As a hobby electronics guy most of the time the equipment that I can afford, or justify the expense of is old, used, substandard or of questionable quality in one way or another. The fact that most of my stuff falls into this category, introduces an number of variables into many of my projects - and it can REALLY suck.
My main bench power supply is a perfect example. It's a B&K 1630 precision 0-30V switching supply. Not a horrible power supply, but the best part about it is the price - Free. I acquired this power supply from a coworker over 10 years ago when his father died, I think. He came into the workroom where I was working at the time and said, "You're into electronics and whatnot right? [fwump!] Here's a box of stuff my Dad had. Take what you want and toss the rest." Inside this box was this power supply. For the most part, it's been working great.
I started a project where I was using some NeoPixles I got from Adafruit. I'd wire up my circuit, upload my code to my Arduino and the NeoPixles would fire up and do their thing. It was getting late one night and I shut everything down and went to bed. The next day after work, I go back in to my home lab and fire everything back up, and my NeoPixles stopped working. My Arduino fires up and I'm seeing things in the serial monitor, but no lights. I go back and download some sample NeoPixle test code and upload that. Nothing. Dead as a door nail. I pull out a spare set of pixels and hook those up. Like magic! they work. I go back to the original set and nothing. Hmmm.. defective? I contact AdaFruit support and they send me a replacement set. Hook 'em up and they work great. I move on with the project, then the same thing happens again later on in the week. What the HECK? These NeoPixels are garbage right? So I order a different type/style. Again, they work for a few days and then die.
I start asking around on forums and whatnot, someone asks about my power supply. "Hook your scope up to your supply and turn it on..." So I did.
Uh oh... So I did it again.
Crap. One more time.
Ok, that looks better.
So I kept doing this like 30 times and my results were random, but about 25% of the time, I saw something that looked like the first and second picture and less like the 3rd.
Frick'n great. I have a bad power supply. This sucks, this thing has been working GREAT, and I REALLY don't want to spend the money on another supply (to clarify, I would LOVE to spend the money on a new power supply, but ya know... priorities), but I don't want to keep smoking projects and how many OTHER things might I have damaged or compromised with this flaky supply? UGGG!!!! This sucks!!!! PLEASE don't make me pull out the lab kit from school I had to build, and use THAT supply. My life is OVER!
I post a similar emotional outburst on some forum or to someone in person, I don't remember honestly, and someone said. "This is switching supply, spikes like this are common in many of them especially in lower end supplies like yours." Ignoring the cheap shot at my equipment, a sense of relief washed over me. After some more conversation I felt better about continuing to use my supply, but now make a point of powering the supply on first, THEN connecting it to my circuit and with the finished project using the NeoPixles, I added zeners to each node, problem....mitigated.
I've been researching this switching power supply spike thing, and I'm not finding a ton of information on it. Is this true? Is my supply compromised somehow? I'd love an answer to these questions, but for now, I'm VERY VERY careful about what is connected to that supply when I switch it on, and I'm keeping my eye out for a new supply.