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How can I make a 15 volt 1.2 amp power supply for less than $30? Answered

So I lost the plug for my Asus Transformer T700 and I don't wanna spend $30+ buying from their store. Is there anyone who can help me figure out how to make one?


ddorrisJack A Lopez

Answer 5 years ago

Yea thats it. Guess I didn't look very hard to find it cheaper. Oh well I would still like to know how to make one.

Jack A Lopezddorris

Answer 5 years ago

The easiest way to "make" a DC power supply is go to the local thrift store, and find that section containing everyone's discarded wall wart, black power brick, etc, (probably yours too), that has been orphaned from its original device, in a big bin, shelf, or pile, for you to sort through. Then you find one of these rated for approximately the same voltage your device wants, at a rated current greater than or equal to the current your device is expected to draw.

Then you cut the cord off from it, and rewire it to a power connector which fits your device. For a typical DC power supply, this is just two wires, and besides the specs for voltage and maximum current draw, the only challenging (but important) part is getting the polarity right.

You might ask,"What about the connector? Where do I find that part?" And that question is more difficult when you've got one of those extra-special shaped power connectors, kind of like the one that fits in your tablet, almost as if the manufacturer of this device wanted to make sure there was only one special shape that would fit this device, or family of Asus(r) brand, devices exclusively.

Essentially what I have described is a cut-and-paste job: i.e. you find an old power brick, then attach a new appropriately shaped connector to it.

If you don't like appropriately shaped connectors, you can (carefully) open up the case of your tablet to discover its tiny-tiny power wiring. Then (carefully) solder the connector of your choice to this.

The traditional image of Frankenstein, from the old movies, includes two stud-shaped electrical terminals sticking out of the sides of the monster's neck, like the stud-shaped terminals on some kinds of car battery. Conceivably you could do something similar, for your tablet's power connection, and it would also look ugly and unnatural, like the cliched Hollywood monster. But, you know, if it works, hey...maybe it's not so bad.

By the way, I don't know if that answer qualifies as how to "make" a DC power supply, because it's too easy, amirite? However, what I have described, is what I believe to be the easiest, cheapest, and most sane and ethical method, (apart from shoplifting, or assaulting somebody on the street and stealing the power supply from their tablet).

But maybe you want to know how to build a DC power supply "from scratch", as they say, starting with things like: transformers, diodes, transistors, ICs, and solder.

Instead of actually telling you how to do that, I am going to offer an analogy.

Suppose I want to make some pancakes.

I could start with an egg, flour, some buttermilk, oil, baking soda, etc, and mix all that stuff together in the right proportions in a bowl to make the batter. Then heat up the griddle. Pour the batter on the hot griddle. Cook one side of each pancake. Flip 'em over with a spatula for to cook the other side. Then stack 'em on a plate.

Or I could start with that powdered pancake mix, the kind you just mix with water. Starting with the mix-in-a-box saves me a lot of time, and it eliminates the much of the possibility of error in the steps for making the batter.

Or, if I was really lazy, I could just drive to some place that sells cooked pancakes, on a plate, like hot and already prepared and everything. A lot of these pancake houses are open 24/7, and there's no shame in going out to get pancakes at 3 in the morning, although I must warn you, that is the time of day when you are most likely to encounter the Ambien(r) zombies.
You know, those people who took a popular prescription sleep medication, and they though they'd be asleep right now, and they kind of are, but not really, and they're out driving around and doing stuff, but not consciously, and sometimes they shoot people or drive over them with their cars, but they'll never remember any of it.

Anyway, the Ambien(r) zombies are a real problem, but I'm kind of getting off topic there.

Back to the analogy. Suppose also, for the sake of argument, I live in a world where eggs, flour, buttermilk, and baking soda, are really expensive, and hard to find. But for some weird reason, the powdered pancake mix is really cheap, and available everywhere. Also suppose for some weird, but related, reason the procedure for making pancake batter is really, really complicated. In fact it's so complicated that hardly anyone makes their own batter, because that would take days, or weeks, with a low probability of making a batter actually fit to eat.

This is kind of the world we live in with respect to shopping for power supplies.

Used, orphaned, DC power supplies, with approximately the right specs, but with the wrong shaped connector, are cheap and easy to find.

New, replacement, DC power supplies, with the exactly the right shaped connector and power specs, are not that hard to find. Also the convenience of geting something that works out-of-the-box *might* be worth it.

Building your own DC power supply from scratch is akin to building your own facility to produce enriched uranium... sort of. While not meeting the strict definition of metaphysical imposibility, it is a task that will be somewhat challenging.



5 years ago

Not a good idea to try and make one yourself. Power supply design is very tricky work even for the experts. The laptop need a very stable and clean 15V otherwise you'll damage the hardware. So precision is important here which further complicates the design process. Besides nothing you could build yourself would cost less than a replacement power brick.


Answer 5 years ago

Would it be any different if I made a battery pack that could output the power needed instead of a plug?