Simple Strip LED Lamp

Strip LEDs are available in different colours powered by direct current (DC) source. These LEDs  are available as surface mount devices with current limiting resistors. Usually there are 300 LEDs in a 5-metre strip. The strip can be cut into pieces so that  the bits having three or four LEDs can  be used with 12V DC source. The circuit given here uses the strip LEDs to  make an automatic white LED lighting  source.

Simple Strip LED Lamp Circuit diagram:

The circuit is powered by a capacitor power supply connected to AC mains. Capacitor C1 drops the 230V  AC, which is further rectified by the bridge rectifier module and is made ripple-free by C2. Zener diode (ZD1) provides 12V DC to the comparator circuit. Resistor R1 is important in the  power supply as it provides discharge path to the voltage stored in capacitor C1 after the circuit is unplugged from  mains.

The automatic working of the circuit is based on the light-sensing property of the light-dependent resistor (LDR). Operational amplifier CA3140 (IC1) is used as a comparator with two potential dividers in its inverting and non-inverting inputs. LDR1 and  resistor R3 form one potential divider  that provides a variable voltage at the  inverting input pin 2 of IC1. Second  potential divider comprises resistors  R4 and R5, which provide half of the  supply voltage (6V) to the non-inverting pin 3 of IC1. The output of IC1 depends on voltage level at inverting  input pin 2 of IC1 as explained below.

In daylight, LDR1 has low resistance and the voltage at inverting input (pin 2) of IC1 is more than that of non-inverting input (pin 3). This makes IC1 output low, which drives transistor T1 into cut-off condition and strip LEDs do not glow. However, at night the light incident on LDR1 is low and its resistance is high. The voltage at inverting input of the comparator decreases, making it lower than the voltage at non-inverting input. This makes IC1 output high. Transistor T1 goes into saturation,  thus connecting cathodes of LEDs to  ground. All the LEDs in the strip turn  on and remain that way till morning.

Assemble the circuit on a general-purpose PCB and enclose it in a suit-able shock-proof case. Strip LEDs are available in ribbon-shaped form. Use 5cm bits (two bits) having three  LEDs each. The strip can be cut at supply-contact points. Strip LEDs are arranged on a flexible belt with  double-sided adhesive on the back  side, so it can be glued to any surface.  Connect the LED strip in the circuit  with correct polarity.

EFY note. Since the circuit uses 230V AC, there is a risk of electrical shock. Do not touch or troubleshoot when the circuit is plugged in.Before connecting the circuit to the power supply section, test it using 12V DC from a battery or DC power supply.

Source:  http://www.ecircuitslab.com/2012/05/simple-strip-led-lamp.html

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White LED Lamp

Nowadays you can buy white LEDs, which emit quite a bit of light. They are so bright that you shouldn’t look directly at them. They are still expensive, but that is bound to change. You can make a very good solid-state pocket torch using a few of these white LEDs. The simplest approach is naturally to use a separate series resistor for each LED, which has an operating voltage of around 3.5 V at 20 mA. Depending on the value of the supply voltage, quite a bit of power will be lost in the resistors. The converter shown here generates a voltage that is high enough to allow ten LEDs to be connected in series. In addition, this converter supplies a constant current instead of a constant voltage.


A resistor in series with the LEDs produces a voltage drop that depends on the current through the LEDs. This voltage is compared inside the IC to a 1.25-V reference value, and the current is held constant at 18.4 mA (1.25 V ÷ 68 Ω). The IC used here is one of a series of National Semiconductor ‘simple switchers’. The value of the inductor is not critical; it can vary by plus or minus 50 percent. The black Newport coil, 220 µH at 3.5 A (1422435), is a good choice. Almost any type of Schottky diode can also be used, as long as it can handle at least 1A at 50V. The zener diodes are not actually necessary, but they are added to protect the IC. If the LED chain is opened during experiments, the voltage can rise to a value that the IC will not appreciate.

Resistors:
R1 = 1kΩ2
R2 = 68Ω
Capacitors:
C1 = 100µF 16V radial
C2 = 680nF
C3 = 100µF 63V radial
Inductors:
L1 = 200µH 1A
Semiconductors:
D1 = Schottky diode type PBYR745 or equivalent
D2-D5 = zener diode 10V, 0.4W
D6-D15 = white LED
IC1 = LM2585T-ADJ (National Semiconductor)

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Up Down Fading LED Circuit

This circuit drives a motor clockwise / anticlockwise via a pot and reduces the speed to zero when the pot is in mid-position. The current is limited to 200mA and the voltage across the motor is less than 6v, but the circuit shows the principle of Pulse Width Modulation (providing powerful bursts of current to the motor to create a high or low RPM under load) and both forward/reverse RPM via the H-bridge arrangement.

Circuit diagram:

 Up/Down Fading LED Circuit diagram

 

Source : 50-555Circuits

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LED Torch using NSI45090JDT4G Constant Current Regulator

A very simple LED torch can be designed using the NSI45090JDT4G adjustable constant current regulator (CCR) designed by ON Semiconductor ,using extreme few external components. NSI45090JDT4G device is designed to provide a cost effective solution for regulating current in LEDs. This Constant current regulator is based on patent-pending Self-Biased Transistor (SBT) technology and regulates current over a wide voltage range. It is designed with a negative temperature coefficient to protect LEDs from thermal runaway at extreme voltages and currents.

LED Torch Circuit Diagram

The Radj pin allows Ireg(SS) to be adjusted to higher currents by attaching a resistor between Radj (Pin 3) and the Cathode (Pin 4). The Radj pin can also be left open (No Connect) if no adjustment is required.The maximum current that can be adjusted using this chip is around 160 mA , and the maximum input voltage is around 45 volts The D1 from the circuit shown here is used for reverse battery protection .

Bellow you can see how simple is to design a circuit using this chip ( all data shown bellow are for this schematic ) .
LED’s = ((Vin − QX VF − D1 VF)/LED VF)
Example: Vin = 12 Vdc, QX VF = 3.5 Vdc, D1VF = 0.7 V
LED VF = 2.2 Vdc @ 30 mA
(12 Vdc − 4.2 Vdc)/2.2 Vdc = 3 LEDs in series.

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LED light flasher

This is a good and simple circuit to flash one or more LED lights.  The circuit uses a NE 555 small IC. This IC is very common and easy to obtain from any electronic components shop.  As you can see in the circuit diagram we have used 10uF capacitor to control the flash speed of the LEDs. If you want to increase the speed simply put a higher value of a capacitor in place of 10uF.

Also you can increase the number of LED lights in parallel way. The maximum we recommend is 18 lights. Use PCB board to build this and supply six volts. Do not supply more than six as it can damage the your components as well as LED bulbs.

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7 Segment LED Counter Circuit With explanation

This simple counter can be used to count pulses, as the basis for a customer counter (like you see at the doors of some stores), or for anything else that may be counted. The circuit accepts any TTL compatible logic signal, and can be expanded easily (see Notes).

Parts

Part	Total Qty.	Description	Substitutions
R1-R7	7	470 Ohm 1/4 Watt Resistor
U1	1	74LS90 TTL BCD Counter IC	7490,74HC90
U2	1	74LS47 TTL Seven Segment Display Driver IC	7447,74HC47
DISP1	1	Common Anode 7 Segment LED Display
MISC	1	Board, Sockets For ICs, Wire

Notes

1. All pulses to be counted are to be TTL compatible. They should not exeed 5V and not fall below ground.
2. You can add more digits by building a second (or third, or fourth, etc...) circuit and connecting the pin 11-6 junction of the 74LS90 and 74LS47 to pin 14 of the 74LS90 in the other circuit. You can keep expanding this way to as many digits as you want.

www.aaroncake.net

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Tips on Choosing a Right Power Source for 12V LED Lights

If you are looking for how to choose a right power source for 12 volt LED lights, you will come to right place, This video gives you things to think about when choosing between a plug-in 12V adapter and a hardware 12V driver; how to choose the best wiring for a large installation; and about how permanent you want your LED light setup to be.

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Blinking LED circuits

This led series will Blinking alternately, The way it works is determined by IC NE555 and transistors are used as reinforcement for each section (20 upper, 20 lower) work optimally. 555 circuit below is a flashing bicycle light powered with four C, D or AA cells (6 volts). 

Two sets of 20 LEDs will flash alternately at about 4.7 cycles per second using RC values ​​shown (4.7K for R1, 150K for R2 and 1uF capacitor). Time intervals for two lights about 107 milliseconds (T1, LED on) and 104 milliseconds (T2 lower LEDs). 

Two transistors are used to provide additional time beyond the current limit of 200mA from the NE555 timer. A single LED is placed in series with the PNP transistor base so that the 20 LED 555 is turned off when the output is high during a time interval T1. High-level output timer 555 is 1.7 volts less than the supply voltage. Adding the LED forward voltage increase is required for the PNP transistor to about 2.7 volts, so the 1.7 volt difference from the supply to the output is not sufficient to activate the transistor.

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Dimming Controlled LED LM3409

This dimming controlled LED driver circuit is designed using LM3409 P-channel MosFET controller for step-down (buck) current regulators.The LM3409 devices use Constant Off-Time (COFT) control to regulate an accurate constant current without the need for external control loop compensation Dimming controlled LED driver electronic circuit require an input voltage of 36 volts and will provide at output a voltage of 24 volts at a maximum current of 700mA 

Components list

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Blinking LED circuits

This led series will Blinking alternately, The way it works is determined by IC NE555 and transistors are used as reinforcement for each section (20 upper, 20 lower) work optimally. 555 circuit below is a flashing bicycle light powered with four C, D or AA cells (6 volts). 

Two sets of 20 LEDs will flash alternately at about 4.7 cycles per second using RC values ​​shown (4.7K for R1, 150K for R2 and 1uF capacitor). Time intervals for two lights about 107 milliseconds (T1, LED on) and 104 milliseconds (T2 lower LEDs). 

Two transistors are used to provide additional time beyond the current limit of 200mA from the NE555 timer. A single LED is placed in series with the PNP transistor base so that the 20 LED 555 is turned off when the output is high during a time interval T1. High-level output timer 555 is 1.7 volts less than the supply voltage. Adding the LED forward voltage increase is required for the PNP transistor to about 2.7 volts, so the 1.7 volt difference from the supply to the output is not sufficient to activate the transistor.

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