Circuit detectors and sensors based electronics projects

An very simple ion detector circuit can be constructed like in the circuit shown bellow .As you can see in this schematic circuit this electronic ion detector circuit require few common electronic components .
This circuit detects static charges and free ions in the air .This ion detector circuit can be used for detecting presence of free ions , static electricity or high voltage leakage . Antenna used in this project is a short whip antenna and the R3 resistor is used to adjust the sensitivity of the circuit . The M1 from this circuit is an 100mA micro-Ampere-meter .

The ground connection is made by either an earth ground or can be attached to the hand using an aluminum foil .
The detector is set up to detect negative ions. It can be made to detect positive ions by simply reversing the polarity of the transistors that comprise the circuit, i.e., PNP units become NPN units, and NPN transistor is replaced by a PNP unit.

This detector circuit project must be powered from a 9 volts battery .

An very simple flow switch circuit can be designed using the LM1830 fluid level detector device that sense the presence or absence of aqueous solutions.
Using this flow switch circuit you can implement HIGH and LOW limit control controlling the operation of pumps or solenoid actuated valves .
The LM1830 is a monolithic bipolar integrated circuit designed to detect the presence or absence of aqueous fluids.
An AC signal generated on-chip is passed through two probes within the fluid. A detector determines the presence of the fluid by using the probes in a voltage divider circuit and measuring the signal level across the probes. An AC signal is used to prevent plating or dissolving of the probes as occurs when a DC signal is used. A pin is available for
connecting an external resistance in cases where the fluid impedance is not compatible with the internal 13 k divider resistance.

CD4016 quad CMOS analog switch allows the LM1830 to be used for HIGH and LOW limit
control applications. The switch sections are opened and closed by a control signal, where a HIGH level turns the switch ON and a LOW level turns the switch OFF.
The last switch section controls the base of a transistor which in turn drives a relay or solenoid actuated valve.

The start and stop probes are set at their appropriate levels in the fluid container, and the ground return is connected to a third probe located at a depth greater than the start and
stop probes. If the container is conductive, it may be used as the ground return.
By reversing the labeling on the probes, as well as reversing the polarity of the relay drive, a container "fill" control is implemented such as would be used in a water tower (necessary circuit changes are shown in Figure 2).
This fluid level detector circuit require a 6 volts dc power supply or it can be connected to the 220 or 110 volts outlets using a transformer .

A very simple Ionization Smoke Detector with Interconnect and Timer alarm circuit can be constructed using the A5367 is low-current, CMOS circuit that provides all of the required features for an ionization-type smoke detector.
A very nice thing at this ionization smoke detector circuit CMOS ic manufactured by Allegro MicroSystems is the interconnection features , which allows as many as 125 units to be interconnected so that if any unit senses smoke all units will sound their alarm. In addition, special features are incorporated to facilitate alignment and test of the finished smoke detector.
The internal oscillator and timing circuitry keep standby power to a minimum by powering down the device for 1.66 seconds and sensing for smoke for only 10 ms. Every 24 on-off cycles, a check is made for a low battery condition. By substituting other types of sensors or a switch for the ionization detector, this very-low–power device can be used in numerous other battery-operated safety/security applications.

This ionization smoke detector needs to be powered by a 9 volts DC power supply (or a 9 volts battery ) .Circuit require few external components and is very easy to be configured .
As you can see in this diagram , the sound alarm is “produced “ by an piezoelectric element .

Use an external resistor in point A to adjust sensitivity for a particular smoke chamber. Select resistor from point B is to reduce sensitivity during Timer mode.A resistor to VSS or VDD may be added to point C pin to modify low battery voltage threshold.
Value of components marked with D will vary, based on the piezoelectric horn used.
An internal timer is provided that can be used in various configurations to allow a period of reduced smoke detector sensitivity, referred to as Timer (or Hush) mode.
Internal test circuitry allows low battery check by holding the FEEDBACK and OSC CAP pins low during power-up, then reducing VDD and monitoring the HORN1 pin.