Circuit Schematic learn

A very simple LED driver electronic project can be designed using the CAT3649 high efficiency quad mode R fractional charge pump IC that can drive up to six LEDs. The inclusion of a 1.33x fractional charge pump mode increases the device efficiency by up to 10% over traditional 1.5x charge pumps with no added external capacitors.Low noise input ripple is achieved by operating at a constant switching frequency which allows the use of small external ceramic capacitors. The multi−fractional charge pump supports a wide range of input voltages from 2.4 V to 5.5 V.



The LED current can be adjusted in different ways. The full−scale LED current is set to 25 mA once the device is enabled. Analog dimming in 32 linear steps is achieved via a 1−wire pulse−dimming input (ADIM)
Further adjustment of the LED current can be done by applying a pulse width modulation (PWM) signal on the PWM input.The CAT3649 can be shut down by holding the ADIM or PWM input in a logic low condition for greater than 30 ms. This electronic design CAT3649 charge pump LED driver can be used in applications like : LCD Display Backlight , Cellular Phones , Digital Still Cameras and some other handheld devices .

If the input voltage is insufficient or falls to a level where the regulated currents cannot be maintained, the CAT3649 automatically switches into 1.33x mode. In 1.33x mode, the output voltage is approximately equal to 1.33 times the input supply voltage . This sequence repeats in the 1.33x and 1.5x mode until the driver enters the 2x mode.While in 2x mode, the output is approximately equal to 2 times the input supply voltage.If the CAT3649 charge pump LED driver detects a sufficient input voltage to drive all LED currents in 1x mode, it will change automatically back to 1x mode.

Using TDA7294 audio amplifier integrated circuit in bridge mode configuration , can be designed another Hi-Fi power amplifier .In this TDA7294 bridge power amplifier the value of the load must not be lower than 8 Ohm for dissipation and current capability reasons.

Bridge Power Amplifier Circuit Using TDA7294

The main advantages offered by TDA7294 bridge mode configuration are:High power performances with limited supply voltage level, Considerably high output power even with high load values ( 16 Ohm).The output power of this amplifier in bridge connection is 150 W with Rl= 8 Ohm , Vs = +/-25V the and 170 W output power for Rl=16 Ohm, Vs = +/-35V.

This simple circuit has helped me out on many occasions. It is able to check transistors, in the circuit, down to 40 ohms across the collector-base or base-emitter junctions. It can also check the output power transistors on amplifier circuits.

Simple Circuit Transistor Checker Schematic
Circuit operation is as follows. The 555 timer ( IC1 ) is set up as a 12hz multi vibrator. The output on pin 3 drives the 4027 flip-flop ( IC2). This flip-flop divides the input frequency by two and delivers complementary voltage outputs to pin 15 and 14. The outputs are connected to LED1 and LED2 through the current limiting resistor R3. The LEDs are arranged so that when the polarity across the circuit is one way only one LED will light and when the polarity reverses the other LED will light, therefore when no transistor is connected to the tester the LEDs will alternately flash.

The IC2 outputs are also connected to resistors R4 and R5 with the junction of these two resistors connected to the base of the transistor being tested. With a good transistor connected to the tester, the transistor will turn on and produce a short across the LED pair. If a good NPN transistor is connected then LED1 will flash by itself and if a good PNP transistor is connected then LED2 will flash by itself. If the transistor is open both LEDs will flash and if the transistor is shorted then neither LED will flash.

A simple test circuit to fault find audio and radio equipment. Can be used to inject a square wave signal, rich in harmonics, or used with headphones as an audio tracer.

Signal Tracer and Injector Circuit diagram

a single pole double throw sitch is used to switch between inject and trace modes. The diagram is drawn in trace mode, the earpiece being connected to the collector of the last transistor. Both transistors are wired as emitter followers, providing high gain. DC blocking is provided by the 1n capacitor at the probe end, and the two stages are capacitively coupled.

When the switch is thrown the opposite way (to the blue dot) both transistors are wired as an astable square wave generator. This provides enough harmonics from audio up to several hundred kilohertz and is useful for testing AM radio Receivers.

Circuit Diagram
Description

Activating sequence:-

Inputs		Coils Energized
D0	D1
0	0	AB
0	1	BC
1	0	CD
1	1	DA

To reverse the motor just reverse the above sequence viz. 11,10,01,00.

This project describes a digital clock with alarm function. It uses a PIC16F877 microcontroller to generate an accurate 1 sec delay with Timer0 using Roman’s zero error method. The time is displayed in large size font on a 4×20 character LCD that uses HD44780 display driver. You can synchronize the time with your computer time through a serial port.

Digital Alarm Clock Using PIC Circuit Diagram

The required power is provided through a 9 V wall adapter which is used to obtain a regulated +5 V power supply using a LM7805 IC. The microcontroller runs with a 20 MHz external clock. The backlight of LCD is driven by a PWM output from the microcontroller so that the back light intensity can be varied. The full software written in JAL is available to download. Source Code.