TASK A:

IC 555 Timer

The circuit diagram for the timer IC 555 is shown in the image below.

Figure 1: IC555 with discrete components

The IC555 has a few discrete components, such as transistors, resistors, and the like, as seen
in figure 1.

A voltage divider with resistors of the same value divides the biasing voltage (Vcc) into three
equal portions. This 1/3 Vcc goes to the trigger comparator's non-inverting terminal, while
the other 2/3% goes to the threshold comparator's inverting terminal. Flip-flop inputs R and S
are connected to the outputs of both comparators.

When Q is high, it drives a discharging transistor, which provides a discharge channel to an

Q rises when the trigger comparator gives a high signal, which triggers flip-flop reset when
the trigger input pin receives a negative trigger voltage of 1/3 Vcc.

The threshold comparator outputs a high voltage, which flips the flip flop when supplied to
the threshold input pin with a positive trigger voltage >2/3 Vcc. The Q output will rise, while
the chip's output will decrease. The discharge transistor, which provides a discharge channel
to an external capacitor, is turned on at that moment. Flip-flops remain enabled when the
reset input is set to a high value. Flip-flops are disabled if the voltage is low, hence the output
will be low.
 Figure 2: 555 Timer IC

There are now eight pins for a 555 Timer IC, as seen in figure 2,

1. Ground
2. Trigger
3. Output
4. Reset
5. Control
6. Threshold
7. Discharge
8. Power or VCC

Pin 1. Ground: It is not obvious what purpose this pin serves. As is customary, it has a ground
line that links it to the earth. This pin has to be connected to the ground in order for the timer
to work properly.

Pin 8. Power or VCC: The purpose of this pin is similarly unknown. Positive voltage is
applied to it. A positive voltage of between +3.6v and +15v must be applied to this pin in
order for the timer's clockwork mechanism to operate properly.

Pin 4. Reset: The timer chip contains a flip-flop, as mentioned above. It is the flip-output
flop's that directly controls the chip's output at pin3.

The flip-MR flop's reset pin is connected directly to the reset pin (Master Reset). If we look
closely, we can make out a little circle on the flip-MR. Flop’s you can see the MR (Master
Reset) pin has been set to the LOW (trigger) condition by looking at the small bubble here.
Flip-flops need a change in the MR pin voltage from HIGH to LOW in order to reset. It is
difficult to get the flip-flop all the way down to the LOW setting using this step-down
reasoning, though. This means that the output is LOW, regardless of whatever pins are
connected.

To prevent the flip-flop from hard resetting, this pin is wired to VCC.
Pin 3. OUTPUT: The purpose of this pin is similarly unknown. This pin is derived from a
transistor's PUSH-PULL arrangement.

Figure illustrates an example of a push-pull setup that may be used. It is possible to link the
output of a flip-flop to the bases of two transistors. If the flip-flop output shows a logic high
and +V1 is present at the output, the NPN transistor will be switched on. When the logic level
at the flip-flop output is LOW, the PNP transistor is activated, and its output is dragged to
ground or –V1 (depending on the implementation).

The employment of flip-flop control logic is what makes it possible to generate a square
wave at the output. The primary purpose of this configuration is to lessen the burden that the
flip-flop places on the user. Because a flip-flop can never provide an output of 100 mA, the
answer to this question is obvious.

Until far, we've only spoken about pins that don't modify the output's state under any
condition. The remaining four pins of the timer chip are the emphasis of this section, since
they determine the output state.

It is linked to the negative input of comparator one's comparator one control pin.

VCC and GROUND are connected at 9 volts, thus we can use this as an example. In the
control pin, the voltage will be VCC2/3 (for VCC = 9, pin voltage=92/3=6V ).

User control of the first comparator is provided via this pin. The reset of the flip-flop is fed
the output of comparator one, as indicated in the image above. A new voltage may be applied
to this pin by connecting it to +8 volts. The flip-flop is reset and the output is dragged down
when the THRESHOLD pin voltage reaches +8V.

After charging the capacitor to 2/3VCC (+6V for 9V supply), the V-out will be at its lowest.
In this case, the control pin has a separate voltage applied to it (comparator one negative or
reset comparator).

Control pin voltage must be reached before the capacitor may be charged. The signal's turn
on and turn off times fluctuate as a result of this force capacitor charging. As a result, the
output has a different turn-on/tear-off ratio than before.

Normally, a capacitor is used to hold this pin low. To keep the working environment free of
unwanted sounds.

Pin 2. TRIGGER: The comparator two negative input is used to drag the trigger pin. One of
the comparator's two outputs is attached to the flip-SET flop's pin for control. We obtain a
high voltage at the timer output when the comparator two output is high. As a result, we can
say that the timer output is controlled by the trigger pin.

Because it is linked to the inverting input of the second comparator, which in turn causes it to
increase, a low voltage on the trigger pin causes the output voltage to rise. This, in turn,
causes the output voltage to climb. The trigger pin voltage must be less than VCC1/3
(assuming VCC is 9 volts, VCC(1/3)=9*(1/3)=3 volts). This means that for a 9-volt power
source, the trigger pin voltage must fall below 3 volts before the timer's output will go high.

It is always high when this pin is linked to ground.

To reset the timer, the threshold pin voltage must fall below a certain level. The
comparator1's positive input is used to power the threshold pin.

The difference in voltage that is present between the THRESOLD pin and the CONTROL pin
is what determines the reset logic. In this particular instance, the flip-flop is reset, and the
output is disabled. If there is a positive difference, the output will be determined by the logic
of the SET pin.

If the control is turned on, the pin will be open. The flip-flop may be reset by applying a
supply voltage that is either more than or equal to VCC*(2/3). As a direct result, the amount
of output is reduced.

As a consequence of this, we are able to declare that the voltage of the THRESHOLD pin
determines whether the control pin should be open while the output should be low.

Pin 7 is called the DISCHARGE pin, and it is linked to the open collector of the transistor.
Because the base of the transistor is connected to Qbar and the discharge pin was
disconnected from Q1, in the event that the output is low or the flip-flop is reset, the
discharge pin will be pulled to ground. When power is supplied to the base of the transistor,
the Q1 transistor is activated since Qbar is in the high state while Q is in the low state.

TASK B:
AC Sweep

Parameters Values
R1 (ohm ) 150000
C1(pF) 1100
Start frequency (Hz) 20
Stop Frequency (Hz) 1370000

Circuit Diagram:
 Figure 3: AC Sweep Circuit

Graph:

Figure 4: AC Sweep Graph

TASK C:
LED Dimmer Circuit with 555 Timer
 Figure 5: LED Dimmer Circuit

Introduction

Dimmers are often used to control the fan's speed in an air conditioning system. The device
can also work with a variety of different devices, whether they be AC or DC. Changing the
speed of your room's fan, for example, may have the effect of altering the speed of other
motors throughout your home. This article, on the other hand, focuses on adjusting the
brightness of light. "LED Dimmer Circuit with 555 Timer IC" is what we'll be making in this
tutorial. Timer, oscillator, and pulse generator circuits all employ 555 timer ICs, which have
8 pins and are the most often used IC. This is also being used to produce PWM pulses in this
instance.

Figure 6: 555 Timer IC

The 555 IC is used in this simple and easy LED dimmer circuit for LED strips. A dimmer
circuit for LED Strips is something I can teach you how to do,
 Figure 7: LED Dimmer Circuit

Working Principle of LED Dimmer Circuit

555 timers provide the foundation of this design. 555 timers are used to generate PWM
pulses. As a result, a N channel power MOSFET is driven by the PWM pulses.

555 timers need additional components, such as resistors, capacitors, and potentiometers.

The duty cycle of the PWM signal may be adjusted using the potentiometer.

Full brightness is achieved at 100% duty cycle, whereas half brightness is achieved at 50%
duty cycle. 0% signifies that the sun will not be shining.

As a result, you'll have the ability to run high-ampere LEDs in this circuit.

When used with larger loads, however, the circuit will still operate for 12v appliances. This
means that the bottom point will remain the same, but the positive voltage will be higher, for
example, 24 Volts instead of the usual 15.

The IRFZ44N n channel MOSFET is used in this project, but if you want to use a different
MOSFET, make sure you've read all the datasheets first.

Note:

The hand tool should be used with a little amount of precision. Soldering will be a lot simpler
on a breadboard.
Make the necessary connections using a heat shrinking tube.

The LED dimmer circuit does not need a flyback diode. To avoid damage to the transistor
from the EMF generated by the motor's reverse current, a flyback diode should be used
instead.

TASK D and E:
MULTISIM SIMULATION

Figure 8: Multisim Simulation

OUTPUT:

Figure 9: Output Graph

Figure 10: Front Side

Figure 11: Back Side

Figure 12: Assemble Components

References
M.H., R. (1999). Microelectronics Circuit Analysis and Design. PWS Publishing Co,.

Nandanavanam, N. (August 2015). An Imprint of IC 555 Timer in the Contemporary.

Rajender Kumar, S. D. (n.d.). Design and Implementation of Astable Multivibrator, Krishan

Sanjay K Tupe, S. S. (2009). Comparative study of different spice software’s using Astable.
IJRTE, page-2829 vol2,.