Why so many AC adapters?
January 11, 2006 6:44 PM   Subscribe

Can someone explain why every battery powered device ever made seems to have a utterly unique AC power adapter?

I don't think that any device (radio, CD player, computer, razor, etc.) I own came with an adapter that is in any way compatible with any other device, leading to an explosion of those little brick devices in my outlets.

Also, why can't they somehow be ganged so that one brick can service multiple devices (presuming that one could find two compatible)?
posted by hwestiii to Technology (20 answers total) 2 users marked this as a favorite
I think it is the same reason printers are so cheap, but ink is so expensive. Once they get their foot in the door, they'll milk you for all the money they can.

Go to Radio Shack. They sell generic power adapters that have a variety of voltages and connecters.

I have a generic one that I have used recently to power a speaker system and recharge a power drill with wildly differing connectors and voltages.
posted by rabbitsnake at 6:50 PM on January 11, 2006

I hate to be cynical about this, but the obvious answer is that if you need a replacement, you will be forced to go to the device's manufacturer and pay a premium for an adapter. It is only in the consumer's interest to have common power adapters, not in the manufacturers' interests.
posted by rachelpapers at 6:51 PM on January 11, 2006

I've found that you can use many devices amongst certain adapters. Try this at your own risk, and take what I say with a pinch of salt, but I find as long as the polarity is correct (that is, positive center or negative center) and the volts are somewhat within range (most devices seem to have a wide tolerance) and of a similar load.. then it'll work. So, a 12V power supply for a 9-12V music keyboard will often plug into a 15V guitar effects box just fine, etc..
posted by wackybrit at 6:52 PM on January 11, 2006

Like wackybrit I've found the occasional appliance pair with the same specs and hence shareable adapter-bricks, but hwestiii, I feel your pain, and I agree with rachelpapers on motive.
posted by Rash at 6:58 PM on January 11, 2006

I think Andy Rooney had a segment on this subject.
posted by Frank Grimes at 7:01 PM on January 11, 2006

And if you feel like experimenting the most important thing is to match polarity -- get to know those little diagrams next to the sockets.

posted by Rash at 7:06 PM on January 11, 2006

There are actually standards, but most device manufacturers save money on the wall adaptor, using a transformer (which is a LOT cheaper) instead of a regulated switch-mode adaptor.

What this means is that output voltage depends on the load placed upon the transformer. A 9 volt adaptor typically outputs 11V, but when you put the load it was designed for on it, say a 300mA load, that will drop to something closer to 9V. But if you put a 500mA load on it, it might drop to 7V.

So if a transformer wall adaptor is being used, then its electrical properties mean it is really only suitable for devices of both the same voltage AND current draw, which will be few and far between.

If you're getting more high-end (or more voltage sensitive) gear, the adaptors are more likely to be regulated. (You can tell from the weight - transformer adaptors are heavy like they have metal inside, switch-mode adaptors are lightweight, like they're mostly plastic). If you have those adaptors you can typically share them across devices of the same voltage, because the plugs and sockets will often (but not always) match by voltage (and sometimes tip color), and more importantly, the voltage they say they deliver is the voltage they actually deliver no matter what device is plugged into them.

You should check that no device load (current) requirements exceeds the adaptor's maximum though - most devices are in the ballpark and will easily fit, but some are way off the usual scale.

You can get regulated switch-mode adaptors with a voltage selector switch and a selection of plug tips. These things will run anything.

Beware - you can also get unregulated transformer-based adaptors with a voltage selector switch that makes crude assumptions about load that are never really correct in the real world, and a selection of plug tips. These things will run a lot of things, but they'll also potentially damage a fair few things.

The former is not as cheap as the later.
posted by -harlequin- at 7:10 PM on January 11, 2006

Lots of equipment has a very basic power brick converting 120V AC to 12V DC, with a small circular plug. These are often interchangeable with other similar devices needing 12V DC with the same sized circular plug... This is common in cheap, non-brand-name equipment.

But the larger answer is: they are made purposely incompatible (by brandname manufacturers), so that you'll have to buy extra cords from the manufacturer of the device. Sony is one of the best at this: you can buy 20 models of Sony notebook computer, and every one will have a different power cord. This is entirely intentional. Joke's on you, sucker. Cell phone companies love this too. Lots of customers need a car charger and a home charger and perhaps even an office charger... if you change the plug design with every new phone, you get to sell them two extra chargers every time they upgrade phones. If you don't change the plug design, they'll use the chargers from their old phone. Step 3: $$$$$!

HistoryFilter: IBM was perhaps the first high-tech company to do this - by screwing with the plugs on their mainframe computers in the 1970's, they were able to keep competitors from making peripherals that interoperated with IBM equipment. They fought a long-running series of antitrust lawsuits over this, and eventually both sides sort of retired from combat - IBM made equipment with standard connectors, but the U.S. government and various other businesses that sued didn't really win either.
posted by jellicle at 7:14 PM on January 11, 2006


I believe they are standardized on one plug per voltage, but it seems to be a standard that is frequently ignored whenever it's not convenient to the manufacturer.

A high-amp power supply won't fry anything assuming the voltage is correct - only the voltage is forced on the device, if the device doesn't need many amps, the adaptor simply operates safely beneath its max capacity.
posted by -harlequin- at 7:17 PM on January 11, 2006

I've bought a USB wall charger. It's basically a wall plug which contains a transformer and a USB socket. So many of my portable gadgets can be charged via USB - iPod, mobile phones, camera, PDA - that I only carry that around with me. Saves loads of hassle.
posted by blag at 7:21 PM on January 11, 2006

Douglas Adams wrote a whole article about this, which is anthologised in "The Salmon Of Doubt":

"there's one possible theory, which is that, just as Xerox is really in the business of selling toner cartridges, Sony is really in the little dongly power supply business..."

Find it on Amazon and do a "Search Inside". it's very funny as you'd expect.
posted by AmbroseChapel at 8:56 PM on January 11, 2006

when i got my casio ht700 from my brother many years ago the adapter that came with it has many different settings and five different plugs you can use ... i don't think it's the one that came with the keyboard ... i've tried it with other stuff once in awhile and it works fine

rabbitsnake is probably right about being able to get one at radio shack
posted by pyramid termite at 9:00 PM on January 11, 2006

As a piggyback question, I've often wondered why wall warts are frequently designed such that they block any neighboring outlets on the wall or on a power strip.

Like wackybrit, I occasionally find wall warts that work for several devices [those are always exciting days], but it's pretty rare.
posted by ubersturm at 9:08 PM on January 11, 2006

Trying to draw too much current from a power brick is a good way to start a fire. I'm not joking. Even if two devices use the same voltage, if you use the brick from the low current one to power the high current one, the brick can smoke, or it can cause the floor it's sitting on (and the rest of the structure) to smoke -- and burn.

Another good way to start a fire is to use a 60Hz brick on 50Hz power.
posted by Steven C. Den Beste at 9:25 PM on January 11, 2006

Interestingly, Nokia has generally used the same charger plug for years across a number of generations of product lines, and I appreciate that.

Now, headset connectors is another story.
posted by xiojason at 10:15 PM on January 11, 2006

Let me underline the importance of getting polarity correct. Incorrect polarity will quite likely kerplode your device permanently. On some "universal" power supplies there is a polarity switch, which it is critical to be aware of.
posted by rudyfink at 2:27 AM on January 12, 2006

Powering devices is a very complex problem that has been solved thoroughly many times. The optimization of cost , profitability, reliability, and feature set is calculated again and again. Since there is no attempt at establishing a standard, you get the chaos you see. Just remember, you never know what you are buying, it might be well designed or it might be on the edge of failure...

The replacement information given so far is good, but it isn't 100% reliable, for example:

A high-amp power supply won't fry anything assuming the voltage is correct - only the voltage is forced on the device, if the device doesn't need many amps, the adaptor simply operates safely beneath its max capacity.

While that is a good rule of thumb, it isn't necessarily true. A high current supply can stress devices more under certain circumstances. When device power dissipation peaks it might 'expect' the supply voltage to drop. If the supply is designed for a much higher load the voltage won't drop, forcing the device outside its safe operating area and causing a failure.

This kind of interaction isn't normally by design, but in cases of truly extreme cost sensitivity it certainly can be. It doesn't really matter to the end user if it is by design or not though. In the case of unregulated supplies it is an important issue that should be considered whenever possible. It is less of an issue with regulated supplies, but it can still happen.

In some circumstances a power supply replacement might be working for a long time before a failure occurs. One day you might push the device harder - by turning the volume a little higher than normal, or because the room temperature is higher than normal - and pop...

I really don't mean to instill fear in people... More like confidence... There will be failures, best to understand as much as you can and learn to deal with problems as they arise.
posted by Chuckles at 3:57 AM on January 12, 2006

Ah Behringer gear:

1) The outlet is proprietary.
2) It's flimsy.
3) There's no power switch on the smaller mixers, so you have to unplug them.

posted by jon_kill at 5:25 AM on January 12, 2006

I read recently (on engadget or gizmodo) that Korean cellphone makers have agreed to harmonize the jacks on their phones—for the Korean market, at least. Maybe this is the start of a positive trend. And I'm hopeful that more and more stuff will be directly powerable by USB.

Apple has been pretty good about plug compatibility on their laptops—I know of only two varieties in recent years (and you could get a cheap step-down converter, and of course now there's that magnetic deal on the Macbook). But insidiously, they've had power bricks with different amp capacities for the different laptops—the 17" Powerbook draws more than the others, and needs a beefier power supply. The two are not distinguishable in any obvious way. Plugging a 12" 'book into a power supply for the 17" is not a problem; the reverse is a problem, and will make the power supply run very hot. This seems to have been a cost-saving measure, but potentially a very problematic one.
posted by adamrice at 7:22 AM on January 12, 2006


Ahh, here is the DC plug standard I was talking about.

More info in this wikipedia entry

So yeah, C+ for effort, but a big red F for companies that foist proprietary garbage on people.
posted by -harlequin- at 3:04 PM on January 12, 2006

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