Saturday, November 30, 2013
Automatic Automotive Burglar Alarm
Automotive Burglar Alarm Circuit Diagram
2x70Watt Amplifier Circuit
55+55w Output Power @ Rl = 4/8 W, Thd = 0.5%
70+70w Output Power @ Rl = 4/8 W, Thd = 10%
High Dynamic Preamplifier Input Stages
External Programmable Feedback Type Compressors
Ac Coupled Input To Class Ab Bridge Output Amplifier
Precision Rectifiers To Drive The Digital Converter
Proportional Over Power Output Current To Limit The Digital Converter
Absolute Power Bridge Output Transistor Power Protection
Absolute Output Current Limit
Integrated Thermal Protection
Power Supply Over Voltage Protection Flexiwatt Power Package With 27 Pin
Bash® Licence Required
Subowoofer audio car amplifier
For the a one amplifier circuit is very suitable for use in applications subwoofer speaker, which allows for higher spending enough bass. Although output was spent not high, but for bass sounds do not undoubtedly. Indeed, the output is only 20W mono amplifier with 8 ohm impedance. With a maximum supply 44Volt DC.Part list
R1 = 47R
R2 = 100K
R3 = 1R 2W
C1 = 2.2uF
C2 = 220uF
C3 = 100uF
C4 = 47uF
C5 = 68uF
C6 = 100uF
C7 = 1000uF
C8 = 0.1uF
U1 = STK024 , STK031 ,STK035
Beat Balance Metal Detector
Beat Balance Metal Detector Schematic
Various embodiments of the BB metal detector have been published, and it has been widely described in the press as a new genre. Instead of using a search and a reference oscillator as with BFO, or Tx and Rx coils as with IB, it uses two transmitters or search oscillators with IB-style coil overlap. The frequencies of the two oscillators are then mixed in similar fashion to BFO, to produce an audible heterodyne. On the surface of it, this design would seem to represent little more than a twinned BFO metal detector. However, what makes it different above all else, and significantly increases its range, is that each coil modifies the frequency of the adjacent oscillator through mutual coupling. This introduces the "balance" that is present in an IB metal detector, and boosts sensitivity well beyond that of BFO. Since the concept borrows from both BFO and IB, I have given a nod to each of these by naming it a Beat Balance Metal Detector, or BB for short. Happy hunting!
Friday, November 29, 2013
Cheap Electronics Component for Amplifier Application
"The series of Mini Amplifier TDA 2030 "The series of mini amplifie can reproduce the power output of 14 Watt with 8 Ohm speaker load. The series of mini-amplifier can be supplied with ource voltage of 12 volts - 15 volts DC. more details, see the following series of pictures.
Daftar komponen
Resistor:
- R1: 150KΩ
- R2: 4.7KΩ
- R3: 100KΩ
- R4: 1Ω 1W
- RA/RB: 100KΩ
Capacitor
- C1: 1µF / 25V
- C2: 2.2µF / 25V
- C3: 100nF
- C4: 22µF / 25V
- C5: 100 µF / 25V
- C6: 220nF
- C7: 2200µF / 35V
IC / Dioda
- IC1: TDA2030 or TDA2030a
- D1/D2: IN4002
Active AM Radio Antenna Amplifier Preamplifier Circuit
Modelsed to work with a telescopic whip antenna, the amplifier circuit operates in the typical AM / MediumWave band of 550 - 1650 kHz (kilohertz), with a power requirement of 12 Volts DC. The circuit also has a gain control feature, so weather signals can be amplifier more, if need be. This amplification alteration is provided via, RV1
The amplifier circuits output impedance is 50 Ohms, which is the standard for all of radio receivers, so it ought to work well along with your AM receiver.
Notes
This circuit is designed to amplify the input from a telescopic whip antenna. The preamplifier is designed to cover the medium waveband from about 550Khz to 1650Khz. The tuning voltage is supplied via RV2, a 10k potentiometer connected to the 12 Volt power supply.
RV1 is the gain control allowing weak signals to be amplified or strong signals to be attenuated. The control voltage is applied to gate 2 of TR1, a dual-gate MOSFET, the signal voltage applied via gate 1; the input signal being double tuned via the 330uH coil and the two KV1235 varicap diodes at the MOSFETs input and by the same components at the BF981 MOSFETs drain terminal. Both tuned circuits provide high selectivity across the entire tuning range. To aid stability the MOSFET stage is fed from a 6.2V zener stabilized supply.
Simple FM transmitter with 2N3904
C4 = 10uF
C5 = 3 - 18pF Adjustable capacitor
Thursday, November 28, 2013
Signal Tracer using LM386 Amplifier Chip
PWM controller with 555 timer chip
PWM controller circuit |
DC motor driver with H Bridge IC L293D
0 0 Motor silent
1 0 motor rotates counterclockwise
0 1 Motor berputer clockwise
1 1 Motor silent
Description: Enable Input given a logic 1 to obtain such data in the table above.
10Mhz to 1 MHz Frequency Converter
Part ListIC1 7404 = 1
IC2 7490A = 1
R 1 K = 2
R 3.3 K = 1
C Trim Polymer 39 pF = 1
C Electrophoresis 4.7 uF 16V = 1
C Milar 47 nF 16 V = 1
C Milar 10 nF 16 V = 1
C Ceramic 68 pF 50 V = 1
Wednesday, November 27, 2013
3 Watt power amplifier schematic
This time I will share a circuit of schematis power amplifier with LM380 IC that has similarities with LM384. Enough with just a few components you have to make this power amplifier circuit . All components with relatively low prices and making a fairly easy. For this amplifier output power has 3W with 4 ohm impedance. Indeed , this amplifier has the output is quite low and certainly will not be maximal if it works on the speakers with high power.Component List :
Resistor
R1______________47K
R2______________2.7R 2W
Capacitor
C1______________10uF
C2______________470uF
C3______________100n
C4______________100n
IC
IC1_____________LM380 , LM384
Condenser Pre Amplifier LM 1458
The circuit takes the audio signal rom the condenser microphone and amplifier it, so you can use the microphone as the input to some device which wouldn’t normally accept microphone level signals .
Schematic Circuit of Microphone Electret
Condenser Pre Amplifier
The circuit requires a 6-9 volt supply. Output of the microphone amplifier can be made variable by connecting a 10kΩ potentiometer . Circuit’s gain can be increased by men perbesar the value of 47K, depending on the input sensitivity of the main amplifier system. The microphone should be housed in a small round enclosure.
List componet of condenser pre-amp mic circuit
Q1,Q2 : LM1458 Op-Amp
R1,R2,R3 : 4.7k ohm resistor
R4, R5 : 10k ohm resistor
R6,R7 : 47k ohm resistor
C1, : 0.22uF ceramic capacitor
C2 : 1uF ceramic capacitor
Absolute maximum ratings of LM 1458 IC
Supply Voltage : ±18V
Power Dissipation : 400 mW
Differential Input Voltage : ±30V
Input Voltage : ±15V
Output Short-Circuit Duration: Continuous
Operating Temperature Range : 0°C to +70°C
Storage Temperature Range : −65°C to +150°C
Lead Temperature :(Soldering, 10 sec.) 260°C
Regulated Dual White LED Lamp
Project Image
I have built about ten of these lamps and they are all going strong after many years of daily operation. The lamps are part of several night-lighting systems that use a SCC3 charge controller to solar-charge a lead acid battery and a DAS1 Dark Activated Switch to turn on the lights at night.
Circuit Diagram
The same circuit can be used with colored LEDs, it makes a great accent lamp if you use one emerald green and one ultra-bright blue LED. The circuit will also drive three LEDs on the red side of the spectrum since they run at a lower voltage than the blue, emerald green and white LEDs. An accent lamp made with deep red, orange and ultra-bright yellow LEDs complements the emerald green and blue lamp nicely.
Specs:
- Nominal Operating Voltage: 12V DC
- Regulated Light Voltage Range: 11-20V
- Operating Current: 20ma
The input power is filtered through an R-C filter consisting of two 100nF capacitors and a 100 ohm resistor, this removes voltage spikes from the rest of the circuitry. The LM317L and 56 ohm resistor act as a current regulator that is set to 25ma. The current regulator is wired in series between the power source and the LEDs to provide a constant current.
Construction:
A small circuit board was made using press-n-peel blue film, the board was sized to fit inside of a 1/2" PVC pipe connector. The parts were soldered into the circuit board and a length of two conductor speaker wire was soldered to the board for the power lead. A knot was tied in the power cable to act as a strain relief. The power cable was fed through a hole in the PVC connector. The entire assembly was filled with clear GE Silicone II caulk and left to dry. Be sure to allow the caulk to dry for several days in a warm place before applying power, the acetic acid that is released when the caulk cures is conductive. Another brand of bathtub caulk was tried, but the caulk stayed electrically conductive and the circuit quickly failed.
Use:
Connect this circuit to a 12V battery or power supply, be sure to observe the correct polarity. The LEDs should put out a bright white light. This light can be used for a night light, a flash light, automotive interior lights and background house lighting. The low current draw allows the lamp to run for many hours on battery power.
Parts:
2x white LEDs, T1-3/4 size
1x 56 ohm 1/4 W resistor
1x 100 ohm 1/4 W resistor
2x 0.1uF capacitors
1x LM317L adjustable voltage regulator
1x 1/2" Schedule 40 PVC pipe junction
GE Silicone II caulk
Two conductor speaker wire
Tuesday, November 26, 2013
Improving Performance Bass Guitar
2. Know your bass character of us, whether inclined treble, middle, or ngebass (low). From here our reference point. If soundnya not in accordance with our desires, try to correction with tone control / equalizer.
3. There are so many factors affecting the bass sounds, ranging from strings, pickups, body wood, neck & fingerboard.
Try to identify the character masing2, eg the influence of wood types, pickup types, etc..
From there we can determine which one should be modified.
Chain audio a bass sound as follows
Strings-> pickup-> Preamp / Tone Control-> Connection Cable-> Amplifier
Well, just select which one would aja in mod.
Actually the material (wood) body / neck / fingerboard also influence:
String-> Body/Neck/Fingerboard-> Pickup-> Preamp / Tone Control-> Connection Cable-> Amplifier (+ Speaker)
Only if you replace the body just wrote instead of bass.
So, if you can choose a distinguished bass wood is good, Ntar if you want to be upgraded more easily.
If wood is not good (Agathis), although the results are less than the maximum upgrade.
Stereo PC Speaker Powered USB Speaker
Schematic Power Amplifier with IC AN7114 or AN7115
See the Schematic (figure 2.0) and package IC (figure 1.0) :
Figure 1.0 |
Figure 2.0 |
Monday, November 25, 2013
Hot Water Level Indicator
Hot Water Level Indicator Schematic
Construction:
Masking tape was used to stick the bead thermistors to the tank. Wires were soldered and insulated at the thermistors ends. A plastic box was used to house the circuit. Battery life will probably be 4 to 5 years depending on how often you use the push switch, SW1.
Sensor Placement:
Thermistors NTC1-4 should be spread evenly over the height of the tank. I placed NTC1 roughly 4 inches from the top of my tank and the others were spaced evenly across the height of the hot water tank. As hot water rises the lowest sensor indicates the fullest height of hot water and should be about 8 to 10 inches from the bottom of the tank.
Calibration:
With a full tank of hot water adjust P1-4 so that all LEDs are lit. As hot water rises, the sensor at the bottom of the tank will be the maximum level of hot water. "Hot" can be translated as 50C to 80C the presets P1-4 allow adjustment of this range.
Parts:
I have used a quad version of the LM324 but any quad opamp can be used or even four single op-amps.
R2-R5 I used 330ohm resistors, but value is not critical. Lower values give brighter LED output.
NTC1-4 The thermistors maximum resistance must roughly equal the resistance of the fixed resistor and preset. As negative temparature coefficient (NTC) thermistors are used, then their resistance decreases for increases in temperature. I used a thermistor from the Maplin Catalogue. Cold resistance was around 300K, hot resistance 15k. Alternative thermistors may be used with different resistance ranges, but the presets P1 to P4 must also be changed as well.
R7-10 series resistance, only required if your thermistors resistance is several ohms at the hottest temperature.
P1 - P4 Chosen to match the resistance of the thermistor when cold.
R1 & R6. These resistors are equal and bias the op-amp inverting input to half the supply voltage. I used 100k.
Fuse Failure Alarm 2 LED
Wireless receiver microphone circuit
Part Series FM Wireless Microphone Receiver Hi Fi
USB Powered Audio Power Amplifier
circuit of multimedia speakers for PCs has single-chip-based design,
low-voltage power supply, compatibility with USB power, easy
heat-sinking, low cost, high flexibility and wide temperature tolerance.
At the heart of the circuit is IC TDA2822M. This IC is, in fact,
mono-lithic type in 8-lead mini DIP package. It is intended for use as a
dual audio power amplifier in battery-powered sound players.
Specs
of TDA2822M are low quiescent current, low crossover distortion,
supply voltage down to 1.8 volts and minimum output power of around 450
mW/channel with 4-ohm loudspeaker at 5V DC supply input. An ideal
power amplifier can be simply defined as a circuit that can deliver
audio power into external loads without generating significant signal
distortion and without consuming excessive quiescent current.
This
circuit is powered by 5V DC supply available from the USB port of the
PC. When power switch S1 is flipped to ‘on’ position, 5V power supply
is extended to the circuit and power-indicator red LED1 lights up
instantly. Resistor R1 is a current surge limiter and capacitors C1 and
C4 act as buffers. Working of the circuit is simple. Audio signals from
the PC audio socket/headphone socket are fed to the amplifier circuit
through components R2 and C2 (left channel), and R3 and C3 (right
channel).
Circuit diagram:
Potmeter
VR1 works as the volume controller for left (L) channel and potmeter
VR2 works for right (R) channel. Pin 7 of TDA2822M receives the
left-channel sound signals and pin 6 receives the right-channel signals
through VR1 and VR2, respectively. Ampl i f ied signals for driving the
left and right loudspeakers are available at pins 1 and 3 of IC1,
respectively. Components R5 and C8, and R6 and C10 form the traditional
zobel network.
Assemble the circuit on a medium-size,
general-purpose PCB and enclose in a suitable cabinet. It is advisable
to use a socket for IC TDA2822M. The external connections should be made
using suitably screened wires for better result.
Sunday, November 24, 2013
Alarm Sound with Control Switch
Alarm Sound with Control Switch |
Mini and simple power amplifier circuits
C2 = 100uF
C5 = 1uF
U1 = S1513
20A Transformerless Power Supply
20A Transformerless Power Supply |
Saturday, November 23, 2013
AT89S51 Microcontroller based on Digital Clock
Digital hours to create this not too tough. This series is not my original project, I trace the series of files and program from the internet, there is no chance the program listing. when I download the file to its hex-hour direct approach. This clock only displays hours and minutes, to seconds but youll install the led associated with a series of I Hz oscillator formed from IC 555 (which I do, because I do not recognize the program listing).
a pair of led in parallel and installed as a bookmark seconds. Led to two installed in the middle of the hours and minutes. though with the approach that seconds and minutes if observed (calculated) decline slightly however i am not the problem, Moreover individuals wont understand it.
The Risks of Self Installation of your Auto Sound System
Schematic diagram of a USB player
Schematic usb player |
Power Supply Failure Alarm
Power Supply Failure Alarm Circuit |
Friday, November 22, 2013
Powerful Bat Detector device
The Powerful Bat Detector is a abundance analysis blazon device. Abundance analysis blazon detectors acquiesce you to apprehend accelerated complete by digitally ascent the abundance bottomward into the animal audition range. For instance, a western pipistrelle bat emits accelerated complete in the ambit of 53 to 91 kHz. If you bisect that abundance by 16, the new abundance ambit is 3.3 to 5.7 kHz, calmly aural our audition range. Because the analysis is done digitally, all amplitude advice is lost. Accelerated sources candy by the detector catechumen to sounds like geiger-counter clicks and chirps.
The basal ambit of the Simple Bat Detector is apparent in the schematic diagram to the right. It is about composed of 3 chip circuits, or ICs. The arresting from an accelerated transducer is fed to IC-1, an LM386 audio amplifier, which is configured to accommodate a arresting accretion of 200. The arresting is accompanying to IC-2, a added LM386, by a .05 uf capacitor. IC-2 is configured to accommodate an added accretion of 20, for a absolute arrangement accretion of 4,000. The achievement of IC-2 is absolute accompanying to the ascribe of IC-3, a 7 date CMOS agenda affiliate circuit. The ascribe date of the affiliate acts as a aught bridge detector, triggering on the abrogating alteration of the arresting from IC-2. The bisect by 16 achievement is affiliated to a potentiometer, which serves as an audio akin control. A aerial impedance bowl earphone is affiliated to the achievement of the akin control. The 10K akin ascendancy is a baby printed ambit pot that is set and forgotten. The detector ambit is powered by a nine volt battery. ( The numbers abutting to the IC nodes accredit to the pin numbers of the ICs. Note the added pins listed at the basal of the schematic that charge to be angry to ground. )
A above advantage of a abundance analysis detector is that it is a advanced bandage accessory ... that agency it will let you apprehend all apparent bat sounds after the charge to tune the detector to any accurate frequency. Heterodyne detectors, which action accelerated complete in the analog domain, alone catechumen a baby ambit of frequencies at any accustomed time - you charge baddest which frequencies to accept to. If you tune up about 60 kHz to accept for a pipistrelle, you may not apprehend the big amber bats aerial nearby. The abundance analysis detector works in the agenda domain, converting the abounding spectrum of complete that the transducer is able to detect. So you get to accept to all of the accelerated sounds about you, after missing annihilation due to adverse affability choices. I feel this no-knobs-needed appropriate of the abundance analysis detector makes it a abundant best for the accidental bat observer, and student.
Binary Coded Decimal BCD Clock
This makes binary counting fairly easy since each digit has a value of twice the one before or 1,2,4,8,16,32,64,etc. Thus the decimal value can be found by simply adding the values of each illuminated LED in the same row, (the total is shown in the box to the right). For example, the binary number 1001 would have a decimal value of 8+0+0+1 = 9. But this is actually a binary coded decimal 9 since only values from 0 to 9 are used 0000 to 1001. A true binary clock indicating minutes of the hour would display values from 0 to 59, or 000000 to 111011. But this would be more difficult to read since adding values 32 + 16 + 8 + 2 + 1 = 59 is not as easy as 8 + 0 + 0 + 1 = 9.
The circuit is powered by a small 12.6 VAC transformer which also provides a low voltage 60 Hz signal for a very accurate time base. The transformer is connected with the secondary center tap at ground which produces about 8 volts DC across the 3300uF filter capacitor. DC power for the circuit is regulated at about 5.5 using a NPN transistor (2N3053) and 6.2 volt zener diode. The 2N3053 gets a little warm when several LEDs are on, and may require a little (top hat type) heat sink.
Binary Coded Decimal (BCD) Clock Circuit Diagram:
A one second clock pulse is obtained by counting 60 cycles of the AC line signal. This is accomplished using a CMOS CD4040 12 stage binary counter (shown in light blue). The 60th count is detected by the two NAND gates connected to pins 2,3,5,and 6 of the counter. When all four of these lines are high, the count will be 60 resulting in a high level at pin 4 of the 74HC14 which resets the counter to zero and advances the seconds counter (74HC390 shown in purple) when pin 4 returns to a low state.
The same process is used to detect 60 seconds and 60 minutes to reset the counters and advance the minutes and hours counters respectively. In both of these cases the 2 and 4 bit lines of the tens counter section will be high (20+40=60). In all three cases (seconds, minutes and hours) a combination 10K resistor and 0.1uF capacitor is used at the input to the 74HC14 inverter to extend the pulse width to about 300uS so the counters will reliably reset. Without the RC parts, the reset pulse may not be long enough to reset all stages of the counter since as soon as the first bit resets, the inputs to the NAND gate will no longer all be high and the reset pulse will end. Adding the RC parts eliminates that possibility.
The reset process for the hours is a little different since for a 12 hour clock we need to reset the hours counter on the 13th count and then advance the counter one count so the display will indicate one ("1"). The 74HC00 quad NAND gate only has 4 sections with two inputs each so I used 3 diodes to detect the 13th hour (10 +1 +2 =13) which drives an inverter and also a transistor inverter (2N3904 or similar). The last 74HC14 inverter stage (pin 12 and 13) supplies a falling edge to the hours counter which advances the hours to "1" a short time after the reset pulse from the transistor inverter ends.
The pulse width from pin 12 of the inverter is a little shorter than from pin 10 which ensures that the hours clock line (pin 1 of yellow box) will move high before the end of the reset pulse form pin 10. If it were the other way around, the reset pulse may end before pin 12 of the inverter had a chance to reach a high level which would prevent the counter from advancing to "1". So it is important to use a shorter RC time at pin 13 than for the other Schmitt Trigger inputs. I used a 10K resistor and a 0.01uF cap to obtain the shorter time, but other values will work just as well. Only 2 sections of the 4071 OR gate are used, so the remaining 4 inputs (pins 8,9,12,13) should be terminated to ground if not used.
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Parts List:
3 - 74HC390 - Dual BCD counters
1 - CD4040 - 12 Stage Binary Counter
1 - 74HC14 - Hex Schmitt Trigger Inverter
1 - 74HC00 - Quad NAND gate
1 - CD4071 - Quad OR gate
1 - 2N3053 - NPN transistor (may need heat sink)
1 - 2N3904 - NPN transistor
3 - 1N914 - Signal diode (1N400X will also work)
2 - 1N400X - Rectifier diodes
1 - 6.2 volt - Zener diode
1 - 3300uF - Filter Capacitor - 16 volt
1 - Power Transformer - Radio Shack 273-1365A or similar
1 - 220K 1/4 or 1/8 watt resistor
1 - 150 ohm 1/4 watt resistor
19 - 220 ohm 1/4 or 1/8 watt resistors
11 - 10K 1/4 or 1/8 watt resistors
2 - 0.01uF capacitors
4 - 0.1uF capacitors
19 - Red LEDs (15 mA)
2 - Momentary push button switches (to set the time)
1 - Toggle switch (to start the clock at a precise time)
Electric Motor Repair
Thursday, November 21, 2013
Simple Remote Control Tester
Simple Remote Control Tester |
Simple Source Voltage Protector
Source voltage surge protector will expressed in this article are general, so that later in their applications to stay adjusted value of the component with the voltage source needs an electronic appliance. Let us start reviewing Protectors Voltage Source by simple and modest.
Source voltage protection with 1 diode |
Source voltage protection with dioda bridge |
Pieces Parts Components and Sound
Traffic Light 20 Chanel based on 74LSxx
This page features a circuit that has twenty open collector outputs that turn on one at a time in a continuous sequence. The circuit make use of the family 74LSxx TTL integrated logic devices. The circuits are designed to drive light emitting diodes or low current and low voltage incandescent lamps, but can also lead to other charges of 80 milliamps.
notes:
- The low output go in sequence from 1 - 0 and back to 1 -0
- At the clock rate of the 555 timer
- c3 = 1uf to 10uf depending on the rate of change desured
- R2 (Variable resistor) in use to determine the timer
Wednesday, November 20, 2013
Amplifier Circuit with IC AN7133
Schematic Audio Power Amplifier with IC TDA2822
TDA2822 is manufactered by PHILIPS , its based on this amplifier . Minimum voltage 3 volts and maximum voltage 15 volts. Power output 2 x 1,8 stereo with 4 Ohm impedance. Quiescent current 6 mA , sensitive input is 30 Hz to 18 kHz. See circuit diagram below :
Automatic Light Controller Using 7806
regulator ICs (78xx series) provide a steady output voltage, as
against a widely fluctuating input supply, when the common terminal is
grounded. Any voltage about zero volt (ground) connected in the common
terminal is added to the output voltage. That means the increase in the
common terminal voltage is reflected at the output. On the other hand,
if the common terminal is disconnected from the ground, the full input
voltage is available at the output. This characteristic is utilised in
the present circuit.
When the common terminal is connected to
the ground,the regulator output is equivalent to the rated voltage, and
as soon as the terminal is disconnected from the ground, the output
increases up to the input voltage. The common terminal is controlled by a
transistor, which works as a switch on the terminal. For automatic
control of light, a light-dependent resistor (LDR1) is connected to the
base of the transistor. In this way, the voltage regulator is able to
operate a light bulb automatically as per the ambient light.
To
derive the power supply for the circuit, the 50Hz, 230V AC mains is
stepped down by transformer X1 to deliver a secondary output of 12V, 250
mA. The secondary output of the transformer is applied to a bridge
rectifier comprising diodes D1 through D4, filtered by capacitor C1 and
fed to the input terminal of the regulator (IC1). The common terminal
(pin 2) of IC1 is connected to the ground line of the circuit through
transistor BC557 (T1). The transistor is biased by R2, R3, VR1 and LDR1.
The
grounding of IC1 is controlled by transistor T1, while light is sensed
by LDR1. Using preset VR1, you can adjust the light-sensing level of
transistor T1. The output of IC1 is fed to the base of transistor T2
(through resistor R4 and zener diode ZD1) and relay RL1. LED1 connected
across the positive and ground supply lines acts as a power-‘on’
indicator. Normally, the resistance of LDR1 is low during daytime and
high during nighttime. During daytime, when light falls on LDR1, pnp
transistor T1 conducts.
The common terminal of IC1 connects to
the ground and IC1 outputs 6V. As a result, transistor T2 does not
conduct and the relay remains de-energised. The light bulb remains ‘off’
as the mains connection is not completed through the relay contacts.
During nighttime, when no light falls on LDR1, it offers a high
resistance at the base junction of transistor T1. So the bias is greatly
reduced and T1 doesn’t conduct. Effectively, this removes the common
terminal of IC1 from ground and it directs the full input DC to the
output. Transistor T2 conducts and the relay energises to light up the
bulb as mains connection completes through the relay contacts.
As
LDR1 is in parallel to VR1 R3 combination, it effectively applies only
half of the total resistance of the network formed by R3, VR1 and LDR1
to the junction at T1 in total darkness. In bright light, it greatly
reduces the total effective resistance at the junction. The circui t is
simple and can be assembled on a small general-purpose PCB. Use a
heat-sink for IC1. Make sure that LDR1 and the light bulb are well
separated. The circuit can be used for streetlights, tubelights or any
other home electrical lighting system that needs to be automated.
The Importance of a Good Auto Sound System
Tuesday, November 19, 2013
14W Class A Amplifier Circuit with 2N3055
555 timer chip tester
Tester schematic |