ProDigit wrote: ↑
Tue Sep 03, 2019 3:00 pm
Imperf3kt wrote: ↑
Tue Sep 03, 2019 12:43 pm
You are confusing voltage and current (amperes)
Don't blindly trust the label.
The charger says it supplies 2A doesn't mean it supplies 5v while you're drawing 2A. As you draw more current, the voltage can drop and this is why you are seeing an 'undervolt' warning.
Also, setting the clock to 1510MHz does not mean your Pi is running at 1510MHz.
I'm not confusing any of them. I happen to have an A2 degree in electromechanics, and know what I'm talking about (unlike a certain user (in my block list), who seems to just enjoy ridiculing people. Take a hint, PeterO).
At a higher load, voltage drops. Chargers with low amp rating, drop voltage quickest. Chargers with high amp rating, maintain voltages best.
Although I won't deny that it is possible that this charger triggers the undervolt warning because it provides 5V at low or zero load, instead of full load. They are Chinese products after all, so maintaining a standard might not be priority for some companies.
As Peter pointed out the labels are fairly meaningless, beyond being a guideline to expectations. This is especially true for the more generic ones, from noname supplies in China. Beyond the inability to actually supply the claimed voltage or current, they may have horrible regulation or not be able to supply the claimed current at the claimed voltage. As noted, repeatedly the Pi is rather susceptible to undervoltage conditions and may start doing funky things... hence the under voltage warnings.
There is no relationship between current rating and ability of a power supply to maintain specified output voltage under full load conditions. That is totally dependant on the actual power supply design. Assuming appropriate input power, a good supply will be able to deliver claimed current and claimed voltage. A crappy supply will not. Having said that, buying a P/S with lots of current headroom may result in a having a supply that will supply the required current without voltage sagging. Beyond the regulation abilities of the supply there is the actual delivered power. This is where the lead size, connection method and power jack come into play. Lower quality supplies will also tend to skimp here resulting in significant voltage drop between the supply and the Pi. Obviously add additional adaptors, like a microUSB to USB C, will worsen the situation.
Not sure what an A2 degree in electromechanics is. We don't have those in the colonies. I have a very pretty piece of paper somewhat that grandly claims BaSC in Electrical Engineering from Waterloo and another one that enthusiastically states I an a licensed Professional Engineer in Ontario. Taken together they will hide a fairly large defect in your standard office wall. However, I have spent most of my professional career doing CAD tool stuff and am much more comfortable with client server architecture, and large multi site design environments than wiring bits and bobs. More relevant to most of the discussion here, is that I have been involved with Unix and Linux in both my professional and private life for almost 40 years. I suspect that many folks on these forums also have fancy degrees and titles. Said titles and degrees may be relevant or not, to the discussion at hand. However, waving them about like a magic wand may not have the result you are expecting or looking for.