solated Full Duplex RS232C Interface Circuit 6N137

This is a Isolated Full Duplex RS232C Interface circuit. This circuit is used to protect PC from direct connection to hazardous voltages. Feature : isolate TxD and RxD lines from the PC serial port , baud rate of 19.2k baud, 5V supply. Component : capacitor, 1N4148 diode, LED, DB9, terminal block resistor, 6N137, CNY17-3, 74HC14. 

HIGH CURRENT DC DEVICES TIP122

  


The Controlling Multiple LEDs Tutorial uses the 2N3904 small current transistor. This works well for controlling additional relatively small current devices with the Arduino. You may want to use the Arduino to control a DC powered device that draws more current that the 2N3904 transistor can supply. A solution for this situation is to use an NPN Darlington Transistor designed for medium power linear switching applications. In this tutorial we will use a TIP122 transistor, which can power devices up to 100VDC at 5 Amps. This can be used to power devices such as motors, solenoids and fans, where the only necessary operation control operation is ON and OFF (see the H-Bridge Tutorial for bi-directional rotation and speed control of DC motors.)

The circuit is identical to the 2N3904 transistor circuit - the base of the transistor (PIN 1) is connected to the Arduino output pin (D6) through a 1K OHM resistor. The emitter (PIN3) is connected to ground and the collector (PIN2) is connected to one end of the coil of the device being driven (in our example we have a 12VDC Solenoid connected). The other end of the coil is connected to the +12VDC external power supply (the ground from this power supply is connected to a common ground with the Arduino - this is necessary for the transistor to function). It is very important to put a diode across the coil of the device being powered to protect the control circuit from a potential voltage spike that can be created when current is released from the device being powered.

Two Wire Arduino Knight Rider PCF8574

This tutorial shows how to interface eight LEDs to an Arduino using only two Arduino pins. This is made possible by using a PCF8574 I/O expander IC. A “Knight Rider” display is shown on the LEDs.

The suggested sequence of building the circuit is:

    Insert the PCF8574 IC
    Make power and ground connections to the IC
    Connect pin 1, 2 and 3 of the IC (U1) to ground
    Insert capacitor C1 (100n) and wire it between power (5V) and ground (GND)
    Insert the eight LEDs with anodes (longer pin) on the left
    Connect resistors R1 to R8 between the LED anodes and the top breadboard rail (5V)
    Wire the cathode of each LED to the correct pins on the IC
    Connect R9 and R10
    Connect the two wires from Arduino pins A4 and A5 to the IC
    Connect the Arduino 5V to the top breadboard rail and GND to the bottom breadboard rail

You may have noticed that the breadboard circuit swaps the position of the LEDs and resistors from the circuit diagram – e.g. R1 and D1 swap positions. This will make no difference to how the circuit operates. It has only been done to simplify the breadboard circuit.

LED Bike Light System 2N3906

This LED Bike Light System can be made to be just a headlight or both a headlight/taillight bike light.

The circuit use simple electronic components such as LM555,PNP Transistor (2N3906),NPN Transistor (2N2222) plus some resistors and capacitors.

 My NiteRider light was off getting fixed at the factory and I needed something for my daily commute. I have used it in a 50 minute pouring rain commute on the way in to work and it worked like a champ.

Blinking LED using AVR ATmega16

         Blinking a LED using 555 timer ic is simple, you can do the similar job using AVR atmega16. This is a simple program, perhaps simplest, and an introduction to ATmega16. To make a led blink you have to set (logic 1) and reset (logic 0) a pin of the controller continuously.
         there's a code for blinking a LED connected to any pin of portA of the controller.


#include<avr/io.h>
#include<util/delay.h>
int main(void)
{
DDRA=0xFF;            // set portA as out put
while(1)                     // run forever
{
PORTA=0xFF;          //All the pins of portA is set
_delay_ms(1000);      //wait  for 1sec
PORTA=0x00;          //all the pins of portA is reset
_delay_ms(1000);      // wait for 1 sec
}
return(0);
}


        DDR is data direct resister, DDR determines whether a particular pin of a port will work as an input or as an output, writing logic 1 to DDR makes the pin behave as output pin, writing logic 1 to DDR makes the pin behave as input pin. As we I wrote DDRA=0xFF, it will make all pins of portA work as output pin. Suppose you need only PA2 ( pin3 of portA ) as output pin, you need to write 1 to Bit 0 of  data direction resister for portA (DDRA). You can write like this

                                                              DDRA=0x01;
                                                                   or
                                                             DDRA|=(1<<PA2);
                                                                   or
                                                             DDRA|=_BV(2);