adc using 555 timer

[MrAl]

Hi Carl,

Oh yes, interesting observation there.

I still think it would be digital because there are only two voltage levels, even though the time can vary. With regular digital signals the time can vary and there's no beef about it. Also, the signal can be passed through a standard logic gate without corruption (except tiny delay of course).

The usage is interesting too. In a buck converter the modulation width can vary continuously in time but not in amplitude (for the most part except for relatively small amplitude changes). The width then causes another analog signal that in principle varies continuously in amplitude so it has to be analog again.

So digital signals can vary continuously in time just not in amplitude, while an analog signal can vary in both time and amplitude.

Then we can ask the question, what about a stepped wave, where it approximates an analog signal with discrete amplitude steps.
Discrete analog anyone?

Perhaps another view is just what does it take to transmit a given signal?
The complexity of analog amplification over digital amplification is much greater. Analog amps have to be linear (usually) and reject noise and stuff like that, while digital counterparts would be much simpler with only two levels to reproduce, just having to be fast.

Anyone would call a sound CD 'digital' im pretty sure, and we could make a CD by burning small pits into the surface in various formats, including PWM (knowing the speed of the disc in rpms). Most would argue that would still be digital because there are only two states for the data, a pit or not a pit, even though the distance between pits might vary. Interestingly that could be converted to high resolution analog

 

[Mr RB]

Good point about there only being 2 states for the data waveform, but it's not totally true as per the DATA.

I don't think the data is "digital" as the data itself is frequency. For sure the waveform appears digital with only 2 voltage levels and a square wave shape. But even if you filtered that into a triangle wave, or something sine-like, and transmitted it the DATA still remains and can still be received or measured (as frequency) with no change to the frequency data based on how "digital" the waveshape appears.

So I would describe the data as frequency, which makes it more accurately a "voltage to frequency" converter rather than a "analog to digital" converter.

On the other hand, a comparator set to 2.5v is a "analog to digital" converter, with one digital bit. The output state is only ever 0v or 5v, and the STATE of the output is the digital data. It's a 1bit ADC.

 

[MrAl]

Hi MrRB,

Voltage to frequency sounds good too. The intended application however is for an analog to digital converter.
A Sigma Delta converter uses something like voltage to frequency but the end result is analog to digital. It's more like "voltage to number of pulses" though.

 

[Mr RB]

Interesting discussion... But I think we killed the OP.