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Showing posts from February, 2012

Electronic Timer Switch

Electronic Timer Switch This electronic timer switch project is a good project to build to simulate the presence of occupants in a house. In these days when security is becoming more of a concern when no one is at home, having this device will deter the thief from breaking in. When power up, after 60 minutes, the relay will turn ON for 100 secs, OFF for the next 100 secs, and ON again for 100 secs before OFF again for the next 60 mins. This sequence will be repeated. A device such as a lamp that is connected to the relay will turn ON and OFF according to this timing.

Schematic Diagram
The schematic of the project is as shown below.  The core of this electronic timer switch project uses a CD4060B binary counter. The binary counter has 10 outputs and the counter are counted by configuring the oscillator. Every negative clock will trigger the counter of the IC internally. The timing of the circuit is affected by resistor R3(1M ohm) and capacitor C2(0.1uF). By connecting t…

Telephone Switch For Phone Recorder Project

Introduction To Phone Recorder This phone recorder project will enable you to record both sides of your telephone conversations. One constructed, this switch will allows you to automatically turn on your tape recorder when you pick up the handset of your telephone. Note that your tape recorder must have both a MIC socket and a REMOTE socket on it so that this device can plug into the recorder and control it. This circuit is designed to work for the newer 1.5V and 3V tape recorders as well as the usual 6V or 12V ones.
Phone Recorder Circuit Description
The circuit falls into two parts and these can be easily seen in the diagram. On the left are the connections to each telephone line and to the MIC socket of the tape recorder. The diode and capacitors ensure that no DC voltages pass through to the input of the MIC while the RC network clips large transients. On the right is the circuit which detects when the handset has been lifted and which then turns on the FET. The trim …

High liquid level activated switch

A method for activating a relay when the liquid level exceeds a predetermined level is shown here. DC voltage is required for driving the relay and AC voltage cannot be used here just like what we did in the case of LED and speaker. Pin 9 of the IC can be used to solve this problem. A capacitor connected from this pin to ground will keep the internal output transistor steadily ON whenever the probe resistance goes higher than the reference resistor. External transistor Q1 is connected to the collector of the internal transistor. The load that is the relay is connected at the collector of Q1. When the probe is not touching the water it equal to an open circuit situation and surely the probe resistance will be many M ohms and it is greater than the Rref(13K). The internal transistor will be switched ON and Q1 whose base is connected to the collector of the internal transistor will be in OFF condition keeping the relay inactive. When the reverse scenario occurs…

Improved 3 Transistor Audio Amp (80 milliwatt)

This circuit is similar to the one above but uses positive feedback to get a little more amplitude to the speaker. I copied it from a small 5 transistor radio that uses a 25 ohm speaker. In the circuit above, the load resistor for the driver transistor is tied directly to the + supply. This has a disadvantage in that as the output moves positive, the drop across the 470 ohm resistor decreases which reduces the base current to the top NPN transistor. Thus the output cannot move all the way to the + supply because there wouldn't be any voltage across the 470 resistor and no base current to the NPN transistor.

This circuit corrects the problem somewhat and allows a larger voltage swing and probably more output power, but I don't know how much without doing a lot of testing. The output still won't move more than a couple volts using small transistors since the peak current won't be more than 100mA or so into a 25 ohm load. But it's an improvement over the…

3 Transistor Audio Amp (50 milliWatt).

Here is a little audio amplifier similar to what you might find in a small transistor radio. The input stage is biased so that the supply voltage is divided equally across the two complimentary output transistors which are slightly biased in conduction by the diodes between the bases. A 3.3 ohm resistor is used in series with the emitters of the output transistors to stabilize the bias current so it doesn't change much with temperature or with different transistors and diodes. As the bias current increases, the voltage between the emitter and base decreases, thus reducing the conduction. Input impedance is about 500 ohms and voltage gain is about 5 with an 8 ohm speaker attached. The voltage swing on the speaker is about 2 volts without distorting and power output is in the 50 milliwatt range. A higher supply voltage and the addition of heat sinks to the output transistors would provide more power. Circuit draws about 30 milliamps from a 9 volt supply. 

Microcontroller Based Electronic Thermostat Project Electronic Thermostat

Electronic Thermostat
Mechanical thermostat has been around for a long time and has been used in industrial control, home appliances control and many other devices to measure and control the temperature of a certain processes. The sensor used usually is a bimetallic sensor that is make from two different metals that expand at different rates as they are heated up. These metal strips are bonded together and when the temperature rises, the strips will bend upward hence making connection to the contact of the circuit so that current can flow through the circuit.
As the temperature cools down, it will go back to its original position and disconnect the current from the circuit. By adjusting the strip and the contact, the temperature can be contolled. Most oven and air conditioners use this type of sensor. The mechanical thermostat is more widely used due to its lower cost compared to electronic thermostat.
The use of electronic thermostat is becoming more popular now a…

Low Frequency Sinewave Generators

The two circuits below illustrate generating low frequency sinewaves by shifting the phase of the signal through an RC network so that oscillation occurs where the total phase shift is 360 degrees. The transistor circuit on the right produces a reasonable sinewave at the collector of the 3904 which is buffered by the JFET to yield a low impedance output. The circuit gain is critical for low distortion and you may need to adjust the 500 ohm resistor to achieve a stable waveform with minimum distortion. The transistor circuit is not recommended for practical applications due to the critical adjustments needed.

The op-amp based phase shift oscillator is much more stable than the single transistor version since the gain can be set higher than needed to sustain oscillation and the output is taken from the RC network which filters out most of the harmonic distortion. The sinewave output from the RC network is buffered and the amplitude restored by the second (top) op-amp whic…

Temperature and relative humidity meter using an inexpensive DHT11 sensor

Project SummaryNumerous studies have shown that the indoor temperature and relative humidity at workplace significantly impacts workers' comfort and productivity. The first step towards optimizing these two ambient parameters is their reliable measurement. This project describes an inexpensive technique of using the DHT11 sensor for measuring temperature and relative humidity in parallel. It uses the PIC16F628A microcontroller to read the sensor output and display the results on a 16x2 character LCD. Project DescriptionDHT11 is the most inexpensive sensor currently available in the market that provides calibrated digital outputs for temperature and relative humidity. It is available in a single row 4-pin package and operates from 3.5 to 5.5V power supply. It can measure temperature from 0-50 °C with an accuracy of ±2°C and relative humidity ranging from 20-95% with an accuracy of ±5%, thus making it suitable for indoor applications. The sensor has got its own propriet…

LG Optimus 4X HD

LG Optimus 4X HD :) Quad-core Tegra 3:) Ice Cream Sandwich:) 4.7-inch display:):) If LG failed to impress so far with the Android 2.3 phones it's shown off in the run up to MWC 2012, perhaps the Optimus 4X HD can turn things around. This 4.7-inch beast will hit Europe in the second quarter and is its first to feature a 1.5GHz quad-core Tegra 3 as its benchmark destroying CPU, a 4.7-inch True HD IPS LCD (1280x720) plus what appears to be a lightly customized version of Ice Cream Sandwich. Perhaps the only logical followup to its Optimus 2X that kicked off all the dual-core madness, it also includes a 2,150mAh battery, 1GB of RAM and 16GB of internal storage. Despite that huge screen, at a depth of 8.9mm it's only slightly thicker than the superwide 4x3 Optimus Vu. Just like the Fujitsu prototype we spent some time with at CES, the Tegra 3 features a 4+1 "Companion Core" design, with a fifth low power unit available to take care of more mundane tasks without dr…

Razer Blade review

Razer Blade review
Typically, when a company wants to meet, you expect more of the same -- not a change in strategy, nor a decision to enter an entirely new product category. So when Razer wanted to meet us one bright, oddly cold San Franciscan morning last August, we certainly weren't expecting to meet its CEO, Min-Liang Tan, and we definitely weren't prepared to find a 17-inch prototype laptop, henceforth known as the Blade.

Shaving puns aside, we listened to Tan proudly wax on about the results of nearly three years of development, much of which involved recruiting a bevy of talent from the now-defunct OQO. What they'd accomplished, according to Tan, was the "world's first true gaming portable." An audacious statement, sure, especially considering the Blade was to be Razer's foray into the PC market. No matter. Tan's impetus was clear: the outfit would cater to gamers who'd been left in a vacuum after formerly gaming-obsessed compan…

5 Watt Audio Amplifier based LA4460

This 5 W audio power amplifier is built for general purpose and can drive speakers approximately 8 to 12 inches. This 5W power amplifier circuit is based on the Sanyo LA4460 IC which used as an audio output.
This Low-power amplifier circuit have built in loudness control, driver amplifier Q1, and the bass/treble controls of around ± 10 dB boost / cut. It would be useful in a wide variety of situations. Either displayed ac supply can be used, or 12 VDC supply can be connected to points A & B (positive) and C (negative).
For stereo circuit can be used two of this circuit by using ganged potentiometer at R2, R7 and R11. T1 is 12V at 1 ampere plug-in transformer.
Notice :
IC1 should be mounted with the heatsink. Power output is around 5 W.
A 4 “x 2″ x 0.050 “aluminum heatsink should be sufficient.

30 watt audio amplifier based TDA2040

A 30 watt audio amplifier circuit using TDA2040 are shown here. TDA2040 is class AB monolithic integrated audio amplifier available in the package Pentawatt. The IC has a low harmonic distortion and has a built in circuit protection for short circuit.
In the circuit, two TDA2040 ICs are wired in BTL (bridge-tied load) configuration to provide 30W of output into 8 ohm speakers at + /-16V DC. The capacitor C1 is the decoupling capacitor DC input. Network with components R2, C4, R3 provides feedback for IC1 while R7, C6, R8 network provides information for IC2. Network C5, R5 and C9, R9 provides stability at high frequency. Capacitors C2, C3 filters the positive supply rail while the capacitors C7, C8 filters the negative supply rail.
30 watt audio amplifier Parts list :
R1, R2, R4, R6, R7 : 22k
R3, R8 : 680 ohm
R5, R9 : 4.7 ohm
C1 : 2.2uF
C2, C7 : 100uF
C3, C8 : 100nF
C4, C6 : 22uF
C5, C9 : 0.1uF
IC1, IC2 : TDA2040

Preamplifier for magnetic phono cartridges

This amplifier circuit is intended to be added to the preamplifier which does not have a phono input. Such a phono input is required for normal record players with a dynamic pick-up, of which millions are still around. Moreover, the amplifier does not only bring the output of the pick-up to line level, it also adds the correction to the frequency response (according to RIAA requirements).
When recording gramophone records, the frequency characteristic is lifted at the high end. This lift must be countered in the playback (pre)amplifier. The corrections to the frequency response characteristic are according to a norm set by the Record Industries Association of America (RIAA) and also by the IEC.
The corrective curve provided by the amplifier is shown in the graph (bold line). The thin line shows the ideal corrective curve. The sharp bends in this at 50 and 500 Hz are nearly obtained in the practical curve by network R3/C2; just above 2 kHz is approached in practice by filte…

1KHz Sine wave Generator

Parts:R1____________5K6 1/4W Resistor
R2____________1K8 1/4W Resistor
R3,R4________15K 1/4W Resistors
R5__________500R 1/2W Trimmer Cermet
R6__________330R 1/4W Resistor
R7__________470R Linear Potentiometer

C1,C2________10nF 63V Polyester Capacitors
C3__________100µF 25V Electrolytic Capacitor
C4__________470nF 63V Polyester Capacitor

Q1,Q2_______BC238 25V 100mA NPN Transistors

LP1___________12V 40mA Filament Lamp Bulb (See Notes)

J1__________Phono chassis Socket

SW1__________SPST Slider Switch

B1_____________9V PP3

Clip for 9V PP3 BatteryCircuit description:This circuit generates a good 1KHz sinewave adopting the inverted Wien bridge configuration (C1-R3 & C2-R4). It features a variable output, low distortion and low output impedance in order to obtain good overload capability. A small filament bulb ensures a stable long term output amplitude waveform.
Notes:The bulb must be a low current type (12V 40-50mA or 6V 50mA) in order to obtain good long term stability and low di…

Headphone Amplifier

Amplifier parts:P1_____________22K Log.Potentiometer (Dual-gang for stereo)

R1____________560R 1/4W Resistor
R2,R3__________10K 1/4W Resistors
R4_____________12K 1/4W Resistor
R5,R6___________2R2 1/4W Resistor
R7_____________22R 1/2W Resistor

C1______________1µF 63V Polyester Capacitor
C2,C3,C4______100µF 25V Electrolytic Capacitors
C5_____________22pF 63V Polystyrene or Ceramic Capacitor
C6_____________22µF 25V Electrolytic Capacitor

IC1___________LM833 or NE5532 Low noise Dual Op-amp

Q1,Q3_________BC337 45V 800mA NPN Transistors
Q2,Q4_________BC327 45V 800mA PNP Transistors

J1______________RCA audio input socket Power supply parts: R8______________2K2 1/4W Resistor

C7,C8________2200µF 25V Electrolytic Capacitors

D1____________100V 1A Diode bridge
D2____________5mm. or 3mm. Red LED

IC2___________7815 15V 1A Positive voltage regulator IC
IC3___________7915 15V 1A Negative voltage regulator IC

T1____________220V Primary, 15 + 15V Secondary 5VA Mains transformer


45 Watt Class B Amplifier

Parts:R1______________18K 1/4W Resistor
R2_______________3K9 1/4W Resistor
R3,R6____________1K 1/4W Resistors
R4_______________2K2 1/4W Resistor
R5______________15K 1/4W Resistor
R7______________22K 1/4W Resistor
R8_____________330R 1/4W Resistor
R9,R10__________10R 1/4W Resistors
R11,R12_________47R 1/4W Resistors
R13_____________10R 1W Resistor

C1_______________1µF 63V Polyester Capacitor
C2_____________470pF 63V Polystyrene or Ceramic Capacitor
C3______________47µF 25V Electrolytic Capacitor
C4______________15pF 63V Polystyrene or Ceramic Capacitor
C5_____________220nF 100V Polyester Capacitor
C6_____________100nF 63V Polyester Capacitor

D1,D2,D3,D4___1N4148 75V 150mA Diodes

Q1,Q2________BC560C 45V 100mA Low noise High gain PNP Transistors
Q3,Q4________BC556 65V 100mA PNP Transistors
Q5___________BC546 65V 100mA NPN Transistor
Q6___________BD139 80V 1.5A NPN Transistor
Q7___________BD140 80V 1.5A PNP Transistor
Q8__________MJ2955 60V 15A PNP Transistor

Plant Watering Watcher-Project

Parts:R1,R4________470K 1/4W Resistors
R2____________47K 1/2W Trimmer Cermet or Carbon
R3___________100K 1/4W Resistor
R5_____________3K3 1/4W Resistor
R6____________15K 1/4W Resistor
R7___________100R 1/4W Resistor

C1_____________1nF 63V Polyester Capacitor
C2___________330nF 63V Polyester Capacitor
C3,C4_________10µF 25V Electrolytic Capacitors

D1__________1N4148 75V 150mA Diode
D2_____________5mm. Red LED

IC1___________4093 Quad 2 input Schmitt NAND Gate IC

Q1___________BC557 45V 100mA PNP Transistor

P1,P2_______Probes (See Notes)

B1______________3V Battery (2xAA, N or AAA 1.5V Cells in series)Device purpose:This circuit is intended to signal when a plant needs water. A LED flashes at a low rate when the ground in the flower-pot is too dry, turning off when the moisture level is increasing. Adjusting R2 will allow the user to adapt the sensitivity of the circuit for different grounds, pots and probe types.
Improvements:This little gadget encountered a long lasting success a…

GNU Radio-Open Source Radio Software

IntroductionGNU Radio is a free & open-source software development toolkit that provides signal processing blocks to implement software radios. It can be used with readily-available low-cost external RF hardware to create software-defined radios, or without hardware in a simulation-like environment. It is widely used in hobbyist, academic and commercial environments to support both wireless communications research and real-world radio systems.
GNU Radio applications are primarily written using the Python programming language, while the supplied performance-critical signal processing path is implemented in C++ using processor floating-point extensions, where available. Thus, the developer is able to implement real-time, high-throughput radio systems in a simple-to-use, rapid-application-development environment.
While not primarily a simulation tool, GNU Radio does support development of signal processing algorithms using pre-recorded or generated data, avoidin…

LG Optimus 3D Cube

LG Optimus 3D Cube is a slimmer ,world's first phone with 3D video editing We're not sure if the world was anxiously awaiting a follow-up to LG's Optimus 3D (the AT&T Thrill 4G here in the states), but here it is: the LG Optimus 3D Cube. Only announced for Korean carrier SK Telecom so far, the Optimus 3D Cube is slightly thinner than its predecessor at 9.6mm vs. the Thrill 4G's 11.9mm, with a faster 1.2GHz dual-core CPU and 16GB of storage built-in, confirming most of the rumors we'd heard previously. According to LG, it will also be the world's first that can handle 3D photo and video editing right on its glasses-free 4.3-inch screen, all shot by the dual 5MP cameras mounted on the back. It also has NFC baked in to support the new LG Tag+ stickers that change the phone's settings when swiped, just like the Optimus LTE Tag. It's scheduled for release in early March with Android 2.3 and although we didn't see it mentioned in the Korean p…