Tuesday, April 30, 2013

Tweeter Used to Sense Vibrations

The creator built a neat looking project which uses a piezoelectric element from a tweeter to detect vibrations. He is using a Zilog eZ8 series microcontroller which seemed to be very popular years ago.

Tweeter Used to Sense Vibrations
This project dependently using a strong vibration while the enclosure has been placed on the top of vibration sensor. The LED matrix has two eyes the wandering around effects. Whenever there is no vibration being detected the eyes will shut down as if they were sleeping.

Tweeter Used in Sensing Vibrations
A button was placed behind to manually switch it into various modes. It uses a four AA batteries and can draw 150uA when asleep while it draws for about 150mA when up.

Source : extreamcircuit
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Sunday, April 21, 2013

PC Power Box with E fuse

This little circuit can assist you to get rid of all surplus tiny ac mains adaptors from your desktop. The circuit is nothing, however a sensible dc power box directly powered by the smps of your desktop pc. Regulated, clean and guarded +12VDC is offered at the output of this unit. additionally, a USB power port is provided to re-charge transportable devices as well as cellphones and music players, etc.

How will the computer power box works

All you would like is to open your system box and connect an unused 4-pin drive power connector from the system smps to the current circuit. +12V (Yellow wire) from the smps is processed by a resettable electronic fuse designed around elements T1, T2 and T3 and feed to the output terminal. equally the +12V is down converted to stable +5V by fastened three pin regulator IC1.

Smart dc power box circuit schematic

As a result, +12V (500 -750mA max, based mostly on the electrical characteristics of T2 used) and +5V (1A max) DC provides are obtainable for external use, while not affecting the traditional computer functions. Switch S1 is that the power on/off cum reset switch. Resistor R3 sets the utmost allowable output current rate and T1 disables the output power switch T3, when output load current exceeds the set price.
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Saturday, April 13, 2013

Protection For Your Electrical Appliances

Here is a very competitively costd circuit to keep your electrically operated home equipment, this type ofs television, tape recorder, fridge, and other devices throughout sudden go back and forthping and resumption of majors supply. Appliances like fridges and air-conditioners are more vulnerable to break because of such stipulations. The simple circuit given here changees off the principles supply to the load as quickly as the energy go again and forths. The provide can additionally be resumed only with the help of handbook intervention. Thus, the provide may be switched on best after it has stabilised.
Circuit diagram :
Protection For Your Electrical Appliances
The circuit comprises a step-down transformer followed by way of a full-wave rectifier and smoothing capacitor C1 which acts as a supply source for relay rl1. Initially, when the circuit is switched on, the energy supply course to the step-down transformer X1 as well as the load is incomplete, as the relay is in de-energised state. To energise the relay, press change S1 for a quick period. This completes the route for the availability to transformer X1 as additionally the weight by means of closed contacts of switch S1. Meanwhile, the availability to relay grow to bes to be had and it will get energised to provide a parallel course for the provision to the transformer in addition to the load.

If there's any interruption within the energy provide, the provision to the transformer is simply no longer to be had and the relay de-energises. Thus, as quickly as the provide is interrupted even for a quick period, the relay is de-energised and you would possibly have got to press change S1 momentarily (when the provision resumes) to make it available to the load. Very short duration (say, 1 to five milliseconds) interruptions or fluctuations is not going to impact the circuit because of presence of large worth capacitor which has to discharge by approach of the relay coil. Thus the circuit provides suitable safety once extrast erratic power supply stipulations.
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Baud Rate Generator

In this article, an RC oscillator is used as a baud rate generator. If you can calibrate the frequency of such a circuit sufficiently accurately (within a few percent) using a frequency meter, it will work very well. However, it may well drift a bit after some time, and then…. Consequently, here we present a small crystal-controlled oscillator. If you start with a crystal frequency of 2.45765 MHz and divide it by multiples of 2, you can very nicely obtain the well-known baud rates of 9600, 4800, 2400, 600, 300, 150 and 75. If you look closely at this series, you will see that 1200 baud is missing, since divider in the 4060 has no Q10 output!
Baud Rate Generator Circuit Diagramv

If you do not need 1200 baud, this is not a problem. However, seeing that 1200 baud is used in practice more often than 600 baud, we have put a divide-by-two stage in the circuit after the 4060, in the form of a 74HC74 flip-flop. This yields a similar series of baud rates, in which 600 baud is missing. The trimmer is for the calibration purists; a 33 pF capacitor will usually provide sufficient accuracy. The current consumption of this circuit is very low (around 1mA), thanks to the use of CMOS components.

Source by : Streampowers
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Low Voltage Cut Out

This circuit will notice when the voltage of a 12v battery reaches a low degree. This is to forestall deep-discharge or possibly to prevent a vehicle battery turning into discharged  to some extent where it will no longer begin a car. This circuit is different to anything else up to now offered. It has HYSTERESIS. Hysteresis is a function the place the higher and decrease noticeion-points are separated by means of a niche. 

Circuit diagram :

Low Voltage Cut-Out Circuit Diagram

Normally,  the circuit will deactivate the relay when the voltage is 10v and when the burden is eliminated. The battery voltage will rise relatively by using as little as 50mV and switch the circuit ON once more. This is referred to as \"Hunting.\" The off/on timing has been diminished by way of adding the 100u. But to stop this totally from taking place, a 10R to 47R is positioned in the emitter lead. The circuit will turn off at 10v however will no longer flip back on except 10.6v when a 33R is in the emitter. The worth of this resistor and the turn-on and turn-off voltages will also depend upon the resistance of the relay. 

Author : Colin Michel - Copyright : 200 Transistor Circuits
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Simple Digital Switching System

This circuit can control any one out of 16 devices with the help of two push-to-on switches. An up/down counter acts as a master-controller for the system. A visual indication in the form of LEDs is also available.  IC1 (74LS193) is a presettable up/ down counter. IC2 and IC3 (74LS154) (1of 16 decoder/demultiplexer) perform different functions, i.e. IC2 is used to indicate the channel number while IC3 switches on the selected channel.

Digital Switching System Circuit Diagram :
Digital Switching System-Circuit Diagram

Before using the circuit, press switch S1 to reset the circuit. Now the circuit is ready to receive the input clock. By pressing pressing switch S2 once, the counter advances by one count. Thus, each pressing of switch S2 enables the counter to advance by one count. Likewise, by pressing switch S3 the counter counts downwards.

The counter provides BCD output. This BCD output is used as address input for IC2 and IC3 to switch one (desired channel) out of sixteen channels by turning on the appropriate triac and the corresponding LED to indicate the selected channel.  The outputs of IC3 are passed through inverter gates (IC4 through IC6) because IC3 provides negative going pulses while for driving the triacs we need positive-going pulses. The high output of inverter gates turn on the npn transistors to drive the triacs. Diodes connected in series with triac gates serve to provide unidirectional current for the gate-drive.

Sorce :
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The Millipede

Me and a friend are both trying to build a millipede. Because of obvious reasons, the millipede is NOT going to have 1000 feet!!! Instead, its going to have 16 pager motors as feet. It will also have 3 MicroMotors to bend towards light, and a backup sensor.

- 16 PagerMotors as feet
- 3 MicroMotors to seek light
- PhotoTrophic
- Obstacle avoidance
- Looks Cool!!! 

Millipede is divided in four segments. Each segment (except the first one) is glued to a MicroMotor turned upside-down. The motor shaft is then glued to the next segment. Each segment can rotate left/right and has 2 PagerMotors on each side. This way, the millipede should turn towards the most lighted area. Ive calculated that the waist motors should turn only 30o-45every second or so. This means that I will need the motors to be 7-15 rpm. Candidates for this job can be the Lego MicroMotor, Solarbotics GM or BabyGM (unless I can get some MU915L Escaps!!!)

Weigth was a major concern since the whole bot was impulsed by pagermotors.  The waist motors should weigth no more than 70g and the body (including electronics) is about <100g. Actually, it seems that 16 pagermotors are more than enough to move the bot!!!

I made up this circuit, as this is my first big BEAM creation I have no idea if it works properly. The upper 3 Ms are the Lego MicroMotors and the lower Ms should be the 16 PagerMotors. On the right, you can see the MicroMotors driver.

Here is the explanation:
1 This is the voltage divider. It divides voltage depending on which side is more iluminated, then, the schmitt changes the signal from a wave to a straight pulse.
2 The (usual) Nv only works when the input receives a HIGH, and that is the job of the schmitts. If the first schmitt outputs a HIGH the the lower strip of Nvs will work, the upper strip should stay calm because the second schmitt inverts the signal to a LOW. Thanks Math!!!
3 I can now be sure that there wont be 2 pulses on a same motor, and that when the first motor turns left  (or right) the next one will also turn that same way, and the next and the next.... Only the first motor is affected by light, the others follow (in a wave pattern) the one before themselves. Since the millipede is moving forward while all this happens, a nice wave should appear when the bot has locked his path towards the light source.
4 This is the backup switch. When the bot bumps into something like... Hmm....anything, the cap is discharged trough the right schmitt. The (now LOW) output of the schmitt will reverse the PagerMotors, thus, reversing the whole bot.
5 This is the PagerMotors driver. I took the 4 transistor circuit design and modified it to be used with only one input signal. I know I wont be able to drive the 16 motors with 2N390X transistors, I used them in the schematic only because I need to find more powerful ones. Probably FETs?
6 As an extra (Yupeee), when the bot reverses it also makes the spinal column think that light is fully comming only from one direction. Because of this, when the millipede reverses, it also turns to one side all the body.

I still need to order the components (Lets just say there are not many 74**14s or 240s in Costa Rica), so the final version may be different than the drawings. Im also thinking about using the Baby GMs that Solarbotics sell instead of the Lego MicroMotors. If you can help me with anything about the schematic, just email me.
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Friday, April 12, 2013

Quality Stereo Wireless Microphone or Audio Link

This stereo FM wireless microphone also makes a great quality audio link. We tested it to beyond 50 meters and it was rock solid. It’s certainly not the first wireless microphone we’ve ever published but this one is a little different. It’s stereo, providing surprisingly good quality sound. Second, it has a really good range. We tested it at well over 50m and it was still performing very well – noise-free, in fact – but at the time we couldn’t get our receiver any further away. So it’s likely to have even better range than that.

Complete Project:


quality-stereo-wireless-microphone-or-audio-link quality-stereo-wireless-microphone-or-audio-link-circuit

Its easy to build, requires very little setup... and its cheap! In fact, the low price might turn some people off, thinking its low quality. Try it - and be pleasantly surprised!


Third, it really is simple to build – the hard work (the transmitter module) is already done for you. It’s just a matter of assembling the microphone module, which contains the electret mics themselves, preamp and level controls, and soldering the transmitter module onto it, "piggy back" style.

FM Transmitter:

Finally, the transmitter module is crystal-locked, so you won’t have the drift probles of some earlier wireless microphones. And just in case you were wondering, that doesn’t mean the output is locked to one particular frequency – it has a nifty synthesis circuit built in to give you the choice of seven different frequencies between 106.7MHz and 107.7MHz.

On-board preset pots adjust the sensitivity of each channel to take into account mic differences or if you require different levels in each channel.


By the way, the transmitter module is quite capable of operating at line level if you want just a line level transmitter (eg, to feed an audio program around your home). Sensitivity is about 100mV. Oatley Electronics, who designed the kit, have the transmitter module available by itself if that’s what you’re after. But more on that anon.


Parts Layout:


You also have the choice of two power supply levels – 3-6V or 7-15V DC. The latter results in a lower current drain. The transmitter module also has a "5V out" rail to supply power to the preamp module.

Circuit Diagram:


Two electret microphone inserts are supplied in the kit. These can be soldered direct to the PC board to make it a fully self-contained project or they can be attached to the board via suitable lengths of mini shielded coax cable. A third option is to use "proper" microphones – they can be electret or dynamic types – but no provision has been made for plugging these in.

Typical Specifications: 
Audio response:.....................20Hz-15kHz.
Channel separation: ........................40dB
Total Harmonic Distortion: ...............0.1%
Output Frequency:...........106.7-107.2MHz
Pre Emphasis: ..................................50μS
DC supply voltage range: ................3-15V
Supply Current: .......................30mA @ 9V
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1999 Chevrolet Chevy Wiring Diagram

1999 Chevrolet Chevy Wiring Diagram

The Part of 1999 Chevrolet Chevy Wiring Diagram: power distribution cell, turn B/U fuse, stop hazard
lamp, IP fuse box, audible warning cell, backup light, pickup, solid state, cruise control, convenience center, turn/hazard flasher, turn hazard switch, stoplamp switch, switch brajes, underhood fuse box, taped to harness.
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Mains Supply Failure Alarm

Whenever AC mains supply fails, this circuit alerts you by sounding an alarm. It also provides a backup light to help you find your way to the torch or the generator key in the dark. The circuit is powered directly by a 9V PP3/6F22 compact battery. Pressing of switch S1 provides the 9V power supply to the circuit. A red LED (LED2), in conjunction with zener diode ZD1 (6V), is used to indicate the battery power level.

Resistor R9 limits the operating current (and hence the brightness) of LED2. When the battery voltage is 9V, LED2 glows with full intensity. As the battery voltage goes below 8V, the intensity of LED2 decreases and it glows very dimly. LED2 goes off when the battery voltage goes below 7.5V. Initially, in standby state, both the LEDs are off and the buzzer does not sound. The 230V AC mains is directly fed to mains-voltage detection optocoupler IC MCT2E (IC1) via resistors R1, R2 and R3, bridge rectifier BR1 and capacitor C1.

Illumination of the LED inside optocoupler IC1 activates its internal phototransistor and clock input pin 12 of IC2 (connected to 9V via N/C contact of relay RL1) is pulled low. Note that only one monostable of dual-monostable multivibrator IC CD4538 (IC2) is used here. When mains goes off, IC2 is triggered after a short duration determined by components C1, R4 and C3. Output pin 10 of IC2 goes high to forward bias relay driver transistor T1 via resistor R7.

Circuit diagram:
mains supply failure alarm circuit schematic
Mains Supply Failure Alarm Circuit Diagram

Relay RL1 energises to activate the piezo buzzer via its N/O contact for the time-out period of the monostable multivibrator (approximately 17 minutes). At the same time, the N/C contact removes the positive supply to resistor R4. The time-out period of the monostable multivibrator is determined by R5 and C2. Simultaneously, output pin 9 of IC2 goes low and pnp transistor T2 gets forward biased to light up the white LED (LED1).

Light provided by this back-up LED is sufficient to search the torch or generator key. During the mono time-out period, the circuit can be switched off by opening switch S1. The ‘on’ period of the monostable multivibrator may be changed by changing the value of resistor R5 or capacitor C2. If mains doesn’t resume when the ‘on’ period of the monostable lapses, the timer is retriggered after a short delay determined by resistor R4 and C3.
Source: EFY Mag
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Ethernet Cable Standards Assignments

Ethernet Wiring on Cat7 Cables  100 Ohm Utp  Unshielded Twisted Pair  Ethernet Wiring
Cat7 Cables 100 Ohm Utp Unshielded Twisted Pair Ethernet Wiring.

Ethernet Wiring on Figure 4   Wiring Diagram For An Ethernet Crossover Cable
Figure 4 Wiring Diagram For An Ethernet Crossover Cable.

Ethernet Wiring on Rj45 Wiring Diagrams
Rj45 Wiring Diagrams.

Ethernet Wiring on Home Network Wiring Diagram
Home Network Wiring Diagram.

Ethernet Wiring on Ethernet Crossover Cable Wiring
Ethernet Crossover Cable Wiring.

Ethernet Wiring on The Difference Between Straight Through  Crossover  And Rollover
The Difference Between Straight Through Crossover And Rollover.

Ethernet Wiring on Ethernet Wiring
Ethernet Wiring.

Ethernet Wiring on Tech Info   Lan Wiring And Pinouts
Tech Info Lan Wiring And Pinouts.

Ethernet Wiring on Cat 5 Ethernet Cable Standards   Pin Out Assignments
Cat 5 Ethernet Cable Standards Pin Out Assignments.

Ethernet Wiring on Cat6 568 A Wiring Diagram
Cat6 568 A Wiring Diagram.

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4017 LED Knight Rider Running Light Circuit Diagram

In this  4017 Knight Rider circuit, the 555 timer is
wired as an oscillator. It can be adjusted to give the desired speed
for the display. The output of the 555 is directly connected to the
input of a Johnson Counter (CD 4017).
input of the counter is called the CLOCK line. The 10 outputs become
active, one at a time, on the rising edge of the waveform from the 555.
Each output can deliver about 20mA but a LED should not be connected to
the output without a current-limiting resistor (220Ω in the circuit above).

first 6 outputs of the chip are connected directly to the 6 LEDs and
these “move” across the display. The next 4 outputs move the effect in
the opposite direction and the cycle repeats. The animation above shows
how the effect appears on the display. Using six LEDs,
the display can be placed in the front of a model car to give a very
realistic effect. The outputs can be taken to driver transistors to
produce a larger version of the display.

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USB Fuse

Life in the 21st century would be almost unbearable without some of the computer peripherals that PC users now look on as essentials - take for example the USB powered teacup warmer; this device is obviously an invaluable productivity tool for all users but it could prove a little tire some if the extra current it draws from the USB port is sufficient to produce a localised meltdown on the motherboard. In a slightly more serious vein a similar situation could result from a carelessly wired connector in the design lab during prototyping and development of a USB ported peripheral. What’s needed here is some form of current limiting or fuse to prevent damage to the motherboard.


The MAX1562 shown in Figure 1 is a purpose-built USB current limiter from the chip manufacturers Maxim. The device operates with a supply voltage from 4.0 to 5.5 V with an operating current of typically 40 µA or 3 µA in standby mode. The circuit introduces a very low resistance in the power line (typically 26 m but guaranteed less than 50 m) from an internal MOSFET. The FET gate bias voltage is generated on-chip from a charge pump circuit.


The chip can distinguish between an overload and a short circuit condition in the supply line by measuring the voltage drop across its internal resistance; if the voltage is less than 1 V a short circuit is assumed and the chip pulses a (limited) output current every 20 ms in an effort to raise the output voltage. This approach will eventually be successful if the short circuit was caused by a large value capacitor across the USB supply pins or an external hard drive which have a high in-rush at start up. If the supply rail is not pulled up within the first 20 ms the FAULT output (pin 2) is driven low. The output current limit is set by a single resistor on pin 4 (ISET): LIM = 17120 / RSET.


The circuit diagram shows a fixed 5.6k resistor in series with a 10k preset giving an adjustable current limit between 1.097 and 3.057 A. This range should be sufficient for the majority of applications. Increasing the preset resistance reduces the current limit level. Any intermittent connection in the preset (caused by a dirty track etc.) will switch the chip into shut down. The MAX1562 also contains a thermal cut out which turns off the output when the chip temperature exceeds 160 degrees C.

Figure 2 shows a diagram of the manufacturer’s application circuit. The FAULT output drives an LED via a series limiting resistor which reduces the LED current to 2 to 3 mA. The MAX1562 is available in a HESA variant (with an active high ON signal) or ESA version (with an active low ON signal). The chip is packaged in an 8-pin SMD outline. Figure 3 shows a small PCB layout for the circuit using mostly SMD components.


R1 = 5k6 (SMD 1206)
R2 = 1k5 (SMD 1206)
P1 = 10k preset
C1 = 1µF (SMD 1206)
C2 = 4µF7 10 V, tantalum
C3 = 220nF (SMD 1206)
D1 = LED, low current
IC1 = MAX1562ESA

Author: Andreas Köhler - Copyright: Elektor Electronics

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Build Door Bell Timer with Adjustable Timing Facility

Yes this simple transistor circuit can be used as a home door bell and it’s ON time can be set as preferred by the user, meaning if you wanted that the sound of the bell to remain switched  ON for a particular period of time, you could easily do it just by adjusting the given pot.
The actual tune  is derived from the IC UM66 and the associated components, while all the included transistors along with the relay are configured for producing the time delay for keeping the music switched ON. Link
Parts List
R1, R2,  R4, R5 = 1K
VR1 = 100K,
D1, D2 = 1N4007,
C1, C2 = 100uF/25
T1, T3 = BC547,
T2 = BC557
Z1 = 3V/400mW
Transformer = 0-12V/500mA,
S1 = Bell Push
IC = UM66
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LA4440 Stereo Amplifier Circuit Diagram

LA4440 is a dual channel audio amplifier IC. It can be used in two modes; one is Stereo amplifier and another Bridge amplifier mode. The LA4440 is a monolithic linear IC from Sanyo. Here I give the both circuit mode of amplifier using IC LA4440.

When the IC LA4440 is Stereo mode in the circuit, its output power is 6w+6w. In stereo mode use two pieces speaker of 2Ωto8Ω.

LA4440 Stereo Amplifier Circuit Diagram

C10 is filter capacitor used to reduce the ripple of supply voltage. Don’t decrease the value of capacitor C6&C7 less than 100uF, 10v, it may causes of the output at low frequencies goes lower. The pin-6 of LA4440 amplifier circuit  is audio input pin; it used in stereo amplifier mode but in bridge mode it is grounded. C8&C9 are polyester film capacitor used to preventing oscillation, and R1&R2 used for the same reason as filter resistor. Though the maximum supply voltage for both circuit of amplifier is 18V but we recommend to use a 12V,3A power supply. Use a good quality heat sink with LA4440.

I think here you see little comparison between stereo and bridge amplifier of LA4440. If you want to make this amplifier project, then I recommend you the bridge one. I think it is ideal for a beginner. And I love its wattage rather than Stereo mode. There is also a possibilities as I say, make two copies of circuit of bridge amplifier for stereo, it will give you 19w+19w of audio power output.
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Thursday, April 11, 2013

How to Build 12 Volt DC Fluorescent Lamp

A number of people have been unable to find the transformer needed for the Black Light project, so I looked around to see if I could find a fluorescent lamp driver that does not require any special components. I finally found one in Electronics Now. Here it is. It uses a normal 120 to 6V stepdown transformer in reverse to step 12V to about 350V to drive a lamp without the need to warm the filaments.

12 Volt DC Fluorescent Lamp Driver circuit diagramParts:

C1 100uf 25V Electrolytic Capacitor
C2,C3 0.01uf 25V Ceramic Disc Capacitor
C4 0.01uf 1KV Ceramic Disc Capacitor
R1 1K 1/4W Resistor
R2 2.7K 1/4W Resistor
U1 TLC555 Timer IC
T1 6V 300mA Transformer
LAMP 4W Fluorescent Lamp
MISC Board, Wire, Heatsink For Q1

  1. Q1 must be installed on a heat sink.
  2. A 240V to 10V transformer will work better then the one in the parts list. The problem is that they are hard to find.
  3. This circuit can give a nasty (but not too dangerous) shock. Be careful around the output leads.
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Spy Camera Solar Power Box

Battery life has always been a critical consideration for most of the electronic gadgets and equipment. When we talk about spy  cameras,  which  normally  function  round-the-clock, they often run out of power within a few days.  Many spy cameras (CCTV cameras) are powered by 9V PP3 type batteries that offer five times more energy  than the regular 9V alkaline battery.

Mini CCTV cameras also accept 6-12V DC supply from AC mains adaptor through the DC IN jack. AC mains adaptor for the camera increases the capacity of the 9V PP3 battery but is bulky and noisy. Whether disposable  or rechargeable batteries, making frequent replacement or recharging them is a cumbersome job. The unique solar power box described here serves an alternative solution to the problem. 

Spy Camera Solar Power Box Circuit diagram :

Spy Camera Solar Power Box-Circuit Daigram

The circuit of the solar power box is simple. It contains a  battery charger and a battery health indicator and  a few other components.  As shown in the circuit,  DC supply available from  the solar panel (SP1) is  directly applied to the in-put of the circuit through  a protection diode (D1).  This diode is used to pre-vent  the  reverse  current  flow from the battery to  the  solar  panel  during  night. Thus, D1 allows  the current to flow from the solar panel  to the battery only. Low-voltage-drop  type 1N5817 diode is perfect for the  job.
At the heart of the circuit is an integrated current source, realised using a  popular 3-pin adjustable voltage regulator LM317T(IC1). 

This IC is designed  to adjust its internal resistance between  the In (pin 3) and Out (pin 2) terminals  to maintain a constant voltage of 1.25V  between the Out (pin 2) and Adj (pin 1) terminals. Here, a 9V, 280 mAh  rechargeable PP3 type Ni-MH battery  (BATT) is used as reservoir. Normally,  a charging current of about 10 per cent  of  ampere-hour  rating  is  safe  for  the  battery. Resistor R1 (39-ohm, 0.5W),  connected between pin 1 and 3 of IC1,  limits  the  charging  current  to  about  30 mA. DC output from the battery is  available at output jack J2. Red LED  ( LED1) is used as a battery ‘health’  indicator. Switch S1 is used to start the  charging while S2 is used for connect-ing the load. Note that suitable heat  sink should be used for the IC1.

The proper selection of solar panel  is important but not critical. A miniature 12V type solar panel with a cur-rent output of about 100 mA can be  used. Even if you have a solar panel  with  higher  voltage  rating,  it  will  not  create a problem as the circuit ensures  that the charging current cannot exceed  the predetermined value.

The circuit can be easily assembled  on a general-purpose PCB and housed  in a small plastic cabinet.

Source :
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LM1875 20 Watt Audio Power Amplifier

20 Watt amplifier
20 Watts Power Amplifier circuit can be made ​​with an IC power amplifier LM1875. IC LM1875 is a single chip power amplifier from National. 20 watts audio amplifier with LM1875 is a low power amplifier with good quality to the room.

To assemble the amplifier 20 watts with IC LM1875 component is not needed much support. 20 watts power amplifier using LM1875 IC in this article using symmetrical power supply. The series of 20 watts audio power amplifier with IC LM1875 can be used as an experiment or first project for the reader, because it is simple and assembly of high success.

LM1875 | 20 Watt Audio Power Amplifier
Schematic Amplifier LM1875

LM1875 amplifier circuit with the above may result in the strengthening of the voltage up to 27dB for each channel (1 channel 1 IC). Strengthening the voltage can be changed by changing the feedback that is R5 R (on the circuit above using R 22K). But the tension reinforcement can not be less than 20 dB because it can cause oscillation. For the power supply or power supply 20 watts power amplifier rngakaian with lm1875 can use travo 2-3A with CT.
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Acoustic Distress Beacon

An ELT (Emergency Locator Transmitter, also known as a distress beacon) is an emergency radio transmitter that is activated either manually or automatically by a crash sensor to aid the detection and location of aircraft in distress. This acoustic ELT project is intended for radio control (RC) model aircraft, which every now and then decide to go their own way and disappear into the undergrowth.
Circuit diagram :
Acoustic Distress Beacon-Circuit Diagram
Acoustic Distress Beacon Circuit Diagram

The audio locating device described here enables model aircraft that have landed ‘off limits’ to be found again and employs its own independent power supply. The small cam-era battery shown in the circuit activates an acoustic sounder when radio contact is lost and produces a short signal tone (bleep) every ten seconds for more than 25 hours. Current consumption in standby and passive (with jumper J1 set) modes is negligible. The timing generator for the alarm tone is the Schmitt trigger AND-gate IC1.B; its asymmetric duty cycle drives a 5 V DC sounder via MOSFET transistor T1. All the time that the RC receiver output is delivering positive pulses, the oscillator is blocked by IC1.A and diode D1. Setting jumper J1 parallel to C2 also disables the oscillator and serves to ‘disarm’ the distress beacon. 

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555 Timer Frequency and Duty Cycle Calculator

Enter values for R1, R2, and C and press the calculate button to solve for positive time interval (T1) and negative time interval (T2). For example, a 10K resistor (R1) and 100K (R2) and 0.1 uF capacitor will produce output time intervals of 7.62 mS positive (T1) and 6.93 mS negative (T2). The frequency will be about 70 Hz. R1 should be greater than 1K and C should be greater than .0005 uF. Scroll down page for basic 555 information (pinout and two basic circuits). 
Positive Time Interval (T1) = 0.693 * (R1+R2) * C
Negative Time Interval (T2) = 0.693 * R2 * C
Frequency = 1.44 / ( (R1+R2+R2) * C) 

First introduced by the Signetics Corporation as the SE555/NE555 about 1971.Pin connections and functions: (See schematic below for basic circuits)
Pin 1 (Ground)    - The ground (or common) pin is the most-negative supply potential of the device, which is normally connected to circuit common when operated from positive supply voltages.

Pin 2 (Trigger)   - This pin is the input which causes the output to go high and beginthe timing cycle. Triggering occurs when the trigger input movesfrom a voltage above 2/3 of the supply voltage to a voltage below1/3 of the supply. For example using a 12 volt supply, the triggerinput voltage must start from above 8 volts and move down to avoltage below 4 volts to begin the timing cycle. The action islevel sensitive and the trigger voltage may move very slowly. Toavoid retriggering, the trigger voltage must return to a voltageabove 1/3 of the supply before the end of the timing cycle in themonostable mode. Trigger input current is about 0.5 microamps.
Pin 3 (Output)    - The output pin of the 555 moves to a high level of 1.7 volts less than the supply voltage when the timing cycle begins. The output returns to a low level near 0 at the end of the cycle. Maximum current from the output at either low or high levels is approximately 200 mA.
Pin 4 (Reset):    - A low logic level on this pin resets the timer and returns the output to a low state. It is normally connected to the + supply line if not used.
Pin 5 (Control)   - This pin allows changing the triggering and threshold voltages by applying an external voltage. When the timer is operating in the a stable or oscillating mode, this input could be used to alter or frequency modulate the output. If not in use, it is recommended installing a small capacitor from pin 5 to ground to avoid possible false or erratic triggering from noise effects.
Pin 6 (Threshold) - Pin 6 is used to reset the latch and cause the output to go low.Reset occurs when the voltage on this pin moves from a voltage below 1/3 of the supply to a voltage above 2/3 of the supply.The action is level sensitive and can move slowly similar to the trigger voltage.
Pin 7 (Discharge) - This pin is an open collector output which is in phase with the main output on pin 3 and has similar current sinking capability.
Pin 8 (V +)       - This is the positive supply voltage terminal of the 555 timer IC.Supply-voltage operating range  is +4.5 volts (minimum) to +16volts (maximum).
The pin connections for the 556 which is a dual 555 timer (2 in one package) areshown in table below. For example, the two outputs for the two timers of the 556 areon pins 5 and 9 which correspond to the output pin 3 of the 555. 
555      556 timer #1        timer #2
Ground         1                  7               7 
Trigger        2                  6               8
Output         3                  5               9
Reset          4                  4               10
Control        5                  3               11
Threshold      6                  2               12
Discharge      7                  1               13+ 
Power Vcc    8                  14              14
The schematics below show the two basic circuits for the 555 timer.

Below is a pictorial view of the 555 timer wired as a LED flasher and powered with a 9 volt battery. The LED will turn on during time T1 and off during time T2. 

The 555 circuit below is a flashing bicycle light powered with three C or D cells (4.5 volts). The two flashlight lamps will alternately flash at a approximate 1.5 second cycle rate. Using a 4.7K resistor for R1 and a 100K resistor for R2 and a 4.7uF capacitor, the time intervals for the two lamps are 341 milliseconds (T1, upper lamp) and 326 milliseconds (T2 lower lamp). The lamps are driven by transistors to provide additional current beyond the 200 mA limit of the 555 timer. A 2N2905 PNP and a 2N3053 NPN could be used for lamps requiring 500 mA or less. For additional current, a TIP29 NPN and TIP30 PNP could be used up to 1 amp. A PR3 is a 4.5 volt, 500 mA flashlight bulb. Two diodes are placed in series with the PNP transistor base so that the lower lamp turns off when the 555 output goes high during the T1 time interval. The high output level of the 555 timer is 1.7 volts less than the supply voltage. Adding the two diodes increases the forward voltage required for the PNP transistor to about 2.1 volts so that the 1.7 volt difference from supply to the output is not enough to turn on the transistor. You can also use an LED in place of the two diodes as shown in the lower schematic.


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Mains Slave Switcher

There are many situations where two or more pieces of equipment are used together and to avoid having to switch each item on separately or risk the possibility of leaving one of them on when switching the rest off, a slave switch is often used. Applications which spring to mind are a computer/printer/scanner etc or audio amplifier/record deck/tuner combinations or perhaps closest to every electronics enthusiast’s heart, the work bench where a bench power supply/oscilloscope/soldering iron etc are often required simultaneously.

The last is perhaps a particularly good example as the soldering iron, often having no power indicator, is invariably left on after all the other items have been switched off. Obviously the simplest solution is to plug all of the items into one extension socket and switch this on and off at the mains socket but this is not always very convenient as the switch may be difficult to reach often being behind or under the work bench. Slave switches normally sense the current drawn from the mains supply when the master unit is switched on by detecting the resulting voltage across a series resistor and switching on a relay to power the slave unit(s).
mains-slave-switcher-circuit diagrams

This means that the Live or Neutral feed must be broken to allow the resistor to be inserted. This circuit, which is intended for switching power to a work bench when the bench light is switched on, avoids resistors or any modifications to the lamp or slave appliances by sensing the electric field around the lamp cable when this is switched on. The lamp then also functions as a ‘power on’ indicator (albeit a very large one that cannot be ignored) that shows when all of the equipment on the bench is switched on.

The field, which appears around the lamp cable when the mains is connected, can be sensed by a short piece of insulated wire simply wrapped around it and this is amplified by the three stage amplifier which can be regarded as a single super-transistor with a very high gain. The extremely small a.c. base current results in an appreciable collector current which after smoothing (by C3) is used to switch on a relay to power the other sockets. Power for the relay is obtained from a capacitor ‘mains dropper’ that generates no heat and provides a d.c. supply of around 15 volts when the relay is off.

Circuit diagram:
Mains Slave Switcher Circuit Diagram

The output current of this supply is limited so that the voltage drops substantially when the relay pulls in but since relays require more current to operate them than they do to remain energized, this is not a problem. Since the transistor emitter is referenced to mains Neutral, it is the field around the mains Live which will be detected. Consequently, for correct operation the Live wire to the lamp must be switched and this will no doubt be the case in all lamps where the switch is factory fitted. In case of uncertainty, a double-pole switch to interrupt both the Live and Neutral should be used.

The sensitivity of the circuit can be increased or decreased as required by altering the value of the T2 emitter resistor. The sensing wire must of course be wrapped around a section of the lamp lead after the switch otherwise the relay will remain energized even when the lamp has been switched off. The drawing shows the general idea with the circuit built into the extension socket although, depending on the space available an auxiliary plastic box may need to be used.

The circuit itself is not isolated from the mains supply so that great care should be taken in its construction and testing. The sensor wire must also be adequately insulated and the circuit enclosed in a box to make it inaccessible to fingers etc. when it is in use.
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Wiring Thermostats

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