Triangle and Squarewave Generator Circuit

Description

Here is a simple triangle/squarewave generator using a common 1458 dual op-amp that can be used from very low frequencies to about 10 Khz. The time interval for one half cycle is about R*C and the outputs will supply about 10 milliamps of current. Triangle amplitude can be altered by adjusting the 47K resistor, and waveform offset can be removed by adding a capacitor in series with the output. 

Circuit Diagram

Source-http://www.electronguide.com/circuits_pages/TriangleandSquarewaveGenerator.html

05:43 0 comments

Frequency doubler with 4069 Circuit

Description 

This frequency doubler using a single 4069 hex inverter IC, a frequency doubler can be constructed to give an output pulse train whose frequency is twice that of a squarewave input signal. The signal is applied to the input of N1. It should be a squarewave with a duty-cycle of approximately 50% at level compatible with CMOS logic (3-15V peak to peak depending on supply voltage). The input signal is buffered and inverted by N1, and inverted again by N2, so the outputs A and B of N1 and N2 are squarewave signals 180° out of phase. The output of N1, is differentiated by C1 and R1 and the output of N2 is differentiated by C2 and R2, giving two spike waveforms of C and D, 180° out of phase. The signals are buffered, inverted and shaped by N3 and N4. These are then combined in a NOR gate consisting of D1, D2, R3 and N5, and finally inverted by N6 to give the frequency twice that of the input signal. The circuit will operate over a wide frequency range. With the component values shown the width of pulses in E and F point is about 500ns, so the duty cycle of the output will be 50% when the frequency is 1MHZ, when the input frequency is 500KHZ

Circuit Diagram

Author: A.M. Bosschaert
Source http://users.otenet.gr/~athsam/frequency_doubler_with_4069.htm

06:16 0 comments

Switchable Output Crystal Oscillator Circuit Diagram

Description 

 This oscillator circuit permits crystals to be electronically switched by logic commands. The circuit is best understood by initially ignoring all crystals. Furthermore, assume that all diodes are shorts and their associated 1kO resistors open. The two 1kO resistors at the non-inverting input of IC1 (LT1016) set the output to half the supply, ie, +2.5V. The RC network from the output to pin 3 sets up phase-shifted feedback and the circuit looks like a wide-band unity gain follower at DC. When crystal X1 is inserted (remember, D1 is temporarily shorted) positive feedback occurs and oscillation commences at the crystal’s resonant frequency. 

Circuit Diagram:

 If D1 and its 1kO resistor are then considered to be part of the circuit, oscillation can only continue if logic input A is biased high. Similarly, the circuit can only operate at crystal X2’s frequency if logic input B is high. Additional crystal/diode/1kO resistor branches permit logic selection of the crystal frequency. For AT cut crystals about a millisecond is required for the circuit output to stabilise due to the high Q factors involved. Crystal frequencies can be as high as 16MHz before propagation delays in the comparator prevent reliable operation.
 Source http://www.extremecircuits.net/2010/05/switchable-output-crystal-oscillator.html

08:29 0 comments

Pulse Rate Monitor Circuit Diagram

Description

This simple circuit enables you to listen to your heartbeat, for instance, while you are exercising. The transducer used for detecting the pulse is an electret microphone, X1 in the diagram. The model used has two (polarized) terminals. As usual with this type of microphone, it functions via a series resistor, R1. The potential drop across this resistor is applied to op amp IC1a via C1. The amplification of the op amp is set to between ´40 and ´1000 with preset P1. Network R4-C3 in the feedback loop of IC1a is a low-pass filter with a cut-off frequency of 34 Hz. Higher frequencies are not needed for the present application. A pulse rate of 180* is equivalent to a frequency of 3 Hz.

So as to cater for a wide range of pulse rates, the cut-off frequency is made just over 11 times as high as that representing the highest pulse rate. Operational amplifier IC1c, in conjunction with push-pull am-plifier T1-T2, creates a headphone amplifier, whose output resistance is equivalent to the value of R9, that is, 47 Ω. This makes the circuit usable for virtually any kind of headset. The output is short-circuit-proof. In case of certain headphones, such as that used with Sony Walkman™ sets, it is best to connect the two earphones in series. Operational amplifier IC1b is used as an active potential divider. The voltage across the actual divider, R5-R6, is half the supply voltage.

Circuit Diagram

This voltage is buffered by IC1b, taken from the low-resistance output, pin 7, of this op amp and used as reference for IC1a, and as operating voltage for the electret microphone. The voltage is decoupled by C4 to remove any interference signals from it. The supply voltage for the pulse rate monitor is decoupled by capacitor C7, immediately after polarity protection diode D1. Owing to the use of CMOS op amps, the current drain does not exceed 10 mA, so that operation from a 9 V battery is perfectly feasible. A dry alkaline manganese battery will have a life of about 50 hours.

Unless you are a young superfit top-class athlete, you should see your GP immediately when you find you have a pulse rate of 180. As a general guide, the absolute maximum pulse rate for a young, very fit person is 180, for a middle-aged person, 160, and for an elderly person, 140. When exercising, the pulse rate of a not very fit person should not exceed 60% of these maxima.

Source - http://www.extremecircuits.net/2010/07/pulse-rate-monitor.html

07:41 0 comments

Bells Ring Generator Circuit Schematic Diagram

Description

This circuit generates a dual-tone bells ringing similar to most door-bell units. It can be used in many applications other than door-bell. In the Notes below several options will be given in order to suit different needs. The circuit as shown in the diagram generates a "Ding-tone" when P1 is pressed and a "Dong-tone" when P1 is released. IC1D is the first-tone frequency generator and IC1F generates the second-tone. Q2, Q5 and related components act as shape and decay controls of the two tones, trying to imitate as close as possible the bells sound. Their outputs are mixed (R7 & R13), filtered (C5) and boosted by a simple class-A audio amplifier (Q3 & Q4) in order to drive the loudspeaker. The amplifier is switched-on by Q1 when P1 is pressed, then is switched-off some seconds after P1 is released: this time-delay is fixed by C1 & R2. In this way the circuit will draw a negligible current when in stand-by mode. 

 Circuit Schematic Diagram

 Part

• R1,R3,R7,R9,R13_10K 1/4W Resistors
• R2_______________1M5 1/4W Resistor
• R4______________27K 1/4W Resistor
• R5,R11__________47K 1/4W Resistors
• R6,R12_________220K 1/4W Resistors
• R8_______________2M2 1/4W Resistor
• R10_____________33K 1/4W Resistor
• C1_______________2µ2 25V Electrolytic Capacitor
• C2______________47µF 25V Electrolytic Capacitor
• C3,C8___________10µF 25V Electrolytic Capacitors
• C4,C7___________10nF 63V Polyester Capacitors
• C5,C6__________100nF 63V Polyester Capacitors
• C9_______________4µ7 25V Electrolytic Capacitor
• C10______________1µF 25V Electrolytic Capacitor
• D1-D5_________1N4148 75V 150mA Diodes
• IC1__________MC14106 or 40106 Hex Schmitt Inverter IC
• Q1_____________BC337 45V 800mA NPN Transistor
• Q2,Q3,Q5_______BC238 25V 100mA NPN Transistors
• Q4 ____________BC327 45V 800mA PNP Transistor
• PH______________Photo resistor (any type) (see Notes)
• P1______________SPST Pushbutton (see Notes)
• SW1_____________SPST Switch
• SPKR____________8 Ohm Loudspeaker
• B1______________3V Battery (two 1.5V AA or AAA cells in series etc.)
• Parts added to optional modification:
• R14____________220K 1/4W Resistor
• R15______________1M 1/4W Resistor 

 Notes:

• To obtain a "Ding-Dong" operation when pushing on P1, no matter when it is released, you must modify the circuit as shown in the frame placed at the low-right corner of the circuit diagram. D4 must be removed. C10 & R15 set the time-delay separating first and second tone.
• To obtain a one-tone-only generator, wire the circuit as in the optional modification, making the following changes:
• C9 = 100nF 63V Polyester Capacitor.
• Omit R9 to R13 & R15; C7, C8 & C10; D2, D4, D5 & Q5.
• Connect to negative supply pins 11 & 13 of IC1 and left open pins 10 & 12.
• An amusing application of this circuit wired as in the original schematic, is to use a photo-resistor in place of P1, then placing the unit near the flashing lamps of your Christmas tree. A soft bell sound may be heard at switch-on and switch-off of the lamp chosen.
• To obtain higher output power you may substitute R8, Q3 & Q4 with an audio amplifier IC like the LM386 or LM380. In this case power supply must be raised to 6 - 12V but at the same time R4 & R10 should be changed to adjust bell-tone frequencies.
• Good tone frequencies are roughly 2000 and 1650Hz respectively.
• When in stand-by mode, current drawing of the circuit is 200µA @ 3V supply: therefore SW1 can be omitted.

07:37 0 comments

Amplifier Timer Circuit Schematic Diagram

Description 

This circuit turns-off an amplifier or any other device when a low level audio signal fed to its input is absent for 15 minutes at least. Pushing P1 the device is switched-on feeding any appliance connected to SK1. Input audio signal is boosted and squared by IC2A & IC2B and monitored by LED D4. When D4 illuminates, albeit for a very short peak, IC3 is reset and restarts its counting.

Pin 2 of IC3 remains in the low state, the two transistors are on and the relay operates. When, after a 15 minutes delay, no signal appeared at the input, IC3 ends its counting and pin 2 goes high. Q1 & Q2 stop conducting and the relay switches-off. The device is thus completely off as also are the appliances connected to SK1. C5 & R9 reset IC3 at power-on. P2 allows switch-off at any moment. 

Circuit Diagram 

Parts:

• R1,R8___________1K 1/4W Resistors
• R2,R3___________4K7 1/4W Resistors
• R4_____________22K 1/4W Resistor
• R5______________4M7 1/4W Resistor
• R6,R9__________10K 1/4W Resistors
• R7______________1M5 1/4W Resistor
• R10___________100K 1/4W Resistor
• R11____________15K 1/4W Resistor
• R12____________10M 1/4W Resistor
• R13_____________1M 1/4W Resistor
• R14_____________8K2 1/4W Resistor
• R15_____________1K8 1/4W Resistor
• C1____________470µF 25V Electrolytic Capacitor
• C2,C3,C6______100nF 63V Polyester Capacitors
• C4,C5__________10µF 25V Electrolytic Capacitors
• D1_____Diode bridge 100V 1A
• D2,D7________1N4002 100V 1A Diodes
• D3__________Red LED 5mm.
• D4_______Yellow LED 5mm.
• D5,D6________1N4148 75V 150mA Diodes
• IC1___________78L12 12V 100mA Voltage regulator IC
• IC2___________LM358 Low Power Dual Op-amp
• IC3____________4060 14 stage ripple counter and oscillator IC
• Q1____________BC557 45V 100mA PNP Transistor
• Q2____________BC337 45V 800mA NPN Transistor
• J1______________RCA audio input socket
• P1_____________SPST Mains suited Pushbutton
• P2_____________SPST Pushbutton
• T1_____________220V Primary, 12V Secondary 3VA Mains transformer
• RL1___________10.5V 270 Ohm Relay with SPST 5A 220V switch
• PL1____________Male Mains plug
• SK1__________Female Mains socke

Notes: 

• Simply connect left or right channel tape output of your amplifier to J1.
• You can employ two RCA input sockets wired in parallel to allow pick-up audio signals from both stereo channels.
• The delay time can be varied changing R13 and/or C6 values.
• Needing to operate a device not supplied by power mains, use a double pole relay switch, connecting the second pole switch in series to the device supply. 

Source http://www.extremecircuits.net/2010/01/amplifier-timer-circuit-schematic.html

08:24 0 comments

Low Voltage, High Current Time Delay Circuit Diagram

Description 

In this circuit a LM339 quad voltage comparator is used to generate a time delay and control a high current output at low voltage. Approximatey 5 amps of current can be obtained using a couple fresh alkaline D batteries. Three of the comparators are wired in parallel to drive a medium power PNP transistor (2N2905 or similar) which in turn drives a high current NPN transistor (TIP35 or similar). The 4th comparator is used to generate a time delay after the normally closed switch is opened. Two resistors (36K and 62K) are used as a voltage divider which applies about two-thirds of the battery voltage to the (+) comparator input, or about 2 volts. The delay time after the switch is opened will be around one time constant using a 50uF capacitor and 100K variable resistor, or about (50u * 100K) = 5 seconds. The time can be reduced by adjusting the resistor to a lower value or using a smaller capacitor. Longer times can be obtained with a larger resistor or capacitor. To operate the circuit on higher voltages, the 10 ohm resistor should be increased proportionally, (4.5 volts = 15 ohms).

Circuit diagram 

Source- http://www.bowdenshobbycircuits.info/page2.htm#igniter.gif

07:54 0 comments

A Bedside Lamp Timer Circuit Diagram

Description 

 The purpose of this circuit is to power a lamp or other appliance for a given time (30 minutes in this case), and then to turn it off. It is useful when reading at bed by night, turning off the bedside lamp automatically in case the reader falls asleep... After turn-on by P1 pushbutton, the LED illuminates for around 25 minutes, but then it starts to blink for two minutes, stops blinking for two minutes and blinks for another two just before switching the lamp off, thus signaling that the on-time is ending. If the user want to prolong the reading, he/she can earn another half-hour of light by pushing on P1. Turning-off the lamp at user's ease is obtained by pushing on P2. 

Circuit diagram: 

Parts:

• R1 = 1K
• R2 = 4K7
• R3 = 10M
• R4 = 1M
• R5 = 10K
• C1 = 470µF-25V
• C2-C4100nF-63V
• C1 = 470µF-25V
• C2-C4 = 100nF-63V
• D1-D4 = 1N4002
• D5 = 5mm. Red LED
• IC1 = CD4012
• IC2 = CD4060
• Q1 = BC328
• Q2 = BC547
• P1,P2 = SPST Pushbuttons
• T1 = 9+9 Volt Secondary 1VA Mains transformer
• RL1 = 10.5V 470 Ohm Relay with SPDT 2A 220V switch
• PL1 = Male Mains plug
• SK1 = Female Mains socket

Circuit operation: 

Q1 and Q2 form an ALL-ON ALL-OFF circuit that in the off state draws no significant current. P1 starts the circuit, the relay is turned on and the two ICs are powered. The lamp is powered by the relay switch, and IC2 is reset with a positive voltage at pin 12. IC2 starts oscillating at a frequency set by R4 and C4. With the values shown, pin 3 goes high after around 30 minutes, turning off the circuit via C3. During the c6 minutes preceding turn-off.

The LED does a blinking action by connections of IC1 to pins 1, 2 & 15 of IC2. Blinking frequency is provided by IC2 oscillator at pin 9. The two gates of IC1 are wired in parallel to source more current. If required, a piezo sounder can be connected to pins 1 & 14 of IC1. Obviously, timings can be varied changing C4 and/or R4 values.

Source - http://www.extremecircuits.net/2009/12/bedside-lamp-timer-circuit-schematic.html

15:05 0 comments

Mains Frequency Monitor Circuit Diagram

Description

Here is a simple frequency counter designed to monitor the 240VAC mains supply. It as a frequency range of 0-999Hz, so it could also be used with 400Hz equipment. Standard TTL/CMOS logic is employed for the counters and display drivers, while an ELM446 (IC1) generates accurate 1Hz pulses for gating. This device utilizes a 3.579545MHz crystal for its timebase, as commonly found in TV and video circuits and even on old PC motherboards.

Circuit diagram:

Mains Frequency Monitor Circuit Diagram

Source http://www.extremecircuits.net/2010/06/mains-frequency-monitor_01.html

Author : Silicon Chip Electronics Magazine

11:31 0 comments

9 Second LED Timer and Relay Circuit

Circuit Diagram

Description

This circuit provides a visual 9 second delay using 10 LEDs before closing a 12 volt relay. When the reset switch is closed, the 4017 decade counter will be reset to the 0 count which illuminates the LED driven from pin 3. The 555 timer output at pin 3 will be high and the voltage at pins 6 and 2 of the timer will be a little less than the lower trigger point, or about 3 volts. When the switch is opened, the transistor in parallel with the timing capacitor (22uF) is shut off allowing the capacitor to begin charging and the 555 timer circuit to produce an approximate 1 second clock signal to the decade counter. The counter advances on each positive going change at pin 14 and is enabled with pin 13 terminated low. When the 9th count is reached, pin 11 and 13 will be high, stopping the counter and energizing the relay. Longer delay times can be obtained with a larger capacitor or larger resistor at pins 2 and 6 of the 555 timer. 

Source

http://www.seekic.com/circuit_diagram/Control_Circuit/9_Second_LED_Timer_and_Relay_Circuit.html

10:09 0 comments

Frequency Divider 2 Circuit

Description 

 This is a classic divider of frequency via two. It is achieved with a classic circuit T-flipFlop, round IC1 [ 4011 ]. In the circuit, the frequency of network, after are limit the negative half-s period of sine wave and transform in square wave, are divided via two. Thus for frequency50 HZ, we will take in the exit pulse of frequency 25 HZ. The supply of circuit it is + 5V and does not need high benefit in current.

Circuit diagram 

Part list

• R1= 10Kohm
• R2= 100Kohm
• R3= 680 ohm
• R4= 1Mohm
• R5-6-7= 100Kohm
• R8= 47 ohm
• R9-10-11= 100Kohm
• C1= 1000uF 25V
• C2-3= 100nF 100V ceramic
• C4-5= 100pF ceramic
• IC1= 4011
• T1= 110/220Vac //8V 100mA
• D1-2= 1N4007
• D3= 5.1V 0.5W Zener
• D4-5= 1N4148 

Source -http://users.otenet.gr/~athsam/frequency_divider.htm

10:59 0 comments

A Very Useful Timed Beeper Circuit Schematic

Description 

This circuit is intended for alerting purposes after a certain time is elapsed. It is suitable for table games requiring a fixed time to answer a question, or to move a piece etc. In this view it is a modern substitute for the old sandglass. Useful also for time control when children are brushing teeth (at least two minutes!), or in the kitchen, and so on. 

Circuit diagram:

Parts:

• R1 = 220R
• R2 = 10M
• R3 = 1M
• R4 = 10K
• R5 = 47K
• C1 = 100nF-63V
• C2 = 22µF-25V
• D1 = 1N4148
• D2 = 3mm. Red LED
• Q1 = BC337
• P1 = SPST Pushbutton (Start)
• P2 = SPST Pushbutton (Reset)
• PS = Piezo sounder (incorporating 3KHz oscillator)
• B1 = 3V Battery (2 AA 1.5V Cells in series)
• IC1 = CD4081 Quad 2 input AND Gate IC
• IC2 = CD4060 14 stage ripple counter and oscillator IC
• SW1 = 4 ways Switch (See notes)

Circuit Operation:

Pushing on P1 resets IC2 that start oscillating at a frequency fixed by R3 & C1. With values shown, this frequency is around 4Hz. LED D2, driven by IC1A & B, flashing at the same oscillator frequency, will signal proper circuit operation. SW1 selects the appropriate pin of IC2 to adjust timing duration:

• Position 1 = 15 seconds
• Position 2 = 30 seconds
• Position 3 = 1 minute
• Position 4 = 2 minutes

When the selected pin of IC2 goes high, IC1C drives Q1 and the piezo sounder beeps intermittently at the same frequency of the LED. After around 7.5 seconds pin 4 of IC2 goes high and IC1D stops the oscillator through D1. If you want to stop counting in advance, push on P2. 

Notes: 

1. SW1 can be any type of switch with the desired number of ways. If you want a single fixed timing duration, omit the switch and connect pins 9 & 13 of IC1 to the suitable pin of IC2.
2. The circuit's reset is not immediate. Pushing P2 forces IC2 to oscillate very fast, but it takes some seconds to terminate the counting, especially if a high timer delay was chosen and the pushbutton is operated when the circuit was just starting. In order to speed the reset, try lowering the value of R5, but pay attention: too low a value can stop oscillation.
3. Frequency operation varies with different brand names for IC2. E.g. Motorola's ICs run faster, therefore changing of C1 and/or R3 values may be necessary.
4. You can also use pins 1, 2, 3 of IC2 to obtain timings of 8, 16 and 32 minutes respectively.
5. An on-off switch is not provided because when off-state the circuit draws no significant current

Source  http://www.extremecircuits.net/2009/12/very-useful-timed-beeper-circuit.html

09:59 0 comments

Frequency Divider Circuit

Frequency Divider Circuit Diagram

This is a frequency divider circuit, or a circuit whose output frequency is a fraction of the frequency of its input.  The main component of this circuit is the 555, a versatile timer IC.  In this circuit, it is configured as a monostable multivibrator, i.e., it will output a single pulse at pin 3 every time its pin 2 is 'triggered' by a pulse.

 

The width of the output pulse at pin 3 of the circuit above is defined by the product of R1 and C1, i.e., increasing the value of R1C1 will increase the output pulse width. Once the circuit above is triggered by a pulse at pin 2, the pin 3 output pulse cycle defined by R1C1 will first have to be completed before any subsequent pulses at pin 2 can trigger the circuit again. R1C1 of the circuit above can therefore be adjusted to define the number of input pulses equivalent to a single output pulse. Thus, this circuit is in effect dividing the input frequency by an integer.  

Source - http://www.ecelab.com/circuit-frequency-divider.htm

09:49 0 comments

24 Second Shot Clock Circuit

Description:
This is a circuit intended to be used in basketball shot clock.
Circuit diagram

Notes:

To start in 24 seconds; 24s LOAD SW and Reset SW should be push simultaneously. If not, the count will start in 99. Pulse input can be connected to 555 astable multivibrator but must be calibrated for real time clock. The PAUSE SW must have a Switch Debouncer so that the counter will count normal when counting is paused and then turn-on.

When the count reach 00, the NOR gate will have an output of logic1 that will turn on the two transistor. The buzzer will rung and light will turn on. The two transistors are continuously turn-on not until LOAD SW and Reset SW is push. All have a +5v power supply.

author:Milardo de Guzman, milardo_dg@yahoo.com

Source: http://www.zen22142.zen.co.uk

10:22 0 comments

5 to 30 Minute Timer

Descriptipn:
A switched timer for intervals of 5 to 30 minutes incremented in 5 minute steps.

 Circuit diagram

Notes:
Simple to build, simple to make, nothing too complicated here. However you must use the CMOS type 555 timer designated the 7555, a normal 555 timer will not work here due to the resistor values. Also a low leakage type capacitor must be used for C1, and I would strongly suggest a Tantalum Bead type. Switch 3 adds an extra resistor in series to the timing chain with each rotation, the timing period us defined as :-

Timing = 1.1 C1 x R1

Note that R1 has a value of 8.2M with S3 at position "a" and 49.2M at position "f". This equates to just short of 300 seconds for each position of S3. C1 and R1 through R6 may be changed for different timing periods. The output current from Pin 3 of the timer, is amplified by Q1 and used to drive a relay.

Parts
Relay 9 volt coil with c/o contact (1)
S1 On/Off (1)
S2 Start (1)
S3 Range (1)
IC1 7555 (1)
B1 9V (1)
C1 33uF CAP (1)
Q1 BC109C NPN (1)
D1 1N4004 DIODE (1)
C2 100n CAP (1)
R6,R5,R4,R3,R2,R1 8.2M RESISTOR (6)
R8 100k RESISTOR (1)
R7 4.7k RESISTOR (1)

author: Andy Collinson
e-mail: mailto:anc@mitedu.freeserve.co.uk
Source: http://www.zen22142.zen.co.uk

11:26 0 comments

24 Hour Timer

Description:

These two circuits are multi-range timers offering periods of up to 24 hours and beyond. Both are essentially the same. The main difference is that when the time runs out, Version 1 energizes the relay and Version 2 de-energizes it. The first uses less power while the timer is running; and the second uses less power after the timer stops. Pick the one that best suits your application.

Notes:
The Cmos 4060 is a 14 bit binary counter with a built in oscillator. The oscillator consists of the two inverters connected to Pins 9, 10 & 11; and its frequency is set by R3, R4 & C3.The green Led flashes while the oscillator is running: and the IC counts the number of oscillations. Although it's a 14 bit counter, not all of the bits are accessible. Those that can be reached are shown on the drawing.
By adjusting the frequency of the oscillator you can set the length of time it takes for any given output to go high. This output then switches the transistor; which in turn operates the relay. At the same time, D1 stops the count by disabling the oscillator. Ideally C3 should be non-polarized; but a regular electrolytic will work, provided it doesn't leak too badly in the reverse direction. Alternatively, you can simulate a non-polarized 10uF capacitor by connecting two 22uF capacitors back to back (as shown).
Using "Trial and Error" to set a long time period would be very tedious. A better solution is to use the Setup tables provided; and calculate the time required for Pin 7 to go high. The Setup tables on both schematics are interchangeable. They're just two different ways of expressing the same equation.
For example, if you want a period of 9 Hours, the Range table shows that you can use the output at Pin 2. You need Pin 2 to go high after 9 x 60 x 60 = 32 400 seconds. The Setup table tells you to divide this by 512; giving about 63 seconds. Adjust R4 so that the Yellow LED lights 63 seconds after power is applied. This will give an output at Pin 2 after about 9 Hours.
The Support Material for the timers includes a detailed circuit description - parts lists - a step-by-step guide to construction - and more. A suitable Veroboard layout for each version is shown below:

 

The timer was designed for a 12-volt supply. However, provided a suitable relay is used, the circuit will work at anything from 5 to 15-volts. Applying power starts the timer. It can be reset at any time by a brief interruption of the power supply. The reset button is optional; but it should NOT be used during setup. The time it takes for the Yellow LED to light MUST be measured from the moment power is applied. Although R1, R2 and the two LEDs help with the setup, they are not necessary to the operation of the timer. If you want to reduce the power consumption, disconnect them once you've completed the setup. If you need a longer period than 24-hours, increase the value of C3.

 

author: Ron J
web site: http://www.zen22142.zen.co.uk

12:14 0 comments

100Hz Square Wave Generator Circuit

A requirement in many applications is a spontaneous source of a series of continuous signal with a regular and definable waveform. One of the most important of these is a square wave.
  
The circuit on the right will control a comparator with positive and negative feedback to the output voltage. Since the negative feedback path uses a capacitor, while the positive feedback path, but there is a time change from the comparator triggered her condition. As a result, the circuit oscillates, or changes the status back and forth on a predictable price.

 Square Wave Generator (100Hz) circuit

Three-phase 100Hz frequencies with 9V battery count, minimal parts

This simple circuit is a good and stable 1V peak to peak square wave at 100Hz, 1kHz and 10kHz with a single cell 1.5V power supply.
A useful feature of this circuit is that frequency changes can be achieved only by switching on a capacitor at a time.
The power consumption is about 600μA.

11:22 0 comments

Long duration timer circuit

Description.

This timer circuit can be used to switch OFF a particular device after around 35 minutes. The circuit can be used to switch OFF devices like radio, TV, fan, pump etc after a preset time of 35 minutes. Such a circuit can surely save a lot of power.

The circuit is based on quad 2 input CMOS IC 4011 (U1).The resistor R1 and capacitor C1 produces the required long time delay. When pushbutton switch S2 is pressed, capacitor C1 discharges and input of the four NAND gates are pulled to zero. The four shorted outputs of U1 go high and activate the transistor Q1 to drive the relay. The appliance connected via the relay is switched ON. When S2 is released the C1 starts charging and when the voltage at its positive pin becomes equal to ½ the supply voltage the outputs of U1 becomes zero and the transistor is switched OFF. This makes the relay deactivated and the appliance connected via the relay is turned OFF. The timer can be made to stop when required by pressing switch S1.

 Circuit diagram with Parts list.

Notes.

• Assemble the circuit on a good quality PCB or common board.
  
• The circuit can be powered from a 9V PP3 battery or 12V DC power supply.
  
• The time delay can be varied by varying the values of C1&R1.
  
• The push button switch S2 is for starting the timer and S1 for stopping the time.
  
• The appliance can be connected via contacts N1 & N2 of the relay RL1.
• The IC U1 is 2 input quad NAND gate 4011.

Source -http://www.circuitstoday.com

12:26 0 comments

CW Practice oscillator

Description.

A circuit diagram that can be used for the generation of CW Morse code is shown here.This circuit can be very useful those who would like practice Ham Radio.The circuit is nothing but an astable multivibrator based on NE 555.The frequency of oscillations of the circuit depends on the components R1,R2 & C1.The circuit can be powered from a 9V PP3 battery.

Circuit diagram with Parts list.

Notes. 

• The POT R2 can be used for frequency adjustments.
• POT R3 can be used for volume adjustments.
• The switch S1 can  be a Morse code key.

Source  http://www.circuitstoday.com

12:02 0 comments

Digital Stopwatch 0-60sec

author: Koukos Konstantinos, Tsormpatzidis Dimitrios - Aristotle University of Thessaloniki
Undergraduate students at Department of Electronics and Telecommunications - Physics Department

By using the same circuit of the Digital Stopwatch 0-99sec , we can add an AND gate, and transform the 0 – 99sec stopwatch to a 0 – 60sec stopwatch.

 We must find a way to control the RESET function of the BCD counter, which is responsible for the counting of the seconds. As we studied above, the circuit resets when we have 99 to 100, that is 1001 1001 à 0001 0000 0000. To make a transformation successfully we must force the pulse from 59 to 60 0011 1001 à 0100 0000 on the output of the BCD counter.

     By placing the AND gate, with its inputs on the Q1 and Q2 of the BCD counter of the decades, we make sure that when the gate closes, the RST input of the BCD counter will be set to logical “1”, which on its turn, will force the circuit to start over. The transformed circuit appears in picture 2.

Source http://www.electronics-lab.com

16:48 0 comments