Air-Gas

PIC16F84A Gas Detector

This is a gas detecting circuit capable of sensing many different types of gases. The sensor used is the GH-312 and from the datasheet it is capable of sensing gases like smoke, liquefied gas, butane and propane, Methane, alcohol, hydrogen, etc. I've used a 9V battery for this project because the sensor requires a 9V input. The output when the sensor is triggered is always 5V which is perfect for a direct connection to any microcontroller. Although I've used a 9V battery, any 12V power supply ( a small wall transformer for example ) will work perfectly since the sensor can handle from 9V up to 20V and the microcontroller's voltage is regulated by a 7805 regulator...

I designed this circuit many years ago to monitor the quality of a mile long column of air for future optical communications experiments. The transmitter system (circuit 72 below) uses a powerful xenon flash in conjunction with a large 12 inch fresnel lens at the transmitter end and a matching 12 inch lens with a PIN photo diode at the receiver. The receiver system was connected to a weather station and a computer to collect the changes in intensity of the light flashes under different weather conditions. It has the potential for a 30+ mile range. I have also used this system to conduct cloud bounce experiments...

This simple circuit uses an incandescent lamp to detect airflow. With the filament exposed to air, a constant current source is used to slightly heat the filament. As it is heated, the resistance increases. As air flows over the filament it cools down, thus lowering it`s resistance. A comparator is used to detect this difference and light an LED. With a few changes, the circuit can be connected to a meter or ADC to provide an estimation on the amount of air flow...

Many electronic components, including fourth-generation µPs, require forced-air cooling. However, the reliability of electromechanical components, such as cooling fans, lags behind that of electronic devices. Even if a fan does not fail, blockage of the air-intake vents can reduce airflow. The circuit in Fig 1 helps you protect against high-temperature-induced system failures by monitoring the performance of the cooling system...

The common thyristor solution used in higher current ac switching is two isolated SCRs. The added hardware and packaging required to provide the needed isolated heat sinking in this configuration is a cost drawback. Triacs allow a single heat sink, but are limited by their thermal performance in current, blocking voltage, and higher frequency applications...

Catalytic bead sensors are used primarily to detect combustible gases. They have been in use for more than 50 years. Initially, these sensors were used for monitoring gas in coal mines, where they replaced canaries that had been used for a long period of time...

The article describes the home combustible gas detector. Main motivation for this construction was my 3 years old son who has very positive relationship with the home hardware. Of course, nice buttons on the gas cooker are very interesting for him and he can hear nice hiss of the gas. The first situation like this accelerated my plan to develop some gas detector...

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]...

Brief (1 sec or shorter) power outages are common in developing countries and seem to be increasing in the United States. They are generally nondestructive, so power-protection equipment should not trip and disconnect the load. Electric motors do not appreciably slow, and electronic equipment can usually ride through the outages on the energy stored in filter capacitors. As a point of reference, a 10-msec outage makes an incandescent light bulb flicker...

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...

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...

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...

I designed up this circuit board because of a request from a visitor to my website. I also assemble the circuit board to Varify the board was correct. It does work, VERY NICELY, but I have no way to varify the accuracy of wind flow that is stated by the author. Since the Circuit Requires a Stable Supply, I have added a 5 Volt Regulator to the Circuit Board...

We are OUT OF STOCK on the surplus brushless DC motor we used to build this project, and since it`s surplus we cannot get any more. The resistor and capacitor values listed in the schematic and on the PC board plan depend on using this exact same motor...

This application note describes a low-cost circuit that can detect when a chassis fan filter has become clogged with dust. It does this by using a temperature sensor to determine the rate of cooling of a transistor in the air path of the cooling fan, thereby implementing a simple thermal anemometer...