Interesting power supply on Kickstarter

Yeah, the LM2596’s are most certainly counterfeits or rejects, as there’s no way they can sell these boards for $1 shipped (the chips would cost nearly that, even in quantities).

All the ones I’ve tested can’t sustain 2A without a heat sink. The diodes are also severely under-specced and tend to blow.

Well, of course ... but you've got to unsolder the suckers. I'm not doing that.

(Just to be clear, since people seem to be totally missing my point: yes, the voltage can be changed, and, yes, many people have the skills needed to do that. My point is that I am not going to do anything involving SMT and soldering, even though it's really not that hard. Everyone else here is welcome to do whatever they want.)

Why? desoldering SMT resistors is not that hard… Just apply a little heat and lateral pressure with the iron and it pops right off. Then you can use normal through-hole resistors on a breadboard or whatever.

You’re going to need to get used to SMT soldering sooner, rather than later, as THP is going the way of the dodo. To be honest, once I got over my initial trepidation, SMT devices are actually easier to solder than through hole, especially when you perfect drag soldering. You can also get a cheap hot air gun, solder paste and a syringe, then it’s really easy! :smiley:

I got on of those hot air guns when I had to replace small resistor’s on about a hundred boards to get them to charge Apple products correctly. Even with the Hot Air Gun + Magnifying Glass + Tweezers it was still a time consuming pain in the ass :smile: but it got the job done :smile:

I’m gonna have to try the Hot Air Gun + Solder Paste + Syringe on some underpopulated boards real soon so hopefully it goes well.

So do the reflow ovens just replace the hot air gun when populating boards yourself?

Yup! A toaster oven and kitchen timer will work just as well.

Do you recommend any particular solder paste? I have a Radio Shack and FRY’s Electronics real close to the house so I should be able to pick some up easily.

http://sra-solder.com Is who I generally go with. I’ve never seen solder paste at Radio Shack.

There’s a good paste extractor too, let me dig up the link.

That happened years ago. :slight_smile:

XD Yeah… Hey, it created an entire cottage industry of breakout boards!

Hi @RWB

Solder paste is great but it is perishable and separates eventually (3-6 months typically)–it is an emulsion like salad dressing but you cannot shake it back up. It should be stored cold (32 to 50F).

So you should probably only buy a small amount for your current project. You can keep it in the fridge but I can say that has a pretty low wife-acceptance factor unless your man cave has a separate fridge!

Thanks for the info @bko !

Very helpful!

I cannot speak for this specific design, but in general, SURE it can! That's what the "efficiency" part is all about. Two amps for a chip that size is run of the mill, these days. No heat sinks in sight.

More efficiency means less heat to dissipate. Many modern switching regulators run at 95%+ efficiency, versus 50% at best, in the case of a 7805 linear regulator.

Further more, the numbers are deceptive. Going from 50% to 90% efficiency, is is not just 40% less heat -- it's 80% less heat. From 40% to 90% efficiency is a fifth better than that, again -- or 96% less heat. (I hope I'm getting this math right.) It's not a straight line on the graph and returns start to really ramp up above 90% efficiency.

So, a good old 7805 in TO-220 package, struggling to deliver 1 amp at 45% efficiency (an educated guess, depending on the input voltage) becomes a monster at 90% efficiency, capable of producing 5A with the same waste heat output -- not just 1.8A, as you might expect.

I have 4A stepper motor drivers, which are about 5x5mm in area, 0.8mm thick and have no heat sinks at all -- each chip providing two separate, co-phased outputs (rated total 4A max). They get mildly warm at full 4A load! So a single rail supply doing 2A is well within normal, modern standards.

I also use a tiny 2.14 x 1.44mm 6 pin buck-boost regulator -- that's smaller than this x, on my screen -- to step up 1.8~4V to 5V at 400mA, without breaking a sweat. (No heat sink at all.)

Today, you can get super MOS-FET transistors rated to 40V at a whopping 350A (with moderate heat sink). This is possible due to the ultra low "ono" resistance across the source/drain junction.

Yeah, I realize they can. I’ve designed a few myself even! :wink:

When I made the original post I was on my iPhone and thought the efficiency was lower than it, in addition to looking at the picture of the 500mA version.

Good stuff @timb. Well, I’ll leave the post there for others who maybe surprised.

EDIT: Oh and, I’ve since read some more of the posts, which I somehow didn’t even notice initially. Think they were still loading on the page or something. This forum does that. It’s a bit of a trap sometimes. hehe

A large, high Q inductor, as you stated above, is essential for high efficiency. Learned that the hard way on a couple designs.

@Raldus: Let me tell you a story, if I may.

About 14 years ago, I gave up on electronics in disgust, firmly of the belief that all these new fangled SMD parts were completely unmanageable by human hand. For ten years -- TEN YEARS -- I mourned my first ever hobby, my obsession and first love. It seems impossible to believe, now.

Then one day, I was chatting with a guy at our model R/C aircraft club, who was at least half my age older than me again. I made some of my usual, well practiced snide remarks about modern electronics for the hobbyist, fully expecting the usual sighs and nodding of heads in agreement. But the dude says, "WHAT?! You're not gonna let some big-ass 0603 surface mount components SCARE you, are you?" .... and then he all but walked away in disgust. If I could find that guy again today, I would HUG him. Maybe even kiss him.

Long story short, the simple fact is that 0603 and even 0402 components (40mil x 20mil in the latter case, for reference) -- even those 100+ pin chips with legs spaced only 0.5mm apart are EASY to handle IF you know how. No, really. REALLY easy. You'd be amazed. I was.

I would implore you to do some searches on YouTube for SMD soldering techniques, just as a start.

For removing the resistors on this regulator thing, all you need is another cheap soldering iron -- one in each hand. SIMPLE. Putting the replacements back is what may scare you. But it's much easier than you think. Seeing is believing and seeing is just a matter of just about any form of magnifying lens, if you even need that. Shaky hands? There are techniques to deal with that, too. You don't even have to use whiskey -- but you can. I won't stop you. :wink:

Trust me. All is not what it seems. There are tricks to learn that will make your head spin, in terms of how ridiculously easy it really is to deal with SMD stuff. It's like magic. The number one trick is to use modern, liquid or gel flux (depending what you're doing) -- and for reasons you won't know unless you research it.

For example, to successfully solder those 0.5mm spaced pins on the 100+ pin chips -- the best method I know, which produces perfect results every time, requires a much BIGGER soldering iron tip, not a tiny one and a microscope. It's true! :smiley: The right flux will perform magic, before your very eyes.

As for myself, just a couple months after that old timer's shock between my ears, I had gone from total phobia and disbelief and then built this and later, this (for just two examples) ... and I've never looked back. Now I'm catching up on those lost 10 years!

Oh and now, it's the weirdest thing, but I far prefer SMD work. It's faster, cleaner and simpler than through-hole. No more turning boards over and over, with stuff falling out and sharp, cut-off pins scratching my fingers and all that jazz.

Sure. I've had to invest in a few more tools to make life even easier. My total spend on SMD soldering and re-work stuff though would be under USD$500 -- and most of it is not actually needed, just nice. eBay is your friend.

Well, that's my story. Hope it helps in some way.

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Never tried, always wanted and you’re making it more doable!

That’s why I’m trying my hands on making the microSD shield and protoshield and more to come! :smiley:

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Hehe, oh, I understand. If I had to, I'm sure I could do it, and I know that putting in the replacements would be easy. As I mentioned, I have an old toaster oven that I can repurpose. I just don't want to do it. :smiley:

I just don't want to remove/install new resistors to change the voltage, or solder up hacky wires to external resistors/pots, or buy multiple units for different voltages. I have one of these, and the only real issue with it is that it doesn't do negative voltages. On the other hand, it's a lot more expensive than the PNMini.

OK. Understood.

Checked out the link to that PSU. Thanks. Nice gadget. I was all excited, until I saw the price. At a whopping $198, it's really in a whole different ball park, compared to the $10 things we were discussing. Hardly something I could afford to be buying more than one of, that's for sure. So I'll stick to re-soldering $0.001 SMD parts any day. Hell, it only takes a a single minute. Each to their own.

Interesting product. As versatile as a bench supply but much smaller, so it can be used in all kinds of things, even as the final solution, I suppose. But super expensive! Slightly larger than purpose-built solutions, but easily configurable and really good for prototyping. I'm kind of perplexed. Seemingly cool product, but whatever its niche market is, I can't find a fit for it around here. Though it does have that, "cool" factor going on, somehow. Just the price. Ouch.

Thanks for sharing anyways. :smile:

The best part about SMD is it makes etching your own boards at home so much easier! No more drilling!!!

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I have a 3x4 ft milling machine. One of the things I wanted do at least once with it is to make a circuit board. I know its really only good for prototyping since you want teh quality stuff for production but it sure would be cool to make your own designs at home without needing a PCB house for prototyping.

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