safety of AC adapaters

I was looking at an FAQ for some small appliance that runs or recharges from an AC adapter, a black box that plugs into the AC and lowers the voltage to 12 or less, and maybe changes it to DC.

And it said this was safe, and I too have been assuming these were safe, but...

Has anyone heard of a short in one of these adapters that sent 110 volts to the thing that was supposed to charge or run off the adapter???

That would be unsafe, if it happens.

Reply to
mm
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I've heard plenty of stories about them catching fire, which is pretty unsafe.

Reply to
CJT

Don`t use them, your TV, computer and monitor all have Power Supplies. Junk them now.

Reply to
ransley

Never heard of such a thing and I check news reports every day.

Reply to
HeyBub

Thanks. That's good. One less thing to worry about.

CJT, worrying about fires is a separate category.

Reply to
mm

Extremely unlikely, the primary and secondary are wound on separate plastic bobbins, it would be very difficult for them to short together. The transformers are class II and are impedance protected too, so they will not heat up enough to catch fire even when shorted. In a nutshell, you should be more worried about getting struck by lightning than one of these wall warts electrocuting you.

Reply to
James Sweet

Hi, If you think like that nothing electrical is safe. Before it happens fuse will blow inside or something will pop cutting off power, also whatever the wall wart is feeding, that device has a fuse and reverse polarity protector, etc. built in for safety. So now what do you say?

Reply to
Tony Hwang

How is it do you think I think? Did you not see the way I phrased the question that I anticipated either a No answer, or maybe 1 or 2 cases out of hundreds of millions.

On the other hand, if I was wrong and it happens a lot, it would be unsafe, but this wouldn't make everything electrical unsafe. Their safety would remain unchanged in my eyes.

Certainly the particular device which leaks 110 into a plug that is expected to be 6 or 12 volts would be unsafe.

I don't think they all have fuses. Even the ones that do only have the fuse on one pole, and the plugs are rarely if ever polarized, so the unfused prong can easily be plugged into the hot slot.

Something? Like the circuit breaker in the basement? Sure, when it gets above 15 amps the breaker will trip. Don't you think it would still be worse to have 110 volts where only 6 are supposed to be?

Or you mean something in the circuit? By the time a non-fuse blows, a burn or worse is pretty likely for anyone in between 110v and a ground.

What if some toddler or pet puts it in his mouth?

Not everything has those. Certainly not cheap things. Are either of these UL requirements? I don't think so.

But I was never worried about the device being ruined. If an important part of any device fails, often that kills the device. That devices that use adapaters are in separate, disconnectable parts means maybe that wouldn't happen, but if it does, no big deal. By "not safe" I meant not save for people (or pets, now that i think about it).

Please, see above.

Reply to
mm

That's part of the reason most countries in NA and Europe require safety testing on products; to insure the designs are such that it can't happen with any normal single failure outside of neglect or misuse or damage to the products. No UL, CSA, CE or equivalent markings, don't buy it; it wasn't tested and it's illegal to sell it.

Reply to
Twayne

Then you wasted people's time if you knew the answer.

Your eyes area't important; only reality is important.

Not necessarily: There is some leakage, even through the air.

ALL are fused in one way or another; you may not be able to change the fuse because it's a fusible link, but it's there. Too high a temp will stop them from working; often permanently.

Good reason for GFCI's if mains is appearing anywhere it shouldn't.

Yes, the fusing is required by all the safety agencies; UL, CSA, CE, etc.. The fusing is often a fusible link inside the transformer, but it's got to be there. Reverse polarity protection isn't necessarily part of the requirements; it's often handled by the item it powers but if it's there it has to be tested.

Right.

That's a lot of what "safety" is about in the eyes of the agencies.

Reply to
Twayne

I have used many of them for year for my electronic projects. I stripped off the plug on the end of the wire and plugged the wire directly into my breadboard. A couple times the wires came out and shorted together which blows the internal diode bridge or the primary winding opens. The primary winding is made of fine wire on these small transformers and acts as a fuse. Never any smoke, fire or oders from a failed one.

Some of the new ones have switch mode power supplies. The secondary is still isolated via a transformer and feedback to the primary switching circuit is through an optoisolator.

Reply to
JohnR66

Nothing is 100% safe

The best suggestions I Have heard, both from the standpoint of safety and economy is to plug them into a power strip and turn them off when not using them.

On the the biggest problems seems to be related to the batteries in many of the new electronic devices. They can be fire hazards even when disconnected from the wall.

Reply to
sligoNoSPAMjoe

These little DC transformers can overheat. Make sure there is adequate ventilation all around them. Replace transformers that have been running 10+ years.

Reply to
Phisherman

I have never heard of ons shorting from the primary to the secondary. Usually they burn out the primary - occaisionally the secondary on the transformer type - while the switchers also fail "open".

Reply to
clare

Why? I have plenty of them that are older than that, they don't really wear out.

Reply to
James Sweet

I have some wall-warts that are 20+ years old and they still work ok when I pull them out of my junk transformer box for some odd project. But, I treat them reasonbly carefully. The odds on a UL or CSA approved unit giving 120 V (Assuming in the USA or Canada) shock is very unlikely, unless the output wire is caught between the wall outlet and the wall-wart itself.

Reply to
hrhofmann

Where did I say I knew the answer?

I said "anticipated". That's not the same as "knew".

I only addressed this because the previous poster said "If you think like that".

But you're wrong. Few people know what reality is. They base their actions on what they think reality is. That's what I do, and I'll bet you do too.

How does leakage in the air make something safe that is unsafe? How would a second danger make a first danger go away?

Also, I've never measured anywhere near 110 volts between the air and ground. Have you?

I've looked inside a bunch of them, and I don't believe all have fusible links.

Even if they all did, you ignore my point about the fuse (or fusible link) being only on one end of the coil, on one prong of the plug, and how easy it is to plug that prong into the neutral and the unfused prong into the hot slot.

It is a good reason, but we all know that not ever receptacle has a GFCI on it.

So my question stands, don't you agree?

Are you only talking about the transformer, the wall wart? Because at this point, the previous poster and I were talking about "whatever the wall wart is feeding". I think you were so eager to contradict me that you didn't read closely. I don't believe fusing is required in the device powered by the wall wart. I've taken many low-voltage things apart that don't have fuses or fusible links.

Didn't someone once say "The eyes of agencies area't important; only reality is important"?

Reply to
mm

As I said, they use class II transformers, the primary winding itself is the fuse in most of them, it is hair thin wire. These windings are on separate plastic bobbins over the iron core, and the windings are themselves insulated wire. The chances of somehow getting 120V on the output are so tiny that they are for all intents and purposes zero. You put your life on the line every time you get into a car, plane, or ship, or even walk out your front door. There are so many daily activities and items that are orders or magnitude more likely to hurt you than a transformer plug that it is not even worth thinking about and this is just paranoia.

If you are really worried about electrical safety in your house, replace all the receptacles that almost certainly use the spring loaded backwire terminals I've been complaining about lately. Install AFCI breakers on all the circuits, inspect the condition of light fixtures regularly for damaged sockets or burned wires, those are all things that really can and do cause shocks and fires.

Reply to
James Sweet

Yes. I saw your answer and I appreciated it. But I'd already told HeyBub that because of him I had one less thing to worry about, so I didn't reply to later posts that said similar things to HeyBub's. Even though your reply was more detailed. I hope I was not rude.

I'm not worried at all. I'm debating Tony and Twayne to try to resolve details of what they said, but it's already clear to me that the claim in the FAQ I saw was justified, that their adapter was safe.

I sort of know the inventor/maker of the product, and I was concerned about his forthrightness or naivete, whichever applied. I really wasn't concerned about my personal safety at all. I will still leave my phone machine adapter plugged in all the time, and the one for the cordless phone, and I've provided switches for some but that is only to save electicity and not because I'm worried about either fire or electrocuting myself.

Reply to
mm

"Never heard of such a thing and I check the news reports every day."

Whoosh!

Reply to
HeyBub

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