A simple method of converting an analog voltage signal (from a sensor) into a digital signal (ones and zeros) that microcontrollers or other digital devices can understand is to use an analog to digital converter ADC circuit that uses a IC 555.
Because it is inexpensive and simple to construct, it is an excellent learning activity.
A simple and affordable way to construct a basic analog to digital converter ADC is with the IC 555 chip.
The 555 IC functions as a continuous ON/OFF pulse generator in this circuit.
The discharge pin and the threshold pin are the two control points on the IC 555 chip that are directly connected to the analog voltage you send in.
A small capacitor C1 inside the circuit stores voltage and the difference between the input and output voltages determines how wide the output pulses are and how long they stay on.
Circuit Working:
Parts List:
| Category | Description | Quantity | Wattage |
|---|---|---|---|
| Resistors | 330Ω | 1 | 1/4W |
| 430Ω | 1 | 1/4W | |
| 100Ω | 2 | 1/4W | |
| Capacitors | Ceramic 0.1μF | 1 | |
| Electrolytic 1μF 25V | 1 | ||
| Semiconductors | IC 555 | 1 | |
| Transistor BC547 | 1 |
IC 555 ADC vs. Conventional ADC:
Conventional ADCs take periodic samples of the analog signal and translate them into digital codes with a predetermined bit count.
The 555 IC in this circuit produces a pulse width modulation PWM output where the analog input voltage is represented by the duty cycle, which is the percentage of the pulse high time in a cycle.
The IC 555 Circuits Operation:
One important component is the timing capacitor C1.
The analog input voltage directly affects how long it takes to charge and discharge.
Higher analog voltages charge C1 more quickly which causes the timer to produce shorter output pulses (lower duty cycles).
A lower voltage, on the other hand causes the C1 to charge more slowly and produces a longer output pulse (higher duty cycle).
Transistor and Improvements:
To change the polarity of the output pulse, the transistor Q1 may be utilized as an inverter.
For applications requiring low resolution this ADC circuit makes an excellent foundation.
Use operational amplifiers and successive approximation approaches for increased precision and resolution.
Formulas:
The IC 555 is frequently used in an astable multivibrator to provide a continuous square wave output.
An analog to digital converter ADC may utilize this kind of circuit to generate a clock signal, among other timing and clock production uses.
The following is how to determine the astable mode of the IC 555 essential characteristics and formula:
Calculation of Frequency:
R1, R2, and C1 parameters determine the oscillation frequency in astable mode.
The oscillations frequency f is determined by:
f = 1.44 / (R1 + 2 * R2) *C1
where,
- The variables that represent the frequency (f) in hertz Hz
- Resistances R1 and R2 in ohms Ω
- Capacitance C1 in farads F.
Duty Cycle Calculation:
The square wave outputs duty cycle D the ratio of the outputs high time to the entire period, is found by:
D = R1 + R2 / R1 + 2 * R2
where,
- The duty cycle D is expressed as a percentage.
The IC 555 is used to create an astable multivibrator circuit using this formula and configuration, which is intended for the purpose of producing a clock signal in analog to digital converter applications.
Based on the particular needs and features of the ADC utilized in the circuit, adjustments should be made to R1,R2 and C1.
How to Build:
To build a Analog to Digital Converter Circuit using IC 555 you need to follow the below mentioned steps:
- Gather all the required circuit parts as shown in diagram above.
- Connect pin 1 of IC1 555 to ground.
- Connect pin 2 with pin 6 of IC1 555.
- Connect pin 3 of IC1 555 to the base of transistor Q1 through resistor R3.
- Connect pin 4 of IC1 555 to positive supply of +5V DC.
- Connect pin 5 of IC1 555 to ground through capacitor C2.
- Connect pin 6 to pin 2 of IC1 555.
- Connect pin 7 of IC1 555 to analog input through resistor R1.
- Connect pin 8 to pin 4 of IC1 555 to positive supply +5V DC.
- Connect collector of transistor Q1 to digital pulse output , connect base of transistor Q1 to pin 3 of IC1 555 through resistor R3, connect emitter of transistor Q1 to ground.
- Connect resistor R4 from collector of transistor Q1 to positive supply
- Connect in series resistor R1, resistor R2 and capacitor C1 from analog input to ground.
Safety Measures:
- Work in a well ventilated area
- Use appropriate tools
- Beware of hot components
- Wear safety glasses to protect your eyes
- If you are a beginner start with a basic circuit and gradually progress to more complex ones.
Conclusion:
To conclude, the 555 IC based Analog to Digital Converter ADC circuit provides an easy and affordable method of converting simple analog data into digital representation.
Its simple design and low component count make it an excellent learning tool even if it lacks the high resolution and precision of specialist ADC chips.
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