LED Circuits and Projects

CircuitsToday.com is introducing some simple LED circuits and projects which can be done even at home. These circuits and projects have already been tested and published along with circuit diagram, schematics, and a detailed working description for each one of them. Also go through the comment of each LED circuit article, so as to get a better understanding of the IC’s used and the modifications that can be brought to the circuit. To know the working of LED, click on the link – LED Working

1. Dancing Light

The circuit uses a 555 timer and a CD 4017 IC. The clock pulses for the CD 4017 IC are provided by the timer IC which is connected as an astable multivibrator. The pin number 14 of the CD 4017 IC is the clock input pin. When the clock pulses are fed to this pin, the 10 output pins become high one by one alternatively. When the LED’s are connected to these outputs, they also continuously turn ON and OFF according to the pulses the timer provides. Take a look at the circuit diagram in the main article.

2. Night Security Light

As the name implies, this circuit is used to make your home secure by automatically switching on a light around two hours after midnight. This is done with the help of a CMOS IC 4060. The circuit will need an LDR, TRIAC, LED’s and resistors from its design. Read more about this interesting circuit from its original content.

3. Delayed ON LED

In this circuit design, the LED connected to the output glows only after a preset time after the power is switched ON. The capacitor plays an important role in switching the transistor ON. A preset andpotentiometer is also needed for the circuit.

4. LED Torch Using MAX660

A MX 66o CMOS type voltage converter IC is used to make this LED torch circuit. The IC has the capacity to drive 3 bright white LED’s. This is a simple LED torch circuit based on IC MAX660 from MAXIM semiconductors. The MAX 660 is a CMOS type monolithic type voltage converter IC. The IC can easily drive three extra bright white LEDs. The LEDs are connected in parallel to the output pin 8 of the IC.

5. Temperature Controlled LED’s

The circuit is nothing but two LEDs (D1 and D2), whose status are controlled by the temperature of the surroundings. A temperature sensor called Lm 35 IC is used in this circuit. With every 1 degree rise in temperature, the output the sensor increases by 10 millivolts. An op-amp called CA3130 also used and the output of the temperature sensor is given to the non-inverting input of the op-amp. The inverting input is given a reference voltage with the help of a potentiometer. When the reference voltage and the non-inverting input voltage become the same due to increase in temperature, the output of the op-amp goes into saturation. This makes the transistor connected to the output of the op-amp ON, and thus causes the LED to glow. Further working of the article can be obtained from the main link above.

6. USB LED Lamp Circuit

This is a practical USB powered lamp circuit that can be used to light up your room during power failure. The voltage required for the working is obtained from the 5 volt available in the USB port. The voltage has to be passed through a current limiting resistor and a transistor. In the circuit two LED’s are used for the lamp. Another LED is needed as an indicator to show the connection between USB port and the circuit.

7. LED Thermometer for Temperature Measurement

A sensor called LM 34 IC and a bar graph driver IC called LM 3914 IC are used to design a high precision LED bar graph Fahrenheit thermometer. The circuit is used to find the temperature in Fahrenheit. This can be modified to measure the temperature in degree Celsius by exchanging the LM 34 sensor IC with LM 35. A voltmeter is used to calibrate the circuit. The detailed explanation of the circuit can be obtained from the circuit above.

8. Automatic LED Emergency Light

This single article contains three emergency light circuits made with 3 different IC’s. The first one is the Simple Emergency Light Circuit that is used to sense daylight and thus turn OFF. The reverse also happens, where the lack of daylight causes the LED to turn ON. The circuit uses an LDR to sense the light. A photograph of the circuit and the PCB design is also available in the original content.

The next article is the automatic LED emergency light circuit using the IC LM 317. The modified version is also available here.

9. Simple Water Level Indicator

This circuit can be used to detect the level of any conductive, non-corrosive liquids. The circuit requires five transistors and its corresponding driving LED. The transistor turns ON when the base current is supplied from the electrode probes that are connected inside the tank. Different probes are connected at different levels of the tank. One electrode probe is (F) with 6V AC is placed at the bottom of tank. All the other probes are placed at quarterly, half, and three quarterly levels. The circuit is connected in such a manner that when the water touches each level probe, the LED corresponding to it begins to glow, showing the correct level. Learn more about the circuit from the link above. Do not forget to go through the notes where the importance of pure ac for the circuit is specified.

10. Flashing LED Unit

This is the cheapest and less power consuming circuit (3 volt button cells are enough) out of the lot. The circuit is designed to work as an LED flasher to produce a rotating effect when the LED’s are arranged properly. The circuit consist of a 555 timer connected as an astable multivibrator with a duty cycle of 50 percent and 4 Hertz frequency so as to drive 6 LED’s. Another timer circuit is also connected as a trigger pulse inverter so as to drive another 6 LED’s. The circuit is arranged such that the ICs sink the current consumed by the LEDs. The detailed explanation and circuit diagram is available in the above post.

11. Water Level Controller

This is one of the most reliable circuits in this site. The circuit uses a 555 timer IC, six transistors, a relay, and a few passive components. The circuit is constructed in such a manner that it automatically switches the motor to OFF position as soon as the water rises above the desired level. The circuit can also be used to start the motor to pump the water into the tank. Four probes are used in the circuit which is connected on the bottom level, half level, medium level, and the full tank level. The water level is sensed using three transistors. The transistors remain off as long as the water level does not exceed more than the quarter level. When the water level touches one of the probes (other than the bottom level one), the corresponding transistors get biased and switches ON. Further working of the relays that are connected to the transistors, and the importance of the 555 timer can be understood from the main article.

12. LED Lamp Circuit from Scrap

This simple LED circuit is based on converting a broken or dysfunctional CFL into a LED based power saving light. The images of the completed circuit and the circuit diagram are also provided in the main article. Do not forget to look at the different procedures listed to assemble the circuit.

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