Wall Wart Woes!

I find it funny that a huge number of AC fed power supplies (only the switchers) will work, no problem at all, if fed with DC.

Since there is no transformer, no cycling is needed.

One cannot do that with a linear, transformer front ended power supply.

Maybe because they are owned by, and their designs are engineered by Cisco now.

These were all pre-Cisco models.

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You can't have a sense of humor, if you have no sense.

No, because the droid in shipping reaches in the bin and pulls one to stick in the kit. There are likely four vendors' wall warts in the bin, which is used for 999 different kits.

We'd mark the case with the "universal symbol" (concentric circles, with a line going to a "+" for CPP) and the voltage. It costs a little. I don't understand why there would ever be CPN, but that's just me.

You think people are going to read a silly sticker before plugging something in? If it fits, it's going to be tried. I tried to code the voltage and current into the connectors (center pin diameter and length) but it cost quite a bit, in both $$ and aggravation, to do it and it didn't always work.

I think that's a UL requirement, but maybe not for really low power devices.

I tried to do that with a TVS and polyfuse. Low voltages were still a problem, though.

Sometimes you can recognise the maker even when it *is* badged. I don't mind so much that the wart doesn't say which product it belongs with so long as both PSU and product both state their ratings and polarity.

I find a dab of coloured paint on the plug and socket helps avoid embarrassing smoke emissions where different scanners/routers have identical connectors but significantly different voltage requirements.

Problem is that the same unit likely powers a dozen different products.

What I want is the product having a case moulding that includes the power polarity, voltage and current requirements of the product. This labelling is mandatory for mains powered equipment, but apparently once you stick a wall wart in the way you can just put a 3.5mm socket labelled "POWER" on the outside and be done with it.

Mass production techniques don't cost more for a few extra characters on the injection moulded back panel, nor would it hurt to include these details in the manual tech ref pages! Virtual ink costs nothing.

It seems most engineers agree with me so how do we get the halfwitted MBAs to make the change? I guess they see customers blowing things up due to badly designed power connectors as a way to increase sales.

EU inspired thing to prevent the insane proliferation of utterly incompatible mobile phone charges using ever more exotic shaped connectors but almost all about the same voltage and power.

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Regards,
Martin Brown

Don't ever get the idea that a vendor has your best interests in mind! You will have to fix this yourself.

The silver sharpies write well on black plastic. I record device, volts, AC-DC, and current.

You need to mark the same info on the devices.

John Ferrell W8CCW

You should get out more. Always is an often misused word.

If there's a connector accessible, that often connects to ground. Then you can measure from that connector to the power socket to determine the ground connection. The other one is often positive.

So, we're supposed to disassemble each such device (think: flimsy snap-together construction... if not *gasp* solvent welded!) and go on a reverse-engineering mission?

You can sort out polarity. And, you can put an upper limit on the

*voltage* (not to exceed the lowest WVDC of the caps on that line). But, no idea as to current requirements.

All this work just so a vendor can AVOID marking his product clearly? Hint to manufacturers: make your corporate logo smaller if you don't have room for this information ()

I had this happen with a network to printer interface, where the wall wart just "walked", and they needed the printer to do the wages. I spent half an hour trying to reach the agent on the phone and then the the case came apart in my hands.

2 sided PCB, power socket , bridge rectifier, capacitor , 7805 I decided 12V, polarity unimportant, and 300ma sould be plenty , (judging from the size of the printed heatsink)

A couple of months later the replacement wall wart walked,

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?? 100% natural

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Yup. I "rescue" quite a bit of surplus medical equipment (which is ultimately shipped to "less fortunate" parts of the world). Losing a wall wart/brick/power supply can easily turn an otherwise useful bit of kit into a pile of scrap.

But, often these devices are made by small outfits (yeah, there are the Siemens/Philips/etc. out there but there are also a lot of MedicalDevices`R'Us folks, too!). They tend to go belly up. Or, get bought up (by whom?). So, chasing down the vendor is often a lot of work (especially if the device has some "age" to it -- you might find the current owner of the design only to discover its no longer supported: "The *guy* who designed that is no longer with the company...")

To make matters worse, they often pick weird voltages that make

*their* life easier knowing that they are going to pay to have a custom "power pack" built, regardless. (I think the appeal of external power is the UL issue).

There's a fair bit of value to "guessing correctly" as medical kit isn't the sort of thing you can walk into the local 99 cent store to purchase: "I'd like two packs of chewing gum, a hair brush and a fetal heart monitor, please..."

I've been looking for a good dremel/mototool for the express purpose of slicing open solvent welded cases -- without making *too* much of a mess of them that they couldn't, later, be reglued.

Wouldn't it be *so* much nicer if the things had 4 parameters printed/encoded on them: voltage, amperage, polarity, connector type? Especially for the commonly used combinations!

But, even *this* wouldn't work! How long does the *barrel* need to be? (a common problem with replacement bricks for laptops -- which seem to have "thick cases" forcing the mating connector to be located too far recessed inside the case for a "normal" barrel connector to completely engage)

And, of course, the fact that these connectors don't stand up well to the sorts of abuse they encounter!

Have you considered one of the 4" table saws, with a very thin blade to cut a grove around the case?

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You can't have a sense of humor, if you have no sense.

Hmmm... never thought of the "tablesaw" approach. That would really be a win when it comes to making sure you just "kiss" the sides of the case (usually, the innards are very close to the case wall, itself, so "too deep" means *toast*).

It would also help (using a fence) to keep the cut straight.

I'd be concerned about the size of the blade (sloppy bearings causing wobble plus it's thickness). The dremel approach seemed safer in that regard -- small diameter/thickness. *But*, dremel means you've got to have a lot steadier hand/eye!

Dremel makes thin, toothed cut off blades as well. Using the abrasive one or the 'concrete saw' type only MELTS its way though the case. That is no 'cutting' at all. The toothed cut-off saw works great though.

Yeah, but since when does one actually need to make a perfectly straight cut in a lame little plastic case?

You mount the dremel, and you HOLD the work in your hand. You could actually make a mini 'table saw' with the dremel itself.

Power is not the reason. The fact that they are fully isolated and in a non-conductive sealed case is the reason it may not be an actual requisite.

Those lttle saws are made for trim work, and making picture frames, so the have to be stable. I've looked at them in person, and plan on buying one later this year.

You could use a piece of sheet metal and make a very thin blade with just a few teeth (to mantain balance) to cut without melting the case. I doubt the dremel can be held steady enough, and cut instead of melting.

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You can't have a sense of humor, if you have no sense.

Damn, that is enough to make me rethink my dremel/rototool DIY solution.

?-)

Cutting plastic was the first thing that came to mind when I spotted one at the HF store. :)

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You can't have a sense of humor, if you have no sense.

The reviews seem to complain that it has no balls. Not even

*prepubescent* balls! :-/ Id wonder if it really could handle hard plastics when you see comments like: "I purchased the tool because I thought it would make cutting balsa and basswood easier. Sadly, it does not."

"I thought the underpowered reviews might be overstated, and it would be fine if you just pushed your item slowly. WRONG. I couldn't even cut through 1/8" thick hobby plywood"

"The engine is super quiet, yet it doesnt cut through anything harder than cardboard. Bought it to cut PVC pipe, however the motor wouldnt last an inch through the thin plastic. Motor needs alot more power"

"In the store it looks great for the work that i do . Small woodwork for fairs and etc . But the motor is not even strong enough to cut through quarter inch birch plywood never mind picture frame material"

I am, now, thinking that I should look to see if they've made a "jig" for the dremel that would effectively turn it into a table saw or chop saw. That should afford the stability and "small blade" features.