My brain got stuck at Power Supply question

[EBK]

Just curious, how much would one of these cost in Austria?

[ElectricDruid]

Just curious, how much would one of these cost in Austria?

I can't see that exact one, but this page suggests "not much" for something pretty much equivalent:

https://www.thomann.de/gb/guitar_and_bass_power_supplies.html?feature-14569=true&filter=true&oa=pra&price-first=0

The first result offering "galvanic isolation" (e.g. transformer, unless I'm much mistaken) is €33 for five outputs. You'll struggle to build anything comparable for that price.

Or is there something super-special about the Voodoo Labs supply?

T.

[EBK]

Or is there something super-special about the Voodoo Labs supply?

Voodoo Lab would say, "Absolutely!" 

I'm going to slightly less enthusiastically say that I just picked a brand I'm familiar with that actually means isolated when their marketing materials say "isolated."

Was curious about the difference between the price of a finished product and the cost of relevant parts in Austria (or something like that). 

[R.G.]

The company I work for happens to make a similar product, with and assortment of isolated outputs, in six, seven and 12 output models.

I try not to flog our stuff here, but in this case, I believe that the cost might be significantly less.

Our stuff uses a switching power supply front end to make several isolated DC outputs, which are then heavily filtered and then regulated with a linear regulator to wash out even more noise.

They are intended to be less expensive to the end user than similar products with good quality.

On the other hand, I have no idea what the various taxes, import duties, and so on would do to the end price.

Just something to consider.

[PRR]

> a similar product, ...in six, seven and 12 output ....in this case, I believe that the cost might be significantly less.

A Well-Known brand sells at Thomann Germany for roughly what the going rate is in the US (not counting 2nd-hand and scratch/dent deals), 124 € (=$145US); the suggested Voodoo Lab ISO5  is €129 for fewer outputs and not all isolated.

[KarenColumbo]

Thing is: I really would like to try and build one myself. If the price was the real deal-breaker, I'd go and order some ready-made stuff - Thomann or "Klangfarbe" in Vienna have some of the relevant key-pieces in stock. "Klangfarbe" would be no problem - some 12 stops with two different underground lines and a helluva lot of pretty and expensive things to browse. Even some fellow musicians working there, so there'd be beer, I'd wager. Before noon, even.

But I'm trying to learn something. Grid power (240V here in Austria) and all necessary precautions aside, there's a lot to gain here for me personally, because it's not rocket science compared to stuff like compressors or even ADSR-relevant circuits which I still can't seem to get my head around. So there'd be a chance to optimze power filtering, PCB layout on a "crude" scale etc. etc. Just wanted to NOT simply copy some existing design, I'd rather study those and arrive at my own conclusion. That's why I walk those dead paths yet again to experience the "Stop!" signs at their ends in person.

But I digress as usual. There's a transformer manufacturer here in Vienna - I e-mailed them yesterday and they answered back: They will calculate what a custom made transformer with 240V on one end and several 12V outputs on the other would cost me. I'm prepared for anything, but maybe they like the DIY spirit. And maybe some other fellow builders'd in the vicinity would be interested, so I'll wait and see.

[KarenColumbo]

Well, those manufacturers from Vienna just replied in German):

Einphasen-Trafo 29.12/19
Pri.: 240 V 50/60 Hz
Sek.: 8x12 V
Nennleistung: 40 VA
offene Ausführung mit Klemmen, Schutzart IP00
Isolationsklasse E, Transformator getränkt
inkl. Montagewinkel, Umgebungstemperatur 40 °C
Abmessung L x B x H: ca. 55 x 55 x 92 mm
Gewicht: 0,8 kg

122,- Euro

I'm inclined to take this leap - it's local business

[ElectricDruid]

Wow, that's pretty cool. I mean, €122 is still quite a lot of money for a transformer, but when it's a custom one-off that does *exactly* what you need, it doesn't seem so bad. One of those followed by rectifiers and regulators, and you'd have a very serious and fully-isolated multi-output power supply.

[KarenColumbo]

Wow, that's pretty cool. I mean, €122 is still quite a lot of money for a transformer, but when it's a custom one-off that does *exactly* what you need, it doesn't seem so bad. One of those followed by rectifiers and regulators, and you'd have a very serious and fully-isolated multi-output power supply.

That's the idea

[KarenColumbo]

Just ordered it. 6 x 12V, 1 x 15V and 1 x 18V secondary.

[EBK]

Thing is: I really would like to try and build one myself. If the price was the real deal-breaker, I'd go and order some ready-made stuff - Thomann or "Klangfarbe" in Vienna have some of the relevant key-pieces in stock.

Yes, sorry for the brief derailment there.   
You did say money wasn't a factor earlier in the thread.  We all understand that DIY is more expensive in terms of £,€,¥,$, and soft values like academic enrichment, entertainment, and personal customizability need to be factored into the economics of DIY in order to understand what motivates us.  I was definitely not trying to suggest that you should just buy something instead of building it. 

[KarenColumbo]

Thing is: I really would like to try and build one myself. If the price was the real deal-breaker, I'd go and order some ready-made stuff - Thomann or "Klangfarbe" in Vienna have some of the relevant key-pieces in stock.

Yes, sorry for the brief derailment there.   
You did say money wasn't a factor earlier in the thread.  We all understand that DIY is more expensive in terms of £,€,¥,$, and soft values like academic enrichment, entertainment, and personal customizability need to be factored into the economics of DIY in order to understand what motivates us.  I was definitely not trying to suggest that you should just buy something instead of building it.

Oh, I know that, no worries!! I think I just needed it written down to motivate me - your input (and everybody's actually) is very highly appreciated and immediately taken in consideration!

[KarenColumbo]

Since i don't want to open a new thread, here's a quick one. For rectifying the AC power I bought a couple of those:
https://www.mouser.at/ProductDetail/Vishay-Semiconductors/VS-2KBP005?qs=EO9n970mpBAgMWCds7jHUQ==

Couldn't find too much about that topic @ Google - maybe I asked the wrong questions. But this should suffice, I gather. And I bought some decent heatsinks, too, for good measures.
The specs look good to me, as far as I can squeeze info out of them:

Max repetitive and non-repetitive peak reverse voltage: 50V
MAXIMUM RECOMMENDED RMS SUPPLY VOLTAGE: 50V
These shall rectify 12, 15 and 18 volts AC.

Am I on the right track with those? (I'm still reading in on the topic power supplies, but a quick answer would help me edge closer to the gist of things)

[Ice-9]

Since i don't want to open a new thread, here's a quick one. For rectifying the AC power I bought a couple of those:
https://www.mouser.at/ProductDetail/Vishay-Semiconductors/VS-2KBP005?qs=EO9n970mpBAgMWCds7jHUQ==

Couldn't find too much about that topic @ Google - maybe I asked the wrong questions. But this should suffice, I gather. And I bought some decent heatsinks, too, for good measures.
The specs look good to me, as far as I can squeeze info out of them:

Max repetitive and non-repetitive peak reverse voltage: 50V
MAXIMUM RECOMMENDED RMS SUPPLY VOLTAGE: 50V
These shall rectify 12, 15 and 18 volts AC.

Am I on the right track with those? (I'm still reading in on the topic power supplies, but a quick answer would help me edge closer to the gist of things)

Those rectifiers are pretty heavy duty for a pedal PSU, that type is suitable for the power supply in amplifiers. You could use some smaller rectifiers for pedal power.

[KarenColumbo]

Since i don't want to open a new thread, here's a quick one. For rectifying the AC power I bought a couple of those:
https://www.mouser.at/ProductDetail/Vishay-Semiconductors/VS-2KBP005?qs=EO9n970mpBAgMWCds7jHUQ==

Couldn't find too much about that topic @ Google - maybe I asked the wrong questions. But this should suffice, I gather. And I bought some decent heatsinks, too, for good measures.
The specs look good to me, as far as I can squeeze info out of them:

Max repetitive and non-repetitive peak reverse voltage: 50V
MAXIMUM RECOMMENDED RMS SUPPLY VOLTAGE: 50V
These shall rectify 12, 15 and 18 volts AC.

Am I on the right track with those? (I'm still reading in on the topic power supplies, but a quick answer would help me edge closer to the gist of things)

Those rectifiers are pretty heavy duty for a pedal PSU, that type is suitable for the power supply in amplifiers. You could use some smaller rectifiers for pedal power.

I thought "better too big than too little". You mean there's gonna be a huge voltage drop because of those hardcore diodes?

[diffeq]

Since i don't want to open a new thread, here's a quick one. For rectifying the AC power I bought a couple of those:
https://www.mouser.at/ProductDetail/Vishay-Semiconductors/VS-2KBP005?qs=EO9n970mpBAgMWCds7jHUQ==

Couldn't find too much about that topic @ Google - maybe I asked the wrong questions. But this should suffice, I gather. And I bought some decent heatsinks, too, for good measures.
The specs look good to me, as far as I can squeeze info out of them:

Max repetitive and non-repetitive peak reverse voltage: 50V
MAXIMUM RECOMMENDED RMS SUPPLY VOLTAGE: 50V
These shall rectify 12, 15 and 18 volts AC.

Am I on the right track with those? (I'm still reading in on the topic power supplies, but a quick answer would help me edge closer to the gist of things)

Those rectifiers are pretty heavy duty for a pedal PSU, that type is suitable for the power supply in amplifiers. You could use some smaller rectifiers for pedal power.

I thought "better too big than too little". You mean there's gonna be a huge voltage drop because of those hardcore diodes?

Not really, they have a typical 1V forward voltage. Their current/surge handling is a bit overkill (2A), you will be paying for a feature that won't be used with a small current draw of pedals. LM7809 regulator can only output about 1A or less, if I recall.

Maybe this type will do?
https://eu.mouser.com/ProductDetail/ON-Semiconductor-Fairchild/DF06M?qs=Ec0VQc59F%252bn%252baq1vrcag0Q%3D%3D
Somewhat more affordable too 

[R.G.]

Couldn't find too much about that topic @ Google - maybe I asked the wrong questions. But this should suffice, I gather. [...]
Am I on the right track with those? (I'm still reading in on the topic power supplies, but a quick answer would help me edge closer to the gist of things)

I suggest you go read http://www.geofex.com/Article_Folders/Power-supplies/powersup.htm at geofex for some detailed info on power supplies.

It is usual in the power supply industry to start with the desired DC output voltage and current and then work backwards through the regulators, filters, rectifiers and transformer, specifying each part earlier in the chain of power from the AC wall socket. But if you are doing what DIY people mostly do, and buying a transformer first, you can calculate what output current and voltages are possible from that.

You probably already know your desired output voltage - usually 9Vdc for pedals.
You will want to regulate it. The two common solutions are the 7809 regulator or the LM317 adjustable regulator. Each of these regulators (and three-terminal regulators in general) need about 2V "headroom" above their output voltage to stay in regulation. So you need to supply them a minimum of 11Vdc (for a 9V output) to avoid having them saturate and letting ripple and noise flow through.
You can reduce ripple to almost any desired level before the regulators by specifying ever-bigger capacitors. As illustrated in "Power Supply Basics", the filter caps get a pulse of DC at the peak of the AC wave feeding them through the rectifiers, and then have to carry the load all by themselves until the next AC wave peak. So the voltage on the caps peaks at each AC peak, then runs down almost linearly At a rate of dv/dt = I/Cfilter. So you can make ripple as low as you want by making Cfilter bigger.

But you can never make the voltage on the filter caps bigger than the peak of the AC power wave minus the rectifier forward drop. So your transformer has to make enough peak voltage so that your regulator never gets below 2V + 2*diode voltage above the desired output voltage. Note that this includes low AC line voltage, so you have to design for more than this.

Your transformer that you ordered already has a fixed amount of output voltage for any given AC power line voltage, so you don't get the luxury of specifying it. You get whatever you get, and have to hope it's OK. In general it will be, but when you finish your testing, you'll know.

As for your question about rectifiers, always ensure your rectifiers can support at least twice the peak of the AC voltage your transformer puts out. Voltage rating is cheap in rectifiers, so feel free to go wild. I think you had one winding at 18Vac if I remember correctly. That's 18Vac*1.414 = 25.45Vpeak. So 50V rated rectifiers would be just barely enough on this one winding. But 100V, 200V, 400V rated rectifiers will not cost more than a few pennies more. Get the higher voltage ones; use 100V or 200V. Current is another issue. There is a bit of calculus to get there, but a full wave rectifier "sees" an RMS current that is about 1.6 to 1.8 times the DC current that leaves the filter capacitor that it feeds. This is worst for very large capacitors and low ripple current. Fortunately again, current rating is cheap in low-power diodes. You can get 1A rectifiers for pennies each. That will support half an amp of DC current out.

Read "Power Supplies Basics", and ask any questions that come up.



To get 11Vdc minimum on your power supply filter caps, you need the peak of the AC voltage feeding your rectifiers to be

[PRR]

> feel free to go wild.

+1

I would have told you: don't fool with 50V diodes even if they are ample. The cost of 400V diodes is so close that they are often same-price at DIY retail. The extra voltage rating does no good or harm UNTIL you need it. R.G. figures with everything nominal you may be 1V shy on your 18VAC winding(*). I'd expect 20% un-sag at no-load. "240V" is very nominal and while my 125V is steady, other folks report wild variations (to over 130V!). And then there is elevator-motor spikes and lightning near-misses. 2X over-rate is really not enough, 4X is better, and frequently 10X is same price.

Also cheaper by the dozen and usable for other things.

Here's your choices for the part you bought:
VS-2KBP005  50 Volt 2.0 Amp $2.26
VS-2KBP04  400 Volt 2.0 Amp $2.26
VS-2KBP10 1000 Volt 2.0 Amp $2.43
You see that 400V is same-price, so why buy less? 1,000V is only pennies more. If you are opposed to high voltage, the 400V part will cover anything you do with ample margin for spikes and mistakes. If you might work near hundreds of Volts, the 1KV part may be worth the 17 cents.

(*)Oh, and don't worry about 51V on your "50V" parts. There was a time when "50V" meant you were sure to never see a 100V breakdown (they'd sell it as 100V and higher price.) But the days of sort-out are declining. The price-list above suggests they aim for 1000V and get >400V almost every time. They list a 50V part for buyers who take a BoM too literally, or in case they have a bad day in the kitchen, but I bet you are really getting hundreds-Volt parts at the 50V price.

[PRR]

oooops... the 400V part is On Order at Mouser. But remember the over-buy concept anyway.

[Ice-9]

For pedal power I would use something like the DB10x series rectifier or even just use 4x 1N400x diodes. Here is the datasheet for the DB10x series which are a DIL package similar in size to a 8 pin Dill op amp package.

http://www.rectron.com/data_sheets/db101-107.pdf