65W Notebook Laptop Power Adapter

Using TOP269EG off-line switcher IC, (U1), in a flyback configuration can be designed a very simple high efficiency notebok laptop power adapter.TOP269EG IC has an integrated 725 V MOSFET and a multi-mode controller. It regulates the output by adjusting the MOSFET duty cycle, based on the current fed into its CONTROL pin.This laptop power adapter […]

Switchable 6V, 9V, and 12V Linear Voltage Regulator

  We can build a multiple voltage power supply 6, 9, and 12V  (AC-DC Adapter) with the circuit shown in the following schematic diagram.  Not only provide multiple voltage output with single voltage supply, this circuit add the benefit of regulating the voltage for better stability. A transformer with rectifier diodes and filtering capacitor can […]

VGA to BNC Adapter (Converter)

There are monitors which only have three BNC inputs and which use composite synchronization (‘sync on green’). This circuit has been designed with these types of monitor in mind. As can be seen, the circuit has been kept very simple, but it still gives a reasonable performance. The principle of operation is very straightforward. The […]

9V DC Adapter With Battery Backup

With just a low cost DC adapter and the circuit described here it is possible to build a low cost stabilized, uninterruptable 9V supply. On the grounds of safety and economy, a simple unstabilized 12V D.C. adapter is used as the power source, a universal adapter with its output set to 12 V will do […]

Battery-Charging Indicator For Mains Adaptor

Although you may well be the proud owner of the very latest NiCd battery charger, you may still come across the odd ‘incompatible’ battery, for example, one having a rare voltage or requiring a much higher charging current than can be supplied by your off-the-shelf charger. In these cases, many of you will resort to […]

RS232 to RS485 Converter

RS485 interface gives some more benefits compared to RS232: simplicity and the robustness for long distance transfer. RS485 is simpler because it uses only two wire (or a single pair) to carry out the data in bidirectional manner, using RS232, we need 3 wires at minimum to carry the data bidirectionally. RS485 cable length can […]

Simple TTL-RS232 Level Converter Using Transistor

Using only transistors as the active components, we can build a simple and low cost TTL-to-RS232 level converter. It uses only two transistors as the active components. Here is the schematic diagram of the converter: TTL-RS232 Level Converter You can use any small signal transistor for this RS232 converter circuit. You can see the collector […]

TTL-RS232 Level Converter Using MAX232 IC

Using MAX232 integrated circuit, you can build a TTL-to-RS232 level converter that totally comply with RS232 electrical specification. The IC generate the higher positive and negative voltage (+10 and -10 Volts)  from TTL power supply (5V DC) using switched capacitor. The switching circuitry is provided inside the chip, so you need only few caps for […]

Current to Voltage Converter

In the simplest form, current to voltage converter can be implemented as simple as one resistor,  since a voltage is developed when an electrical current flow against a resistance. The problem is that the resistance always affect the current by  decreasing the current flow, and the current to voltage conversion is not accurate. In some […]

USB-RS232 Converter

Many new computers now only has USB port, and this serial to USB adapter might be the only help for old devices that provides only RS232/COM Port. This serial adapter uses FT232 USB-RS232  converter IC from FTDI (Future Technology Devices International).  The main features of this USB serial adapter chip are: 384 byte receive buffer […]