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345 results found, displaying items 301 - 320
Programmable speed control targets stepper motors using 8254
This design idea describes a basic speed controller for stepper motors implemented by programming a common 8254 programmable counter timer IC. The speed control of the stepper motor is achieved by varying the OFF time in its clock’s duty cycle. All...
Transformerless EL display driver uses lower-voltage 555 IC
The 555 timer has been manufactured in greater volumes than any other linear IC. Regarded by many as one of the most successful devices of all time, the 555 timer is perhaps only equaled in popularity by the 741 op amp. The success of the part can be...
Reduce hum in video digitizer circuits
Low-frequency noise, especially hum, often is a problem in video systems. Fortunately, most hum experienced in such systems is common-mode. Hum and other low-frequency signals can be rejected by using the common-mode rejection capability of a...
Optically isloated and powered 1-kHz ADC
Some data-conversion applications require complete galvanic isolation of the signal source from system ground. Examples include industrial process monitoring using ion-selective and pH electrodes, and biological and medical diagnostics such as...
Control circuit keeps dc motor running at constant speed
The aim of the circuit presented here is to keep the permanent magnet dc motor running at a constant speed, set externally. To do this, the current through, and the voltage across, the brushes of the motor are monitored. The voltage consists of two...
Visible-laser driver has digitally controlled power and modulation
In the circuit presented here, a 10-bit digital-to-analog converter with a three-wire serial input operates and maintains a visible-light laser diode at constant average optical output power. A separate digital input line (MOD) enables a comparator...
Servo-motor acceleration control via armature current integration
Whenever the speed of a dc servo motor must be controlled with absolute accuracy, there’s no substitute for tachometer-based feedback combined with a fullblown servo loop. But in other applications, adequate steady-state precision and sometimes...
Digital logic interface for power-MOSFET control
Power MOSFETs have become increasingly popular for use in numerous high-power applications. But the major drawback of a typical industrial power MOSFET is that it requires a minimum gate threshold voltage of about 4 V (preferably about 8 V for...
Window Comparator Features Independent Adjustments
Window comparators, sometimes called limit comparators, determine when the input voltage is within a preselected range. The output voltage usually goes to a TTL high when the input voltage is within this preselected range. A typical windowcomparator...
Battery-Charger IC Doubles As Current Sensor
It’s always fun to try and find applications for an IC which its designer never intended. The circuit shown here is one such design. Many applications require a circuit that provides a ground-referenced output voltage that’s proportional to a measured...
Circuit senses high-side current from negative supply
The circuit shown monitors the flow of load current into a negative voltage source (Fig. 1). This requirement often arises in private branch exchanges, in ISDN power supplies, when monitoring supply currents...
Program gives asymmetrical Spice tolerance
Spice is unable to accommodate asymmetric tolerances for worstcase analysis. However, the DISTRIBUTION statement available in Monte Carlo analysis can accommodate asymmetric tolerances by creating histogram bins. Asymmetric tolerances can easily occur...
Robust, low-cost continuous phase FSK modulator
In bandpass data transmission, one common way to design low-cost frequency-shift-keying (FSK) analog modulators is to use two independent oscillators that have outputs switched according to the binary input wave to be modulated. While this approach is...
Multiplex A/D inputs without software
The circuit described here uses hardware instead of software routines and multiple I/O ports to select multiplexer channels in a data-acquisition system. It features an 800-ksample/s 14-bit ADC (U1), which receives and converts signals from an...
Series LED driver operates on 3-V input
The circuit described here consists of a constant current source with a voltage compliance of 30 V (see the figure). It’s capable of driving a series string of LEDs at currents up to 100 mA. A switching...
High-voltage power pulse circuit
Fast rise-time high-voltage pulses have many uses ranging from EMC testing to device characterization. The simple, low-cost circuit described here deals with the latter. It’s able to generate 0- to 1000-V pulses with currents up to 50 A, and a rise...
An accurate analog delay circuit
There are several ways to introduce an analog delay into a signal channel. If you have enough room in your product, an appropriate length of coax cable can be introduced. Inductorcapacitor delay lines can be purchased. My preference is to create the...
DC-controlled low-pass filter has variable breakpoint
When maximum performance is demanded from communications systems, test equipment, or any other frequency-sensitive systems, it’s imperative to get the point where the filter response is −3 dB (the breakpoint of the low-pass filter) placed...
Quick And Practical Design Of A High-Pass Third-Order Bessel Filter
In the design of a proximity switch using PIN diodes as the receiving element, the signal is first amplified and then must be filtered from any noise before proceeding to the several signal-conditioning stages of the proximity switch. Typically, to...
Wide-Band Analog White-Noise Generator
Commercially available white noise generators are rather expensive. The circuit presented here, however, is an inexpensive version that produces frequencies up to about 300 MHz. Its operation is based on the noise generated by the Zener breakdown...
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