Circuits & Schematics

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 ...

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 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 ...

There are many applications when a remote switch’s on/off status needs to be monitored. Reed relay sensors, toggle control switches and security alarms contacts are just a few examples. Routing a switch directly to a computer system hundreds ...

A self-heated Darlington transistor pair makes a simple, sensitive, and sturdy airflow sensor. But first an annoying non-linearity needs unbending. If you take a self-heated transistor in a TO-92 package and force it to hold a constant temperature ...

Converting frequency signals to loop current signals creates an economical result for process industry applications. Process industry applications commonly employ multiple motors. Their speeds are monitored by tachometers using magnetic pickups ...