LED.

This wireless-powered LED can be used in mobile phone battery chargers, electric tooth brushes and low-powered loads such as LEDs, SMPSes, rotors and so on. The author’s prototype is shown in Fig. 1.

Author’s prototype for Wireless LED
Fig. 1: Author’s prototype


Visual and Audible Monitor for Electronic Interfaces

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Introduction

Most of the modern PCs and embedded systems have digital interfaces as RS232, printer ports, LIN, etc. for exchanging of commands and data with intelligent peripherals.

Figure 1 is showing typical case of RS232 interface between two computerized units.


Simple Audio Power Amplifier With NE5534/А And Darlington Transistors With Up To 30W Of Output Power

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Simple Low-Noise Audio-Distribution Amplifier

This article describes a low-cost audio-distribution low noise EFY Testedamplifier based on hybrid or mixed technology. Input to the amplifier is from low-noise, high-gain npn transistor. Output buffers are implemented with voltage followers using an operational amplifier (op-amp). The combination of low-noise transistor and push-pull output stage of the op-amp guarantees good characteristics of the hybrid amplifier.

Often we are required to send signals from one audio source to many loads/speakers. For that we use audio-distribution amplifiers. This circuit employs low-noise bipolar transistor BC550 and op-amp LM324, which are widely available at low cost.