I see oscilliscopes that range from $30 for a 'kit' and jump to about $300 and up. Maybe that's overkill for my needs.
Point is, I am often trying to find a "clean" power source to use for projects that need precise low noise analog pin readings, or projects involving the ESP8266 modules. So, I have been tinkering around with regulators and different sources.
Is there a cheap/easy way to simply get an idea how much noise one supply has over another?
Perhaps it would have something to do with simply reading an analog pin in some way.
An oscilloscope is the correct tool. I have a $3xx siglent one, and a $90 super-portable one the size of a cellphone (much worse electronically, but incredibly convenient in some situations, because you can easily place it so you can see the screen without looking away from the board you're probing). Both have their place.
The ADC on an Arduino is fine for what it is (analog inputs on a $2 microcontroller), but it's pretty crude compared to a 'scope.
It's not hard to get 3.3v power clean enough for an ESP8266; you don't need analytic equipment for that. A 1117-series regulator (pick your brand - I like ZLDO1117s, as their specs are slightly better) with capacitors in accordance with the manufacturer datasheet is entirely sufficient, as will any other decent regulator that can supply the spec'ed current. The only reason there is so much talk about supplying power to the ESP8266 is that Arduino boards come equipped with a rice-grain-sized 3.3v regulator that can't supply the current required by the ESP8266.
For a DC voltage source, to measure how much voltage ripple the output has, you can use a digital volt meter in AC mode to measure the voltage. Any ripple will be measured by the volt meter as AC voltage. It certainly isn't terribly accurate in any way and widly depends on the frequency of the ripple and the ability of your digital volt meter to accurately measure AC voltage at various frequencies, but it usually provides useful information for comparison purposes.
DrAzzy:
. . . The only reason there is so much talk about supplying power to the ESP8266 is that Arduino boards come equipped with a rice-grain-sized 3.3v regulator that can't supply the current required by the ESP8266.
This isn't quite right. The ESP8266 current surges when the transmitter is switched on which can cause the voltage to the module to dip. While this may be due to a regulator that simply can't supply enough current, it also can be a result of poor circuit layout. By poor circuit layout, I mean the ESP module is separated from a perfectly adequate regulator and bypass capacitors by a length of wire that has significant resistance and/or inductance.
As for an oscilloscope to look at such issues, you want a instrument that can capture short single-shot events. Any digital scope with at least 10 MHz bandwidth should be adequate.
Finally, for anyone getting started with ESP8266, I'd recommend using a module with on board power regulation such as a NodeMCU, Adafruit Huzzah, or similar device to mitigate problems due to power supply layout.
Good ideas. I'll try the non-oscilliscope ones first.