Friday, November 25, 2011

Telephone Line Powered LED Lamp

This small and bright LED lamp is telephone line powered, means it uses the power of our telephone line. There are about -40v to -50v at telephone line, LM317T is used to adjust them according to our demand.

Wednesday, November 16, 2011

PIC Based Auto Dimmer

The operation of the dimmer is based on phase control; during a full cycle of an AC waveform, a thyristor will only allow a part of the waveform to be delivered to the load. Take a look at the following waveforms:


The only difference is that the waveform on the left will bright the lamp higher than the waveform on the right. That is because, on the left waveform, the triac will be conductive earlier than the triac shown in the right waveform.

Saturday, November 12, 2011

Serial Communication With PIC18F452

In this tutorial I will explain how to practically do a simple communication over RS232 interface. In this tutorial i ll send and receive the data using serial port, in two devices. Also you can control your home appliances using PC serial port with the help of PIC. RS232 is serial interface that means that data is transferred BIT by BIT at a time. Since data is transferred BIT by BIT so we need only a single wire two send data and an another one to receive data. One more common wire (called GND) is required between two separate circuit to enable current flow. So a total of three wire are required for communication.

Monday, November 7, 2011

LED Flasher

This LED flasher is based on 555 timer. One can use this flasher circuit either on bike/cycle or in police car!. The operating voltage of the circuit is 9v, but you can also use it at 6v. 

Two sets of six LEDs are used here, but you can extend it to 40 each set. Flash cycle is determine by the RC time constant. However by using the pot you can set the flash rate of your choice.

Saturday, November 5, 2011

LM3914 Based Battery Voltage Monitor

This voltage monitor is made to display the voltage of 12v battery (for UPS) on LEDs. For this purpose LM3914 is used. The voltage range decided to display is 10v to 13.5v for 12v battery. LM3914 is display driver that can be used in dot  mode or in bar mode; dot mode, with only one led is lit at a time, and in bar mode where it lights leds progressively when the voltage increases.

Thursday, November 3, 2011

UPS Battery Charger

The battery charger used in the ups are very slow in nature, means the charging current is low (about 1 - 2 A). So they required a lot of time to charge a high AH batteries. This charger is build around LM338 that can charge the battery with 5a current and fast in nature.

This circuit has Auto cut off facility also. This High current charger can be used for the Fast charging of sealed lead acid batteries. This charger can give 5 Ampere current for quick rejuvenation of the battery. It uses an Adjustable voltage regulator so that 6 volt and 12 volt batteries can be charged. When the battery acquires full charge, charging process will be terminated.