Friday, January 10, 2014

Simple Mini Power Inverter

Even robot systems occasionally need a negative supply voltage for some purpose or other, and in this kind of application in particular there is a need for an effective circuit that does  not  make  greater demands  then  necessary in terms of current or space. If a low current 5 V supply is needed and only +5 V is available, a natural manufacturer to turn  to  is  Maxim,  and indeed in this case they do not let us down.The best known integrated  circuit made by this company is the MAX232, a level shifter for serial ports with an integrated charge pump that does not need an external inductor.

Simple Mini Power Inverter   image:
Mini Power Inverter Img

Along the same lines, although with a more stable output voltage and higher efficiency, is the MAX660. The device can ‘mirror’ any input voltage between 1.5 V and 5.5 V. With a 5 V input the output is typically –4.7 V with a load of 100 mA. Efficiency at 10 mA is around 96 % and at 100 mA is around 88 %. With an open-circuit output the IC draws a quiescent current of just 120 μA.There is little to say about the circuit itself.

Simple Mini Power Inverter Circuit diagram:
Simple Mini Power Inverter Circuit Diagram

The 0 Ω resistor on pin 1 selects the operating frequency. With R1 fitted, the circuit operates at 80 kHz; without it, at 10 kHz. The combination of L1 and C5 slightly reduces ripple on the output voltage; the choice of inductor is not as critical as it would be if it formed part of the switching circuit.Gerber files for the printed circuit board (which uses some SMD components) are available for download from the Elektor website, ref. 070279-11.zip. R1, C1 and C4 are 0603 SMDs and C3 is an SMD tantalum electrolytic capacitor. Either the MAX-660CSA or the MAX660M can be used; both come in SO8 packages. L1 is a 10 μH SMD inductor rated at 300 mA.

Source: http://www.ecircuitslab.com/2011/11/even-robot-systems-occasionally-need.html 

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Security Alarm

Thwart any attempt of burglary in your house using this alarm circuit. When someone opens the door of your room, it sounds an alarm intermittently and flashes light as well. The circuit can also be used as an audio/visual alarm in case of fire or other emergency by momentarily pressing switch S3.

The circuit (refer Fig.1) is built around transformer X1, a standard bar magnet, reed switch S2, timer IC NE555 (IC1), opto-coupler IC MOC3020 (IC2), TRIAC BT136 and a few discrete components. Timer IC1 is wired as an astable multi-vibrator whose reset pin 4 is controlled by the reed switch. The reed switch fitted in the door frame acts as the sensor. A magnet is fixed on the door panel close to the reed switch.

Fig.1: Simple Security Alarm Circuit Diagram :

Security-alarm-circuit-Daigram

The reed switch consists of a pair of contacts on ferrous metal sealed in a glass envelope. The contacts may be normally-open (which close when a magnetic field is present) or normally closed type (which open when a magnetic field is applied). A normally open- type reed switch is used here.

When the door is closed, reed switch S2 is in open state. When the door is opened, the bar magnet moves away from reed switch S2. As a result, reset pin 4 of IC NE555 goes high. The high output at pin 3 of IC1 enables IC2. Pin 4 of IC2 is connected to the gate of TRIAC1. When the door is opened, bulb B1 flashes and the bell sounds (provided switch S4 is closed) indicating that the door has been opened. Flashing of the bulb and the alarm continue until the door is closed.

Assemble the circuit on a general purpose PCB and enclose in a suitable cabinet. Connect the call bell at the back side and the bulb at the front side of the cabinet. Install the unit on the door of the room as shown in Fig.2.

Fig.2: Reed Switch Fitting in Door :

Reed-switch-fitting-in-door-d

The circuit is powered by mains supply.

Source : http://www.ecircuitslab.com/2012/09/simple-security-alarm.html
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Simple 250W Inverter Circuit Diagram

This is a simple 250W Inverter Circuit Diagram. A 555 timer (IC1) generates a 120-Hz signal that is fed to a CD4013BE flip-flop (ICl-a), which divides the input frequency by two to generate a 60-Hz clocking frequency for the FET array (Ql through Q6). Transformer Tl is a 12-/24-V center-tapped 60-Hz transformer of suitable size. 

250W Inverter Circuit Diagram

250W Inverter Circuit Diagram

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Friday, December 27, 2013

Flyback Converter Circuit Diagram

A low-current fly-back converter is used here to generate ±15 volts at 20 mA from a +5 volt regulated line. The reference generator in the SG1524 is unused with the input voltage providing the reference. Current limiting in a fly-back converter is difficult and is accomplished here by sensing current in the primary line and resetting a soft-start circuit.

Flyback Converter Circuit Diagram

Flyback Converter Circuit Diagram

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Wednesday, December 25, 2013

If you desire the personal touch then skins

Look for special discounts and credit offers such as "no payments for 90 days for purchases over a certain dollar amount." These offers enable you to buy multiple items and make payments later without paying high credit card interest. Its a great way to do your holiday shopping from your computer while avoiding the crowded stores. Browse your favorite shopping mall online today to see what latest cell phone accessories are available to fit your budget.The popularity the new smart phones, many of which are multi-functional mobile devices are creating a wave of useful cell phone accessories. As more and more users rely heavily upon these devices items like cell phone chargers, cell phone cases, smart cell phone applications and more are breaking into the marketplace rapidly.Users now demand more flexibility with their devices and even more options with respect to various accessories that are used to personalize their smart phones. An emergence of custom made cell phone cases, multi-device mobile charging units and multi-faceted smart phone applications are emerging for every type of cell phone on the market.
If you desire the personal touch then skins, charms and faceplates will allow you to express your style. They turn the subdued or plain phone into a work of art.
Belt Clips and Vibrating Belt Clips - keeps your phone conveniently in place and lessens the chance of dropping or misplacing your investment.
The mobile communication products, the goal is to identify and introduce innovative products, very attractive and substantial benefits. For example, cell phone interceptor allows to control the traffic in one direction to provide much-needed peace of mind. Simply put, it filtered out the clutter. When the phone is located in mobile interceptor place, it sends a signal to the mobile phone operating at the same frequency, interference success.
Mobile phone interceptor can also be used as a means of combating terrorism. Within the communication range of business areas, from preventive measures to curb organized crime and assassin for remote activation of explosives.The problem has to eat sugar metabolism, it does not just burn.
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Monday, December 23, 2013

DC 12V Car Battery Charger

The circuit has been designed to produce a battery charger for automobiles that are using 12V batteries only. BTY79 is a 10A Silicon controlled rectifier with an operational temperature range from 0ºC to 125ºC. C106D is a 4A sensitive gate Silicon controlled rectifier that functions as reverse blocking thyristors designed for high volume consumer applications such as light, speed control, temperature, process and remote control, and warning systems where reliability of operation is important.

Circuit Diagram:


DC 12V - Car Battery Charger Circuit Diagram
DC 12V - Car Battery Charger Circuit Diagram

The typical car battery chargers have simple designs that produce a few amperes during its operation while charging the battery continuously. In the event that the charger is not turned OFF, overcharging will occur with due to evaporation which looses electrolyte and might cause damage to its elements. With the design of this circuit, this type of problem can be avoided by monitoring the condition of charging of the battery via the retroactive control circuit.

This is done by imposing a high current charge until the charging is complete. The LED LD2 will indicate that charging is full which will eventually deactivate the charging circuit. In creating this design, the cables that connect the transformer to the circuit should have enough cross-sectional area to prevent voltage drop when heat is produced as the current flows through. The adjustment of the circuit comes after the design, with the adjustment of TR1 to null value.

The LEDs are checked without connecting the battery initially and allowing them to turn ON. By connecting a battery, a 2A to 4A current is permitted to flow while ensuring that LD2 is turned OFF. TR1 is carefully adjusted to a few hundred milliamps until LD2 turns ON. This is done using the hydrometer technique. The correct adjustment allows LD2 to begin flickering as the battery is being charged. Connected to the battery is Q1, since it functions as a rectifier and charges the battery, which can be fired in each half cycle by R3-4 and LD2.

In case an uncharged battery is connected, a low terminal voltage is obtained. When the voltage of the battery exceeds the predetermined value, Q2 is activated by the combination of C1, TR1, R2, and D2. Q1 is deactivated with the current supply cut off as the battery terminal voltage is increased where Q2 shifts the control of Q1 gate after TR1 fixed the increased battery terminal voltage above the level. A heat sink should be mounted on the bridge rectifier GR1 and Q1 to prevent overheating. A 5A DC ammeter M1, connected in parallel, is used to measure the charge current.

The circuit’s theory of design will only be applied to batteries with rating of 12V. These batteries are mainly used in a variety of vehicles used in land, air, and water such as personal watercraft like boat, yacht, Jet Skis, and other marine applications. They are also utilized widely in automobiles and motorcycles such as quad bike, RVs, snowmobile, motor scooter, utility vehicle, and riding mower. It can also be beneficial to disabled persons by providing aid to wheelchairs and mobility scooters.

Parts:


R1= 1Kohms
R2= 1.2Kohms
R3= 470 ohms
R4= 470 ohms
R5= 10Kohms
C1= 10uF 25V
D1= 1N4001
D2= 6.8V 0.5W zener
TR1= 4.7Kohms trimmer
Q1= BTY79 or similar 6A SCR
Q2= C106D SCR
GR1= 50V 6A Bridge Rectifier
T1= 220V/17V 4A Transformer
LD1= Green LED
LD2= Red LED
M1= 0-5A DC Ampere meter
S1= 10A D/P On Off Switch
F= 5A Fuse
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Saturday, December 21, 2013

Four Tone Siren

UM3561 PROJECT CIRCUIT

        UM3561 IC includes  oscillator and selector circuits so few external component is used for construction of four tone siren.
   The UM3561 contains programmed mask ROM to simulate siren sound. Power consumption of IC is low.It is powered by 3 Volt. One NPN Transistor is used for amplification of audio signal.

       Circuit Diagram of Four Tone Siren
Part List :
IC UM3561
Resistance = 220 Ohms
Condenser 100Mfd
Transistor BC548
Battery Container 3V
Switches
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