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analog to digital??

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shanky25

New Member
hello friends!!

what actually i wanted to know is.. how can i convert analog signal to digital or vice versa!! without using an IC.. i already did it using a comparator using hold circuit. but that dint give me fruitful results!! plzz help me out!!
 

dknguyen

Well-Known Member
Most Helpful Member
YOu need an ADC whehter using an IC or building it from scratch. If use many MANY comparators and divide each comaprator to a different voltage range, you have a flash ADC- the fastest, most expensive, largest, most power hungry of power converters.

THere are also others that charge and discharge a capacitor through a resistor and measure how long it takes to reach a certain voltage. Others like successive approximation keep on redistributing the charge in a charged capacitor back and forth to figure it out. THere are other kinds too.

To make digital to analog you can use a resistive divider with many resistors and a of switches in parallel with each resitor. YOu can also output a PWM wave through a filter (like an RC filter) and only the average of the PWM waveform will appear on the output and you vary the duty cycle to change the average (and thus the output voltage). YOu can do it yourself or use ICs (especially for the resistor divider one since it's not fun working with a hundred or more resistors and switches).

Try google.
 

kchriste

New Member
Forum Supporter
For digital to analog an R2R resistor network is simple and easy:
https://en.wikipedia.org/wiki/Resistor_Ladder
For analog to digital without an IC is a little more tricky. I guess you could use a VCO to convert a voltage to a frequency. Better to use an ADC IC.
 

Pommie

Well-Known Member
Most Helpful Member
D2A use a R2R network.
A2D use a R2R network and feed the output to a comparator with the unknown voltage on the other input. You start by just setting the highest bit, if it produces a voltage higher than the unknown then that bit is zero (otherwise one) and you move on to the next bit.

Mike.
 

dknguyen

Well-Known Member
Most Helpful Member
Pommie said:
D2A use a R2R network.
A2D use a R2R network and feed the output to a comparator with the unknown voltage on the other input. You start by just setting the highest bit, if it produces a voltage higher than the unknown then that bit is zero (otherwise one) and you move on to the next bit.

Mike.

THat's the cheaper way to do a resistor divider ADC rather than using a bunch of comparators with different sources- you just have to switch the switches in the dividers much faster than the signal is changing.
 

Pommie

Well-Known Member
Most Helpful Member
dknguyen said:
THat's the cheaper way to do a resistor divider ADC rather than using a bunch of comparators with different sources- you just have to switch the switches in the dividers much faster than the signal is changing.

Or, use a sample and hold.

Mike.
 

shanky25

New Member
using ic?

can i do that using an IC 555? connect the IC in monostable mode.. and feed the output to a hold circuit? will this work?
 

shanky25

New Member
and moreover.. in resistor ladder circuit! the inputs should be in digital ryt? then how can convert a to d using this circuit?
 

dknguyen

Well-Known Member
Most Helpful Member
You can't. When using the R2R ADC, the digital inputs decide which resistors in the R2R ladder are on via the switches (thus bypassing that resistor if the switch in paralle with that resistor is on). You can;t use it to convert analog to digital UNLESS you use a comparator and have it;s reference as an R2R circuit (then you switch the switchines in the A2d circuit back and forth to change the reference on the comparator)
 

shanky25

New Member
will u plzz be a little more clear!! coz when digital signals are to be given to a rtr circuit.. how can it be used as an a to d converter!! sorry if i bothered u!!
 

Hero999

Banned
shanky25 said:
will u plzz be a little more clear!!
Asks someone who always writes in a clear and concise manner.:rolleyes:
 

shanky25

New Member
no it's t a school assignment.. i jus wanted to know all the diff methods of a to d conversion!! and moreover.. i already did it using an IC.. i wanted to do that without using any IC!!
 

Roff

Well-Known Member
The only way I know of to make an A/D without using a comparator is to make a voltage-to-frequency converter. The problem with this is, you still need a microcontroller or computer to convert the frequency to digital numbers.
There are plenty of tutorials on the Internet describing various A/D conversion techniques, and they will all require at least one comparator (except the aforementioned V/F converter, which might also have a comparator in it). Here is a good tutorial on D/A and A/D conversion. I'm sure there are lots of other ones available on the Internet.
If you want to ask specific questions about what you need, it would be much easier for someone to answer.
And please stop speaking in shorthand, or whatever that is called.
u, plzz, dint, ryt, coz
This might be easier for you to type, but for old farts like me, it makes the reading more difficult.
 
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