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125 results found, displaying items 61 - 80
Digital Potentiometers Vary Amplitude In DDS Devices
Direct digital synthesis (DDS) devices are used in many applications to generate signals of different frequencies. The devices have frequency registers that enable users to alter the frequency of the signal, and phase registers to allow phase...
Dual Current-Limiting Switch For USB Applications
The number of hot-plug applications has increased dramatically due to its benefits of system down-time reduction and portability. The consequence of implementing hot-plug capability is that inrush or surge currents are produced when any uncharged...
Software Utility Generates Line Numbers For Code Listings
Several vendors of integrateddevelopment-environment (IDE) software don’t provide the capability of printing line numbers with program code listings. This additional line-number information can improve code readability and make the debugging process...
Multiplexer Restores Analog Inputs To Flash Microcontroller
The Microchip PIC16F877 microcontroller provides data acquisition, digital I/O, and parallel port communication in an easy-to-use package. However, by design, if the parallel slave port is used, the analog input channels 5 through 7 aren't...
Comparator Features Symmetrical Thresholds
The comparator often is the simplest bridge between analog and digital worlds, but crossing this bridge isn't as simple as might be thought. Keep in mind, we are leaving the analog world with an indefinite number of states and entering into a vastly...
87C751 MCU Programmer Has Serial-Bus Interface
The Philips 87C751 is an 8-bit 8051-compatible microcontroller with a small footprint (the 24-pin "skinny DIP" package is discussed here) and special enhanced capabilities. It has 2 kbytes of EPROM program memory and 64 bytes of RAM. The most useful...
Eliminate RTD Self-Heating Errors
Synchronous detection, long used in telecommunications because of performance potential, can now be effectively applied to sensor interface circuitry due to advances in low-cost ICs. This circuit (see...
Roll Your Own Electronic Lock
Electronic security locks, popularly known as “dongles,” are commonly used to deter software piracy. This idea describes a simple yet-powerful design of such a security lock using the linear feedback shift register (LFSR) principle. The lock, which is...
High-Current, Low-Voltage Shunt Regulator
This design idea describes a high-current (up to 8 A) shunt-regulator built around the TLV431 low-voltage, adjustable, precision shunt-regulator IC. Special attention was paid to implementing this design as a "two-terminal" circuit block, greatly...
3.3-V Supply Taps Power From The 12-V PCI Bus
The backplanes of popular multi-supply buses (such as VME, VXI, and PCI) each provide power-limited outputs of 3.3 V, 5 V, and ±12 V (or ±24 V). If adding line cards to these systems increases the requirements for 3.3- or 5-V power, the...
Current Loop Has 5-kV Isolation
This Idea for Design was originally published Jan. 7, 1993, p. 113. By using an AD7245A DACPORT, a linear optoisolator, and a discrete V-I converter to control loop current, a 4-to-20-mA isolated current loop may be digitally...
Solid-State Multiplexers Reduce Half-Bridge Error
The half-bridge configuration is handy when using nonlinear sensors, such as thermistors, since it can partially compensate for the sensor's nonlinearity. However, multiplexing a single resistor to multiple sensors generally requires the use of...
Alternating Relay Preserves Pumps By Equalizing Run Time
In many industrial pumping applications, two identical pumps are used for the same job. A standby unit is available in case the first pump fails. However, a completely idle pump might deteriorate and provide no safety margin. Alternating relays...
MOS Switches Find An Application In An Analog ATE Circuit
MOS switches have for the most part been excluded from a large number of analog and mixed-signal test applications because of their high leakage currents and larger on-resistances. Relays, particularly low-picofarad relays and low-thermal-EMF...
An Internet Oven Monitor
The functional test department of our electronic subcontracting firm burns in several products for our customers, some for several days. Our burn-in chamber runs over the weekend, and has several...
Resistors Protect Microcontrollers From Capacitively Coupled Spikes
The microcontroller circuit shown in the figure initially behaved very strangely—rebooting the microcontroller at odd moments, and often latching one...
PWM Motor Speed Control Uses AC Tachometer Feedback
Many dc servo motors provide an ac tachometer output for speed measurement or regulation. The circuit in Figure 1 uses such a tachometer output (output...
PIC Microcontroller Self-Regulates Its Power Supply Using PWM
Developing consumer products can often involve the design of small, low-cost, handheld, battery-powered circuits with an embedded controller. Thanks to the availability of inexpensive 8-bit...
Simple Circuit Creates Magnetic-Card Lock
This is a simple but interesting circuit to make a magnetic card lock. Using this lock system, shown in the figure, you can open a door, switch on a...
RFID Tag Reader Uses FSK To Avoid Collisions
The RFID (radio-frequency identification) system consists of an RFID tag, a reader, and a user-interface computer. The passive RFID tag contains a silicon chip and an LC antenna circuit. The...
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