Off Line-UPS Offers (100 -5000 Watts)
Off Line-UPS Offers (100 -5000 Watts)


Off Line-UPS Offers (100 -5000 Watts)


With increased dependency on electric power for various domestic, commercial purposes and the seemingly declining capacity of power utilities in many countries, the need for additional backup power sources is on the rise. Various modules are already available to address these different needs. However, most modules are too expensive, too bulky, or too rigid in their power capacity, capability, and flexibility. The circuit described here is an off-line uninterruptible power supply. It has an expandable power stage design that can be easily modified for use with power ranges from as low as 100 W to as high as 5000 W with forced cooling.

The design is based on the LM3524D, a popular industrial-grade, pulse-width-modulation (PWM) controller. This device is fully self-contained and has all of the necessary logic built-in to ensure a compact and cost-effective product. The controller offers:
Complementary power drive output stage with 180° out-of-phase switching.
Stable oscillator with shutdown capability and noise suppression.
Current-sense and voltage-sense circuitry.
Dead time between the two complementary switching stages to prevent cross conduction and subsequent core saturation.
Low voltage cutoff.

The on-chip oscillator frequency is controlled by the RC pair R2 and C1, and the required frequency is calculated as fOSC = 1/(R2 × C1). Depending on the country, fOSC = 50 Hz or 60 Hz. The low-power drive stage, containing transistors Q1 and Q2, is driven by the outputs at pin 12 and 13 of the controller; out-of-phase switching is handled by its own internal logic.

The final switching stage is comprised of transistors Q5 and Q6 wired across the main step-up transformer. These transistors are switched on in tandem to drive current through the two halves of the primary winding of transformer T2, independently.

Power diodes D2 and D3 are included to protect the power-stage transistors against reverse currents. Switching pulses from the drive transistors are transferred to the power stage via transistors Q3 and Q4, which serve as current amplifiers.

Resistor R10 is used to feed back the current to the current-sense monitor via pin 5. The current-sense logic monitors this feedback and triggers shutoff in event of either overload or power-stage failure.

The value of R10 is calculated as IMAX = 200 mV/R10, where IMAX is proportional to the power rating of the load, and 200 mV is the minimum required potential drop across R10 to trigger a shutdown by the current-sense logic.

The transformer T1 is connected to the standard mains supply and the rectified dc is fed to the shutdown pin (pin 10). This pin serves to turn off the LM3524 during the presence of the standard mains supply. If the mains supply fails, the bias on the shutdown pin is removed, thus starting the oscillator and hence the drive stages.

The power stages and transformer T2 must be appropriately rated for the required output power. The power transistors (Q3, Q4, Q5, and Q6) can be paralleled with similar devices for increased power-handling capacity. In addition, forced cooling can be used to achieve an even higher output power rating. However, for low- or medium-output power ratings, these transistors must be mounted on a large heat sink. Transformer T2 is a standard 12 V: 0:12 V to 230-240 V step-up winding, while T1 is a small 230-V to 12-V step-down transformer rated for 50 mA on the secondary windings. Additional filter and shaping circuitry can be added on the secondary winding of T2 to obtain a near sine-wave output. The RC network comprising R3 and C2 is included for compensation.

Accurate LC Meter Capacitance Inductance Meter with 16F628 and LCD
Volt Ampere Meter with 16F876 Microcontroller and LCD display
Accurate LC Meter

Build your own Accurate LC Meter (Capacitance Inductance Meter) and start making your own coils and inductors. This LC Meter allows to measure incredibly small inductances making it perfect tool for making all types of RF coils and inductors. LC Meter can measure inductances starting from 10nH - 1000nH, 1uH - 1000uH, 1mH - 100mH and capacitances from 0.1pF up to 900nF. The circuit includes an auto ranging as well as reset switch and produces very accurate and stable readings.
PIC Volt Ampere Meter

Volt Ampere Meter measures voltage of 0-70V or 0-500V with 100mV resolution and current consumption 0-10A or more with 10mA resolution. The meter is a perfect addition to any power supply, battery chargers and other electronic projects where voltage and current must be monitored. The meter uses PIC16F876A microcontroller with 16x2 backlighted LCD.

50MHz 60MHz Frequency Meter / Counter with 16F628 & LCD
1Hz - 2MHz XR2206 Function Generator
60MHz Frequency Meter / Counter

Frequency Meter / Counter measures frequency from 10Hz to 60MHz with 10Hz resolution. It is a very useful bench test equipment for testing and finding out the frequency of various devices with unknown frequency such as oscillators, radio receivers, transmitters, function generators, crystals, etc.
1Hz - 2MHz XR2206 Function Generator

1Hz - 2MHz XR2206 Function Generator produces high quality sine, square and triangle waveforms of high-stability and accuracy. The output waveforms can be both amplitude and frequency modulated. Output of 1Hz - 2MHz XR2206 Function Generator can be connected directly to 60MHz Counter for setting precise frequency output.

BA1404 HI-FI Stereo FM Transmitter
USB IO Board PIC18F2455 / PIC18F2550
BA1404 HI-FI Stereo FM Transmitter

Be "On Air" with your own radio station! BA1404 HI-FI Stereo FM Transmitter broadcasts high quality stereo signal in 88MHz - 108MHz FM band. It can be connected to any type of stereo audio source such as iPod, Computer, Laptop, CD Player, Walkman, Television, Satellite Receiver, Tape Deck or other stereo system to transmit stereo sound with excellent clarity throughout your home, office, yard or camp ground.
USB IO Board

USB IO Board is a tiny spectacular little development board / parallel port replacement featuring PIC18F2455/PIC18F2550 microcontroller. USB IO Board is compatible with Windows / Mac OSX / Linux computers. When attached to Windows IO board will show up as RS232 COM port. You can control 16 individual microcontroller I/O pins by sending simple serial commands. USB IO Board is self-powered by USB port and can provide up to 500mA for electronic projects. USB IO Board is breadboard compatible.

ESR Meter / Transistor Tester Kit
Audiophile Headphone Amplifier Kit
ESR Meter / Capacitance / Inductance / Transistor Tester Kit

ESR Meter kit is an amazing multimeter that measures ESR values, capacitance (100pF - 20,000uF), inductance, resistance (0.1 Ohm - 20 MOhm), tests many different types of transistors such as NPN, PNP, FETs, MOSFETs, Thyristors, SCRs, Triacs and many types of diodes. It also analyzes transistor's characteristics such as voltage and gain. It is an irreplaceable tool for troubleshooting and repairing electronic equipment by determining performance and health of electrolytic capacitors. Unlike other ESR Meters that only measure ESR value this one measures capacitor's ESR value as well as its capacitance all at the same time.
Audiophile Headphone Amplifier Kit

Audiophile headphone amplifier kit includes high quality audio grade components such as Burr Brown OPA2134 opamp, ALPS volume control potentiometer, Ti TLE2426 rail splitter, Ultra-Low ESR 220uF/25V Panasonic FM filtering capacitors, High quality WIMA input and decoupling capacitors and Vishay Dale resistors. 8-DIP machined IC socket allows to swap OPA2134 with many other dual opamp chips such as OPA2132, OPA2227, OPA2228, dual OPA132, OPA627, etc. Headphone amplifier is small enough to fit in Altoids tin box, and thanks to low power consumption may be supplied from a single 9V battery.

Arduino Prototype Kit
RF Remote Control 433MHz Four Channel
Arduino Prototype Kit

Arduino Prototype is a spectacular development board fully compatible with Arduino Pro. It's breadboard compatible so it can be plugged into a breadboard for quick prototyping, and it has VCC & GND power pins available on both sides of PCB. It's small, power efficient, yet customizable through onboard 2 x 7 perfboard that can be used for connecting various sensors and connectors. Arduino Prototype uses all standard through-hole components for easy construction, two of which are hidden underneath IC socket. Board features 28-PIN DIP IC socket, user replaceable ATmega328 microcontroller flashed with Arduino bootloader, 16MHz crystal resonator and a reset switch. It has 14 digital input/output pins (0-13) of which 6 can be used as PWM outputs and 6 analog inputs (A0-A5). Arduino sketches are uploaded through any USB-Serial adapter connected to 6-PIN ICSP female header. Board is supplied by 2-5V voltage and may be powered by a battery such as Lithium Ion cell, two AA cells, external power supply or USB power adapter.
200m 4-Channel 433MHz Wireless RF Remote Control

Having the ability to control various appliances inside or outside of your house wirelessly is a huge convenience, and can make your life much easier and fun. RF remote control provides long range of up to 200m / 650ft and can find many uses for controlling different devices, and it works even through the walls. You can control lights, fans, AC system, computer, printer, amplifier, robots, garage door, security systems, motor-driven curtains, motorized window blinds, door locks, sprinklers, motorized projection screens and anything else you can think of.

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