Switching Regulator (L296) Power Supply

L296 is a high current switching regulator that can provide up to 4 ampere current and its output voltage range is from 5.1v to 50v. For more information concern its datasheet.

Power supply current can be adjust by changing the value of P1 pot. P2 and P3 pots are used to vary the output voltage. C7-C10 capacitors are used for input voltage filtering whereas C2-C6 are for output voltage filtering purpose. 

Output voltage can be taken across X1-1 and X1-2 terminals or either X1-2 and X1-3 terminals. Note that the maximum input voltage of L296 is 50v so we have to step down ac voltage by using 50v 4amp or appropriate transformer. Don't forget to use heat sink for L296.

Schematic:

Final Assembly:

 

Components Required:
R1,R3,       10kΩ  Resistor
R2,            15kΩ  Resistor
R4,            3.2kΩ Resistor
R5(R6),     0.1Ω 5watt Resistor
P1-P2,      100kΩ  Pot
P3,            2k Pot
IC1,          L296
D1,           Byw29
D2,           6.8v Zener Diode
B3,           Bridge 5amp or higher
C1,           1.5nF Ceramic Capacitor
C2,           2.2uF/50v Electrolyte Capacitor
C3-C6,     220uF/50v Electrolyte Capacitor
C7-C10,   1000uF/100v Electrolyte Capacitor
C11,          33nF Ceramic Capacitor
C12,          390pF Ceramic Capacitor
C13,          10uF/50v Electrolyte Capacitor
C14,          100nF Ceramic Capacitor
L7,             SFT1240 inductor
Q1,            BC637
mics,          Heat Sink for L296 (optional for bridge rectifier)
                  2-way terminal for input voltage
                  3-way terminal for output voltage
                  Transformer

Bi-directional DC Motor Control

This simple circuit lets you run a DC motor in clockwise or anti-clockwise direction and stop it using a single switch. It provides a constant voltage for proper operation of the motor. The glowing of D1 through D3 indicates that the motor is in stop, forward rotation and reverse conditions, respectively.

Timer IC2 is wired as a monostable multivibrator to avoid false triggering of the motor while pressing switch SW1. Its time period is approximately 500 milliseconds (ms).

Suppose, initially, the circuit is in reset condition with Q0 output of IC1 being high. Since Q1 and Q3 outputs of IC1 are low, the outputs of IC3 and IC4 are high and the motor doesn’t rotate. D1 glows to indicate that the motor is in stop condition.

When you momentarily press switch SW1, timer 555 (IC2) provides a pulse to decade counter CD4017 (IC1), which advances its output by one and its high state shifts from Q0 to Q1. When Q1 goes high, the output of IC4 at pin 3 goes low, so the motor starts running in clockwise (forward) direction. D2 glows to indicate that the motor is running in forward direction.

Now if you press SW1 again, the high output of IC1 shifts from Q1 to Q2. The low Q1 output of IC2 makes pin 3 of IC4 high and the motor doesn’t rotate. D1 glows (via diode D2) to indicate that the motor is in stop condition.

Pressing switch SW1 once again shifts the high output of IC1 from Q2 to Q3. The high Q3 output of IC1 makes pin 3 of IC3 low and the motor starts running in anti-clockwise (reverse) direction. D3 glows to indicate that the motor is running in reverse direction.

If you press SW1 again, the high output of IC1 shifts from Q3 to Q4. Since Q4 is connected to reset pin 15, it resets decade counter CD4017 and its Q0 output goes high, so the motor does not rotate. D1 glows via diode D1 to indicate that the motor is in stop condition. Thereafter, the cycle repeats.

Schematic:

Final Assembly:

Components Required:
R1,            10kΩ  Resistor
R2,            47kΩ  Resistor
R3-R5,      330Ω (or 680) Resistor
R6-R7,      10kΩ  Resistor
IC1,           CD4017
IC2-IC4,   555 Timer
D1-D3,      LEDs
D4-D5,     1N4007 Diode
C1,           100nF Ceramic Capacitor
C2,           10uF/25v Electrolyte Capacitor
MT1,        DC Motor
SW1,        Push Button
B1,           9v Battery

Logic Probe

This Logic Probe is a low cost circuit analysis and troubleshooting tool for digital circuits like; microprocessor, and microcontroller circuits. The Seven Segment LED (Light Emitting Diode) display will visually show the binary state ("H" for Hi) and ("L" for Low) of the target digital, microcontroller, and microprocessor circuit under test or analysis. 

When the voltage is 2v or less than 2v it will indicate L. And high range is from 3v to source supply.

Schematic:

Components Required:

R1-R2,   1kΩ  Resistor
RP1,       330Ω Resistor Bank
DS1,       Seven Segment CA
IC1,        74ls04
B1,          5v Battery (Error in schematic voltage)

 

OPAMP FUNCTION GENERATOR

Square, sine and triangle waves are produced using an LM348 and passive components. The LM348 is a quad operational amplifier IC package; that is, it contains four separate opamps all in the one IC. They are marked A, B, C & D in the schematic diagram.

Square Wave:

One opamp (LM348:D) is used. The voltage level to pin 13 is set by the resistor divider pair R1 and R2. The input to pin 12 depends on two things; firstly the potential of pin 14, and secondly, the voltage output of opamp C at pin 8. When the input at pin 13 is higher than the input at pin 12 the output goes low. If it is lower then the output goes high. Switching back and forth between the two states causes a square wave to be produced. The time constant (R4+R5)C2 determines the frequency.

Triangle Wave:
You can also consider that opamp D is set up as a bidirectional threshold detector with positive feedback provided by R3. R3 also gives hysteresis. The output provides a bias which tends to keep it in its existing state before allowing switching to take place. The inverting input is set up at about half the opamp output swing voltage by resistors R1 and R2. Accordingly the signal required from opamp C to cause switching is offset from this midpoint voltage by R11/(R11+R3) which is approximately2/3 the voltage from midpoint to swing limit and is symmetrical above and below the switching point.

Opamp C is set up as an integrator. It performs the mathematical operation of integration with respect to time. For a constant input the output is a constant multiplied by the elapsed time, that is, the output is a ramp. Since the input signal goes to the inverting input, a high input will produce a ramp down and a low input will produce a ramp up. The input signal is a square wave symmetrical about the midpoint potential. The current this potential produces through R4 and R5 is constant so the up and down ramps are of equal gradient and the resultant triangular wave is symmetrical. Any increase in the trimpot R5 reduces the current and the integration constant which lowers the gradient of the ramp. The switching levels havenot changed so the frequency reduces while the amplitude remains constant. In a similar way the current depends on the value of integration capacitor. Accordingly the integration constant and hence the frequency vary with the value of the capacitor. (Higher value, lower frequency since the capacitor takes longer to charge.) If C2, for example, is increased to say 680nF then the minimum frequency will be less than 1Hz. The output triangle wave does not require amplification but it does require buffering so that that loading does not affect the waveform generator circuit. It is buffered here with opamp A connected as a unity gain buffer. Unity gain is achieved by directly coupling back the output to the inverting input.

Sine Wave:

A pseudo or imitation sine wave is produced by a wave shaping circuit. A diode is a non-linear device. As the potential difference across it increases the current rises in the characteristic way published in all textbooks. This circuit 'joins together' this characteristic curve to produce an approximation to a sine wave. Two diodes have been joined together as a series pair in order to provide a higher amplitude than would be obtained using only a single diode. The shape of the pseudo sine wave could be improved at any particular frequency by filtering, but filtering will cause distortion at lower frequencies and loss of amplitude at higher frequencies. You can have perfect sine waves at particular frequencies by switching in appropriate filters at those frequencies. 

The sine wave is sensitive to loading and must be buffered. It is also low in amplitude and needs amplification. R9 & R10 set the gain of opamp B by forming a voltage divider between the source and the output. If the wave shaper voltage is 1 volt higher than the reference (at the non-inverting input) the opamp reduces the output voltage until the inverting input voltage set by the divider is equal to the non-inverting voltage. The ratio of the values of R10 to R9 give the gain. The gain here is about 2.

Schematic:

Final Assembly:

 

Components Required:

R4,   560Ω  Resistor
R7,   820Ω  Resistor
R8,   1kΩ  Resistor
R11,   8.2kΩ  Resistor
R6,   10kΩ  Resistor
R3,   15kΩ  Resistor
R1,   82kΩ  Resistor
R2,   100kΩ  Resistor
R9,   470kΩ  Resistor
R10,   1MΩ  Resistor
R5,   1MΩ  variable Resistor
D1-D4,   1N4004 Diode
IC1,    lm348
C1-C2,  47n ceramic capacitor

White LED Flood Lamp

The circuit is too simple and energy saving design. Its current consumption is practically nil but can provide light like a 20 watt CFL lamp.

The circuit uses capacitive reactance to drop high volt AC to low volt AC. This reduces power loss due to heat dissipation. The value of the AC capacitor can be calculated using the formula X c= 1/ (2 π f C) where, Xc is the reactance in ohms, C the capacitance in farads and f the mains frequency. Xc = Vrms / I where Vrms is the input voltage and I is the current flowing through LEDs. The low volt AC (around 100 volts) dropped by C1 is then rectified by a full wave rectifier formed of D1-D4.

Capacitor C2 act as a ripple remover and buffer. Zener diode ZD regulates DC to 68 volts and prevents excess reverse voltage across the LEDs during the negative half cycles.R1 is a must in the circuit to bleed the stored current from C1 when the circuit in unplugged. C1 can store more than 400 volts for many days if R1 is not connected.

Note! Do not touch any points or trouble shoot when the circuit is connected to mains.

Schematic:

Components Required:

R1,   470KΩ  Resistor 

R2,   100Ω  1w Resistor  

C1,    225k, 400v capacitor 

C2,    1000uF, 100v electrolyte capacitor  

BR1,   1N4007 Diodes or bridge

D2-D21,   ultra bright white LEDs 

D1,   68v 1w Zener Diode