proyects leds

8/3/2019 Proyects leds

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1.5 volt dual LED flasher (runs one year)

This 1.5 volt led fasher runs more than a year on a single 'd" cell andalternately flashes 2 LEDs at about a 1 second rate. The circuit employs a

74HC14 CMOS hex inverter that will operate at very low voltages (less than 1

volt). One section is used as a squarewave oscillator (pins 1 and 2), while the

others are wired to produce a short 10mS pulse on alternate edges of the

square wave so the LEDs will alternate back and forth. The output sections

each use a capacitor charge pump to increase the voltage for the LEDs. Thecircuit draws an average current of 800uA from the 'D' battery and the LED

peak current is about 40mA with a fresh battery and drops to about 10mA asthe battery voltage falls to 1.1 volts. The capacity of a alkaline 'D' cell is about

12 amp hours with a cutoff voltage of 1.1 so the circuit should run about

12/.0008 = 15000 hours or maybe 625 days, but I haven't verified that yet. The

idea for this circuit came from a single 1.5 volt LED flasher by Dave Johnsonthat can viewed at

http://www.imagineeringezine.com/PDF-FILES/ac14fls.pdf

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Descrete Multistage Light Sequencer

The drawing below illustrates a multistage light sequencer using descrete parts

and no integrated circuits. The idea is not new and I hear a similar circuit was

developed about 40 years ago using germanium transistors. The idea is to

connect the lights so that as one turns off it causes the next to turn on, and soforth. This is accomplished with a large capacitor between each stage that

charges when a stage turns off and supplies base current to the next transistor,thus turning it on. Any number of stages can be used and the drawing below

illustrates 3 small Christmas lights running at about 5 volts and 200mA. The

circuit may need to be manually started when power is applied. To start it,
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connect a momentary short across any one of the capacitors and then remove

the short. You could use a manual push button to do this.

Detailed operation:

Assume the circuit doesn't start when power is applied amd all lights are offand all three capacitors are charged to about 5 volts. We connect a jumper

across the 220uF capacitor on the left which discharges the capacitor and turns

on the 2nd stage transistor and corresponding light. When the jumper is

removed, the capacitor will start charging through the base of the stage 2

transistor and stage 1 light. This causes the stage 2 transistor to remain on

while the capacitor continues to charge. At the same time, the capacitorconnecting stage 2 and 3 will discharge through the 100 ohm resistor and

diode and stage 2 transistor. When the capacitor charging current falls below

what is needed to keep stage 2 turned on, the transistor and light will turn offcausing the voltage at the collector of the stage 2 transistor to rise to 5 volts.

Since the capacitor connecting stage 2 and 3 has discharged and the voltage

rises at the collector of stage 2, the capacitor from stage 2 and 3 will chargecausing the 3rd stage to turn on and the cycle repeats for sucessive stages

4,5,6,7.... and back to 1. The sequence rate is determined by the capacitor andresistor values (220uF and 100 ohms in this case), load current (200mA in this

case), and current gain of the particular transistor used. This arrangement runs

at about 120 complete cycles per minute for 3 lights, or about 167mS per

light. Faster or slower rates can be obtained with different capacitor values.

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16 Stage Bi-Directional LED Sequencer

The bi-directional sequencer uses a 4 bit binary up/down counter (CD4516)

and two "1 of 8 line decoders" (74HC138 or 74HCT138) to generate thepopular "Night Rider" display. A Schmitt Trigger oscillator provides the clock

signal for the counter and the rate can be adjusted with the 500K pot. Two

additional Schmitt Trigger inverters are used as a SET/RESET latch to controlthe counting direction (up or down). Be sure to use the 74HC14 and not the
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74HCT14, the 74HCT14 may not work due to the low TTL input trigger level.

When the highest count is reached (1111) the low output at pin 7 sets the latchso that the UP/DOWN input to the counter goes low and causes the counter to

begin decrementing. When the lowest count is reached (0000) the latch is

reset (high) so that the counter will begin incrementing on the next risingclock edge. The three lowest counter bits (Q0, Q1, Q2) are connected to both

decoders in parallel and the highest bit Q3 is used to select the appropriate

decoder. The circuit can be used to drive 12 volt/25 watt lamps with theaddition of two transistors per lamp as shown below in the section below titled

"Interfacing 5 volt CMOS to 12 volt loads"

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Interfacing 5 volt CMOS to 12 volt/ 25 Watt Loads

The circuit below is designed to be used with the bi-directional lampsequencer shown above on this same page. Two additional transistors are used

to increase the current from the 74HCT138 decoder to control 12 volt 25 watt

lamps. A 6.8 volt/1 watt zener diode is used in series with the ground

connection of all the CMOS ICs (74HC14, CD4516 and 74HC138s) so that

the total voltage across the CMOS devices will be about 5.2 volts and theoutputs will move from +12 to about +7 when selected. The 2N2905/PNPtransistor stage is connected as an emitter follower which provides a high

impedance to the decoder output and supplies about 80 mA of current to thebase of the 2N3055 NPN power transistor which then supplies 2 or more amps

to the 12 volt lamp. The voltage across the PNP transistor will be about 7

volts when it is turned on and the heat dissapation will be about 0.6 watts.

That should't require a heat sink if several lamps are sequencing but it may get

quite warm if the circuit is idle on a single output. The 2N3055 power

transistor operates as a switch and drops very little voltage (less than 0.5)when conducting, and will not require a heat sink. Other transistors may be


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substituted such as the TIP29 or TIP31 for the 2N3055 and most any medium

power (500mA) PNP for the 2N2905.

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Expandable 16 Stage LED Sequencer

The circuit below uses a hex Schmitt Trigger inverter (74HC14) and two 8 bit

Serial-In/Parallel-Out shift registers (74HCT164 or 74HC164) to sequence 16

LEDs. The circuit can be expanded to greater lengths by cascading additional

shift registers and connecting the 8th output (pin 13) to the data input (pin 1)of the succeeding stage. A Schmitt trigger oscillator (74HC14 pin 1 and 2)

produces the clock signal for the shift registers, the rate being approximately1/RC. Two additional Schmitt Trigger stages are used to reset and load the

registers when power is turned on. Timing is not critical, however the outputat pin 8 of the Schmitt Trigger must remain high during the first LOW to

HIGH clock transition at pin 8 of the registers, and must return low before the

second rising edge to load a single bit. If the clock rate is increased, the length

of the signal at pin 9 of the Schmitt Trigger should be reduced proportionallyto avoid loading more than one bit. The HCT devices will normally provide

about 4 mA (source or sink) from each output but can supply greater currents(possibly 25 mA) if only one output is loaded. The common 150 ohm resistor

restricts the current below 25 mA using a 6 volt power source. If the circuit is

operated with two or more LEDs on at the same time, resistors may be needed

in series with each LED to avoid exceeding the maximum total output currentfor each IC of 25 mA. For greater brightness, individual buffer transistors can


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be used as shown in the 10 stage LED sequencer on this same page.

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10 Channel LED Sequencer

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18 Stage LED Sequencer

The question sometimes comes up of how to cascade 4017 decade counters

for more than 10 sequencial stages. The LED sequencer below shows a

possible solution using a few extra parts.
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When power is applied, the 15K resistor and 10uF cap at pin 15 will reset the

counters to the zero count where pin 3 is at +12 and all other outputs are atzero. The 2 diodes (1n914) and 15 resistor form a AND gate so the clock

pulse will be passed to the right side counter when the sequence starts. When

the right counter reaches the 10th count, pin 11 will move high enabling theAND gate on the right to pass the clock pulse to the left side counter. As the

left side counter advances, pin 3 will be low so that clock pulses cannot

advance the right counter. When the left counter turns over and pin 3 againmoves high, the sequence will repeat. Thus we get 18 total counts, 9 from the

first counter, and 9 from the second.

Note that the 4017 counter will not deliver much current, and so the LED

current is set to about 6mA using a 1.5K resistor in series. For more current,

you could use transistors on each output as shown in the drawing above, (10

Channel LED Sequencer). But some of the newer bright LEDs are fairlybright at 6mA.

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Two Transistor LED Flasher


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Fading Red Eyes

Circuit description:

This circuit is used to slowly illuminate and fade a pair of red

LEDs (light emitting diodes). The fading LEDs could be installed

as 'eyes' in a small pumpkin or skull as a Halloween attraction,or mounted in a Christmas tree ornament. Or, they might be used

as a fancy power indicator for your computer, microwave oven,

stereo system, TV, or other appliance.

In operation, a linear 3 volt (peak to peak) ramping waveform is

generated at pin 1 of the LM1458 IC and buffered with an emitter

follower

transistor stage. The 22uF capacitor and 47K resistor connected to

pin 2 establish the frequency which is about 0.5 Hz. You can make the

rate adjustable by using a 100K potentiometer in place of the 47K

resistor at pin 2.

The circuit consists of two operational amplifiers (opamps),one producing a slow rising and falling voltage from about 3 volts to

6 volts, and the other (on the right) is used as a voltage comparator,

the output of which supplies a alternating voltage switching between

2 and 7 volts to charge and discharge the capacitor with a constant

current.

Each of the op-amps has one of the inputs (pins 3 and 6) tied to a

fixed voltage established by two 47K resistors so that the reference

is half the supply voltage or 4.5 volts. The left opamp is connected

as an inverting amplifier with a capacitor placed between the output

(pin 1) and the inverting input (pin 2). The right opamp is connected

as a voltage comparator so that the output on pin 7 will be low when

the input is below the reference and high when the input is higher


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than the reference. A 100K resistor is connected between the

comparator

output and input to provide positive feedback and pulls the input

above or below the switching point when the threshold is reached.

When the comparator output changes at pin 7, the direction of the

current changes through the capacitor which in turn causes the

invertingopamp to move in the opposite direction. This yields a linear ramping

waveform or triangle waveform at pin 1 of the inverting opamp.

It is always moving slowly up or down, so that the voltage on the

non-inverting input stays constant at 4.5 volts.

Adjustments to the point where the LEDs extinguish can be made

by altering the resistor value at pin 3 and 6 to ground. I found

a 56K in place of the 47k shown worked a little better with the

particular LEDs used. You can experiment with this value to get

the desired effect.

Parts List:

Description Mfg Part# Allied Part# Quantity Cost

Operational Amplifier LM1458 288-1090 1 .48

47K Resistor 296-2182 4 .42

100K Resistor 296-5610 1

100 Ohm Resistor 895-0465 1 .24

Transistor 2N3904 568-8253 1 .1

22uF Capacitor 852-6516 1 .07

Solderless Breadboard 237-0015 1 6.99

Red Light Emitting Diode (LED) 670-1224 2 0.50

Note: The LED listed has a narrow viewing angle of 30 degrees and

appears brightest when looking directly at it. It's not a pure red

color, and a little on the orange side, but should be brighter

compared to other selections. For a wider viewing angle at reduced

intensity, try part number 670-1257 which is viewable at 60 degrees

and has a red diffused lens.

Construction details:

Layout of the solderless breadboard:

Refer to the drawing below the schematic diagram and note the

solderless breadboard is arranged in rows labeled A-J, and

columns numbered 1 to 65. Each group of 5 holes in the same column

are the same connection, so that holes A1,B1,C1,D1 and E1 are all

connected together. Likewise holes F1,G1,H1,I1 and J1 are all

the same connection. The outer rows along the length of the

board are also connected together and are normally used for

power supply connections. However, there is a break in the

mid section of the outer rows, so a short jumper wire connecting

the mid section of the outer rows should be installed to connect

the entire outer row together. If you have a DMM, use the low

ohms range and probe the various holes to get familiar with the

board layout.

Installing the components:

Orientate the LM1458 so the nook or punch mark on one edge

is near column 30 and the opposite edge is near column 33.


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Install the LM1458 on the breadboard so the pins straddle

the center section of the board and pin 1 of the IC is occupying

hole E30 and pin 8 is in hole F30. The pins are numbered counter

clockwise, so pin 4 will be occupying F33 and pin 5 will be in E33.

Possible connections for the LM1458, 9 volt battery, and a couple

other parts is illustrated in the lower drawing of the solderless

breadboard, but it is not complete with all parts.

Refer to the schematic diagram, and install the various other

components so they connect to the appropriate pins of the

LM1458. Use whatever connection holes are convenient.

For example, the 22uF capacitor connects between pins 1 and 2

of the IC, which occupy holes (F30,F31) so it could be placed

in the holes (H30, H31) or (J30,J31) or (I30,I31). But not all parts

will conveniently fit, so you may have to use a short jumper

wire (#22 preferred) to connect parts from one side of the chip

to the other.

The board I assembled was connected this way:

LM1458 F30 to F33, and E30 to E33

22uF capacitor H30 to H31

47K resistor I30 to I35

47K resistor C27 to C31

47K resistor F25 to Positive battery row

47K resistor J25 to Negative Battery row

100K resistor B31 to B33

2N3904 Transistor G36, G37, G38 with emitter at G38

100 Ohm resistor D38 to F38

LED B43 to B44 (Cathode at B44)

LED I43 to I44 (Cathode at I43)

Jumper A30 to Positive battery row

Jumper F36 to Positive battery row

Jumper J33 to Negative battery row

Jumper J43 to Negative battery row

Jumper H25 to J32

Jumper J30 to J37

Jumper E27 to G31

Jumper D32 to G32

Jumper D33 to H35

Jumper C38 to C43

Jumper E44 to F44

9 Volt Battery Postive battery row to negative row.

The circuit below illustrates two pairs of LEDs that operate out of phase so as

one pair slowly illuminate, the other pair will


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fade.

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Automobile Interior Lights Fader

This circuit is similar to the fading eyes circuit above and is used to slowly

brighten and fade interior lights of older cars.

The circuit is based around the LM324 low power opamp which draws around

3mA of current, so it won't bother the battery if left connected for extended

periods.

The top two opamps (pins 1,2,3 and 5,6,7) form a triangle wave oscillator

running at about 700Hz while the lower opamp (pins 8,9,10) produces a

linear, 5 second ramp, that moves up or down depending on the position of thedoor switch. The two transistors and associated resistors serve to limit the

ramp voltage to slightly more and less than the upper and lower limits of thetriangle waveform. These two signals (700 hZ. triangle wave and 5 second

ramp) are applied to the inputs of the 4th opamp (pins 12,13,14) that serves as

a voltage comparator and generates a varying duty cycle square wave that

controls the IRFZ44 MOSFET and lamp brightness. The 5 second fade time

can be adjusted with the 75K resistor connected to the door switch. A largervalue will increase the time and a smaller value will speed it up.

When the door switch is closed (car door open) the voltage on pin 8 slowly

rises above the negative peaks of the triangle wave producing a short dutycycle output and a dim light. As the ramp moves farther positive, a greater

percentage of the triangle wave will be lower than the ramp voltage producing

a wider pulse and brighter light. This process continues until the ramp is 100%

above the positive peaks of the triangle wave and the output is maximum.

When the door switch is open, the reverse action takes place and the lamps

slowly fade out.


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The IRFZ44 shouldn't require a heat sink if the total load is 50 watts or less

but the temperature of the MOSFET should be monitored to insure it doesn'toverheat. The on-state resistance is only 0.028 ohms so that 4 amps of current

(48 watts) is only around 100mW. For larger loads, a small heat sink can be

added to keep the MOSFET cool.

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28 LED Clock Timer

This is a programmable clock timer circuit that uses individual LEDs to

indicate hours and minutes. 12 LEDs can be arranged in a circle to represent

the 12 hours of a clock face and an additional 12 LEDs can be arranged in an

outer circle to indicate 5 minute intervals within the hour. 4 additional LEDsare used to indicate 1 to 4 minutes of time within each 5 minute interval.

The circuit is powered from a small 12.6 volt center tapped line transformerand the 60 cycle line frequency is used for the time base. The transformer is

connected in a full wave, center tapped configuration which produces about

8.5 volts unregulated DC. A 47 ohm resistor and 5.1 volt, 1 watt zener

regulate the supply for the 74HCT circuits.

A 14 stage 74HCT4020 binary counter and two NAND gates are used to

divide the line frequency by 3600 producing a one minute pulse which is usedto reset the counter and advance the 4017 decade counter. The decade counter

counts the minutes from 0 to 4 and resets on the fifth count or every 5 minutes

which advances one section of a dual 4 bit binary counter (74HCT393). The 4bits of this counter are then decoded into one of 12 outputs by two 74HCT138


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(3 line to 8 line) decoder circuits. The most significant bit is used in

conjunction with an inverter to select the appropriate decoder. During the firsteight counts, the low state of the MSB is inverted to supply a high level to

enable the decoder that drives the first 8 LEDs. During counts 9 to 12, the

MSB will be high and will select the decoder that drives the remaining 4LEDs while disabling the other decoder. The decoded outputs are low when

selected and the 12 LEDs are connected common anode with a 330 ohm

current limiting resistor to the +5 volt supply. The 5th output of the seconddecoder (pin 11) is used to reset the binary counter so that it counts to 11 and

then resets to zero on the 12th count. A high reset level is required for the 393counters, so the low output from the last decoder stage (pin 11) is inverted

with one section of a 74HCT14 hex Schmitt trigger inverter circuit. A 10K

resistor and 0.1uF cap are used to extend the reset time, ensuring the counter

receives a reset signal which is much longer than the minimum time required.

The reset signal is also connected to the clock input (pin 13) of the second 4bit counter (1/2 74HCT393) which advances the hour LEDs and resets on the12th hour in a similar manner.

Setting the correct time is accomplished with two manual push buttons which

feed the Q4 stage (pin 7) of the 4020 counter to the minute and hour reset

circuits which advance the counters at 3.75 counts per second. A slower rate

can be obtained by using the Q5 or Q6 stages. For test purposes, you can useQ1 (pin 9) which will advance the minutes at 30 per second.

The time interval circuit (shown below the clock) consists of a SET/RESET

flipflop made from the two remaining NAND gates (74HCT00). The desired

time interval is programmed by connecting the anodes of the six diodes

labeled start, stop and AM/PM to the appropriate decoder outputs. For

example, to turn the relay on at 7:05AM and turn it off at 8:05AM, you would

connect one of the diodes from the start section to the cathode of the LED thatrepresents 7 hours, the second diode to the LED cathode that represents 5

minutes and the third diode to the AM line of the CD4013. The stop time isprogrammed in the same manner. Two additional push buttons are used to

manually open and close the relay. The low start and stop signals at thecommon cathode connections are capacitively coupled to the NAND gates so

that the manual push buttons can override the 5 minute time duration. That

way, you can immediately reset the relay without waiting 5 minutes for the

start signal to go away.

The two power supply rectifier diodes are 1N400X variety and the switchingdiodes are 1N914 or 4148s but any general purpose diodes can be used. 0.1 uF

caps (not shown on schematic) may be needed near the power pins of each IC.

All parts should be available from Radio Shack with the exception of the

74HCT4017 decade counter which I didn't see listed. You can use either74HC or 74HCT parts, the only difference between the two is that the input


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switching levels of the HCT devices are compatible with worst case TTL logic

outputs. The HC device inputs are set at 50% of Vcc, so they may not workwhen driven from marginal TTL logic outputs. You can use a regular 4017 in

place of the 74HCT4017 but the output current will much lower (less than 1

mA) and 4 additional transistors will be required to drive the LEDs. Withoutthe buffer transistors, you can use a 10K resistor in place of the 330 and the

LEDs will be visible, but very dim. Using the 4017 to drive LEDs with

transistor buffers is shown in the "10 Channel LED Sequencer" at the top ofthis page.

Time Interval Relay Circuit

for the clock circuit above


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72 LED Clock

In the circuit below, 60 individual LEDs are used to indicate the minutes of aclock and 12 LEDs indicate hours. The power supply and time base circuitry

is the same as described in the 28 LED clock circuit above. The minutessection of the clock is comprised of eight 74HCT164 shift registers cascaded

so that a single bit can be recirculated through the 60 stages indicating the

appropriate minute of the hour. Only two of the minutes shift registers are

shown connected to 16 LEDs. Pin 13 of each register connects to pin 1 of the

next for 7 registers. Pin 6 of the 8th register should connect back to pin 1 of

the first register using the 47K resistor. Pins 2,9,8, 14 and 7 of all 8 minutesregisters (74HC164) should be connected in parallel (pin 8 to pin 8, pin 9 to

pin 9, etc.). The hours section contains two 8 bit shift registers and works thesame way as the minutes to display 1 of 12 hours. Pin 9 of all 74HCT164s

(hours and minutes) should be connected together. For 50 Hertz operation, the

time base section of the circuit can be modified as shown in the lower drawinglabeled "50 Hertz LED Clock Time Base". You will need an extra IC

(74HC30) to do this since it requires decoding 7 bits of the counter instead of

4. The two dual input NAND gates (1/2 74HC00) that are not used in the 50Hertz modification should have their inputs connected to ground.

When power is applied, a single "1" bit is loaded into the first stage of boththe minutes and hours registers. To accomplish this, a momentary low reset

signal is sent to all the registers (at pin 9) and also a NAND gate to lock out

any clock transitions at pin 8 of the minutes registers. At the same time, a high

level is applied to the data input lines of both minutes and hours registers atpin 1. A single positive going clock pulse (at pin 8) is generated at the end of


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the reset signal which loads a high level into the first stage of the minutes

register. The rising edge of first stage output at pin 3 advances the hours (atpin 8) and a single bit is also loaded into the hours register. Power should

remain off for about 3 seconds or more before being re-applied to allow the

filter and timing capacitors to discharge. A 1K bleeder resistor is used acrossthe 1000uF filter capacitor to discharge it in about 3 seconds. The timing

diagram illustrates the power-on sequence where T1 is the time power is

applied and beginning of the reset signal, T2 is the end of the reset signal, T3is the clock signal to move a high level at pin 1 into the first register, T4 is the

end of the data signal. The time delay from T2 to T3 is exaggerated in thedrawing and is actually a very short time of just the propagation delay through

the inverter and gate.

Two momentary push buttons can be used to set the correct time. The button

labeled "M" will increment the minutes slowly and the one labled "H" muchfaster so that the hours increment slowly. The hours should be set first,

followed by minutes.


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50 Hertz LED Clock Timebase

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60 Light Sequencer using a Matrix

The circuit below illustrates using a 10x10 matrix to sequence up to 100 LEDs

with just three ICs and 20 transistors. The two 4017 decade counters controlthe 10 rows and 10 columns so that one LED is selected depending on the

output of the decade counters.

The LED circuit is drawn showing 25 LEDs and 10 transistors but can be

expanded up to a 100 by using sucessive stages of the 4017 counters.

For example, to expand the circuit to 60 LEDs for displaying minutes or

seconds of a clock, the rows counter could be reset from pin 12 (carry out)

rather than pin 1 as shown, and the columns counter will be reset from pin 5

rather than pin 1 as shown. And then add transistors to pins 1,5,6,9,and 11 ofthe rows counter and pin 1 of the columns counter. Take a look at the "10


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Stage LED Sequencer" for a listing of all the connections of the 4017 decade

counter.

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25 Light Sequencer using Xmas lamps

This circuit is same as the above setup to drive 25 small Xmas lights. Thelights operate at about 200mA and 3 volts. The supply voltage is set to 5 volts

and the 4017 counter output will drop about a volt using the 2N3053

transistors. The voltage on the emitters of the rows transistors will be about

0.7 volts less than the base so the lamp voltage will be about 3 volts. You canadjust the supply voltage for the desired current if necessary. It works the

same way as the LED version but you need diodes in series with each light.Most any small diode rated at 500mA or more should work. I used 1N4001

diodes. Various NPN transistors can be used, I tried 2N2219A and 2N3053.

The 2N3053 worked out better with a higher gain than the 2N2219A, buteither one should work.


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proyects leds

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