Radio Control > PCM

[MinnesotaStateUniversity]

Transmitter: Toggle > Encoder > Modulator > RF Amplifier

Receiver: Decoder > Servo


At what point does the Anolog signal get changed into digital? After the encoder on the transmitter & before the servo on the receiver?

All communcation is sent w/ bits. What do these bits correspond to? Movement only?

 

[rfredel]

Hello,

The enconder change the analog signal to digital and the decoder back to analog.

Regards

Rainer

 

[betwixt]

It depends on the system being used.

Older systems used "Proportional control" which is a system similar to PWM. A stream of pulses was continually sent but their width was changed to convey the positioning information. Short pulses meant one servo position, longer ones meant further servo movement. The pulses were created analog using a potentiometer (often in a joystick) then converted to digital pulses and transmitted as on/off carrier from the transmitterl.

More modern and sophisticated systems use digitally produced commands from a microprocessor, and send them either as AM or FM to the receiver. At the receiver, the command is decoded and locally used to generate the servo control signals.

Brian.

 

[MinnesotaStateUniversity]

Transmitter: Toggle > Encoder > Modulator > RF Amplifier



^Assume the "Toggle" is me singing for a length of 1 minute. Let's also assume that I've kept a constant amplitude of 10V.

From my understanding, the encoder takes an extracted portion of the analog signal & converts it into binary code (1's & 0's). Okay, that's great & all. However, at what rate? How often/how many times does the encoder extract these portions from an analog wave?

I assume the more "portions" extracted, the more accurate the sound reproduction will be.




If the analog signal is converted to Binary Code at the Encloder, then what does the modulator do? Or do BOTH the encoder & modulator work together. Like the encoder extracts these analog signals & the modulator puts them together in correct sequence.



So, what exactly does a microprocessor consist of? All of the above in a single IC chip? How about microcontrollers? Am I speaking of such?

 

[betwixt]

I'm getting confused, Radio Control and servo are terms used in remote controlled position systems but you are talking about singing, sound reproduction and analog to digital conversion.

What is your application? It sounds like you are trying to use the wrong technology for your purpose.

Brian.

 

[MinnesotaStateUniversity]

I used singing for an example.

I would like to build a RC vehicle, specifically a quadcopter. For learning purposes, I would like to go DIY.

Transmitter: Toggle > Encoder > Modulator > RF Amplifier

^The above would be an RC transmitter. As noted above, I have an understanding of what makes up a transmitter. I just want to know how the components operate w/ one another inside.

Therefore,

If the encoder translates an analog signal to digital, then what does the mudulator do?



Note: I am under the impression that all ADC's work the same. I used "singing" for an example as human voice is naturally analog in format. Perhaps I should have mentioned that I was singing into a Mic that was fed into an audio recording center where my voice was translated digitally on a CD.



Encoder + Modulator = ADC, correct?

So, the encoder does the "timing" & the modulator "sequences" ???

If so, how often or at what rate does the encoder extract portions of the analog signal? Remember that ADC's take portions of the analog signal & convert them into Binary. Okay, at what rate? I assume the more portions it extacts, the more accurate it'll be.


For example,

(keep in mind I am in an audio recording studio where my voice is being converted into digital format)

Assume I was singing into a Mic for 1 minute. Every 30 seconds, I would increase the output of my voice (voltage, correct?).

At 30 seconds, assume I am at 5V. Let's call this "Point A."
At 1 minute, assume I am at 10V. Let's call this "Point B."



1 minute = 60 seconds. Every 30 seconds I changed the amplitude of my voice, therefore I only changed it twice. So, the ADC only took 2 portions of the analog signal, correct? One portion was from 0 seconds to 30 seconds & the other portion extracted was from 30 seconds to 60 seconds.

Remember that 0-30 seconds is calld "Point A"
& Remember that 30-60 seconds is called "Point B"



Well if "Point A" or "30 seconds" was at 5V, then what Voltages are given from 0-24 seconds?

What if my I decided to scream as loud as I could 10 seconds into the recording, increasing the amplitude significantly. If the ADC converter, only extracted 2 portions, one at 30 seconds, & the other at 60 seconds, then that's only 2 values!

Therefore, if the CD I made was played, you would NOT hear me "screaming" 10 seconds into the recording. You would ONLY hear at Point A & Point B.


I can change the amplitude of my voice every second. Heck, probably milliseconds.

So, I am going to assume that an ADC BETTER be extracting portions nearly every couple milliseconds to give an accurate reproduction.

It seems logical to me that in order to convert an analog signal to a digital signal, one needs to know the "max rate at which amplitude can change." This would of course tell you the # of portions & the rate that need to be extracted out of the analog signal.

 

[betwixt]

Your ADC theory is well off course. You are assuming that what is digitized is only the loudness of your voice. It actually takes several measurements per cycle of the audio waveform. To carry the loudness and tone, it periodically samples enough information to be able to reconstruct the wave shape and hence a copy of the original. For CDs the sampling rate is normally 44,100 samples per second or roughly one per 23 uS. In other words if you sang at 1KHz it would take around 44 samples per cycle of the waveform.

The modulator is the part of the circuit that applies the signal, whether analog or digital to the radio waves being transmitted. So for AM it would vary the amplitude of the transmission according to the signal and for FM it would vary its frequency. Although some modulators are better suited to analog and some to digital, in both cases their purpose is to change the radio waves in such a way that a remote receiver can recover the information later.

Brian.