• Skip to main content
  • Skip to primary sidebar

Homemade Circuit Projects

Get free circuit help 24/7

New Projects | Privacy Policy | About Us | Contact | Disclaimer | Copyright | Videos 

Op Amp Basics | 555 Circuits | Hobby Circuits | LED Driver | For Beginners | Basic Circuits | Transistor Circuits | Voltage Regulators 

Transistor Astable Calculator

  • The negative voltage passing through the capacitor C2 turns off the transistor Q1 which causes the capacitor C1 to initiate charging through resistor R and Vcc, as well as through the base emitter of transistor Q2. This causes the transistor Q2 to acquire the momentary ON state.
  • During the process, the capacitor C2 gradually discharges until it's completely empty, and then it starts charging from opposite direction through R2.
  • As soon as the voltage in capacitor C2 is sufficient to turn ON transistor Q1, Q1 switches ON and forces capacitor C1 to initiate discharging.
  • The above process keeps recycling causing a sustained and alternate switching of the transistors as long as the circuit in the powered state.

Design

 

R – Collector Resistor

The resistance R needs to be dimensioned so that it is able to limit the collector current Ic below the specified threshold.

The following formula represents it:

R = V/Ic ,

where V is the voltage across the resistor R.

Normally this could be expressed as, V = (Vcc – Vce) = (Vce – 0.3)  however in cases where an emitter load such as an LED is utilized, the expression may be modified as:

V = (Vcc – Vce – Vled) , where Vled is the voltage drop across LED.

In most cases the maximum collector current Ic could be much higher than than the required for emitter load current. During such instances Ic could be tailored in such a way that it stays below the max current specification of emitter load.

Therefore,

  • R = (Vcc – Vce – Vload) / Ic

R1 & R2 – Base Resistors

R1 & R2 must be selected to obtain the desired collector current during saturation state.

  • Min. Base Current, Ibmin = Ic / β, where β is the hFE of the transistor
  • Safe Base Current,Ib =  10x Ibmin= 3 x Ic / β
  • R1, R2 = (Vcc – Vbe) / Ib

T1 & T2 – Time Period

  • T2 = OFF Period of transistor Q1 = ON Period of Transistor Q2 = 0.693R2C2
  • T1 = OFF Period of transistor Q2 = ON Period of Transistor Q1 = 0.693R1C1

From these expressions we can evaluate the value of C1 and C2.

Duty Cycle

It may be defined as the ratio of  time Tc when the output is high to the total time period T of the cycle.

Thus here, Duty Cycle = Toff/(Toff + Ton) when the output is acquired from the collector of the transistor T.

 

Calculator

 

  Seconds
  Seconds
  V
  V
  V
  mA
  V





Reader Interactions

Have Questions? Please post your comments below for quick replies! Comments should be related to the above artcile Cancel reply

Your email address will not be published. Required fields are marked *



Primary Sidebar

Categories

  • 3-Phase Power (15)
  • 324 IC Circuits (19)
  • 4017 IC Circuits (52)
  • 4060 IC Circuits (27)
  • 555 IC Circuits (99)
  • 741 IC Circuits (20)
  • Arduino Engineering Projects (83)
  • Audio and Amplifier Projects (126)
  • Battery Chargers (83)
  • Car and Motorcycle (96)
  • Datasheets (78)
  • Decorative Lighting (Diwali, Christmas) (33)
  • Electronic Components (101)
  • Electronic Devices and Circuit Theory (36)
  • Electronics Tutorial (121)
  • Fish Aquarium (5)
  • Free Energy (34)
  • Fun Projects (14)
  • GSM Projects (9)
  • Health Related (22)
  • Heater Controllers (31)
  • Home Electrical Circuits (107)
  • How to Articles (20)
  • Incubator Related (6)
  • Industrial Electronics (28)
  • Infrared (IR) (40)
  • Inverter Circuits (98)
  • Laser Projects (13)
  • LED and Light Effect (98)
  • LM317/LM338 (22)
  • LM3915 IC (25)
  • Meters and Testers (69)
  • Mini Projects (150)
  • Motor Controller (69)
  • MPPT (7)
  • Oscillator Circuits (25)
  • PIR (Passive Infrared) (9)
  • Power Electronics (35)
  • Power Supply Circuits (86)
  • Radio Circuits (10)
  • Remote Control (50)
  • Security and Alarm (66)
  • Sensors and Detectors (132)
  • SG3525 IC (5)
  • Simple Circuits (75)
  • SMPS (29)
  • Solar Controllers (63)
  • Timer and Delay Relay (55)
  • TL494 IC (5)
  • Transformerless Power Supply (9)
  • Transmitter Circuits (42)
  • Ultrasonic Projects (17)
  • Water Level Controller (45)

Calculators

  • AWG to Millimeter Converter
  • Battery Back up Time Calculator
  • Capacitance Reactance Calculator
  • IC 555 Astable Calculator
  • IC 555 Monostable Calculator
  • Inductance Calculator
  • LC Resonance Calculator
  • LM317, LM338, LM396 Calculator
  • Ohm’s Law Calculator
  • Phase Angle Phase Shift Calculator
  • Power Factor (PF) Calculator
  • Reactance Calculator
  • Small Signal Transistor(BJT) and Diode Quick Datasheet
  • Transistor Astable Calculator
  • Transistor base Resistor Calculator
  • Voltage Divider Calculator
  • Wire Current Calculator
  • Zener Diode Calculator

© 2023 · Swagatam Innovations