analog to digital

[Mr CCE]

hi all,

do U know a way I can convert sound into digital form (bits)? say..I want to convert some audio (from a microphone, for example) into a bit stream in order to transmit it??

thx

 

[ke5frf]

Transmit it how? Over the air?

Many RF transmitted digital signals are done with software.

 

[Sceadwian]

Mr CCE, what you're looking for is an Analog to Digital Converter.

 

[MikeMl]

Actually, CCE is looking for a Codec.

 

[smanches]

I think he's looking for both.

 

[ke5frf]

If you are looking for a technique to transmit digital information over RF paths, first I suggest you educate yourself on how digital is transmitted via radio in the first place.

There are several techniques. I suggest you learn about Phase Shift Keying and Frequency Shift Keying. You should also learn about modems and digital signal processing.

The key here is MODEM. (Modulator/demodulator). To transmit digital over radio, the signal has to be modulated over an RF carrier. The frequency and bandwidth of the carrier must be high and broad enough to accomodate a modulation scheme with high bit rate transfer. Broadbanded transmissions are typically undesireable, so digital broadcasting at higher bit rates is typically done at at VHF or UHF or above where the higher frequency permits higher data throughput over a narrower signal. Slower speed data is also feasable at HF and some narrow mode voice techniques have been developed. Simple mono-voice can be efficiently replicated digitally with narrow bandwidth by sampling only the critical voice frequency range required for audibility. Lower end bass and high end treble can be elimated with L-C filtering, for instance.

Remember, you need a MODEM. A modem is a device that converts audio into digital, and vice versa. A computer soundcard can be used as a modem. The transmitted radio signal is actually high frequency shifts of audio frequency. The RF signal that the radio pics up is demodulated by the radio and the audio is fed to the computer soundcard, accomplished with an audio transformer typically to impedance match the microphone input to the radio. The signal processor in the sound card then converts the signal into digital format that the computer microprocessors and software can understand. This will then be converted back into analog audio, but now it will be recognizeable as a human voice or music or whatever through the computer speakers.

All of this can also be accomplished with special radio equipment with built in modems , microprocessors, and signal processors/soundcards. But it is much easier to just outfit a radio with a computer connection and utilize whats already there.

The computer needs software written to communicate with the soundcard and analyze the waveforms that the soundcard signal processor is recieving. The software must be able to convert the audio presented to it into a specific digital language and vice versa.

I suggest you get ahold of the current ARRL publication on digital communication techniques. If you would like to experiment with transmitting digital voice, there are plenty of amateur radio experimenters who can guide you and help you set up the equipment.

 

[ke5frf]

**broken link removed**

Here is a brief presentation on various digital techniques from the ITU which governs international treaty for the RF spectrum.

If RF tranmission is what you are after, I am not sure what frequencies you plan on experimenting with, just remember that certain frequencies require a license and/or power limitations to legally operate. Also, experimental techniques are typically developed on higher frequency bands at low power where interference issues are less likely to occur, particular on amateur radio.

I highly encourage you to get a ham license if you plan on experimenting with digital data over RF.

 

[Sceadwian]

The only thing he asked about was how to get an anlog signal from a microphone into a digital one, nothing else, anything else is inferring information the poster did not present.

 

[ke5frf]

The only thing he asked about was how to get an anlog signal from a microphone into a digital one, nothing else, anything else is inferring information the poster did not present.

Well, he did use the word transmit as well. It is difficult when posters ask such vague questions. My answer was framed in the context that he wanted to learn how to digitally transmit his voice. I offered a lot of information. If it is useful for him, great. If not, perhaps my time wasn't wasted if it helps someone else.

 

[Sceadwian]

Ke5 look up the word transmit in the dictionary.

You offered a lot of information for him to transmit his voice via RF, this was based on your expertise not his question. Such as Mike suggesting MR CCE needing a codec, a codec is not required to digitally encode analog data to digital, in fact it has nothing to do with the basic question, which was how do you get an analog signal from a microphone as an example into bits, the answer is with an analog to digital converter. The poster provided no more or less information than to provide that simple of an answer and nothing else.

I'd strongly recommend viewing a few of the threads in these forums that have gone on to 20-50+ or more posts with theoretical discussions running the gambit from at least three different fields when the original poster said not so much as one other word other than the original post (as thus far the OP has been completely silent)

This 'conversation' is effectively over, the argument is only just beginning =) Especially if the poster comes back and one person has managed to guess correctly about the particular tangent away from the basic thread that he started.

This is post #10 and no OP response yet. In science you're supposed to only deal with one postulate at a time, or chaos reins... Believe me it will =)

 

[ke5frf]

Next time I post, I will send it to your message box for editing and approval.

Just kidding!!! I don't really care. It was my time to waste typing it out...I enjoyed writing it down and sharing. Like I said, if he got anything from it, fine. If not, oh well. I shared my bit of expertise on the matter and if he wants anymore he can ask.

He may have not have asked exactly what I answered, but he certainly didn't ask anyone to stand guard over his post and decipher it for him either.

(Just messing with ya man)

 

[ke5frf]

Sorry if I came across in an ugly fashion. I tried to post lightheartedly

But the more I think about the OPs post, the more I question why someone typing on a computer likely equipped with a microphone input jack would ask if there was a way to transmit his voice digitally if he was referring to transmitting over cables. And if he was asking about that, as lengthy as my post was, at least I gave him the obvious tutorial on soundcards that he needed.

OK, I'm done with the late night debate session LOL. Good night.

 

[parag saraf]

i wnt to mitutoyo digital circuts

 

[parag saraf]

where i can get lcd disply for mitutoyo vernier

 

[bountyhunter]

hi all,

do U know a way I can convert sound into digital form (bits)? say..I want to convert some audio (from a microphone, for example) into a bit stream in order to transmit it??

thx

get PYRO software and you can record audio from a microphone or audio device into digital files of either WAV or MP3 types. You can also display them.

 

[Roff]

The OP said he wants to

convert some audio (from a microphone, for example) into a bit stream in order to transmit it

He needs, at least, a serial output A/D.

 

[Mr CCE]

Now that's Comedy!

Hi all,

first of all I want to thank "ke5frf" for the really long lesson about the MODEM thing. But the thing is, I'm not so stupid as to not know what the hell a modem means and does! Besides "Sceadwian" was right about me only asking for a way to convert an anlog signal from a microphone into a digital one, nothing else, and I see that "ke5frf" has plenty to say, but thx anyway for underestimating me.

About the transmission thing, I've already been successful in transmitting digital data via wireless means; at an amatuer radio frequency of 433 MHz and > 1 Km power range, which was also efficiently received and level-regulated at 5V (plus-minus 0.6 approx)

Finally I just wanna ask about the A/D converter: Is it as simple as a microcontroller's ADC module?

thx in advance!

 

[Sceadwian]

I think I'll just sit here and bask in the glow of being proven correct by the original thread poster.... Okay okay enough of that I'm sure I'll shoot myself in the foot on another post soon enough, but I gotta gloat when I get the chance =)

Micro controllers are perfectly serviceable for decent quality voice or AM quality radio as far as their ADC's go in general. You just need a pre-amp for the mic to adjust your audio level so that it's within the range of the ADC, the most complex part is biasing the signal, an MCU's adc typically reads from GND to VCC, no negative rail so you need to use an opamp to output a DC shifted signal so that the negative portion is above ground, unless you don't mind losing the lower portion of the cycle, so there is often a bit of analog work to go along with it. You can also buy seperate ADC's that will interface readily with a micro controller or your own logic which are a lot more flexible and may support a negative rail so you don't need to do that messy Dc shifting.

Generally the ADC's on micro controllers are for control interfacing but they can record 8bit audio of passing quality.

 

[Roff]

@ Mr CCE:Maybe you were just trying to protect your ego, but comments like that sting. You could have told us you already know all about modems and transmission without reprimanding ke5frf, who was only trying to help. After all, you've told us nothing (until now) about your level of expertise. You have nothing posted in your profile. Are we supposed to read your frickin' mind? I think twice about helping people who come back like you did.

@ Sceadwian: It's audio. A capacitor and a voltage divider generally suffice for level shifting.

 

[3v0]

We answer a lot of question for a lot of people here.

I took a look at your original post to see what it was that made people respond at the level they did.

hi all,

do U know a way I can convert sound into digital form (bits)? say..I want to convert some audio (from a microphone, for example) into a bit stream in order to transmit it??

The hold text indicates that you are not sure that the digital form of sound is bits. Maybe it was just a poor choice of words but it is there. Starting the post with "do U" could easily lead some to think you were a kid.

What were people supposed to think? Be thankful you had so many good replies and stop chewing on the people who help people.

3v0