Water level Controller

Water level controller circuit

Note:- We have developed another water level controller circuit using micro controller AT89S51 from Atmel. If you are interested, read that too :- Water level controller using micro controller

Are you familiar with the basics and the different applications of the 555 timer IC. If not, we recommend you 3 books that provide a very good understanding of the IC and its applications. You can check out the reviews and buy the book from our online store:- 3 Great Books to Learn 555 Timer Circuits and Projects.

Description.

A simple but very reliable and effective water level controller circuit diagram is shown here. The circuit uses 6 transistors, 1 NE555 timer IC, a relay and few passive components. The circuit is completely automatic which starts the pump motor when the water level in the over head tank goes below a preset level and switches OFF the pump when the water level in the over head tank goes above the full level.

Probe D is positioned at the bottom level of the tank while probes A, B and C are placed at full, half and medium levels of the tank respectively. The level sensing part of the circuit is built around transistors Q1, Q2 and Q3. When water level is below the quarter level probes A, B and C are open and the transistor Q1, Q2 and Q3 remains OFF. When the water level rises and touches the probes the corresponding transistors gets biased and switches ON. Resistors R1, R2, R3 limit the bases current of corresponding transistors while resistors R4, R5, R6 limit their collector current. LEDs D1, D2 and D3 provide a visible indication of the current water level.

Temperature Controlled DC Fan

This circuit can cool your heat generating electronic devices by operating a DC fan when the temperature in its vicinity increases above the preset level. Its operation is fully automatic and turns off when the temperature returns normal. It uses a small 12V DC brush less fan used in computers.

Schematic of DC Fan Controlled by Temperature Circuit

Note by P Marian: this is an updated version of the old circuit designed by D Mohankumar that didn’t function at

LIGHTENING DETECTOR

Clouds can carry such huge electric charges that may to cause lightning flashes of thousands of volts. It is really a fascinating phenomenon.
When a lightning flash takes place a broad spectrum of radio-frequencies is generated. In this broad spectrum there is special intense emissions of the VLF (Very Low Frequency) band. This project will allow you to build a receiver to pick up a band near 300 KHz. An LED will flash to indicate the lightning flashes.THE CIRCUIT
The radio-signal generated by the lightning flash is picked up by the telescopic antenna with the help of a 10mH choke. The choke L1 resonates with the antenna and allows current to flow into the receiver circuit.
The L2 of 330uH in parallel with the 680pF capacitor C1 forms a tuned circuit for 300KHz. This parallel-tuned tank circuit is coupled to the base of Q1 via D2. The amplified radio signal is again coupled into the base of Q2. Transistors Q2 and Q3 form an LED flasher circuit. Transistor Q4 is the LED driver.
The flasher is biased so that when VR1 is carefully adjusted the LED flashes only when a radio burst appears at the input due to a lightning flash.
Positive feedback ensures the LED to be full on. The circuit quickly resets by charging C4 capacitor through diode D1.
The circuit draws only about 100uA in idle state. Therefore it can run on two cells for many hours.
 

AC DETECTOR

This circuit will detect AC line currents of about 250mA or more without making any electrical connections to the line. Current is detected by passing on of the AC lines through an inductive pickup (L1) made with a 1 inch diameter U-bolt wound with 800 turns of #35 magnet wire. The pickup can be made from other iron type rings or transformer cores that allows enough space to pass one of the AC lines through the center. Only one of the current carrying lines, either the line or the neutral should be put through the center of the pickup to avoid the fields cancelling.
This is most important is very difficult to achieve. The best method is to make a short extension cord with the three conductors separated from each other.
If you make a 3-turn loop with say the active line, and pass a straight rod such as a metal bolt, containing 400 or more turns through the centre of the 3-turns, you will produce a very sensitive pick-up.
The magnetic pickup produces about 4 millivolts for AC line current of 250mA, or AC load of around 30 watts. The signal from the pickup is increased about 200 times at the output of the op-amp pin 7 which is then peak detected by the capacitor and diode connected to pin 7. The second op-amp is used as a comparator which detects a voltage rise greater than the diode drop. The minimum signal
needed to cause the comparator stage output to switch positive is around 800mV which corresponds to about a 30 watt load on the AC line. The output of the 1458 op-amp will only swing within a couple volts of ground so a voltage divider (1k/470) is used to reduce the no signal voltage to about 0.7 volts. An additional diode is added in series with the transistor base to ensure it turns off when the op-amp voltage is 2 volts. You may get a little bit of relay chatter if the AC load is close to the switching point so a larger load of 50 watts or more is recommended. The sensitivity can be increased by adding more turns to the pickup.

Instrument controlled by brightness of light!

Create a functional circuit diagram that makes an instrument controlled by brightness of light!

This is one of the 48 projects for our Instructables: Made In Your Mind (IMIYM)exhibition at the Children’s Museum of Houston showing from May 26, 2012 - November 4, 2012. Produced in partnership with Instructables, IMIYM is an exhibit where families work together to build different fun, toy-like projects that help construct knowledge and skills related to science, technology, engineering, and mathematics while instilling a “do-it-yourself” attitude in kids so they feel empowered to explore, tinker, and try to
make things themselves. To learn more, check out the article here.

For this project, we were inspired by the How to Make an Easy PhototheraminInstructable created by TigrisLi (which, as I discovered is based on the Audible Light Probe by Forrest M. Mims III of Radio Shack books fame) , but there may be others on Instructables that are also similar. Often, the materials and process for building our projects are designed for use with a large number of visitors (we see over 800,000 annually) and the need to ensure safety in a mostly non-facilitated environment (in other words, no soldering). So, yes, many of these projects have room for improvement in both materials and methodology, which is PRECISELY what we want to encourage the kids to do. So please do share your ideas for improvement and

Dark Sensor ( light sensor / automatic street light )

Here is my new simple Electronics project about  Automatic Street Light Control System or Dark Sensor.

it is a simple and powerful concept , which uses transistor ( BC 547 NPN) as a switch to switch ON and OFF the street light system automatically .
It automatically switches ON lights when the sunlight goes below the visible region of our eyes. ( e.g in evening after Sunset ).

it automatically switches OFF lights when Sunlight fall on it ( e.g in morning ) , by using a sensor called LDR (Light Dependent Resistor) which senses the light just like our eyes.

Needs no manual operation for switching ON and OFF...

Dark Sensor with LDR, transistor and a LED

You wan't do a dark sensor with a LDR, one transistor and one LED and you don't know how to do it? In this small tutorial I will explain to you how you can do that even if you know only the basics of electronic.

Parts you need:

1 Breadboard;
1 Power source of 12v;
1 Transistor (in this case we use the BC547);
1 Resistor of 1KOhm;
1 Resistor of 680KOhm;
1 LED (in this case blue);
1 LDR:
Some condutor cables to connect the parts.

Step 1: Connecting parts in the breadboard

In the above image we can see the circuit we will construct. It's a simple electronic circuit and if you know how to do something on a breadboard, you should be able to do that dark sensor.

Night light with ldr

with ldr

Step 1: Things Needed

1. Transistor (2N3906)
2. leds
3.resistor (brown-black-orange-gold)
4.LDR
5. Another resistor for saving the led from burning out(red-red-brown-gold)
6.some hookup wires for connecting
the parts together
7. Breadboard

Steam sensor

Here is the circuit diagram of a simple steam sensor, wired around a handful of inexpensive components. This steam sensor can be connected to a microcontroller’s I/O port directly. The steam sensor works by having a sensor pad with series of exposed traces connected to ground rail, and interlaced traces between the grounded traces connected to the input of a comparator. The output voltage will change when the humidness of the sensor pad surface goes up. There is also an onboard potentiometer to adjust the system sensitivity. You even could use it as a rain/moisture sensor.

Features

• Low power consumption
• Adjustable sensitivity
• Onboard status indicators
• Digital and Analog output
• uC-compatible operating voltage: VCC = 5V

In the prototype, the home-made sensor pad – built from a rectangular copper clad board with the pattern etched as shown below – has a dimension of 4×3 cm. However, you are free to build your own sensor pad as per your requirement and taste.

steam sensor pad

Here, one-part of the LM393 (IC1) works as the voltage comparator, a reference voltage at the inverting input (pin 2 of IC1) is set by the multi-turn potentiometer (P1). When the analog value, inputted to the non-inverting input (pin 3 of IC1) from the sensor pad goes beyond this pre-setted value, IC1 will output a digital value to indicate that the setup threshold value is reached, and the sensor is activated.

Note that, this steam sensor circuit offers two outputs; Digital (DO) and Analog (AO). If you only want a logic-low (L) level output when a threshold is reached, just use the Digital (DO) output. But if you are looking for a varying voltage value as the output to indicate the sensing parameters, the Analog (AO) output is your best option. The green-LED (LED1) works as the power-on indicator, and the red-LED (LED2) indicates active-state of the sensor circuit.

LM393 datasheet

As stated, the steam sensor circuit is based on a single comparator in the LM393 (IC1). Similar to an operational amplifier (op-amp), the comparator has inverting (–) and non-inverting (+) inputs. If the noninverting input is at a higher voltage than the inverting input the output goes high, and if the inverting input is at the greater voltage the output goes low. This is again the same as for an opamp, but there is a subtle difference in that the output stage of a comparator is usually an open collector type, that is to say, there is a switching transistor at the output that can used to control an external load of some kind.

The inverting input (–) of the comparator is fed with a pre-setted fixed voltage, and the non-inverting input (+) is fed from the sensor pad. In case of a steam detection, a certain fraction of the supply voltage is therefore fed to the non-inverting input, and this fraction is controlled by the humidity level on the sensor pad surface. If the potential fed to the non-inverting input falls, and the inverting input is at a higher voltage, the output transistor of the comparator switches on and a logic-low level is outputted through the comparator’s output terminal.

Construction of the circuit is extremely simple indeed, and it should be within the capabilities of complete beginners. To some extent the way in which the unit is constructed and used will depend on the precise application. It can be built into a small plastic or metal box and connected to the sensor pad via a twin lead. In most cases, however, it is more likely to be incorporated into another project. For highly critical applications the threshold levels can be “fine tuned” by tweaking the values of resistors R1, P1 and ofcourse by changing the dimension/track layout of the sensor pad.

HELP TAKEN:-

http://www.electroschematics.com/