If you ever look at construction notes for building old detector type radio the type of headphones specified always have an impedance of 2 × 2000 Ω. Nowadays the most commonly available headphones have an impedance of 2 × 32 Ω, this relatively low value makes them unsuitable for such a design. However, with a[…]
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Voltage Reference for Battery Powered Circuits Schematic Circuit Diagram
The LM4050 from National Semiconductor is a high precision micropower shunt voltage reference in a sub-miniature, surface-mount, three pin, SOT-23 package. The unit operates in the industrial temperature range of –40°C to +85°C. The design eliminates the need for an external stabilizing capacitor and is at the same time stable when operated into any capacitive[…]
Read moreMains Powered Schematic Circuit Diagram
Many circuits can be powered directly from the mains with the aid of a series capacitor (C1). The disadvantage of this approach is that usually only one-half cycle of the mains waveform can be used to produce a DC voltage. An obvious solution is to use a bridge rectifier to perform full-wave rectification, which increases[…]
Read more2 × Dual = 1 × Quad Schematic Circuit Diagram
This is a sort of sequel to the article ‘2 × single = 1 × dual’. In this case, two dual opamps are combined to make one new quad opamp. This allows many possible variations, and again it allows two completely different types of dual-opamps to be used. It is very easy to replace a[…]
Read moreInfra-Red Light Barrier Schematic Circuit Diagram
This is a short-range light barrier for use as an intruder alarm in doorposts, etc. The 555 in the transmitter (Figure 1) oscillates at about 4.5 kHz, supplying pulses with a duty cycle of about 13% to keep power consumption within reason. Just about any infra-red LED (also called IRED) may be used. Suggested, commonly[…]
Read moreBattery Discharger Schematic Circuit Diagram
The battery discharger published in the June 1998 issue of this magazine may be improved by adding a Schottky diode (D3). This ensures that a NiCd cell is discharged not to 0.6–0.7 V, but to just under 1 V as recommended by the manufacturers. An additional effect is then that light-emitting diode D2 flashes when[…]
Read moreSerial-to-Parallel Converter Schematic Circuit Diagram
This converter may help if just the serial port on a personal computer is free, whereas the printer needs a parallel (Centronics) port. It converts a serial 2400 baud signal into a parallel signal. The TxD line, pin 3, CTS line, pin 8 and the DSR line, pin 6, of the serial port, are used[…]
Read moreHow to make a mobile phone charger (Part-2) Schematic Circuit Diagram
In Part-1 We have designed 5 volts smooth DC source for the mobile charger. In this section, we are going to make a short circuit protection circuit so that if any short circuit occurs the whole circuit will not be damaged. This circuit is enough to charge a battery. As shown in the schematic diagram[…]
Read moreSimple Frequency Doubler Schematic Circuit Diagram
Using just a few discrete components and two inverters, it is possible to build a simple TTL square wave frequency doubler for signals up to about 100 kHz. The input signal is applied to the differentiating circuit R1-C1. This converts the rising edge of the square wave into a positive pulse and the falling edge[…]
Read moreHow to make a mobile phone charger (Part-1) Schematic Circuit Diagram
This is the first tutorial on power electronics category and In this tutorial, we are going to make a mobile phone charger using easily available components. This is ongoing series and in the first part, we will design a smooth DC voltage source from 230 volts 60 Hz power supply which is generally used in[…]
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