These beefy Lambda power supplies have inspired me to tell my story of how I learned that my power supply leads just suck. My sister recently, at my request, got me a Raspberry Pi 3 B+ board for my birthday. Yeah, it was like two weeks before the Pi 4 came out but I didn't know that was going to happen.
So first thing I did was burn an image of the latest Raspian OS to a flash drive and plug it into one of the USB ports, because with the Pi 3 B+ you can now boot off USB, and I didn't have a CF card handy that I wanted to erase. But it won't boot, so I move the flash drive to a different USB and it boots up. But now my keyboard and mouse won't work in the other ports.
Turns out I have a Pi with only one working USB port. Did some googling and found that the first thing people blame USB problems on is power supplies that can't supply enough current to power everything plugged into the USB. I measure the voltage at the USB ports at something like 4.8V.
So I figure I'll just hook up my bench power supply that can do 3.2 amps directly to the 5V pins on the GPIO header to make sure power problems aren't an issue. I didn't really think this was the problem because the ports don't work at all, but I wanted to be able to tell tech support I already eliminated this possibility.
But when I set my supply to 5.000V, and the Pi starts sucking down about 700 mA, I'm still getting low voltage warnings, and
I measure only 4.8V or so at the GPIO header. Hmmm... Turns out my leads drop that much? Really?
So even though I have two bench supplies with three outputs each, I actually have only two power supply leads.
I try the other one, and it's even worse, but I expected that because I knew it was even lower quality. Probably something I got from China for $1.68.
So I did some testing. The better lead is 48 inches long. At 700 mA it drops 0.18 V. At the full 3.2 amps the supply can put out, it drops 0.8V. In the damn wire.
The second crap lead is 40 inches and apparently made with
WET STRING inside, because at 700 mA it drops 1.7V. Now, I still have the supply set to 5V, I dial the current limit up to 3.2 amps, and when I short it out, it drops the
FULL 5V across the leads and draws only 2.6 amps. I actually have to
dial the voltage up to 6.2 volts just to FORCE 3.2 amps through that POS wire. I go out to the garage and get a good length of 18 guage stranded copper wire I salvaged from something. Kind of stiff and not convenient for bench use, but I need some wire that can take the current. I solder it to a header on one end, using two power pins and two ground pins to make sure I can get the Pi the power it needs. My supplies are up on a shelf and I've always been annoyed that the leads I have aren't long enough to reach the ends of my bench, so I make this one 60 inches. Don't have any bannna plugs handy. Or maybe I do but don't have a clue where they are, so I twist and tin the ends with solder so I can put them in the wire holes on the power supply.
So to finish the Pi part of the story, this new power lead is significantly longer,
and at the 700 mA the Pi draws it drops only 40 mV. I dial the supply up to 5.1 volts as well just to make sure the Pi isn't going to bitch about low voltage. USB ports still don't work but I have no more low voltage warnings in the logs. After talking to Adafruit tech support they decided to send me a new Pi. New Pi arrives and all ports work fine with the same devices.
And the moral of this story is I need some REAL power supply leads that can actually take the current these supplies put out. But made out of some kind of wire that is appropriate for work bench use, not made out of wire that some electrician pulled out of a conduit at work and I grabbed from the junk pile.
Wasn't mnem talking a while back about some good high current wire for power leads? Guess I should go back and look for those posts...