The easy way to change sensor voltage (analog) to digital (1 and 0) is by using Analog to Digital Converter Circuit using IC 555.
This method is cheap and easy for good learning.
IC 555 chip can make simple ADC with low cost.
In this circuit 555 IC work like ON/OFF pulse maker.
Two pins like discharge and threshold connect to analog input voltage.
One small capacitor C1 store voltage.
How long output stays ON depends on input voltage and output voltage difference.
Circuit Working:
Parts List:
| Category | Description | Quantity |
|---|---|---|
| Resistors | 330Ω 1/4 watt | 1 |
| 430Ω 1/4 watt | 1 | |
| 100Ω 1/4 watt | 2 | |
| Capacitors | Ceramic 0.1μF | 1 |
| Electrolytic 1μF 25V | 1 | |
| Semiconductors | IC 555 | 1 |
| Transistor BC547 | 1 |
IC 555 ADC vs Normal ADC:
Normal ADC take signal samples at set time and give digital number with fixed bits.
IC 555 give PWM signal.
Analog voltage control duty cycle how long pulse stay high.
How 555 Circuit Work:
Important part is capacitor C1.
Analog voltage control how fast C1 charge and discharge.
High voltage charge C1 fast with short pulse and with low duty cycle.
Low voltage charge C1 slow with long pulse and with high duty cycle.
Transistor and Better Circuit:
Transistor Q1 can flip the output pulse and works like inverter.
This circuit is good for simple and low resolution use.
For better accuracy use op-amp and better ADC methods like further approximation.
Formulas:
IC 555 in Astable Mode:
IC 555 often used in astable mode to make square wave again and again.
This square wave can be clock signal for ADC or other timing uses.
How to Calculate Frequency:
Parts R1, R2 and C1 control how fast it oscillate.
Formula:
f = 1.44 / (R1 + 2 * R2) * C1
where:
- f is the frequency in Hz
- R1, R2 are the resistors in ohms Ω
- C1 is the capacitor in farads F
How to Calculate Duty Cycle:
Duty cycle D is how long pulse stay high in one cycle.
Formula:
D = (R1 + R2) / (R1 + 2 * R2)
where,
- D is in percent %)
Use in ADC:
This design makes astable circuit to give clock for ADC.
We can change R1, R2, C1 values to match ADC needs.
How to Build:
To build a Analog to Digital Converter Circuit using IC 555 we need to follow the below mentioned steps:
- Get all parts like shown in diagram.
- Pin 1 of IC 555 goes to ground.
- Pin 2 connect with pin 6.
- Pin 3 connect to base of transistor Q1 through resistor R3.
- Pin 4 connect to +5V power.
- Pin 5 connect to ground through capacitor C2.
- Pin 6 connect again to pin 2.
- Pin 7 connect to analog input using resistor R1.
- Pin 8 connect to pin 4 and goes to +5V power.
Transistor Q1:
- Collector goes to digital pulse output.
- Base connect to pin 3 of IC through resistor R3.
- Emitter goes to ground.
- Resistor R4 connect between collector and +5V power.
From Analog Input:
- Connect in series with R1, R2, C1 and ground.
Safety Tips:
- Work in fresh air place.
- Use right tools.
- Be careful with hot parts.
- Wear eye safety glasses.
- If new to electronics then start with easy circuit first.
Conclusion:
This Analog to Digital Converter Circuit using IC 555 is cheap and simple way to change analog signal to digital.
It is good for learning but not with high accuracy like special ADC chips.