Circuits & Schematics

One of my electronics interests is building radios, particularly those featured in older UK electronics magazines such as Practical Wireless, Everyday Electronics, Radio Constructor, and The Maplin Magazine. Most of those radios are designed to run ...

There are times when you would like to control a DC motor using a simple +5 V logic swing signal. The circuit below performs this feat and also includes an automatic motor braking circuit. When the input logic signal swings from 0 V to +5 V, the ...

The circuit below can switch up to 4 Amps of current with a peak voltage up to 20 V. It is fully isolated using two inexpensive red LEDs. One LED forms a red light source, which illuminates a second red LED. The circuit takes advantage of the 1.5 V ...

In many applications, you would like to hold the speed of a motor constant, even as variations in the power supply voltage or mechanical load try to change its speed. In other applications, the average current to the motor needs to be limited, so ...

Single-cell lithium-ion (Li-ion) chargers are widely used, yet many practical designs rely on highly integrated ICs that conceal their internal operation. The type of Li-ion charger outlined in this design is, somewhat surprisingly, not readily ...

This easy-to-build PWM source is a handy testing tool for hobbyists, technicians, engineers and other RC-based device developers. I work at a university where I’m charged with designing and developing all manner of circuits and systems for ...

This is a 12-key numeric keypad for use in a range of microcontroller projects (Figure 1). It has the advantage that you only need one analogue input to interface it. It's on a small 1.2 × 1.6 (30 × 40 mm) PCB, and I've also ...

Convert a 4-20 mA signal to 0-20 mA and deliver it to a grounded load with no additional power supply needed. Recently, EDN kindly published a design of mine for a micropower 4-20 to 0-20 mA current loop converter ( Ref. 1 ). Shortly thereafter, in ...

Version 1 A single lithium ion battery cell needs 4.2 V from a current source to insure it is fully charged. A solar panel with just enough individual cells wired in series to produce the needed voltage would be more efficient than one with more ...

The iconic LM2917 tackles frequency-to-current conversion with (very) few externals. Almost exactly 50 years ago in June 1976, to be precise National Semiconductor introduced the LM29x7 series, offering deceptively simple monolithic solutions to a ...