A humidity sensor with temperature compensation built-in. Never apply a DC voltage to the sensor, even measuring the sensor with an ohmmeter will damage the device, always ensure that an AC voltage is applied. Avoid condensation, freezing, dust, mist, oil, alcohol, etc. To set up this circuit replace the H14DL with Min Res 22Kohm and Min Res 51Kohm as shown, Acjust RV1 until a voltmeter between output and ground reads 1.40V. ..
The main (and only) job of this circuit is to activate a buzzer or a relay, each time the level of humidity takes a specific value. Main stage is a memory based on a flip-flop consisting of gates and IC1a IC1 b. The output of this step activates an oscillator (IC1c), which in turn leads to a piezoelectric speaker. At the start of operation of the circuit, the flip-flop is driven to logical '0' or through the C1 or through C2. From the moment you excited, the reintroduction.....
This circuit combines two LTC1043s with a based humidity transducer in a simple charge-pump based circuit. The sensor specified has a nominal 400 pF capacitance at RH = 76%, with a slope of 1.7 pF/% RH. The average voltage across this device must be zero. This provision prevents deleterious electrochemical migration in the sensor. The LTC1043A inverts a resistively scaled portion of the LT1009 reference, generating a negative potential at pin 14A. ..
The sensor is an RC oscillator in which, a water-absorbent plastic film is the insulator in the capacitive element. The capacitance of the film increases with the amount of water it absorbs from the air, and thus reduces the oscillation frequency. A frequency counter produces a digital output that represents the change inirequency and hence the change in relative humidity. The sensor can be used to measure humidity in the atmosphere, in the soil, and in industrial.....
When the 14B-12B pair opens, 12B is connected to Al's summing point via 13B. The sensor now discharges into the summing point through the 1 µ capacitor. Since the charge voltage is fixed, the average current into the summing point is determined by the sensor's humidity related value. The 1 µ value ac couples the sensor to the charge-discharge path, maintaining the required zero average voltage across the device. The 22M resistor prevents accumulation of charge, which.....
Dew (condensed moisture) ad- versely affects the normal per- formance of sensitive electronic devices. A low-cost circuit described here can be used to switch off any gadget automatically in case of excessive humidity. At the heart of the circuit is an inexpensive (resistor type) dew sensor element. Although dew sensor elements are widely used in video cassette players and recorders, these may not be easily available in local market. However, the same can be procured from.....
By combining the responses of an Analog Devices (www.analog.com) AD590 temperature sensor and a Humirel (www.humirel.com) HS1101 humidity sensor, you can generate a single TTL-level signal containing information from both sensors (Figure 1). This design uses a 74HC123 monostable multivibrator, IC1, to form a free-running oscillator. The AD590 current source (1 µA/K), IC2, and a fixed 1-nF capacitor, C1, control the timing of the first monostable multivibrator in the 74HC123...
Dew (condensed moisture) ad- versely affects the normal per- formance of sensitive electronic devices. A low-cost circuit described here can be used to switch off any gadget automatically in case of excessive humidity. At the heart of the circuit is an inexpensive (resistor type) dew sensor element...
This simple circuit can detect the invisible fields of voltage which surround all electrified objects. It acts as an electronic "electroscope." Regular foil-leaf electroscopes deal with electrostatic potentials in the range of many hundreds or thousands of volts. The above device can detect one volt. Its sensitivity is ridiculously high. Since "static electricity" in our environment is actually a matter of high voltage, this device can sense those high-voltage electrically.....
Dew (condensed moisture) ad- versely affects the normal per- formance of sensitive electronic devices. A low-cost circuit described here can be used to switch off any gadget automatically in case of excessive humidity...
The circuit in Figure 1 translates the level of humidity from 0 to 100% into a stable, respective dc signal of 0 to 100 mV. The heart of the circuit is IC1, the IH3602-C relative-humidity sensor (Microswitch/HyCal Sensing Products, Freeport, IL). This device operates on 5V at 200 mA and provides a dc output of 0.8 to 4.0V over the 0 to 100% humidity range...
Using ac-line power sources and batteries for remote humidity sensors is undesirable because these sources can be troublesome if you mount them in inaccessible points, such as smokestacks, cold-storage chambers, or darkrooms, where maintenance is difficult and inconvenient. Figure 1 shows a simple way to remove the power source from the humidity-sensor circuit. The circuit uses a 160- to 200-pF, capacitor-type HS1101 humidity sensor from Humirel for the circuit...
Dallas Semiconductor, in conjunction with Texas Weather Instruments, Inc., previously developed a basic weather station that used 1-Wire technology to measure wind speed, wind direction, and temperature [1]. The stations capability was next expanded to include a rain gauge that was connected to the 1-Wire net by simply plugging it into the expansion connector on the weather station board [2]...
Traditional control-system designs use separate switches to control power and various system functions, but adding a few components to a small, microprocessor-based system can combine a control function with the system`s on/off switch. For example, you can design a system to display relative humidity and temperature (Reference 1)...
IC1D is a CMOS Schmitt trigger oscillator at about 2KHz. It starts and continues to oscillate with a supply down to 1.24V (the lowest output voltage of my LM317 variable power supply) or less. IC1A is an inverter. IC1B is a Schmitt trigger NAND gate. Its output is low only when both inputs are at, or higher than the upper Schmitt trigger threshold voltage. With 47 ohms or less between the probes, an input is always low, so the output is always high. With a resistance of.....
By combining the responses of an Analog Devices (www.analog.com) AD590 temperature sensor and a Humirel (www.humirel.com) HS1101 humidity sensor, you can generate a single TTL-level signal containing information from both sensors (Figure 1). This design uses a 74HC123 monostable multivibrator, IC1, to form a free-running oscillator...
This is a circuit thich I originally included in my book, 22 Tested Transistor Projects, published by Babani Press in 1976 (ISBN 0 900162 63 S). It is one I had great fun with. It uses the PUT Complimentary Feedback Pair as a sensitive detector of changing electric fields to switch on an oscillator and make a noise. It is so sensitive that it can be difficult to get it working on a test bench because of all the electric fields, but put it on a table and leave it. Then when.....
The circuit in Figure 1 translates the level of humidity from 0 to 100% into a stable, respective dc signal of 0 to 100 mV. The heart of the circuit is IC1, the IH3602-C relative-humidity sensor (Microswitch/HyCal Sensing Products, Freeport, IL). This device operates on 5V at 200 mA and provides a dc output of 0.8 to 4.0V over the 0 to 100% humidity range. The output impedance is 5 mA when sourcing, and on-chip circuitry preconditions the humidity-related charge of a.....
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