Multi Color LED

How many different conditions do you reckon may be signalled with just one LED? Two, maybe three? Using this simple circuit, a lot more!

Admittedly, a two-colour LED is used here. Such a device consists of two light-emitting chips, usually red and green, encapsulated in the same case. It has three pins: two for the anodes, and one for the common cathode. In this way, each diode can be activated separately. Various mixed colours may be obtained by varying the current through the two diodes. At least four discrete colours are then easily perceived: pure red, pure green, orange (IR ≈ 2IG) and yellow (IG ≈ 2IR).

In the present circuit, the LED elements are driven by CMOS three-state buffers type 4503, which, unlike most CMOS ICs from the 4000 series, are capable of supplying up to 10 mA of output current. The LED cur-rents are limited by resistors R1 through R6, whose values invite experiments with brightness and colours according to your own taste.

Simple Multi-Color LED Circuit diagram:

The circuit was originally developed to indicate the state of three inputs, a, b, and c (non-binary, i. e., only one of these is at 1 at any time), with the con-figuration (a=b=c=0) representing the fourth state. The latter is decoded by NAND gate IC1. An additional effect is produced by gates IC1a and IC1b, which are connected up into an oscillator circuit producing approximately two pulses per second. These pulses are used to control the common-enable input, DA (pin 1) of the 4503, so as to produce a flickering effect. The oscillator is controlled by means of inputs ‘d’ and ‘e’. Pulling both of these logic high disables the oscillator and the LED driver. With e=0 and d=1 the outputs of the 4503 are switched to three-state, and the circuit is in power-down standby mode.

Although designed for a 12-V supply voltage, the circuit will happily work at any supply volt-age between 5 V and 16 V. Non-used inputs of CMOS ICs must, of course, be tied to ground via 10-100 kW resistors.

Source: http://www.ecircuitslab.com/2012/06/simple-multi-color-led.html

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LED Volt Meter Circuit

Here is a Simple LED Volt meter to Monitor the charge level in Lead Acid Battery or Tubular battery. The terminal voltage of the battery is indicated through a four level LED indicators. The nominal terminal voltage of a Lead Acid battery is 13.8 volts and that of a Tubular battery is 14.8 volts when fully charged. The LED voltmeter uses four Zener diodes to light the LEDs at the precise breakdown voltage of the Zener diodes. Usually the Zener diode requires 1.6 volts in excess than its prescribed value to reach the breakdown threshold level. When the battery holds 13.6 volts or more, all the Zener breakdown and all LEDs light up. When the battery is discharged below 10.6 volts, all the LEDs remain dark. So depending on the terminal voltage of the battery, LEDs light up one by one or turns off.

Circuit diagram:

 LED Volt Meter Circuit Diagram

Author: D. Mohan Kumar Copyright: electroschematics.com

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230V LED Indicator circuit

This is very useful circuit for you.You can use this circuit as a current indicator.The special thing of this circuit is this circuit operates 110V to 230V.I myself have use this circuit for my door bell.so visitors who come home at night can easily see the door bell.you your self think different way and do something newly
Parts

R2 = 1M-1/2W
R1 = 470R-1/2W
D1 = 1N4007
D2 = 1N4007
D3 = 1N4007
D4 = 1N4007
D5 = 5mm. Blue LED
C1 = 220nF-275vAC

Note

# When you deal with 230V be careful.If you are too little Dont try this circuit
#Use Quality parts.Specially think about the W of your parts

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LED Matrix Horizontally

LEDs provide a befitting way to electronically display information. whereas the seven-segment LED brandish, organized in the pattern of the digit 8, is common, it does not permit the brandish of some alphanumeric individual features. A 5×7 commanded matrix permits the display of all ASCII individual features, as well as graphics shapes.

The circuit in this conceive concept displays an unconventional way to use a 5×7 LED matrix.You can use a conceive encompassing a set of 5×7 commanded flats without altering any thing in the circuitry, except for the arrangement of the commanded units. 

 Using one 5×7 LED matrix, or N units, horizontally instead of vertically allows the display of two characters, or 2×N characters. The minimum pattern for lowercase and uppercase letters requires only a 3×5 LED configuration, except for the letters M and m, which require at least a 5×5 LED configuration and need a dedicated subroutine.

The circuit in Figure 1 uses an 8-bit, 18-pin PIC micro controller and a decade counter to drive one or two 5×7 LED units to provide a display module of two or four digits. The circuit uses a small pushbutton switch to increment the counter. By default, the circuit works in high-brightness mode. If you press the pushbutton during power-on, the circuit works in low-power mode.

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Make this Temperature Indicator Circuit with Sequential LED Display

In some of my earlier articles we have seen a few simple and interesting temperature indicator circuits. All these circuits are useful in some or the other ways, however these are not equipped with  step wise temperature level indicator arrangement and therefore tracking the varying levels of temperature cannot be identified using them.

The present design eliminates the above issue, as here the entire temperature range becomes visible through an arrangement of an LED array.
The LEDs in this circuit reads the temperature levels discretely via 20 steps of LED indications.
The proposed sequential LED temperature indicator circuit is definitely the simplest to build, since it is based on a single outstanding IC LM3914 from TEXAS INSTRUMENTS, which single handedly performs the whole action of displaying the readings in a sequential manner.
The LEDs show an incrementing temperature through a single illuminated LED at the relevant positions of the array, thus the present design shows a dot mode indication instead of a bar graph. The dot mode arrangement specifically helps to save battery power because only one LED is involved for the required indication at any instant.  

The IC LM3914 is basically a millivolt measuring device which is able to convert a varying milli volt input into a corresponding LED readout at its output pin outs.

Here the input is derived from another interesting IC LM35 from TEXAS INSTRUMENTS, which is configured as an ambient temperature sensor device.

The IC LM35 coverts the temperature differences around it, directly into varying milli volts across its output.
For every single degree change in the temperature, the IC LM35 generates an output with a 10 mV variation.
This correspondingly varying milli volts is applied at the input of the IC LM3914, which readily accepts these variations, making them visible at the output through the connected LEDs.
Thus as the temperature around the IC LM35 increases, it generates a correspondingly increasing mV  across its outputs which is in turn transformed by the IC LM3914 into an LED readout, displaying the relevant level of the sensed temperature.
The LED array should be appropriately calibrated, through some trial and error and some practical experimentation.

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Self Writing LED Display Sign Controller

This is a design for a circuit of self-writing LED display sign controller. This circuit consist of eight power shift register which are installed in cascade. The shift registers are used to turn on a string of 64 lamps or LEDs sequentially. This is the figure of the circuit;

When the shift register clock (SRCK) is clocked, the register is clocked, so that the display is update after each bit of data is shifted in. The LEDs strobe on from left to right and until the LEDs strobe off in the same manner because of the serial input data (SER IN) is held alternately high and low for any period greater than 64 clocks. The display sign is dynamic and attractive because the LEDs arranged sequentially as in written message.

This circuit uses LM556 timer to generate the clocks and requires only one IC in addition to the shift register. To blanking or blinking the LEDs, this circuit uses the output enable. [Circuit diagram source: Texas Instruments Application Report]

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