Schematic Reference

A number of people have been unable to find the transformer needed for the Black Light project, so I looked around to see if I could find a fluorescent lamp driver that does not require any special components. I finally found one in Electronics Now. Here it is. It uses a normal 120 to 6V stepdown transformer in reverse to step 12V to about 350V to drive a lamp without the need to warm the filaments.

Circuit diagram:

12 Volt DC Fluorescent Lamp Driver Circuit Diagram

Parts:

C1 100uf 25V Electrolytic Capacitor
C2,C3 0.01uf 25V Ceramic Disc Capacitor
C4 0.01uf 1KV Ceramic Disc Capacitor
R1 1K 1/4W Resistor
R2 2.7K 1/4W Resistor
Q1 IRF510 MOSFET
U1 TLC555 Timer IC
T1 6V 300mA Transformer
LAMP 4W Fluorescent Lamp
MISC Board, Wire, Heatsink For Q1

Notes:

1. Q1 must be installed on a heat sink.
2. A 240V to 10V transformer will work better then the one in the parts list. The problem is that they are hard to find.
3. This circuit can give a nasty (but not too dangerous) shock. Be careful around the output leads.

Source : www.extremecircuits.net

This circuit is designed to drive the 1W LEDs that are now commonly available. Their non-linear voltage to current relationship and variation in forward voltage with temperature necessitates the use of a 350mA, constant-current power source as provided by this supply. In many respects, the circuit operates like a conventional step-down (buck) switching regulator.

Transistor Q1 is the switching element, while inductor L1, diode D1 and the 100mF capacitor at the output form the energy transfer and storage elements. The pass transistor (Q1) is switch-ed by Q2, which together with the components in its base circuit, forms a simple oscillator. A 1nF capacitor provides the positive feedback necessary for oscillation. The output current is sensed by transistor Q3 and the two parallelled resistors in its base-emitter circuit.

Circuit diagram:

1W LED Driver Circuit Diagram

When the current reaches about 350mA, the voltage drop across the resistors exceeds the base-emitter forward voltage of transistor Q3 (about 0.6V), switching it on. Q3’s collector then pulls Q2’s base towards ground, switching it off, which in turn switches off the main pass transistor (Q1).

The time constant of the 15kW resistor and 4.7nF capacitor connected to Q2’s base adds hysteresis to the loop, thus ensuring regulation of the set output current. The inductor was made from a small toroid salvaged from an old computer power supply and rewound with 75 turns of 0.25mm enamelled copper wire, giving an inductance of about 620mH. The output current level should be trimmed before connecting your 1W LED. To do this, wire a 10W 5W resistor across the output as a load and adjust the value of one or both of the resistors in the base-emitter circuit of Q3 to get 3.5V (maximum) across the load resistor.

Author: Nick Baroni - Copyright: Silicon Chip

It sometimes comes as a bit of a shock the first time you need to replace the batteries in an LED torch and find that they are not the usual supermarket grade alkaline batteries but in fact expensive Lithium cells. The torch may have been a give away at an advertising promo but now you discover that the cost of a replacement battery is more than the torch is worth. Before you consign the torch to the waste bin take a look at this circuit. It uses a classic two-transistor astable multivibrator configuration to drive the LEDs via a transformer from two standard 1.5 V alkaline batteries. The operating principle of the multivibrator has been well documented and with the components specified here it produces a square wave output with a frequency of around 800 Hz.

This signal is used to drive a small transformer with its output across two LEDs connected in series. Conrad Electronics supplied the transformer used in the original circuit. The windings have a 1:5 ratio. The complete specification is available on the (German) company website at www.conrad.de part no. 516236. It isn’t essential to use the same transformer so any similar model with the same specification will be acceptable.

The LEDs are driven by an alternating voltage and they will only conduct in the half of the waveform when they are forward biased. Try reversing both LEDs to see if they light more brightly. Make sure that the transformer is fitted correctly; use an ohmmeter to check the resistance of the primary and secondary windings if you are unsure which is which. The load impedance for the left hand transistor is formed by L in series with the 1N4002 diode.

Circuit Diagram :

Two-Cell LED Torch Circuit Diagram

The inductance of L isn’t critical and can be reduced to 3.3 mH if necessary. The impedance of the transformer secondary winding ensures that a resistor is not required in series with the LEDs.Unlike filament type light sources, white LEDs are manufactured with a built-in reflector that directs the light forward so an additional external reflector or lens glass is not required.

The LEDs can be mounted so that both beams point at the same spot or they can be angled to give a wider area of illumination depending on your needs. Current consumption of the circuit is approximately 50 mA and the design is even capable of producing a useful light output when the battery voltage has fallen to 1 V. The circuit can be powered either by two AAA or AA size alkaline cells connected in series or alternatively with two rechargeable NiMH cells.

Author :  Wolfgang Zeiller Copyright : Elektor

Here is an emergency lighting based on white LEDs offer the following advantages:

1. It is very bright thanks to the use of white LEDs.

2. The light turns on automatically when the mains fails and shuts down when power resumes.

3. It has its own office. When the battery is fully charged, the charging stops.

The circuit consists of two parts: the charger from the socket and the power LED part driver.The Charger is built around the 3-terminal adjustable regulator (IC1) LM317, while the LED driver is built on part of the transistor BD140 (T2). In the power charger power transformer in the AC input is a step down to give a 9V 500mA bridge rectifier consisting of diodes (IN4007x4). Filter capacitor (25v/1000uf) to eliminate the ripples. Unregulated DC power is fed to IC1 pin 3 and provides a charging current through the diode IN4007 (D5) and limiting resistance (16ohm) R16. By providing pre-k 2.2 (VR1), the output voltage can be adjusted to provide the required charging current. When the battery may require a 6.8V, and the barrier makes the charging current regulator (IC1) to find a path through the transistor BC547 (T1) to ground and stops charging. LED driver section is used a total of twelve 10 mm white LEDs.

Circuit diagram :

Automatic Low Cost Emergency Light LM317  Circuit diagram

All LEDs are connected in parallel with the resistance of 100 ohms in series with each other. junction common anode for all twelve LED is connected to the collector of PNP transistor T2 and the emission level of the transistor T2 is directly related to the positive terminal of 6V battery. Unregulated DC voltage produced by the cathode junction of Bridge (diodes), is fed to create a transistor T2 through a resistor of 1k. When the voltage is available, the fund is still high transistor T2 and T2 does not happen. The lights are off. On the other hand, if the power does not, the transistor T2 will be a small fund and it does. This causes all the LEDs (LED1 through LED12) is lit. Network, as it is available, download and keep the lights off the battery as an indicator of transistor T2 is cut-off. During the blackout, the workload is steady and makes the battery will light up.

Assemble the circuit on a general purpose PCB and enclose in a cabinet with enough space for the battery and switches. Mount the LED in the housing to illuminate the room. A hole in the box must be drilled to connect the 230V AC input to the transformer primary. I tested the circuit with twelve white 10 mm LEDs.You can use several diodes, provided that the total energy consumption does not exceed 1.5. Driver transistor T2 can provide up to 1.5 In accordance with a proper heat sink.

Source : freecircuit.net

This is one of the most cost effective (cheap) and simple emergency light circuit developed for CircuitsToday – This is an automatic emergency lamp with day light sensing, means it senses darkness/night and turns ON automatically. Similarly it senses day light and turns OFF automatically.

A simple emergency lamp which does not require any special equipment; even a multimeter to assemble and use. Any individual who can do a good quality soldering must be able to build this circuit successfully. This can be easily accommodated in the defunct two 6 watt tube National Emergency Lamp or any PL tube type emergency lamp. The difference will be in the working; it will work non stop for more than 8 hours. Deep discharge is taken care by the LED characteristic and over charge protection is taken care by the fixed voltage regulator.This uses a simple 3Pin fixed regulator which has a built in current limiting circuit. The only required adjustment is the preset which has to be set to ensure the LEDs just light up (it should be left at that position). The 5mm LDR is just mounted on top of the emergency light as shown in the photograph. LDR is used to avoid it lighting up during day time or when the room lights are ON. 2 LEDs are used in series; the dropping resistance is avoided and 2 LEDs light up with current that is required for a single LED,  by which energy is saved to a great extent.

Circuit diagram :

Simple Emergency Light Circuit Diagram

Note:

This circuit is developed by Mr.Seetharaman for readers of CircuitsToday. This particular circuit has been kept so simple for people who has limited access to components or in other words this is an emergency light that you can build with minimum components. In addition to circuit diagram, He has shared photographs of the prototype he made in National emergency light and a PCB design.

Source :www.circuitstoday.com

The circuit uses a flashing LED to flash a super-bright 20,000mcd white LED

This is a novel flasher circuit using a sin istor that takes its flashrate from a flashing LED. The flasher in the photo is 3mm. An ordinary LED will not work.

The flash rate cannot be altered by the brightness of the high-bright white LED can be adjusted by altering the 1k resistor across the 100u electrolytic to 4k7 or 10k. The 1k resistor discharges the 100u so that when the transistor turns on, the charging current into the 100u illuminates the white LED.If a 10k discharge resistor is used, the 100u is not fully discharged and the LED does not flash as bright.

Circuit diagram:

LED Flasher With One Transistor circuit diagram

All the parts in the photo are in the same places as in the circuit diagram to make it easy to see how the parts are connected.

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

This circuit drives a 3x3x3 cube consisting of 27 white LEDs. The 4020 IC is a 14 stage binary counter and we have used 9 outputs. Each output drives 3 white LEDs in series and we have omitted a dropper resistor as the chip can only deliver a maximum of 15mA per output. The 4020 produces 512 different patterns before the sequence repeats and you have to build the project to see the effects it produces on the 3D cube.

Circuit diagram

 3x3x3 LED Cube Circuit diagram