Battery charger circuit using SCR.

A simple battery charger based on SCR is shown here.Here the SCR rectifies the AC mains voltage to charge the battery.When the battery connected to the charger gets discharged the battery voltage gets dropped.This inhibits the forward biasing voltage from reaching the base of the transistor Q1 through R4 and D2.This switches off the transistor.When the transistor is turned OFF,the gate of SCR (H1) gets the triggering voltage via R1 & D3.This makes the SCR to conduct and it starts to rectify the AC input voltage.The rectified voltage is given to the battery through the resistor R6(5W).This starts charging of the  battery.

When the battery is completely charged the base of Q1 gets the forward bias signal through the voltage divider circuit made of R3,R4,R5 and D2.This turns the transistor ON.When the Q1 is turned ON the trigger voltage at the gate of SCR is cut off and the SCR is turned OFF.In this condition a very small amount of charge reaches the battery via R2 and D4 for trickle charging.Since the charging voltage is only half wave rectified ,this type of charger is suitable only for slow charging.For fast charging full wave rectified charging voltage is needed.

IR transmitter using AT89C2051

Hello dear friends
If you are trying to design an IR transmitter very similar to your TV remote control. I can help you in achieving this task. Here is program and circuit diagram. it use pin 3.3 (pin 7) of micro controller. Use the given simple program and check it from oscilloscope that it will transmit modulated 38KHz signal.
Circuit diagram is given below

Here is program you can run it using software for assembly language and then create file. After that burn hex file in your microcontroller.

;IR Transmitter using 89c2051

Program

ORG 0000H

Start:

IR EQU P3.3          ;IR trx CONNECTED TO THIS PIN

 

MOV TMOD,#00010001B ; TIMER-0, MODE 1 TIMER-1, MODE 1

sjmp MAIN

;--------------------------;-------------------------------------

;--------------------------;-------------------------------------

ONE:

MOV    TL1,#0CAH ;LOWER BYTE 1.728 MSEC

MOV    TH1,#0F9H ;UPPER BYTE

SETB  TR1

HERE:

MOV    TL0,#0F4H ;LOWER BYTE 38 KHZ

MOV    TH0,#0FFH ;UPPER BYTE

SETB  TR0

CPL   IR

JNB  TF0,$

CLR   TF0

JNB   TF1,HERE

CLR   TF1

Clr IR

RET

;--------------------------;-------------------------------------

;--------------------------;-------------------------------------

;--------------------------;-------------------------------------

;--------------------------;-------------------------------------

ZERO:

MOV    TL1,#0CAH ;LOWER BYTE 1.7728 MSEC

MOV    TH1,#0F9H ;UPPER BYTE

SETB  TR1

SetB  IR

JNB   TF1,$

CLR   TF1

Clr IR

RET

;--------------------------;-------------------------------------

;--------------------------;-------------------------------------

;--------------------------;-------------------------------------

;--------------------------;-------------------------------------

MAIN:

Acall ONE

Acall ZERO

Sjmp MAIN

;--------------------------;-------------------------------------

;--------------------------;-------------------------------------

END