Transformerless PSU using a capacitor

Yeah, I think you are right, that would be a holiday.

--

Rick C

I want to know what is wrong with using a five buck transformer rather than creating a shock hazard.

Such a scheme beats on the cap and it may go bad. In fact it may short out and teach you why they do not do this. Hopefully your fire insurance is paid up.

This is worse than those little transformerless cellphone chargers. They should not be allowed to sell those things.

There is a right way and a wrong way, and a capacitively coupled doodad like this is the wrong way.

an creating a shock hazard.

t and teach you why they do not do this. Hopefully your fire insurance is p aid up.

should not be allowed to sell those things.

ike this is the wrong way.

Yes, but I believe it was only an exercise in a class. But you can use thi s technique on the secondary of a transformer instead of using a dropping r esistor, although I can't recall seeing it done.

The only time I used it was very recently on an old AC/DC radio from the 30 s that had about 80V worth of filaments but needed to run on 120V. The rad io originally used a resistive AC cord which consisted of two normal conduc tors and one length of asbestos yarn wrapped in a spiral of nichrome wire t hat ran the entire length of the AC cord and connected to one side of the A C plug. This long wire resistor provided the necessary drop for the filame nt requirement. The cord was shot so I put in a two wire cord and used some thing like 6uf worth of film caps out of Panasonic plasma sustain to get do wn to the proper voltage for the tube's series string. It's fused, but it' s a temporary solution just to get the radio operational. If I ever restor e the radio I'll probably locate a replacement cord as there's no room for a dropping resistor of the necessary wattage in the case (miniature mantle radio).

** No shock hazard if built sensibly.

Smoke detectors use dropping caps all the time.

** They sometimes go open.

** A fuse or fusible resistor in series with the incoming AC is wise.

.... Phil

Yeah, another thing that raises the cost of fire insurance.

I remember when GM used resistive wire as a ballast for the coil, which was shorted out during cranking by the extra terminal on the solenoid. We have advanced past that and resistive power cords. WE now know how to control power pretty accurately.

If you really must restore some old thing to its original, unsafe and inefficient state, by all means do so. But don't come crying to me if it burns your house down. Mainly, don't fall asleep with the thing running.

Sorry, I tend to err on the side of safety. Things need to be isolated and that means a transformer. A capacitive coupled device ? I would not have it in the house.

I have had dangerous things, for one guns. Then my buddy brings over this oxygen hydrogen separator that runs on 12 volts. And he didn't realize that it was better to separate those two gases, because together they are most dangerous.

He wanted to use it to boost his car, but we found out that the thing was pulling like 11 amps at 12 volts and the load on the alternator would negate most of the gain.

It is like what I have been saying, fossil fuel beats about anything, that is why it sells. When something better comes along, the oil companies won't be oil companies, they will be selling whatever it is.

But anyway, dropping voltage/current with a capacitor is not the way to do it. There are times when you just cough up the money for a transformer.

---------------------------

** Your toaster isn't isolated, nor is your hair dryer and a host of everyday appliances.

The only appliances that NEED isolation are electronic ones that have external connections to other devices. The rest can safely rely on being fully insulated or by safety grounding any external metalwork.

FYI: transformers do not automatically provide *safety isolation* unless that are designed to meet class 2 requirements. Very few off the shelf ones are.

Your constant posting of rambling drivel is getting worse - jurb.

You have way too many loose screws.

.... Phil

Really? All the ones I have taken apart (and not just for cellphones) are switch-mode with tiny transformers. Admittedly I don't know how they make them miniature secure isolation devices...

Mike.

--------------------

** The term "transformerless" sometimes only means there is no iron transformer - just small ferrite cored one instead.

Nowadays,they can be made as SMD devices and be incredibly small for DC powers of 1 watt or so.

** Enough insulation is there to tolerate the AC supply voltage and not fail from overloading.

The latest thing is a "piezo transformer" but I have no evidence that are being used in cell phone chargers.

.... Phil

are being used in cell phone chargers.

I hadn't heard of that, but I suppose it is a no moving part (in usual interpretation of that phrase) motor+dynamo combination; brilliant!

Mike.

yday appliances.

ernal connections to other devices. The rest can safely rely on being full y insulated or by safety grounding any external metalwork.

that are designed to meet class 2 requirements. Very few off the shelf one s are.

thanks to you all for that fruitful discussion. As indicated by Phil its not all appliances that need to be duly isolated. A device like an automatic dawn to dusk light switch can be safe without an isolation transformer besides during the day the transformer's primary wil l still take some power and warm up. I have also seen a Chines made portable radio set without transformer. It w as boldly written on it "transformerless AC radio" apparently the manufactu rer was boasting. A guy opened it to find out what was inside and showed us this cap drop power supply so he warned the friend against possible electr ic shock when he touch any metal part. the friend replied there were no met al parts so its safe. Not long before that he got zapped when he forgot tha t the antenna was made of metal. l am going to let him read all your post. Thanks once again. i ve asked him to read all your post

fficient state, by all means do so. But don't come crying to me if it burns your house down. Mainly, don't fall asleep with the thing running.

If you're referring to the resistance line cord in my example, there aren't many options even if you don't care about originality (I don't). That rad io in my example has 5 tubes, two IF XFRs, a gang tuner and a dynamic speak er all crammed into a 4X10 chassis pan. The plastic cabinet covers this li ke a glove. There's simply no room to mount a 25W resistor or mitigate the heat that it produces.

Still, in the trade, the resistive AC line cord was known as a "curtain bur ners" because people would often coil them up in a neat little ball instead of spreading them out as the owner's manual directed.

I do restore an occasional antique radio for my customers, and even after a dding fuses and polarized line cords to them, I instruct them on the danger s of line connected metal chassis and never plug in the radio if one of the plastic knobs falls off. I also instruct them to leave all old radios unp lugged when not in use and to not leave them running unattended.

The sovereign remedy for a curtain-burner is a unique plug to an external box that contains the resistor and heat-sink assembly. A nice, fat DALE aluminum resistor of the appropriate rating does well.

In this way, the radio does not get plugged into the wall by accident (nor anything else), and the external box can have a fuse, switch and other niceties as well as serve multiple radios.

Safety is a good thing, and despite the fact that our parents survived all sorts of deadly things such as a lack of seat belts, hard dashboards, Open-mesh electric fans with metal blades, and much more, there is no reason to lean into a punch.

Peter Wieck Melrose Park, PA

box that contains the resistor and heat-sink assembly. A nice, fat DALE al uminum resistor of the appropriate rating does well.

r anything else), and the external box can have a fuse, switch and other ni ceties as well as serve multiple radios.

True, but that doesn't preclude the possibility that someone in the future will find the radio, cut off it's unique plug, and replace it with a standa rd AC cord. The radio also loses some of it's charm having to be connected to a life support box instead of being independent.

BTW, does anyone else remember the Sanyo/Fisher receivers of the 80s that u sed LV AC taps off the transformer to power the matching Sanyo/Fisher tuner , CD, and cassette deck? I saw a bunch that had the unique plugs cut off a nd replaced with regular AC plugs. Feeding 120V into a tuner that worked o n 16VAC left a big black smudge inside the cabinet.

The 1930s radio in question was only powered up with capacitive voltage dro pping as a triage to assess the rest of the radio. I haven't yet decided w hether to restore it. If so, I may keep the capacitors and add a diode, fu se, and zener crowbar to eliminate any possibility of a shorted cap running amok. These things can be safely installed below the deck and produce no heat.

Generally, if I make any sort of functional change to any given radio - dro pping resistor, dropping capacitor, whatever, a 3 x 5 card will go under th e chassis with such notes on it. I am not above using an etcher as well to make sure that something really important is not lost over time.

Stuff "below the chassis" has its significant advantages but unless explain ed becomes a mystery to the next user.

Peter Wieck Melrose Park, PA

Actually, the load on the alternator must be MORE than any gain, otherwise you would have a perpetual motion device. Eric

s oxygen hydrogen separator that runs on 12 volts. And he didn't realize th at it was better to separate those two gases, because together they are mos t dangerous.

s pulling like 11 amps at 12 volts and the load on the alternator would neg ate most of the gain.

The HHO guys say you can get "free" energy out of tap water by building a h ydrogen generator and feeding the resulting hydrogen into the intake of the engine giving it more power and using less gasoline. What the poster was saying was any gain (if any) from any hydrogen produced and burned would be negated by electrical toll it took to create it.

Even if the hydrogen scheme produced a net positive, it still wouldn't be p erpetual motion (or breaking the conservation of energy law) any more than a gas engine is because the water is an expendable fuel.

What you are saying is that it would be not be breaking any conservation of energy law if you get more power from an engine by feeding it hydrogen or even HHO that the power required from the engine to break the water molecule apart into HHO. I don't get it. Please explain. Eric

When you burn the hydrogen and oxygen you produce more water that could be fed back into the tank along with the water produced from burning the hydrocarbons resulting in *MORE* fuel than you started with. But the problem is that the energy produced by separating the oxygen and the hydrogen is at *least* as much as what you get from burning the hydrogen. Taking into account all the losses and you get a net loss of energy by some

80% or more.

Eric is right. Water is not a fuel. The fact that in any practical machine you just refill it is because of the cost rather than the issue of it providing any energy.

--

Rick C

rickman wrote on 8/3/2017 5:23 PM:

Err, that should read, "energy *consumed* by separating the oxygen and the hydrogen"

--

Rick C