· LM3909 replacement using discrete components
This page features a replacement circuit for the LM3909 LED Flasher / Oscillator using discrete components. The circuit is functionally the same as the integrated LM3909 but has a minor variations in values of the components used. The LM3909 can still found but is fairly expensive, one possible source is Futurlec. The LM3909 is also available through some surplus electronics sources but usually only in quantities of hundreds or thousands of pieces. Naturally the circuit will not be as compact as the integrated circuit but it does offer the ability to adjust individual component values and can be less expensive than the integrated circuit itself.
· Color fade
Let's blink some leds again. Well, fading could be more accurate term. Meaning of this article is to show you an easy circuit that lets you light up your case with slowly alternating colors or just to make your power led come alive. Color changing FireWheel could be also cool, what do you think? This is by no means a step by step how to but I think that it will be enough anyway. In LM324 there are 4 operation amplifiers. We used only two of them so you have an option to build another similar circuit around the IC. This way you can use second potentiometer to control the another circuit and it's fading speed etc. LEDs shimmer randomly as though on fire LED power supplies for AA cells 1.5 Volt LED Flashers AC Line Powered LEDs Astable Multivibrator 9 Second Digital Readout Timer 9 Second LED Relay Timer 16 Stage Bi-Directional LED Sequencer, other sequencer and flaser circuits 10 Stage LED Sequencer
28 LED Clock Timer Fading Red Eyes Two Transistor LED Flasher 16 Stage Bi-Directional LED Sequencer Expandable 16 Stage LED Sequencer LED Photo Sensor Circuit
· LED chaser
I don't know why, but people like blinking lights. You see LED chasers everywhere, in TV shows (Knight Rider), movies, and store windows. This schematic is my version of a simple 10 LED chaser. There is no 555 timer used because at my local electronics store they are over $4 Cdn. Instead, an oscillator made up of two sections of a 4011 NAND gate is employed. This chip is very inexpensive and extremely common. 4017 CMOS Counter,4011 CMOS NAND Gate. You can also use incandescent lamps instead of LEDs. Use transistors to drive them by connecting the base of the transistors to each of the outputs of the 4017 through a 1K resistor. Connect one end of the lamp to the positive supply. Then connect the other end to the collector of the transistor. The emitter then goes to ground. Depending on the lamps, you may need power transistors that are heat sinked.
· 7 Segment LED Counter
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 7490,74HC90,7447,74HC47, Common Anode 7 Segment LED Display,
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.
· 7 by 10 LED Moving Sign ( 27C512 EPROM)
7 by 10 LED Moving Sign
This sign I designed uses no microprocessor. It has an eprom and multiple counters. As in most electric signs, the LEDs are matrixed, and strobed very quickly to make it possible for all 70 LEDs to appear lit. This sign is strobed horizontally, unlike most large signs which are strobed vertically. I did it this way because electrically it was simpler. The eprom has 8 outputs, of which I used 7 of them to drive the 7 horizontal rows. The eprom outputs are not strong, so they are buffered. The 10 vertical columns are activated in sequence, giving a 1/10 duty cycle. I used the 8th output of the eprom to drive the reset for all the counters, so the circuit loops when empty memory is reached, allowing for short or long messages. With a 27C512 eprom(64k bytes), messages and animations can be almost a minute long.
Sequencial LED Flasher with Reversable Direction Tri Color LED Controller with Serial Interface
· 1.5V LED flasher B (PDF)
AVERAGE CURRENT = 40uA PEAK LED CURRENT = 20mA 3mS FLASH 2 SEC BETWEEN FLASHESEFFICIENCY = 90% APPROX. 12 MONTHS OPPERATION FROM N-CELL 1.5V LED FLASHER CIRCUIT
· Low current LED flasher (PDF)
2 SEC BETWEEN FLASHESAVERAGE CURRENT = 30uA PEAK LED CURRENT = 15mA 2mS PULSEAPPROX. 6 MONTHS OPPERATION FROM 150mA-HR CELL 3V LED FLASHER CIRCUIT, HIGH EFFICIENCY RED, GRN OR YELllow,150mA-HRLITHIUM CELL.
· 1.5V LED flasher A (PDF)
AVERAGE CURRENT = 120uAPEAK LED CURRENT = 20mA4mS PULSE 1 FLASHE/SEC MONTHS OPPERATION FROM N-CELL2 MONTHS OPPERATION FROM AA CELL 1.5V LED FLASHER CIRCUIT
· Flashing LED advertising badge (PDF)
AVERAGE CURRENT = 75uA ROX. 2000 HOURS OPERATION,ZVNL110A, ADVERTISING BADGE FLASER 4013
· Flashing LED advertising badge (PDF)
PULSED LED TESTER LED PEAK CURRENT ADJ PULSE RATE1KHz - 10KHz NON-INDUCTIVERESISTOR
· Pulsed LED test circuit (PDF)
TOP VIEWPANASONIC MN13811-G2.4V TRIP POINTSTANDBY CURRENT = 1uAAVERAGE CURRENT = 20uA WHEN FLASHING UNDER VOLTAGE LED FLASHERAA UNDRVFLS.DSN1 1Thursday, December 24, 1998Date: Sheet of
· Low battery voltage flasher (PDF)
NDER-VOLTAGE LED FLASHER CIRCUIT TOP VIEW PANASONIC MN13811-G 2.4V TRIP POINT STANDBY CURRENT = 1uA ,AVERAGE CURRENT = 20uA WHEN FLASHING UNDER VOLTAGE LED FLASHER
· Adjustable flashing LED
Adjustable flashing LED, Use a 555 timer IC as the (resistor controlled) frequency source, choose component values to run at 2 x desired flash rate - get the data sheet for this part, it's pretty comprehensive. Use the output to clock a flip flop (e.g. 74HC74). Feed flip-flop Q and /Q outputs to simple transistor stages, Drive transistor 1 from Q, drive transistor 2 from Q or /Q via a switch. Run the whole thing from +5V. If you want to run it from +9V, no problem, us a 4000 series CMOS flip-flop and change the emitter resistor to 560. If you don't want the hassle of transistors then the ULN2003 darlington driver array could replace the transistor stages.
PWM white LED drivers
· Heart of LEDs
Grantronics ProjectsHeart of LEDs, Using a PC parallel port to control external devices is a popular approach these days but imagine the response when you present Mum with a flashing Heart attached to an umbilical cable running into the next room! No, self- contained is better. The answer is to use a small microcontroller. They are cheap and easy to use. And if the software doesn’t work first time, you simple change the program and re-program the micro. The Atmel AT89C2051 is a relatively recent derivative of Intel’s "industry standard" 8051. It includes the following features:
20 pin skinny-DIP plastic package
2k bytes of Flash program memory
128 bytes of RAM
15 programmable I/O lines
on-chip oscillator (24MHz max)
two 16 bit counter/timers
six interrupt sources
a full duplex serial port (UART)
the I/O pins can sink 20mA for directly driving LEDs
two I/O pins are connected to an on-chip analogue comparator
As the design is derived from the Christmas Star, those readers who saw that article will notice that the schematic is very similar. The major differences between the Heart and the Star are in the physical layout of the LEDs and in the software.
· Christmas Star
Grantronics Projects Christmas Star, Or put it in the front window to impress the neighbours, This project started just before last Christmas when my daughters asked "why don’t we have any flashing Christmas tree lights?" So, while they were out shopping, my son and I grabbed a dozen LEDs, some ribbon cable and a microcontroller. While my son wired up the LEDs, I wrote some simple software. It was all installed and running when they came home after spending all my money. Another reason for using a micro is that micros are the future of electronics. While it is useful to know how to design with 4000-series logic, most new products require more than can be easily done in discrete logic. I believe there is actually a commercially available toaster that uses a micro! While some would say that this is an extreme example, it does indicate how far micros have entered our lives.
· Christmas tree
Here is a fun project to put on your Christmas Tree or in your front window to impress the neighbours. Next is the microcontroller or MCU. In previous projects, we used the Atmel AT89C2051. However, the I/O port structure is not quite suitable for this application so we have used the similar Atmel AT90S2313. The main feature influencing this decision is that the ‘2313 outputs can be "turned off" while the ‘2051 outputs always have pullups enabled. When I said the ‘2313 is similar to the ‘2051, I was referring to the arrangement of I/O pins and their functions. Inside, the two chips are quite different. See the sidebar "What’s in the AT90S2313" for a description of the microcontroller. the LEDs are multiplexed. To control so many LEDs with so few MCU pins, we connect the LEDs in a matrix of 4 columns with 8 LEDs in each and use 12 pins. Multiplexing is where each column of LEDs is activated for a short time followed by the next column. If each time slot is short enough, our eyes don’t see any flicker.
The AT90S2313 is a member of the Atmel AVR family of microcontrollers that range from tiny 8 pin packages to a 64 pin feature-packed "monster". Here is a short summary of the features of the ‘2313:
118 instructions, most single clock cycle execution
32 x 8 bit general purpose working registers
Up to 10 MIPS throughput at 10MHz
2k bytes (1k words) of In-System-Programmable Flash for program storage (endurance 1,000 erase/write cycles)
128 bytes of SRAM
128 bytes EEPROM (endurance 100,000 erase/write cycles)
May be locked for program and EEPROM data security
One 8-bit timer/counter with separate prescaler
One 16-bit timer/counter with separate prescaler, compare and capture modes and 8, 9 or 10-bit PWM
On-chip analogue comparator (rail to rail inputs)
Programmable watchdog timer with separate on-chip oscillator
SPI serial interface (for In-System programming only)
Full duplex UART
Low power idle and power down modes
External and internal interrupt sources
15 programmable I/O lines in a 20 pin package
I/O pins can sink up to 20mA for direct driving LEDs
2.7 – 6.0V (4MHz parts) or 4.0 – 6.0V (10MHz parts)
LED Counter PIC16F84 LED chaser PIC16F84 LED signboard PIC16F84 LED signboard 2
LED Stroboscope - Maintains constant brightness at all flash rates
LED Stroboscope - Maintains constant brightness at all flash rates circuit diagram and explaniantion. It is a real pain to operate this circuit without a proper switch. You can put multiple 4017 ring counters in series to reduce the duty cycle in order to obtain a more focussed strobe image but you will have to increase LED current to maintain the same level of brightness and that will shorten LED life. This circuit can be improved a bit by using a more stable STROBE RATE oscillator or by using a regulator to power the oscillator and associated logic. If you do this you should switch to 74HC class devices.
· White LED circuits
Using white LEDs? how to use white LED with microcontrollers. Technical data about white LED is as follows : Typical Voltage 3,6 volt
Calculation of resistors :(Supplyvoltage - LED-voltage)/LED-current = Resistor
Example : Supply-Voltage = 20 Volt ,LED-Voltage = 3Volt;LED-Current = 20mA => (20V - 3V)/0,02A = 850 Ohm.;Use 0,5-1 Watt resistors (the above uses 0.34 Watt)
Max. Voltage 4 volt at 20 mA., Max. Current 25 mA., Light Strength max. 2000 mcd - Typical 400 mcd,View Angle 60 Degrees, Life Span 60.000 - 100.000 Hours (7-11 Years) The value of zener diode and the resistor,
· Assorted LED circuits
1.5 Volt LED Flashers, The LED flasher circuits below operate on a single 1.5 volt battery. The circuit on the upper right uses the popular LM3909 LED flasher IC and requires only a timing capacitor and LED. the same voltage doubling principle is used with the addition of a transistor to allow the capacitor to discharge faster and supply a greater current (about 40 mA peak). A larger capacitor (1000uF) in series with a 33 ohm resistor would increase the flash duration to about 50mS. The discrete 3 transistor circuit at the lower right would need a resistor (about 5K) in series with the 1uF capacitor to widen the pulse width.The 4017 is a CMOS decade counter with 10 decoded outputs. Inputs include a CLOCK (pin14), a RESET (PIN15), and a CLOCK INHIBIT (pin 13). The clock input drives an internal schmitt trigger circuit for pulse shaping and allows for unlimited clock rise and fall times. The counter is advanced one count at the rising edge of the clock signal if the CLOCK INHIBIT line is low. A high RESET signal resets the counter to the zero count. The circuit may be configured for counts less than 10 by connecting RESET to an output pin one above the desired count. Thus, a five channel sequencer could be made by connecting pin 15 to pin 1. A CARRY-OUT signal (pin 12) may be used to clock subsequent stages in a multi-device counting chain (ones, tens, hundred, etc). Small signal NPN transistors are used to increase the output current for the LEDs to about 20ma which is set by the common 120 ohm resistor. Other NPN transistors may be substituted for the 3904. The 555 timer generates the clock signal, the frequency being determined by the 1uF capacitor and 47K resistor which is approximately = 1.44 / 2RC = 15 Hz.
· LED Mood Light
This circuit makes a nice lamp that consumes little power, runs cool, and has an incredibly long lifetime. The lamp puts out a warm yellow shade of light, the color may be adjusted by changing the number of red or green LED strings.