Electronic Circuits and Tutorials
Electronic Schematics - D

Humidity Sensors and Detectors Circuits

Connection Tester -  A low resistance ( 0.25 4 ohm) continuity tester for checking soldered joints and connections

Dew Sensor - Dew (condensed moisture) adversely affects the normal performance 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.

Environmental Compensation on the AD7142 -  AN-829 Analog Devices Application Notes....[App Note]

Circuitry for Inexpensive Relative Humidity Measurement -  National Semiconductor Application Note....[App Note]

AN-829: Environmental Compensation on the AD7142: The Effects of Temperature & Humidity on Capacitance Sensors -  AN-829 Analog Devices Application Notes....[App Note]

AN-256: Circuitry for Inexpensive Relative Humidity Measurement -  National Semiconductor Application Note

741 Based Light Sensor -  The circuit as shown act as a light sensor. Under normal conditions the resistance of the LDR is high, keeping pin 2 low. When light falls onto the LDR the resistance drops to a couple hundred ohms and triggers pin 2 high which biases the base of Q1 via pin 6 and R4 and in turn activates the relay.…. [Tony van Roon's circuit]

Circuit Tests Power Outage Susceptibility -  03/03/97 EDN-Design Ideas.... EDN is migrating links. This link is not verified.  Search the "title" EDN for new link.

Low-cost relative humidity transmitter uses single logic IC -  8-Nov-01 Issue of EDN  The low-cost percentage-relative-humidity radio transmitter in Figure 1 operates in a cold-storage warehouse for vegetable storage at temperatures of 1 to 5°C. It is generally difficult to collect such data from a low-temperature area with high humidity and low illumination. The transmitter design is simple  It uses a readily available, capacitor-type percentage-relative-humidity se.... [Design Idea by Shyam Tiwari, Sensors Technology Ltd, Gwalior, India]

Measure humidity and temperature on one TTL line -  30-Aug-01 Issue of EDN  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.... [Design Idea by Shyam Tiwari, Sensors Technology Pvt Ltd, Gwalior, India]

Remote humidity sensor needs no battery -  4-Apr-02 Issue of EDN  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.... [Design Idea by Shyam Tiwari, Sensors Technology Private Ltd, Gwalior, India]

Signal Conditioning Precisely indicates Humidity -  02/02/98 EDN-Design Ideas....The circuit in Figure 1 translates the level of humidity from 0 to 100% into a stable, respective dc signal of0 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 of0.8 to 4.0V.... [Design Idea by William White head, Lafayette, CO]

Tiny Dew Sensor -  ....

Transmitter senses triple relative-humidity figures -  26-Sep-02 Issue of EDN  The circuit in Figure 1 is a triple, relative-humidity sensor and radio transmitter. Sensors 1 and 2 form two gated oscillators with natural frequencies of 10 and 5 kHz, respectively, at relative humidity of 50%. The gated oscillators use variable resistances R2 and R3, respectively. Together, these two oscillators generate FSK-modulated outputs at output of IC1B, Pin 6.... [Design Idea by Shyam Tiwari, Sensors Technology Ltd, Gwalior, India]

Wireless Temperature & Humidity Sensor with USB -  this project is based on obdev's Remote Sensor example and their firmware-only USB implementation; the main change is the replacement of the analog sensors with a Sensirion SHT11 digital temperature and humidity sensor

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