That blue supply is nuts because it's such a nice lever hanging off of two prongs of an electrical plug. How often do these fall out of outlets? I bet they do!
A wall wart with a 3" or 6" cable will hang from the plug with more force on the plug than the blue power supply, so it's more likely to come loose. That's a reason not to have a cord that short. Even 12" might be too short. It has to be plug into a normal house outlet, usually 12" to 16" off the floor, then not hang by the wire. That might even be a UL requirement, who knows?
On October 26, 2014 at 10:47, Anthony said...
Not really
1) UL certification is not strictly necessary (and so nothing stops a company from selling a product with out it)
No product that plugs into the wall can legally be sold in the City of Los Angeles unless it is UL approved. My recent quest for European sockets revealed that some companies will not sell them in the United States because they are not UL approved. So what you say may be true, but in practice UL is "needed" at some point.
2) UL certification can be applied to internal parts just as much as external (for example my desktops internal power supply has been UL certified)
Well, duh: that's the entire freakin' reason for going with an external power supply! A manufacturer can have twenty products that only see low voltage; use external, UL approved wall warts, and when they want to introduce a new product, that product does not need to have its power supply approved by UL, costing time and money.
3) UL certification is not only for power supplies
That's irrelevant. The fact that it is not only for power supplies has nothing to do with the subject, which is its requirement for power supplies.
I think it is more for
1) ease of manufacture - think of a wireless router, you won't bring it with you on vacation, it is a fixed universal standardfor everywhere in the world, so it is easier for the manufacturer to build them all 100% the same and then add the right wart to the box depending on where it will be shipped
You don't see the lack of need for UL, or CE, certification of each product to be an advantage for the manufacturer? This is not just ease of manufacture, though that is true. It also lowers the cost of manufacture.
2) size - people are stupid and say "look how small ____ is" when it does not matter so removing the power supply helps with that
True, but you can't fix stupid. "Look, if we (manufacturer) meet our goal of spending less money on a product by avoiding the need for UL approval for every SKU, the unit will be smaller and people who can't see our main goal will think we worked hard to make it smaller!"
3) heat - power supplies run hot, having them external means it is one less issue to deal with in the design of the product.
Another benefit that goes along with lowering costs by using external power supplies.
But what ever the reasons for why external is better than internal it is not all that interesting.
Okay, except that is the subject of interest at the moment. Sure, I'm not going to think over this post several times today -- it's not that interesting. But I think it's worthwhile to be able to see big issues like manufacturing costs and assign big value to them, instead of littler issues like the size of the unit.
Since Instead of something like the one on the left with the plug built into the wart and is a bitch to use the manufacturers of the warts could easily build something like the one on the right with a 6" or even 3" cable going to the plug and the issue of why use an external power supply would be mostly moot and the wart issue solved.
Once again, you do not seem to want to see the cost of doing it one way versus the other. The supply on the left is cheaper to make than the supply on the right. The cost of the two different enclosures are very different, the wall wart being much cheaper. Yes, the manufacturers could easily build the one on the right. In fact, the manufacturer of the actual product usually doesn't built the supply AT ALL, so there is ZERO DIFFICULTY for the product manufacturer in choosing to use the product on the left or the right. That leaves cost and size as the determining factors.
I'm not saying that anything you have pointed out is wrong. I'm saying that cost is probably the deciding factor and every other advantage just follows along.
