Saturday, March 27, 2010

Multi PIC Programmer

This Multi PIC Programmer works as a usual JDM Programmer,  This Multi PIC Programmer works as a usual JDM Programmer. When the switch-2 is on, this Multi PIC Programmer changes into VPP-FIRST mode.

The switch-2 will be used only when both INTOSC and internal MCLR options are selected (PIC12Cxxx,PIC12CExxx,PIC12F629, and PIC12F675,etc. Please refer to the data sheet of each PICs for more details).                                                                                                                                                                       Read more


Components Required: 
R1,  1.5k ohm 
R2,  10k ohm 
R3,  1k ohm 
R4,  100 ohm
R5,  10k ohm
D1-D4,  1N4148 
D5,   5.1v Zener
D6,  6.2v Zener 
D7,  Red LED 
C1-C2,   100uF, 16v Electrolyte
C3,   100nF Ceramic
Q1-Q2,  BC54
Q3,   BC557 
40 Pin ZIF Socket
 SW1, sliding switch
 SW2, on/off switch
 BD-9 Female
    The Circuits and PCB layouts can be downloaded from here

    Friday, March 12, 2010

    Automatic emergency light

    • It is highly bright due to the use of white LEDs.
    • The light turns on automatically when mains supply fails, and turns off when mains power resumes.
    • It has its own battery charger. When the battery is fully charged, charging stops automatically.

    The circuit comprises two sections: charger power supply and LED driver.The charger power supply section is built around 3-terminal adjustable regulator (IC1) LM317, while the LED driver section is built around transistor BD140(T2).

    In the charger power supply section, input AC mains is stepped down by transformer to deliver 9V, 500mA to the bridge rectifier, which comprises diodes (IN4007x4). Filter capacitor (25v/1000uf) eliminates ripples. Unregulated DC voltage is fed to input pin 3 of IC1 and provides charging current through diode IN4007(D5) and limiting resistor (16ohm) R3. By adjusting preset 2.2K(R16), the output voltage can be adjusted to deliver the required charging current.
    When the battery gets charged to 6.8V, zener diode conducts and charging current from regulator (IC1) finds a path through transistor BC547(T1) to ground and it stops charging of the battery. 
    The LED driver section uses a total of twelve 10mm white LEDs. All the LEDs are connected in parallel with a 100-ohm resistor in series with each. The common-anode junction of all the twelve LEDs is connected to the collector of pnp transistor T2 and the emitter of transistor T2 is directly connected to the positive terminal of 6V battery. 
    The unregulated DC voltage, produced at the cathode junction of Bridge(Diodes), is fed to the base of transistor T2 through a 1k resistor. When mains power is available, the base of transistor T2 remains high and T2 does not conduct. Thus LEDs are off. On the other hand, when mains fails, the base of transistor T2 becomes low and it conducts. This makes all the LEDs (LED1 through LED12) glow. The mains power supply, when available, charges the battery and keeps the LEDs off as transistor T2 remains cut-off. During mains failure, the charging section stops working and the battery supply makes the LEDs glow. 
     D1-D5,   1N4007
     D6,  6.8v Zener
     TR1,   9v 500mA transformer
     IC1,   LM317
     C1,  1000uF/25v electrolyte capacitor
     T1,   BC547
     T2,   BD140
     G1,   6v 4.5ah battery
     R1,   180 ohm
     R2,   1.2K ohm
     R3,   16 ohm  5watt
     R4,   1K ohm
     R5-R15,R17,  100 ohm  0.5 watt
     R16,  2.2K trimpot
     LED1-12,   10MM white

    Saturday, March 6, 2010

    RS-232 level converter

    This is a basic RS-232 transmit/receive circuit that is necessary for PIC microcontrollers to communicate with a PC serial port. The PIC microcontroller operates at TTL levels (0-5 Volts). The MAX233 IC allows you to convert microcontroller voltages to RS-232 compatible levels with no required external components.


    Components Required:
    Max233 IC
    DB-6 Female
    1uF/25v Electrolyte Capacitor
    20 pin IC Socket
    JP1, 2 pin connector/jumper