Basic concept of : Oscillating circuit, Circuit oscillators

1 - Circuit oscillators

1.1 - The concept of the oscillating circuit.

Oscillation circuit is used very much in the electronic equipment, such as the local oscillator circuit in block RF Radio, in the color TV channels, pulse generator circuit flow oscillations, pulses in TV screens, creating a sinusoidal wave for IC Vi handling operations v v ...

• Sine oscillator circuits


• Multi-harmonic oscillation circuit


• Oscillation circuit congestion


• Using IC oscillator circuit

1.2 - sine oscillator circuit
One might oscillators sine components from L - C or from quartz.

* Sine oscillator circuit using L - C

Sine oscillator circuit using L - C

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  Mach oscillation capacitor C1 // above oscillator circuit L1 forming L -C To maintain this oscillation signal is put into vacuum oscillations of Transistor B, R1 is becoming bias for transistors, R2 is becoming burdens to retrieve the oscillator signal, the winding-down play from foot E Transistor mass take the feedback effect to maintain oscillation. The oscillation frequency of circuit C1 and L1 depends on the formula

f = 1/2 p. (L1.C1) ^1/2

* Sinusoidal oscillator circuit using quartz.

Circuit with quartz oscillators.

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  X1: quartz oscillators, the oscillation frequency is indicated on the body of quartz, quartz-powered when it self-oscillating output wave frequency sin.thach he usually ranges from several hundred KHz to a few tens of MHz.


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  Q1 amplify the signal lights ranging from quartz and finally the signal is removed at the foot C.


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  Both the resistor R1 supplies power to both the natural quartz lamp Q1


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  R2 is to be found ghanh generate voltage drop to obtain a signal.

Quartz oscillators in color televisions, computer

1.3 - multi-harmonic oscillation circuit.

Multi-harmonic oscillation circuit square pulse generator

* You can order installation diagrams on the following parameters:

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  R1 = R4 = 1 K W


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  R2 = R3 = 100K W


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  C1 = C2 = 10μF / 16V


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  Q1 = Q2 = Lamp C828


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  Two LEDs


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  Source Vcc is 6V DC


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  The total cost of all 4,000 VND Components

* Explain the operating principle: When powered up, assuming Q1 lights ahead, Q1 lamp voltage reduction Uc => C1 as voltage Ub through Q2 lamp fell => Q2 off => Q2 increased lamp voltage Uc => via C2 do Q1 increased lamp voltage Ub => Q1 established state leads storm
Air and Q2 is off, after the time t, the current load on the capacitor C1 through R3 when this voltage> 0,6V the Q2 light guide => Q2 lamp voltage reduction Uc => continue so until Q2 saturated lead and Q1 is off, repeated state and create oscillation, oscillation cycle depends on the C1, C2 and R2, R3.

2 - Design by IC oscillator

XX555 IC oscillators; XX can be a TA or LA etc ...

Pulse oscillation circuit created by IC 555

• 
  
  Please purchase an IC 555 and mounting them yourself an oscillator circuit according to the principle diagram above.


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  Vcc supply IC can be used from 4,5V to 15V, the red line is positive pulse source, black bottom circuit is sound source.


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  Capacitor 103 (10nF) from 5 to mass foot is fixed and you can ignore (not fitting well)


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  When changing the resistors R1, R2 and C1 capacitor values ​​you
  will acquire oscillation frequency and pulse width at will according to
  mode.

T = 0.7 × (R1 + 2R2) × C1 and f =	1.4
	(R1 + 2R2) × C1

T = Time of a full cycle equal (s)
f = frequency of oscillation equal (Hz)
R1 = Resistance measured in ohm (W)
R2 = Resistance measured in ohm (W)
Capacitors C1 = calculated by Fara (W)

T = Tm + Ts
T: full cycle
Tm = 0.7 x (R1 + R2) x C1 Tm: time highs electricity
Ts = 0.7 x R2 x C1
Ts: time power low

Overall cycle time T including a high power Tm and low power time Ts

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  From the above formula we can create an oscillating pulse width square Tm and Ts any.


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  After you have created momentum with Tm and Ts T = Tm + we have Ts and f = 1 / T

* For example, you design the pulse generator circuit as shown below.

Pulse generator circuit has Tm = 0,1s, Ts = 1s

Exercise: Put on the oscillator circuit parameters:

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  C1 = 10μF = 10 x 10 ^-6 = 10 ^-5 F


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  R1 = R2 = 100K W = 100 x 10 ³ W


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  Count Ts and Tm =? Count frequency f =?

Bai:

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  We R2 Ts = 0.7 x 0.7 x 100.10 x C1 = ³ x 10 ^-5 = 0.7 s
  Tm = 0.7 x (R1 + R2) x C1 =
  = 0.7 x ³ x 10 ⁵ = 200.10 1.4 s


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  => T = Tm + Ts = 1,4s 0,7s = 2,1s +


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  => F = 1 / T = 1 / 2.1 ~ 0.5 Hz

3 - Oscillating congestion

Oscillation circuit congestion (Blocking OCS)

Mah oscillation principle stuffy fairly simple operation, widely used circuit in pulsed power supply (switching) circuit is made up as follows:

Oscillation circuit congestion

Oscillation circuit congestion include:

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  Transformer primary winding included 1-2 and 3-4 roll back, the secondary coil 5-6


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  Transistor Q engaged oscillate and act as light breaks open a capacity of variations generate electric current through the primary coil.


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  Back to disasters R1 (resistor primer)


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  R2, C2 is the resistor and capacitor feedback

There are two types of feedback are getting positive feedback and negative feedback, we consider the structure and principles of operation of each circuit.

* Oscillating stuffy negative feedback.

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  Negative feedback circuit with feedback coil wrapped 3-4 reverse with the primary winding 1-2, and resistor R1 bait small value of about 100K W, circuits are often used in the manufacture of small power approximately 20W return down


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  Operating principle: When powered up, the natural flow through R1 stimulus for Q1 led lights hard, flow through the primary coil 1-2 increased rapidly generate varying magnetic field => induction coil to feedback, negative way roll given feedback on foot lamp Q B through R2, C2 as B leg lamp voltage reduction Q <0V => Q lights immediately transitioned to interrupt, after the time t current through R1 loaded into capacitors C2 Q lamp foot B as pressure increases => Q lights cycle repeat guide
  Monday => fluctuating form.


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  Oscillation circuit congestion negative feedback has the advantage of fast oscillations, but have the disadvantage of electric shock damage prone lamp circuit Q therefore often not used in the large capacity power supplies.

* Oscillating stuffy positive feedback.

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  Oscillation circuit congestion positive feedback coil wrapped positive feedback 3-4 with 1-2 primary coil, resistor R1 primer large value of about 470K W


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  Because large numbers of R1, R1 to flow through the small initial bias => Q led lights ascending => generate varying magnetic field
  touch-up roll feedback => voltage obtained the positive feedback via feedback R2, C2 increases led lamps Q => and continue until saturation led lamp Q, Q When leading lights saturation, current through 1-2 coil unchanged => feedback voltage loss => B leg lamp voltage and lamp Q Q rapid decrease immediately transitioned to interrupt, second cycle repeated as Condition
  Initial Status and fluctuating form.


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  The advantage of this circuit is very safe from being varied from electric shock, and is used in the manufacture of large power line as the source of color television.

* Review the theory of electromagnetic induction:

The experiment on the phenomenon of electromagnetic induction in the transformer.

In experiments it was found that, bulbs flashed just in time to close or disconnect switch, meaning that when current flows through the primary coil changes, in case a current flows through the primary coil unchanged but also not make sense voltage on the secondary coil.