# Analouge and digital signal question

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#### fredy

##### New Member
Hi guys just wandering can a analouge signal got in to a digital input Ψ

Yes, it is called an Analog to digital converter.

The question to you is how many levels do you want to quantize the analog signal into?
If just two; i.e. on/off, high/low, or >XV/<YV, then all that takes is a "comparator".

If more than two, that takes an "analog to digital converter" or ADC. There are a variety of ADCs that can quantize the analog signal into 2^8 (256) up to 2^24 (16million) levels.

What are you trying to do?

so you could use a comparator to convert a anolouge signal to a digital signal is what your saying

I'm tryin to make a robot it ifared sensor ouput is analog but the proceser is made up of digital logic gates

so you could use a comparator to convert a anolouge signal to a digital signal is what your saying

If you can state your problem like this: "If the voltage output from the sensor is greater than x Volts, then do ONE Thing, else do OTHER thing" then you can get by with just a comparitor.

OTOH, if you state your problem like this: "I have a stepping motor (digital). I want the rotation speed of the motor to be proportional to the voltage out of the sensor" then that would take a ADC...  Thanks

what really is the difference between analouge and digital

Digital is saturated analog. ie: A digital node can be either ON or OFF. Analog node can be ON (The highest voltage possible for that circuit), OFF (The lowest voltage possible for that circuit), or ANY voltage in between. To put it another way, an analog node can have an infinite number of valid voltages where as a digital node can have only two.

what really is the difference between analouge and digital
I assume you referring to analog and digital signals.

In analog, the signal value is represented by the signal voltage level. It can have any value between zero and the maximum voltage the circuit will accept. The precision is determined by the accuracy and noise level of the analog circuits.

In digital, the signal value is represented by a digital number (or word). The number of bits determines the precision of the representation. For example, 8 bits has 256 allowable states (0 through 255) so the precision (minimum step) is 1/256. Thus the better or more precise you want to represent a signal value, the more bits you use (at the expense of requiring more data storage, and more and faster circuits to transfer the data).

If you want to understand the difference between analog and digital then its better that you actually go through how an analog signal is converted in to digital.

Sampling>Quantization>Coding

Sampling: Converting a Cont Valued Cont Time signal to a Discrete Value Discrete Time signal.

Quantization: Converting a Discrete value Discrete Time signal in to a Cont Value Discrete time signal.

Coding: To encode the bits(i-e represent the values by a digital number as stated above).

thanks for the help   