Watchdog Timer set for 36 Hrs -  A watchdog timer is often used in computer systems to detect when a computer is hung up and is no longer running properly. If it does become locked up and is not able to supply a reset pulse to the circuit within a defined time frame the timer times out a . . . [Hobby Circuit designed by David A. Johnson P.E.,  04/11/10]

Watchdog-reset catcher aids embedded-system debugging -  11/19/98 EDN Design Idea  (File has serval designs)  Power op Amps have a real need for active output-current limiting. Most power-amplifier designs rely on the voltage drop across a user-supplied sense resistor to turn on an internal transistor. This method has several drawbacks, notably, an inability to change the current-limit point under program control. The current-limit circuit in Figure 1 allows you to establish the setpoint by applying a voltage to one of the Amplifier's pins. With this design, it is possible to set the current-limit point with the output of a DAC, possibly under the control of an embedded µC. . .  [by Joe Engle, Burr-Brown Corp, Tucson, AZ]

Water Filling Station Controller -  This circuit was requested by a company needing a simple way to fill a large tank with water with little fuss. They wanted a low tech method to automatically fill the tank with water without constant monitoring. They wanted to press a single pushbutton switch and then walk away . . . [Hobby Circuit designed by Dave Johnson P.E.,  04/24/11]

Water Flowing in Pipe Indicator -  The vibrations associated with water flowing through a pipe are picked up by an inexpensive piezoelectric wafer.   The signal from the wafer is first boosted by a micropower transistor Amplifier and then fed to an ultra low power voltage comparator.    When the vibration signal has sufficient Amplitude, a FET transistor switch is activated…[Circuit designed by Dave Johnson P. E. , 6/06/2009] . . . [Circuit by David Johnson P.E.,  07/26/09]

Water Level Detector -  . . .  [electronic design by Lennie Zink]

Water Level Monitor -  This system operates much like a classic float switch but without any moving parts. The illustration shows how a system using two copper coils sealed inside a plastic pipe, can detect the level of water outside the pipe. Whenever the water level is lower . . . [Hobby Circuit designed by David Johnson P.E.,  07/09/06]

Water Pump controlled by Solar Power -  A Discover Circuits visitor had a problem. He needed a simple on/off controller for his solar powered water pump. His system used two 12v 50 watt solar panels wired in series. The power from the solar panels drove a submerged water pump. However, during . . . [Hobby Circuit designed by David A. Johnson P.E.,  10/03/10]

Water Seepage Alarm -  This simple circuit sounds a beeper when its electrodes detect water. It is powered by a single 1. 5v N cell. A small 1. 5v button battery will also work . . . [Hobby Circuit designed by David Johnson P.E.,  06/11/00]

Water Seepage Monitor -  A while back I received a request from a company who needed a water seepage detector. They wanted a device that ran on 24vac and detected water using a fully isolated circuit. They wanted a circuit which switched off 24vac to a load when water was detected . . . [Circuit by David Johnson P.E.,  01/16/11]

Water-level Indicator -  Simple, two-wire, remote monitoring unit; Three-LED level display, 9V battery powered. . .  [Flavio Dellepiane's web site]

Waterman S-10-A Pocketscope oscilloscope schematic -  . . . 

Water-Softener Brine-Tank Salt-Level Monitor -  If you have hard water, did you ever forget to add salt to the water softener tank? This electronic device monitors how full the tank is using a Sharp DP2D12 infrared distance monitor. The results are displayed on a custom wall plate with a multicolor LED bar graph. The project also includes several photosensors to save power. . . .  [Robot Room website]

Watt Meter Measures True RMS Watts -  Measure All your AC Household Appliances. . . .  [G.L. Chemelec, designer]

Watt-Hour Energy Meter Based on the AD7755 Chinese Version-5/2000 -  AN-559 Analog Devices App Note - . . . 

Watt-Hour Energy Meter Based on the ADE7755 -  AN-559 Analog Devices App Note - . . . 

Watt-Hour Energy Meter Based on the ADE7757 -  AN-679 Analog Devices App Note - . . . 

Watt-Hour Meter Monitor -  Have you ever wondered how much power your house or apartment is using?  Most watt-hour meters are like the one shown below. Some newer ones have a digital display but there millions of these older models still in use . . . [Hobby Circuit designed by David Johnson P.E.,  09/28/08]

Watt-Hour Meter using PIC16C923 & CS5460 -  Application Note Published 16-Oct-00. . .  [Microchip]

Wattmeter -  The extra input B is for a later SWR bridge project, also the TX serial output will be in use later. The uncalibrated signal response is: +1/-1 dB from 1MHz to 450MHz. Input SWR vill vary from 1. 00 to 1. 30, depending on input frequency. To make the SWR this good, you need to assemble the input circuit correct and adjust the capacitor. Input power range: -60 to +30dBm that is 1 nW to 1 Watt. . . . 

Waveform Generator provides Flexible Frequency tuning for Sensor  Measurement -  12/17/04  EDN Design Idea   Variable-resistance sensors convert a fixed dc excitation voltage or current into a current or voltage that's a straightforward function of the quantity undergoing measurement. In another class of sensors, moving objects or fluids p. . .  [by Colm Slattery Analog Devices, Limerick, Ireland]

Waveform Generator provides Flexible Frequency tuning for SensorMeasurement -  12/17/04  EDN Design Idea   Variable-resistance sensors convert a fixed dc excitation voltage or current into a current or voltage that's a straightforward function of the quantity undergoing measurement. In another class of sensors, moving objects or fluids p. . .  [by Colm Slattery Analog Devices, Limerick, Ireland]

Waveform Monitor with LCD -  The result was a project that includes a waveform capture circuit, a graphic LCD (Liquid Crystal Display) and a control panel with LED indicators. The details of the Graphic LCD display unit, composed of the LCD module, a serial interface, and bias supply were published earlier on this site, . . .  [From Dick Cappels' project pages]

Weighting Filter -  Weighting filters are used to determine the "loudness" of sounds, particularly noise. You can very much discuss and criticise sense and nonsense of different weighting filters. . . . 

Wet Bulb Psychrometer -  The LTC2990 is used to monitor system temperatures, voltages and currents. Through the I2C serial interface, the device can be configured to measure many combinations of internal temperature, remote temperature, remote voltage, remote current and internal VCC. The internal 10ppm/°C reference minimizes the number of supporting. . .  [Linear Technology App Note - , Oct 26th 2010]

Whistle Responder -  Beeps when hears your whistle; A gadget suitable for key-holders, games etc. . .  [Flavio Dellepiane's web site]

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