Power Point (555 Timer Ic and Stepper Motor)

8/3/2019 Power Point (555 Timer Ic and Stepper Motor)

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555 IC TIMER


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INTRODUCTION


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The 555 timer is one of the most popular andversatile integrated circuits ever produced.

It includes 23 transistors, 2 diodes and 16resistors on a silicon chip installed in an 8-pinmini dual-in-line package (DIP).

8-pin IC

It is an integrated circuit (chip) implementing avariety of timer and multivibrator applications.

Composed of 2 comparators, one ohmic ladder,one flip- flop and discharging transistor.

Capable of producing accurate time delays oroscillations.

Use in analog and digital application.


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Pins of the 555 timer are as follows:

Ground- connection for chip.

Trigger 555 timer- triggers when this pin transitions from voltage at Vcc to 33%

voltage at Vcc.

- Output pin goes high when triggered.

Output pin of 555 timer

Reset - Resets 555 timer when low.

Vcc- 5V to 15 V supply input.

Discharge - Used to discharge a capacitor.

Threshold - Used to detect when the capacitor has charged.

- The Output pin goes low when capacitor has charged to 66.6% of

Vcc.

Control Voltage- Used to change Threshold and Trigger set point voltages.


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ADVANTAGES

Low- cost

High operating voltage (5- 15V)

High powered IC

Can be triggered by small amount of current


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HISTORY The IC was designed and invented by Hans R.

Camenzind.

It was designed in 1970 and introduced in1971 by Signetics (later acquired by Philips).

The original name was the SE555/NE555 andwas called "The IC Time Machine".

Even today, Samsung in Korea manufacturesover 1 billion units per year (2003).


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DIFFERRENT VERSIONS OF 555 IC

TIMER

NE555

- it is the most popular version of 555 IC.


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SPECIFICATIONS OF NE555:

Supply voltage (VCC)- 4.5 to 15 V

Supply current (VCC = +5 V)- 3 to 6 mA

Supply current (VCC = +15 V)- 12 to 15 mA

Output current (maximum)- 200 mA

Power dissipation- 600 mW

Operating temperature - 0 to 70 C


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ICM7555

- low power version of 555 IC TIMER- has a maximum output current of 20mA with

a 9V supply

- same pin arrangement as a standard 555 IC


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556

Dual version of the 555

Housed in 14-pin package


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LM555 TIMER

It is a highly stable device for generatingaccurate time delays or oscillation.

Additional terminals are provided for

triggering or resetting if desired. In the time delay mode of operation, the time

is precisely controlled by one external resistor

and capacitor.


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Features:

Direct replacement forSE

555/NE

555 Timing from microseconds through hours

Operates in both astable and monostable modes

A

djustable duty cycle Output can source or sink 200 mA

Output and supply TTL compatible

Temperature stability better than 0.005% per C

Normally on and normally off output

Available in 8-pin MSOP package


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1. Monostable Operation

2. Astable Operation

3. Bistable Operation

4. Inverting Buffer Operation


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A monostable circuit produces a

single output pulse when triggered. It iscalled a monostable because it is stable

in just one state: 'output low'. The

'output high' state is temporary.

Monostable Operation


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The monostable (one-pulse) operation can be understood as

consisting of these events in sequence:

(up to t = 0) A closed switch keeps the C uncharged:

Vc = 0, Vout is low.

1. (at t = 0) A triggering event occurs: Vtriggerdrops below Vcontrol/2, very

briefly. This causes the switch to open.

2. (0 < t < t1) Vc(t) rises exponentially toward Vcc with time constant

RC. Vout is high.

3. (at t = t1) Vc reaches Vcontrol. This causes the switch to close, which

instantly discharges the C.

4. (from t = t1 on) A closed switch keeps the C uncharged: Vc = 0, Voutis low.


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The monostable 555 timer circuit can beused in the following applications:

1. Debounce a momentary / pushbutton

switch.2. Turning on an actuator for a set period

of time.

3. Turn an output from a resistive sensor

from analog signal to digital signal.


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Astable OperationAn astable circuit produces a 'square wave',

this is a digital waveform with sharp transitionsbetween low (0V) and high (+Vs). Note that the

durations of the low and high states may be

different. The circuit is called an astable

because it is not stable in any state: the outputis continually changing between 'low' and

'high'.


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The astable (pulse train) operation can be understood as consisting of

these events, starting at a point where Vc = Vcontrol/2:

1. (at t = 0) Vc = Vcontrol/2, and the switch opens.

2. (0 < t < t1) Vc(t) rises exponentially toward Vcc with time constant

(R1+R2)C. Vout is high.

3. (at t = t1) Vc reaches Vcontrol. This causes the switch to close.

4. (t1 < t < t1 + t2) Vc(t) falls exponentially toward zero with time

constant R2C. Vout is low.

5. (at t = t1 + t2 = T) Vc reaches Vcontrol/2. This causes the switch toopen. These conditions are the same as at step 1, so the cycle

repeats every T seconds.


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The astable 555 timer circuit can be usedin the following applications:

1. Modulate transmitters such as

ultrasonic and IR transmitters.

2. Create an accurate clock signal.

3. Turn on and off an actuator at set time

intervals for a fixed duration.


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Bistable Operation

The circuit is called a bistable

because it is stable in two states:

output high and output low. It is also

known as a 'flip-flop'.


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It has two inputs:

Trigger(555 pin 2) makes the output high.

Trigger is 'active low', it functions when < 1/3 Vs.

Reset (555 pin 4) makes the output low.

Reset is 'active low', it resets when < 0.7V.


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Inverting Buffer Operation

It is an Inverting Buffer or NOT Gate

because the output logic state (low/high) is theinverse of the input state:

Input low (< 1/3 Vs) makes output high, +Vs

Input high (>2

/3 Vs) makes output low, 0V


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555 inverting buffer circuit(a NOT gate)

NOT gate symbol


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APPLICATIONS


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1. Dark Detector

It will sound an alarm if it gets too dark all over

sudden. The LDR enables the alarm when light

falls below a certain level.


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2. Power Alarm

This circuit can be used as a audible 'Power-out Alarm'. It uses the 555 timer as an oscillator

biased off by the presence of line-based DC voltage.


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3. Tilt Switch

It shows how to use a 555 timer and a smallglass-encapsulated mercury switch to indicate 'tilt'.


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4.. Metronome

A device that produces a regulated aural, visualor tactile pulse to establish a steady tempo in the

performance of music.


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5. Ten-Minute Timer

Can be used as a time-out warning for HamRadio.


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6. Schmitt Trigger

It cleans up any noisy input signal in a nice,clean and square output signal.


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Other Applications

Generate a single pulse.

Debounce a switch create a clean pulse when a

noisy switch is pressed.

Generate a time delay.


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Measure time elapsed between events.

Measure time duration of events.

Measure frequency of a pulse train.


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Generate a pulse train of specified duty cycle andfrequency.

Create a variable-frequency train of pulses.

Generate interesting sounds (sirens, two-tone

alternation, dial tone, busy signal, etc.).


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STEPPER MOTOR


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STEPPER MOTOR

Astepper motoris a digital version of the

electric motor.

The predecessor of the stepper motor was theservo motor. Today

Stepper motor vs servo motor.


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Characteristics

Stepper speed characteristics.


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OPERATION


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FULL STEP

Using a simple two phase stepping motor with one pole

pair as an example the phase switching sequence when

driven in full step mode is as follows:

PHASE SWITCHING SEQUENCES


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Start = Step angle 0 -WindingsW1 andW2 are energized producing a

north and south pole which attracts the rotor's respective poles and

holds the rotor in position.Step 1 = Step angle 90 -WindingW1 remains the same but the current

flow in windingW2 is switched (reversed). This results in a movement of

the stator's magnetic field which the rotor follows until it is held at the

new position.


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HALF STEP

Using the same stepping motor driven in half step

mode doubles the resolution (steps per rotation).

Although the switching sequence is similar, instead of

just reversing the flow of current through a phase, a

phase is switched off, allowing the rotor to follow and

take up even more positions. The sequence for one

rotation is as follows:



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Construction

Stepping motors are electromagnetic, rotary,

incremental devices which convert digital

pulses into mechanical rotation


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The benefits offered by stepping motors include:

a simple and cost effective design

high reliability maintenance free (no brushes)

open loop (no feed back device required)

known limit to the 'dynamic position error'


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Although various types of stepping motor

have been developed, they all fall into three

basic categories.

variable reluctance (V.R)

permanent magnet (tin can)

hybrid


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variable reluctance or V.R.

motor consist of a rotor and stator each

with a different number of teeth. As the

rotor does not have a permanent

magnet it spins freely


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permanent magnet (PM) or tin can

motor is perhaps the most widely used stepping motor innon-industrial applications. In it's simplest form the motor

consists of a radially magnetized permanent magnet rotor and

a stator similar to the V.R. motor.


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The Hybrid

probably the most widely used of all stepping motors.

Originally developed as a slow speed synchronous PM motor

it's construction is a combination of the V.R. and tin can

designs. The Hybrid consists of a multi-phased toothed stator

and a three part rotor (single stack).


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The increasing demands on the modern

stepping motor system of reducing acoustic

noise, improving drive performance while at

the same time reducing costs were satisfied in

the past with two main types ofHybrid

stepping motor. The 2 phase which has

generally been implemented in simpleapplications and the 5 phase which has

proven to be ideal for more the demanding of

tasks


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The advantages offered by the 5 phase included:

higher resolution lower acoustic noise

lower operational resonance

lower detent torque


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Although the characteristics of the 5 phase

offered many benefits; especially when micro

stepping, the increased number of power

switches and the additional wiring required

could have an adverse affect on a system's

cost.


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With advances in electronics allowing circuits

with ever higher degrees of integration and

ever more features to be realized, SIG Positec

saw an opportunity and took the initiative in

their ground breaking development in

stepping motor technology.


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The 3 phase Hybrid stepping motor

Although similar in construction to other

Hybrid stepping motors (see fig. 4),

implementing 3-phase sine drive technology

made it possible for the number of motor

phases to be reduced leaving the number of

rotor pole pairs and the drive electronics to

determine the resolution (steps perrevolution).


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As 3-phase technology has been used for

decades as a cost effective method of

generating rotating fields, the advantages of

this system are self evident. The 3-phase

stepping motor was therefore a natural

progression incorporating all the best features

from the 5-phase system at a significant costreduction.


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Stepping motor resolution and step angle

As already mentioned, the resolution (number

of steps) and step angle of a stepping motor is

dependent on:

the number of rotor pole pairs

the number of motor phases

the drive mode (full or half step)


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RESONANCE


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The term used for the effect which occurs

when a stepping motor is stepped at its

natural oscillating frequency. Stepping at this

natural frequency can result in the stepping

motor desynchronizing or even stalling.


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A stepping motor's resonance can be

calculated using the formula:


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Stepper Motors, Servos, and RC

Servos


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STEPPER MOTOR

Astepper motor (or step motor) is a

brushless, synchronous electric motor that can

divide a full rotation into a large number of

steps. The motor's position can be controlled

precisely, without any feedback mechanism


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SERVOS

Aservomechanism, or servo is an automatic device

which uses error-sensing feedback to correct the

performance of a mechanism. The term correctly

applies only to systems where the feedback or error-correction signals help control mechanical position

or other parameters. For example an automotive

power window control is not a servomechanism, as

there is no automatic feedback which controlspositionthe operator does this by observation.


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RC SERVOS

RC servos are hobbyist remote control devices servos typically employedin radio-controlled models, where they are used to provide actuation forvarious mechanical systems such as the steering of a car, the flaps on aplane, or the rudder of a boat.

RC servos are composed of a DC motor mechanically linked to apotentiometer. Pulse-position modulation (PPM) signals sent to the servoare translated into position commands by electronics inside the servo.When the servo is commanded to rotate, the DC motor is powered untilthe potentiometer reaches the value corresponding to the commandedposition.

Due to their affordability, reliability, and simplicity of control bymicroprocessors, RC servos are often used in small-scale roboticsapplications.


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Power Point (555 Timer Ic and Stepper Motor)