It is a Easy make Electronic Circuit Project of Fiber optic led driver Circuit. The pull-up transistor of the totem-pole output is used-to turn on the LED and the pull-down transistor is used to turn off the LED. The lower impedance and higher current handling capability of the saturated pull-down transistor is used as an effective method of transferring the charge from the LED`s anode to ground as its dynamic resistance increases during turn-off. The slightly higher output impedance of the pull-up stage ensures that the LED is not over peaked during the less difficult turn-on transition.

Fiber Optic LED Driver Circuit Diagram:


This asymmetric current handling capability of the output stage with its variable impedance substantially reduces the pulse-width distortion and long-tailed response. As the signal propagates through two NAND gates, each transition passes through the high-to-low and low-to-high transition once, normalizing the total propagation delay through the circuit.

This 6 channel LED driver circuit is designed using MCP34845 ic manufactured by Frescale Semiconductor with integrated power supply. The MCP34845 6 channel LED driver circuit operates from 5 to 21 volts and is specially designed for use in backlighting LCD displays from 10” to 17”+ for devices like: PC Notebooks, Netbooks, Picture Frames, Portable DVD Players , Small Screen Televisions , Industrial Displays, Medical Displays, etc.

6 Channel LED Driver Circuit Diagram:


The MCP34845 LED driver is capable of driving up to 16 LEDs in series in 6 separate strings. PWM dimming is performed by applying a PWM input signal to the PWM pin which modulates the LED channels directly.

Main features of this driver electronic project are : input voltage of 5.0 to 21 V , boost output voltage up to 60 V, 2.0 A integrated boost FET , fixed boost frequency - 600 kHz or 1.2 MHz , OTP, OCP, UVLO fault detection , LED short/open protection , programmable LED current between 3.0 mA and 30 mA.

This is a very simple Electronic Circuit Project for LED Circuit Project Using with 555 IC. This circuit LED reproduces the first LED sequence at this time used by FISA on behalf of Formula single racing. It may perhaps be alive used with slot car sets (such for example HO shin up AFX/Life Like/Tyco sets) or else means of communication controlled cars. IC1, a 555 timer IC, is used as a watch pulse generator. Its output is fed via NAND gates IC2a and IC2c to IC3, a 4024 binary counter. IC2b inverts the O4 output of 4024 binary counter IC3. originally, IC3 is reset and all its outputs are low, together with O4, which causes IC2b to present-day a rational climax to the pin 8 input of IC2c which after that passes pulses from the 555 timer circuit to the clock input of the 4024. IC3 then begins together with.

LED Circuit Project Using with 555 IC:



Following the count has reached binary 1111, the subsequently pulse sends the O4 output of IC3 high, which disables IC2c and IC3 stops with. The four used outputs of IC3 are connected to a resistor ‘ladder’ which acts to the same degree a clear-cut digital to analog convert-er (DAC). As the count increases so does the voltage produced by the side of the top of the ladder and this is connected to the inverting inputs of four comparators inside IC4 (an LM339) and to IC5, which is a 741 op amp furthermore connected while a comparator.

The categorical inputs of the comparators are connected to the taps of a voltage dividing wall, with the drumming voltages settle on using VR1, a 100kO trimpot. As IC3 counts, the rising stepped voltage from the DAC ladder switches the comparators on clothed in sequence, preliminary with IC4d and working up to IC5. in the same way as both comparator is curved on, its pair off of LEDs is lit; former LEDs 1 & 2, next LEDs 3 & 4 and so on. as soon as all five pairs of LEDs are lit, the then pulse from IC1 moves the binary count of IC3 to 10000, so the DAC voltage drops back to zilch and all LEDs are extinguished. by the same spell, with too stops, for the reason that the area of high pressure on O4 causes IC2c to check extra gate pulses. The circuit in that case remains reserve until the counter is reset by urgent pushbutton switch S1. This allows a recent sequence to initiate.


source By:w3circuits
 

Light emitting diodes are advantageous due to their smaller size, low current consumption and catchy colours they emit. Here is a running message display circuit wherein the letters formed by LED arrangement light up progressively. Once all the letters of the message have been lit up, the circuit gets reset. The circuit is built around Johnson decade counter CD4017BC (IC2). One of the IC CD4017BE’s features is its provision of ten fully decoded outputs, making the IC ideal for use in a whole range of sequencing operations.In the circuit only one of the outputs remains high and the other outputs switch to high state successively on the arrival of each clock pulse.

Running Message Display Circuit Diagram:



The timer NE555 (IC1) is wired as a 1Hz astable multivibrator which clocks the IC2 for sequencing operations. On reset, output pin 3 goes high and drives transistor T7 to ‘on’ state. The output of transistor T7 is connected to letter ‘W’ of the LED word array (all LEDs of letter array are connected in parallel) and thus letter ‘W’ is illuminated. On arrival of first clock pulse, pin 3 goes low and pin 2 goes high. Transistor T6 conducts and letter ‘E’ lights up. The preceding letter ‘W’ also remains lighted because of forward biasing of transistor T7 via diode D21. In a similar fashion, on the arrival of each successive pulse, the other letters of the display are also illuminated and finally the complete word becomes visible. On the following clock pulse, pin 6 goes to logic 1 and resets the circuit, and the sequence repeats itself. The frequency of sequencing operations is controlled with the help of potmeter VR1.

The display can be fixed on a veroboard of suitable size and connected to ground of a common supply (of 6V to 9V) while the anodes of LEDs are to be connected to emitters of transistors T1 through T7 as shown in the circuit. The above circuit is very versatile and can be wired with a large number of LEDs to make an LED fashion jewellery of any design. With two circuits connected in a similar fashion, multiplexing of LEDs can be done to give a moving display effect.

This proximity detector circuit is designed using a temperature sensor and TLC272 op amp. The temperature sensor can react to any heat generated by body heat.

Proximity Detector Using TLC272 Circuit Diagram:



The sensor used in this TLC272 proximity detector circuit has a sensitive surface which was divided in two, so that it can sense if the heat source is coming from the left or right. Indication for cold objects will be exactly opposite of the warm objects. IC1b form a symmetrical power circuit. Terminal "s" is the sensor output. Signal over the "s" will be amplified in IC1a, with a gain factor of 70, before being delivered to the output detector.

This circuit can be made to produce interesting and attractive light effects using just a cluster of red LEDs and one of green LEDs. One effect is first alternating bet ween red  and green, and then lighting red and green together. With the exception of the triple LED devices (Rapid Electronics # 56 - 0205  for green, # 56 - 0200 for red) all parts are cheap and easy to find, possibly even in your junkbox

Green-Red Multi flasher Circuit Diagram:


The values of networks R3/C3, R4/C4 and R5/ C5 govern the length of the flashes. Using the  indicated values, these are about 18 seconds  with a 0.5 second interval.

Because the colours used do not have equal  luminous intensity (expressed in millican-delas) D1 and D2 are silicon diodes and D3 and D4, germanium, with Schottky devices (BAT82) as an alterative because they also exhibit a low forward drop of about 0.3 V. As germanium devices, look for the OA91, OA85 or AA119. If D1 and D2 are omitted, Green and Red are brighter by themselves than when on simultaneously.

MOSFE T T2 switches both LED devices on simultaneously arranging for roughly equal luminous output. The display has an integrated LDR that causes  the LEDs brightness to adapt automatically to darkness and bright light conditions. The circuit has lots of openings for experimentation and adaptation, for example, the flash rate is determined by the value of C1, while the link between the counter’s R (reset)  input and O3 output determines if a space is inserted after the last flash, or not. Colour-ful and lively effects may also be obtained by  using tri-colour LEDs with a common anode.
The power consumption of the circuit depends  largely on the LEDs used. With the Rapid LED  types shown, about 70 mA may be expected  at a 6 volts supply voltage.

How to build a 40 LED Bicycle Light Electronic circuit Project? This is a very Simple to build This electronic circuit project of 40 LED bicycle light.  The 555 circuit below is a flashing bicycle light powered with four C,D or AA cells (6 volts). Two sets of 20 LEDs will alternately flash at approximately 4.7 cycles per second using RC values shown (4.7K for R1, 150K for R2 and a 1uF capacitor). Time intervals for the two lamps are about 107 milliseconds (T1, upper LEDs) and 104 milliseconds (T2 lower LEDs). Two transistors are used to provide additional current beyond the 200 mA limit of the 555 timer.

Simple 40 LED Bicycle Light Circuit Diagram:


A single LED is placed in series with the base of the PNP transistor so that the lower 20 LEDs turn off when the 555 output goes high during the T1 time interval. The high output level of the 555 timer is 1.7 volts less than the supply voltage. Adding the LED increases the forward voltage required for the PNP transistor to about 2.7 volts so that the 1.7 volt difference from supply to the output is insufficient to turn on the transistor. Each LED is supplied with about 20 mA of current for a total of 220 mA.

The circuit should work with additional LEDs up to about 40 for each group, or 81 total. The circuit will also work with fewer LEDs so it could be assembled and tested with just 5 LEDs (two groups of two plus one) before adding the others.

The LED bicycle light that we described in the July/August 2009 edition of Elektor has proved very  popular. The author was particularly struck by the basic design, but as always, there is room for a little improvement! Below we describe two enhanced variations on the original theme.

Both circuits are, like the 2009 original, powered from a 6 V (rechargeable) battery, shown here as Vl. The simpler of the two circuits, which consists of four transistors, is in function essentially the same as the original version. lt takes the form of a boost converter with feedback provided by the voltage drop across a current sensing resistor, in this case R2. A value of 6.2 O for R2 is suitable for use with four white LEDs at D4 to D7, and gives an LED current of approximately 20 mA. The 250 mW Zener diode D10 is provided to limit the output voltage in the case that the LED chain should go open-circuit, pulling  the gate of the  MOSFET to ground via T3, T1 and T2 if the output voltage exceeds the breakdown voltage of the Zener. A breakdown voltage of between 15 V and 24 V is recommended. L1 is a 100 pH coil with a current rating of at least 0.5 A and should have a very low DC resistance.

LED Bicycle Light Revisited Circuit Diagram:

 
LED Circuit Diagram

Transistor T1 provides a low-impedance source to charge the gate of MOSFET T5. Transistor T2 (the  author used an SMD BC846S dual transistor) is wired as a diode, and is responsible for discharging the gate of T5 via T3. This extension to the original circuit means that MOSFET T5 switches more quickly, which improves overall efficiency. As a side-effect the switching frequency also rises significantly. With a switching frequency of over 150 kHz ceramic or film capacitors must be used at the input and outPUt, as electrolytics will gradually fall off in  effectiveness. ln the original circuit a type NTD4815N MOSFET with an on resistance Rorlony of 1 5 mO (at V55=10  V) was recommended, although almost any N-channel MoSFET with similar on-resistance characteristics  will be equally suitable.


Light Circuit Diagram

The second circuit employs five transistors, and differs from the first in that it uses a secondary current regulation loop based around transistorT4. This makes the design more suitable for use at higher LED currents, giving greater current stability in the presence of power supply voltage fluctuations. The voltage drop across resistor R6 due to the current flowing through the LEDs turns transistor T4 on. Via T3 this in turns modulates the switching of T5, hence keeping the output current constant. Transistor T4 is a type BC856B; an alternative device in a leaded package is the  BC556B. T3 is a  BC546B. The BC8465 dual SMD transistor used for T1 and T2 can be replaced by a BC546B (forT1) and a type 1N4148 diode (for  T2).

This little circuit provides a surprisingly spectacular bright strobe flash which is adjustable with P1, the 200K trimmer potentiometer. P1, R1, R2, and C1 provide the flashrate. R1 sets the upper flashrate. The flashrate for the above circuit was measured at 12Vdc. If the supply voltage is steady or regulated, the flashrate is very stable.

Capacitor C2 on pin 5 of the IC is to filter off noise when used in motorized vehicles. For battery power it can be eliminated. Resistor R3, 47 Ohm, is there to protect the Leds for burn-out. Depending on your application and power source, increase or decrease the value of R3. Like, for a 9V power source decrease the value to 22-33 ohms or so. For a 15V power sourse increase the value to 680-1000 ohms.

Circuit Diagram:


The duty-cycle is about perfect at 50% so will give a nice strobe when adjusted with P1 to a fast flash. I experimented with several color Leds and basically they all strobe very bright especially the white ones. Current draw of this circuit (measured with two leds in series) is 21mA with white leds, 26mA with Green leds, 40mA for the yellow, 38mA for the Red, and 26mA using only 1 Blue led. Again, this is the *total* circuit amps, not the led amps. The strobe effect with the white leds was very impressive.

I use this circuit as anti-collision strobe in the wingtips of my radio control airplane with a 9-volt power source. I first carved out a nice little pocket of about 2 inches in each of the wingtips. Then I glued in reflectors (taken from a $1 camera from the recycle store) and then installed the the two leds and wired up the to the strobe circuits. I used one circuit in each of the wing tips rather than using long wires between the leds. The copper in the wires for the length needed is much heavier than using two separate circuits. Unless of course you're concerned with the possible uneven flash between the wingtips? I'm not. Anyways, the circuit itself weighs almost nothing so lending itself for use in radio control very nicely. I also installed a red led on the tailvin tip of my helicopter. Gives a very nice effect. Many other r/c applications are there for the taking. Or use it as a brake-light strobe for your motorcycle, etc.

You can use several leds in series if you need more strobe-effect. I have used as many as 10 without problems on my motorcycle to make sure I'd be seen, especially at dark. Works great!

This charming little circuit is a genuine four-digit running-text display, complete with a Christmas / New Year’s greeting. Naturally, any competent programmer can easily arrange to have a different text scroll across the display. The associated soft-ware, including the source code, can be downloaded from the Free Downloads section of our website or obtained from Readers Services on diskette (order number 020365-11).

Circuit Image :

As can be seen from the schematic, the hardware consists of little more than an AT90S1200 micro-controller, a 4-digit LED display and a 5-V voltage regulator. The only external circuitry needed by the micro-controller consists of a reset circuit and a 4-MHz crystal, and the remainder of the components are limited to a few decoupling capacitors.

Mini Running Text Display Circuit diagram :

In the prototype model, an Osram SLO2016 display module was used. Although this four-digit module measures only 10×20 mm, it provides an especially clear and bright display. In order to give the 7805 voltage regulator sufficient ‘breathing room’, the supply voltage should be at least 8 V. A standard 9-V mains adapter should thus be perfectly adequate. The supply voltage does not have to be estabilised, and the adapter does not have to provide an especially large amount of current, since the running-text display draws scarcely more than 50 mA

For making a simple smooth flash light take ordinary LED flashers turn the LED on and off abruptly, which can get a little irritating after a while. The circuit shown here is  more gentle on the eyes: the light intensity changes very slowly and sinusoidally, helping to generate a relaxed mood. The circuit shows a phase-shift oscillator with an adjustable current source at its out-put. The circuit is capable of driving two LEDs in series without affecting the current. The frequency is set by three RC networks, each of which consists of a 100 µF capacitor and a 22 kΩ resistor.  

Smooth Flasher Circuit Diagram: