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adc (analogue to digital converter) how it works?

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h.galeh

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I am going to learn adc . but there are some problems. the books think that I previously worked with adc . please introduce me adc.
I know adc is : converting analogue inputs to equivalent digital output . reference voltage is the maximum input voltage . nothing else.
please tell me other concepts of adc for example : difference of avref,avcc , adc0..adc7 , ... and many other things
thank you
 

Easyrider83

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avref+ - positive reference voltage
avref- - negative
avcc - integration capacitor output
adc0...adc7 - adc input channels
adc code value = Vin * 2^adc_resolution / (avref+ - avref-)
 

bobsanjose

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There are different sorts of ADCs the most common are SARs and Delta Sigma converters. SAR = successive approximation. Instead of me writing you can use these terms to google.
Most micros that have an ADC included use a SAR. In general the SAR is faster than the Del-Sig but does not offer such as high resolution.
Most important about the signals you described above is that they are very clean, no noise on avref +/- because noise will have a negative impact on your ADC result.
For many other things, you should at least invest the time to write them down if you expect somebody else to spend their time to answer your questions. Questions that are not asked are usually not answered ;-)


Bob
 

poorchava

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To the kinds of ADCs I would also add 'flash' type. It's generally the simplest of all. It just has 2^n comparators who caompare input to every possible discrete voltage at the same time. It offers best speed, but also lowest resolution, since 8bit one already has 256 PRECISE comparators and 12 bit would need to have 4096.

Analog-to-digital conversion is very, very wide topic. I think you can get more basic info on wikipedia or similar sites.
 

bobsanjose

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You are correct, I skipped the flash converter. They are power eaters and require a lot of chip size for a higher resolution. In the microcontroller forum I thought I focus on ADCs that are integrated in micros.
I would also agree with your recommendation for the original poster that he should get the basics with self study not asking other members.

Bob
 

PIFA F

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I want to make an A to D and D to A converter but without using Ic's that can perform built in ADC features like 0804
so is there any way ? or any circuit diagram in which we can make A to D and D to A using gates or op amps??
 

dr pepper

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You can make a d to a converter fairly easy with an r2r ladder (do a google) I've done this a couple of times using microcontrollers to produce a waveform.
A a to d is much more complex, you wouldnt really want to do that unless it was for educational purposes or a highly specialized application.
You can still build one, you'd need a load of op amps, counters, analogue switches etc, and it would probably be very slow, if your fairly new to electronics then I reccomend you get a little more experience before trying to design something like this.
Have a look at this you'll find it interesting, and there is a super simple a to d made from comparators:

http://www.seas.upenn.edu/~ese206/labs/adc206/adc206.html
 

tpetar

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I am going to learn adc . but there are some problems. the books think that I previously worked with adc . please introduce me adc.
I know adc is : converting analogue inputs to equivalent digital output . reference voltage is the maximum input voltage . nothing else.
please tell me other concepts of adc for example : difference of avref,avcc , adc0..adc7 , ... and many other things
thank you
See this material, will help you to better understand ADC :
 

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