RJ45 Port Pinout Circuit

 

RJ45 connector is used for connecting Ethernet port on computer and in Internet system. There are two configuration: straight and cross. This is the figure of the RJ45 connector;

Intercom Circuit Using LM390

This is a circuit for an intercom is a is a stand-alone electronic communications system intended for limited or private dialogue. Below schematic shows the application circuit of LM390 on intercom. Gain control can be done by capacitively coupling a resistor (or FET) from pin 6 to ground. This is the figure of the circuit;

Intercom Circuit

This is a simple form circuit for a 2-station intercom using common 8R mini speakers. The “press-to-talk” switches should have a spring-return so the intercom can never be left ON. This is the figure of the circuit;

Power the speaker from a separate power supply is the secret to preventing instability (motor-boating) with a high gain circuit like this. An extra station (or two extra stations ) can be connected to this design.

Intercom Circuit

This is a simple form circuit for a 2-station intercom using common 8R mini speakers. The “press-to-talk” switches should have a spring-return so the intercom can never be left ON. This is the figure of the circuit;

Power the speaker from a separate power supply is the secret to preventing instability (motor-boating) with a high gain circuit like this. An extra station (or two extra stations ) can be connected to this design.

SPI Interface Circuit for Big 7 Segment LED

This circuit is uses for the general purpose Big LED with SPI serial interfacing. The circuit is using a serial-in-parallel out shift register, 74HC595 for receiving serial data from microcontroller board. This is the figure of the circuit.


For wiring the schematic is SER is for data input, SRCLK is shift clock and RCLK is Latch clock. Each data bit is shifted into the register on rising edge of the shift clock. When all data bits are shifted into the 8-bit register, the rising edge of RCLK will clock the data to be latched at each output bit, i.e. QA - QH. The Big LED is made from cheap dot LED. Each segment has five dot LED connected in series with a limiting resistor tied to +12V. The logic high at the input of ULN2003 makes the output active low, thus sinks the LED current into the chip. The driver has 7-bit for segment a, b, c, d, e, f, and g. Q1 is for optional point display.

Multiple digits can easily be made by connecting the QH to the next digit serial input bit, see the circuit below. Please note that, the shift clock and latch signal are tied to every 74HC595.

Pulse Generator And Signal Tracer Circuit Using Transistor

This is a simple circuit that can used to generate narrow pulses at about 700-800Hz frequency. The pulses, containing harmonics up to the MHz region, can be injected into audio or radio-frequency stages of amplifiers, receivers and the like for testing purposes. This circuit is built by two transistor. This is the figure of the circuit.


Operation of the circuit is Q1 & Q2 form a complementary unstable multi vibrator, whose operating frequency is set mainly by R3, C2 & C3 values. Output pulses are taken at Q2 Collector and applied to the probe by means of decoupling capacitor C1. D1 provides a symmetrical shape for the output waveform. If an earclip or headphone jack is plugged into J1, the connection from Q2 Collector and C1 - C2 is broken by the switch incorporated into J1: in this case the circuit becomes a two-stage amplifier. If you intend to use the circuit to test valve operated devices C1 must be a 630V type. Working with low voltage supply transistor devices the voltage of C1 can be lowered to 63 or 100V. A crystal (high impedance) earpiece is a good solution, provided you substitute J1 with a mono switched jack socket.

In below is the listing component that can be used to built up the circuit.
R1 1M 1/4W Resistor
R2, R4 2K7 1/4W Resistors
R3 150K 1/4W Resistor
C1 2n2/630V
C2, C3 4n7/ 63V
D1 1N4148 75V 150mA Diode
Q1 BC547 45V 100mA NPN Transistor
Q2 BC557 45V 100mA PNP Transistor
SW1 SPST miniature Slider Switch (See Notes)
J1 Stereo switched 3mm. Jack socket (See Notes)
Probe Metal Probe 3 to 5 cm. long
Clip Miniature Crocodile Clip
B1 1.5V Battery (AA or AAA cell etc).

Micro Flasher Circuit Using 555IC

This is a simple and compact flasher circuit that can be used where ever a flashing LED is needed. The circuit finds application in flashing beacons, alarms automobile and more. The circuit is nothing but an astable multi vibrator based on IC NE 555 (IC1). This is the figure of the circuit.


The frequency of the oscillation depends on the values of R1, R2, R3 and C2. The LED glows when the out put (pin3) of IC1 goes high. The IC1 NE 555 can easily drive a LED. The resistor R4 acts as a current limiter for LED. The circuit is powered by a 6V battery or 6V DC power supply. If you don’t need frequent changes in the flashing rate use a preset for R2 and set it for the required rate. The capacitor C2 must be rated 10V.