ONE-SPOT Power supply scheme?

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lynessmy
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Post by lynessmy »

Had anyone seen schematic for ONE-SPOT power supply around?
I was wondering how it supply 1.7A with that small package....

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Post by Brian M »

i dont have a schematic, but i can tell you the reason why it is smaller than a typical power supply. It has no transformer.

It is becoming a more and more common way of making DC power supplies. Essentially what they do is they use an electronic switch (probably just a beefy transistor with a heat sink) it turns on when the mains power reaches a certain voltage (usually peek) and charges a capacitor. When the capcitor gets to a certain voltage the switch gets turned off. The charge goes to a voltage regulator, and from there you have your voltage output. Since they primarilly rely on the regulator for their output voltage they will run off a wide range of input voltages and frequencies if designed corectly.

The active switching puts a bit of a limit on how much current you can economically get out of this type of power supply.

Most of these types of of power supplies have other stuff in them to make sure they turn off if they start to fail, although the earlier onespots supposedly fried a lot of pedals a few years ago. Not sure if they have changed anything.

edit- also, when i was working in the energy, as these types of power supplys were becoming more common, they were actually causing electrical problems in large office buildings. Lots of fax machines, and computer equipment uses them these days. Since the load the mains power sees is not at all linear the cumulative effect, especially in large buildings (long cable runs) ends up causing a lot of harmonic distortion on the mains power. When this happens, the neutral connections at the breaker box heats up and can start a fire. fun stuff

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Post by marmora »

Brian,
What type of power supply do you recommend building/using?
Thanks

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Post by R.G. »

Let's be accurate, OK? I happen to know a great deal about the 1Spot in particular and other wall adapters in general, as well as having designed switching power supplies for a living a ways back.
Brian M wrote:i dont have a schematic, but i can tell you the reason why it is smaller than a typical power supply. It has no transformer.
Actually, it does have a transformer. It has a high frequency transformer. The power a transformer can handle is limited by its temperature rise and the lowest frequency it has to pass. By rectifying the AC power line to DC, then switching the DC at a few hundred kilohertz to maybe a megahertz, the size of the transformer needed is vastly decreased FOR THE SAME POWER TRANSFERRED. The isolation transformer in the 1Spot is about the size of the end-section of your thumb.
Brian M wrote:It is becoming a more and more common way of making DC power supplies.
It's not only becoming more common. California has LEGISLATED that all wall adapters sold there must be switching type (based on the required efficiency). This goes into effect this year.
Brian M wrote:Essentially what they do is they use an electronic switch (probably just a beefy transistor with a heat sink) it turns on when the mains power reaches a certain voltage (usually peek) and charges a capacitor. When the capcitor gets to a certain voltage the switch gets turned off. The charge goes to a voltage regulator, and from there you have your voltage output.
Close, but moderately wrong on all counts. As I started with above, what they do is to first rectify the incoming AC power line to either 170 or 340Vdc. Then they use typically a power MOSFET (used to be bipolars, but they're too slow in general) to chop the DC into rectangular square waves which are fed to a transformer. The transformer provides the necessary safety isolation (4kV) between the power line and the secondary, as well as stepping the voltage down. The secondary is rectified to DC again and used as an output. The output is fed to an optoisolator back to the control IC on the primary side for regulation. The circuit regulates itself by the pulse width in the chopped waveform fed to the transformer.
Brian M wrote:Since they primarilly rely on the regulator for their output voltage they will run off a wide range of input voltages and frequencies if designed corectly.
Since they rely ENTIRELY on the pulse width regulation of the IC in the primary side, they can run off a wide range of input voltages, generally 80Vac to 260Vac and still maintain regulation if designed properly.
Brian M wrote:The active switching puts a bit of a limit on how much current you can economically get out of this type of power supply.
The active switching allows you to get vastly more current out of the same size, weight or price power supply compared to a non-switching power supply in all but a few instances. One of those used to be the very small size power supplies. No longer, as the 1Spot and its ilk show. I don't think you can get a non-switching power supply for the same price and size that produces as much power (i.e. voltage x current) as the 1Spot. Switching is the way to get high current and power in small packages with low waste heat.
Brian M wrote:Most of these types of of power supplies have other stuff in them to make sure they turn off if they start to fail, although the earlier onespots supposedly fried a lot of pedals a few years ago. Not sure if they have changed anything.
Unless you're using "onespots" as a generic term like "xerox" for copier and "kleenex" for facial tissue, you are incorrect. "1Spot" is a trademark for the single-AC-plug power adapter sold by Visual Sound. There are other brands, as I mention below that have copied the concept. One very common one appeared less than six months after the company had a booth next to the Visual Sound booth at NAMM.

It is true that some switching style plug in 9V adapters are poorly designed and probably have fried effects. It is not true that there was ever a 1Spot frying epidemic. I know, I work for the company (Visual Sound) and part of that work is to evaluate *every* 1Spot related issue where the adapter has supposedly fried a pedal. We have given some people the benefit of the doubt, and we have had a few die in the field, but overall, the 1Spot has an incredibly (even to me) good track record. It was designed specifically for powering pedalboards over a long design period, and does it very well; to the best of my knowledge, it is the ONLY adapter designed solely for powering pedals, not adapted from some other use. The 1Spot is not perfect - but the statistics show it's very, very good at what it does.

It does it so well that it has of course attracted imitators. Take your own chances with the imitators. It is possible that the imitators inspired what you heard about as fried pedals.

The 1Spot has also been the target of some effects makers blithely saying that the 1Spot kills their pedals. We have investigated a number of these down, provided free 1Spots and technical data for them to do their own tests and also conducted OUR own test on reliability. I believe that all of the pedal makers who have had this position and worked with us have changed their minds and now have no issues with the 1Spot.

We have yet to find a case where the 1Spot, even the earliest ones, wantonly killed pedals. The insides of the 1Spot provide a number of safety measures designed to keep the pedals safe, in fact.
Brian M wrote:edit- also, when i was working in the energy, as these types of power supplys were becoming more common, they were actually causing electrical problems in large office buildings. Lots of fax machines, and computer equipment uses them these days. Since the load the mains power sees is not at all linear the cumulative effect, especially in large buildings (long cable runs) ends up causing a lot of harmonic distortion on the mains power. When this happens, the neutral connections at the breaker box heats up and can start a fire. fun stuff.
When I was working in power supply design, that was indeed an issue, and is a recognized one in the power distribution industry. You don't go far enough. I can't think of a single current-manufacture office machine other than "dumb" stuff like refrigerators and coffee makers that do not have a switching power supply. With California and other places legislating power efficiency, you can assume that the power distribution is simply going to have to cope. However, it's the aggregate of the zillions of kilowatts of switching power supplies doing that, not the 1Spots.

The 1Spot meets or exceeds every standard for safety, performance, efficiency, radio emissions and even power factor issues (that's your distortion/neutral current issue), as well as being the only pedal power adapter I know of that is 100% tested on the power line for working with no switching noise in a high-gain distortion pedal. Every single one is plugged in to power a high gain pedal that's selected for being finicky, and must not produce audible hum or whine. I've watched them do this on the assembly line.

Do you get the idea that you hit a nerve? :lol:

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Post by super velcroboy »

nice post RG. Make me want to break open my 1spot (unused) and see for myself

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Post by R.G. »

super velcroboy wrote:nice post RG. Make me want to break open my 1spot (unused) and see for myself
Cool, go for it.

Be aware that opening it will void the warranty, on safety grounds. But frankly, they're not expensive enough for that to be a huge issue, so if you're willing to lay out the bucks to satisfy your curiousity, I'd be the last one to tell you not to do it.

There are critical issues with safety in there, so I recommend that you not try to put an opened one back into service because it's safety performance may be compromised.

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Post by R.G. »

WormBoy wrote:
R.G. wrote:We each have to go with the numbers we see.
Well, the statistics are on your side; my n=1 does not really make a case in court :lol: But the human brain (mine included) primarily works by extrapolation from personal experience, so you'll have to excuse my less-than-total-confidence in the 1Spot for now while I'm trying to confince my brain to work differently
I was excusing your less-than-total-confidence based on the number of cases, just telling you why mine's different. Both views are equally valid, based on the experience. :D

In point of fact, this particular forum is populated with people who for one reason or another want to believe the opposite from whatever a pedal maker says. Which is OK, and in many ways a relief from the mojo-heads who only know what the ad copy tells them. Lord knows there's been a torrent of BS out of the boutique makers; that is one reason I'm here. In today's hyper-marketing based online world, a healthy skepticism of advertising copy is almost a survival characteristic.

I don't like the blast of "hand wired point to point carbon comp tropical fish silver solder oxygen free copper they-don't-make-them-anymore" that spews out of the sales machines. I write a column in Premier Guitar (used to be Musician's Hotline) and I spend a lot of the articles debunking the casual, almost de rigeur stuff that stokes the boutique market. I kind of think that the sound ought to speak for itself. If a pedal sounds good, it doesn't matter whether it's made out of denatured plutonium refined by Icelandic virgins on the night of the full moon at the only crossroads in Iceland or laminated belly-button lint. The sound's the thing. Follow the sound.

People laugh at me for saying this, but it really is the reason I went to work for Visual Sound instead of a number of other places: their motto is "Real tone for real people" and they mean it.

So that's my Pollyanna-ism for today. You may now laugh at my naivety. :lol:

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Post by modman »

I sliced out the discussion on MAX1044 causes of damage & alternatives and moved it the FAQ's & Howto's folder.

Learned the hard way about the max1044 myself ...
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Post by Brian M »

Hey RG, thanks for correcting me on that.

The info I have on these types of power supplies was from Square D, circa 1999 or so. Their explanation was essentially what I paraphrased, although I added in my own assumptions due to the simplification of their literature. they are not the kind of company that actually makes wall wart power supplies. they just have to deal with the consequences of them for power distribution. Basically their simplified "schematic" showed no transformer. Perhaps this is something else entirely, and I just assumed the one spot was similar, or maybe their explanation was overly simplified.

I suppose having no transformer could be quite problematic now that I consider that most wall warts are Class II devices. I'm not sure that's even possible with a transformerless desing, simply because there is no real isolation from the in coming AC voltage.

Anyways, I have a one-spot among many other power supplies that i use, and it works great, and it has never failed. I do however recall a number of people claiming to have problems with the early ones... but no experience with with them failing my self.

Thanks for the lesson RG :)

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Post by ubersam »

R.G. wrote:...
It's not only becoming more common. California has LEGISLATED that all wall adapters sold there must be switching type (based on the required efficiency). This goes into effect this year...
Aw cr@p... I wonder what will happen with adapters like the Voodoo Labs Pedal Power :hmmm:

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Post by soulsonic »

ubersam wrote:
R.G. wrote:...
It's not only becoming more common. California has LEGISLATED that all wall adapters sold there must be switching type (based on the required efficiency). This goes into effect this year...
Aw cr@p... I wonder what will happen with adapters like the Voodoo Labs Pedal Power :hmmm:
"Required Efficiency"? What? 60Hz transformers aren't inefficient, they're just big.
If they want to really solve problems like that, they need to raise the mains frequency... but of course they'll never do it, just force us to use half-assed "solutions" to problems that aren't even really problems.
This is why I use batteries. :P
"Analog electronics in music is dead. Analog effects pedal design is a dead art." - Fran

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Post by Mitch T »

Very nice and informative post, thanks for that R.G.
Anyway, this rumor of Onespot-type wall warts frying pedals, is that the reason why Teese is so anal about "Max 200mA" for his wahs lately?
I really don't get that...

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Post by R.G. »

soulsonic wrote:"Required Efficiency"? What? 60Hz transformers aren't inefficient, they're just big.
If they want to really solve problems like that, they need to raise the mains frequency... but of course they'll never do it, just force us to use half-assed "solutions" to problems that aren't even really problems.
This is why I use batteries. :P
60Hz transformers are not inefficient, no. However, a regulated wall wart does eat some standby current, and using a 60Hz plus linear regulators wastes a fair amount of power when the unit is supplying a load. It offended the California Energy Commission that it should be legal for Evil Big Companies to build products that were powered by wall warts that simply stayed plugged in and that people would buy them in large quantities.

Iactually suspect that they toyed with making wireless telephones, phone answering machines, cell phones, network modems and switches, scanners, modems, yada, yada, yada illegal without a state-issued permit, registration and a two-week waiting period for a background check and DNA sample on file, but rejected that as being too onerous on the state legislators and their campaign contributors. :lol:

It's one of those things where some yo-yo thinks that we can save the world (literally!) if we'll all just say "No" at the same time.

California has decided that it will not allow any significantly more individual energy consumption than exists now; it is doing that by preventing construction of any electrical generating capability, oil exploration, or oil refining capacity, and probably increasingly any manufacturing industry at all. This has the effect of generating a number of "crises" where people can't turn on a light bulb, drive a car, communicate, eat, drink, all those selfish things that people want to do, and so the people will approve ever more draconian intrusions in the name of curing the crisis. It's a neat political trick. Every time the local city government here wants to issue road bonds, they re-time the stop lights on major highways and streets for the rush hours so the lights are just a ...bit... shorter.

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Post by R.G. »

Mitch T wrote:Very nice and informative post, thanks for that R.G.
Anyway, this rumor of Onespot-type wall warts frying pedals, is that the reason why Teese is so anal about "Max 200mA" for his wahs lately?
I really don't get that...
We did work with Geoffrey - great guy, by the way, known him by phone and internet for over a decade - on that topic a little.

Without getting into Geoffrey's business too much, I believe that Geoffrey meant exactly what he said - don't use ANY power supply with over 200ma available. The 1Spot does happen to fall into that area, but I believe he did actually mean any power supply with over 200ma available.

I do not know all of the ins and outs of Teese pedals by any means, but from that interaction, I'm fairly sure that early rumors about the 1Spot did not factor into it.

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