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Thermostat
for 12v Cooling Fan - This circuit will turn on a 12v
DC powered cooling fan when the air temperature reaches a certain high temperature and will keep the fan turned
on until the temperature drops below a second lower level. Both the high and low temperatures are both adjustable
. . . [Hobby Circuit designed by David A. Johnson P.E., 02/06/11]
Two buttons
provide safe start - 07/06/00 EDN Design Idea The
circuit in Figure 1 provides a safety interlock that checks the actuation of two pushbuttons before enabling a
relay. When you push both buttons, the circuit actuates the relay. At that point, you can release one of the
switch. . . [by Vincent Himpe, Alcatel Microelectronics, Desselgem, BelgiumVincent Himpe, Alcatel
Microelectronics, Desselgem, Belgium]
Ultra-High-Speed
Phase Discriminator Has no Dead Zone - File contains
several designs, please scroll to find this circuit. . . . [Analog Devices-Analog Dialogue by Jordan, Perry]
Version 4 of a DC
Current Indicator - The circuit below uses some common
components to turn on an LED whenever DC current above a certain level is detected. The circuit uses a very
popular LM393 dual voltage comparator from National Semiconductor and a common 1N4148 signal diode. The diode . .
. [Hobby Circuit designed by Dave Johnson P.E., 10/16/05]
Voltage Comaparator and Q Multiplier make a stable Sine Wave Oscillator (in PDF format) - It is a known fact that sinusoidal oscillators must rely on the action of some
amplitudelimiting mechanism in order to achieve good frequency and Amplitude stabilities. Likewise, accurate
loop-gain control and high-Q tuned circuits are required for the attainment of low-distortion output levels. . .
. [Designed by Ramon Vargas]
Voltage Comparator - This experiment only requires a single operational Amplifier. The model 1458 and 353 are
both "dual" op-amp units, with two complete Amplifier circuits housed in the same 8-pin DIP package. I recommend
that. . .
Voltage Comparator
Forms Pulse Demodulator - 11/19/98 EDN Design Idea (File
has serval designs) To process low-level ultrasound or radio-range pulses, you need a signal-conditioning
amplifier followed by a pulse demodulator to translate the signals to dc pulses. Traditionally, you would use a
diode-demodulator configuration (for example, the circuit in Figure 1a) with one stage of a single-supply op Amp.
The circuit in Figure 1b does the same job but uses a voltage comparator instead of a diode demodulator. The key
to the method is choosing a threshold voltage (VTH) on the negative comparator input that is slightly higher than
the dc level of the Amplifier output, which is equal to or close to VCC/2. The R4-to-R6 resistive divider
determines the difference between the op-amp bias and the threshold voltage. . . [by Abel Raynus, Armatron
International, Melrose, MA]
Voltage Comparator
Switch - This circuit will provide an indication whenever
the input voltage differs from two defined limits, V1 and V2. The supply voltage, VCC must be higher than the
highest input voltage by at least 2 volts. One application here is to monitor a 12V car battery. . . [Andy
Collison's website]
Wide Band Zero Cross
Detector - This circuit was designed to convert a low
amplitude 40KHz signal into a clean square wave signal. It will work with inputs as small as 5mv peak-to-peak or
as large as 3 volts peak to peak. The input frequency can range from a few kilohertz to about 150 . . . [Circuit
by David A. Johnson P.E., 02/18/06]
Zero-Cross Detector-Wide Band - This circuit was designed to convert a low Amplitude 40KHz signal into a clean square wave
signal. It will work with inputs as small as 5mv peak-to-peak or as large as 3 volts peak to peak. The input
frequency can range from a few kilohertz to about 150 . . . [Hobby Circuit designed by David A. Johnson P.E.,
02/18/06]
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