Three-in-one-power... this right/safe???

[NaBo]

I've been searching archives and scanning through articles all morning and i put together this wiring diagram for what I hope will be my single 9V power supply... 3 outputs, one for high gainers, one for modulationers, and one for backup/spillover.

Can someone check and make sure im not forgetting something?

[toneman]

regulators need *DC* input.
U have xfmr(AC) going to "reg block".
T

[nelson]

HAve a look at some 15V EH schematics power input sections. the delx elec mistress on GGG should give you some Ideas.

then use your 9v regulator instead of a 15v regulator.

[NaBo]

tone- sorry bout that...  :oops:  the "9V reg" block is a full 9v regulated power supply board, with the bridge rectifiers included.  suppose i shouldve shown that or labelled it better

nelson - hunh?  there's plenty of 9V regulated power supply projects all over... shouldnt you direct me to one of those if thats what you think i need?  :wink:

it's basically three entire GGG 9v reg'd power supplies in parallel, all using the same mains connections, with fuse protection and some LED switching- I'll focus my question a bit:  is the fusing, and switching wiring all correct?

[Hal]

you want to switch them individually?  I don't think it would be a problem switching the secondaries - you'll waste a bit of power becuase of the resistance of the primary coils, but you would be able to use a lighter duty switch.

[NaBo]

i have 4 or 5 125V / 5A switches  

[nelson]

:oops:  :oops:  :oops:  :oops:

Yeah...9v, either would work lol

[NaBo]

aww, don't sweat it nelson, i appreciate that you were trying to help

hmmm, so it seems that i do indeed have some idea of how to wire up a safe functional power supply... hopefully i can work out a nice layout for all three supplies and build this within the next couple of weeks, and stop wasting batteries

thanks for all you guysesses help and suggestions

[Johnny G]

my only thought is quite why you'd need three transformers? i realise that you want seperation between high gain pedals/modulators to stop power supply coupling etc. but it would probablly be easier to have on larger transformer and then 3 seperate 9volt regulator circuits off that.

actually thinking about it, might you not also possibly be getting some gnarly ground loop action like that? im not totally sure but it may be something to think about

[NaBo]

well, i have a bunch of those 400mA transformers handy... got a bunch for 2 bucks each... Most people can probly run their entire pedal board off that much... but i'm gonna have about 25 pedals boxed up, and tricked out with all sortsa LEDs (bypass indicators, power indicators, rate when practical, mode when possible, etc) and you never know, i might wanna use em all at once  :twisted:  :twisted:  :twisted:  

It's based on the principle of the spyder, which can either use that custom wound single transformer with several 9V taps, or a ton of small ones (RG suggests 60mA ones from mouser at something like 2 bucks each)...  and the whole purpose of the spyder is to eliminate ground loops without using ground-wire-snipped patch cords.  Granted, i'll be running daisy chains off the outputs, but it shouldn't cause anymore of a ground loop issue than any other single-transformer supply powering multiple effects.  and, since i'm only having about 6 multi-effect enclosures, and one power jack each, I don't mind making a couple special patches for the short connections between units that are sharing the same supply.  So, unless there's some huge oversight on my part, it should work out pretty well...  :? make sense to you guys or no?

[Johnny G]

well it all does make sense to me, i can see what you mean about the sypder-esque design and i fully understand the "bigger is better approach" lol

go for it id say. hell if you really screw up then it only cost you $15 bucks

[niftydog]

what are the blue things? They concern me. Are they switches? Why would you need/want to switch a power supply, ESPECIALLY ON THE PRIMARY SIDE?!?!

hell if you really screw up then it only cost you $15 bucks

yeah... or your life!

Mains power is not something to fool with unless you are confident you know what you're doing.

Since you felt the need to ask, NaBo, I since that perhaps you aren't 100% confident, and are therefore taking a serious risk in futzing with mains power.

Granted, i'll be running daisy chains off the outputs, but it shouldn't cause anymore of a ground loop issue than any other single-transformer supply powering multiple effects.

so, why not just keep it simple and go with a conventional single transformer design? You are not gaining anything by using multiple transformers in this case, except that either you already have the transformers and wish to use them or that you have a sizing issue with larger transformers.

[ethrbunny]

What values will you use for Ra,b,c? Seems like the resistances at each output jack will be quite variable. Wouldn't that give you varying LED brightness?

[NaBo]

Thanks nifty!--- see, now this is why i asked... i want to be 100% confident.  I'd rather not take unnecessary risks. I have a good handle on how to work safely with high voltage, as in not electrocuting myself... I would most definitely not futz!  I'd work extremely carefully and read every possible piece of safety advice i could, 100 times over, before i ever started... and have my pops, who has done a fair bit of diy lighting and such around the house and garage, help out to make sure i don't do anything really stupid... (mains wiring he can handle- but electronics elude him, and i dont expect him to learn at 60 ) ... I'm just not sure if i was getting everything right on the design side.  Thanks for the customary concern, nifty

First, why i want the tthree 3 transformers:

-Power handling (total 1.2 amps) enough to power ALL my finished pedals with a ton of LEDs, and ruby amp... i have 6 of those 117-24V, 400mA transformers in total, which were cheap and available...

-A backup supply... i'll probly only be using two at a time, so i'll have a useable backup right there at my feet... with a single supply, if a regulator overheats or a fuse pops, you're out of commision.  In this case its a matter of moving a plug over an inch

-Isolating high gain pedals from modulation pedals.  Running them off two separate supplies will cut back on noise, as opposed to just daisy chaining them all together from one big single transformer supply

-One unit, one enclosure...  enclosures are pretty expensive, and i have a project box that should fit the three 3 power supplies perfectly.

Looking at R.G.'s spyder article, it seems that this part of the design would be rather practical and feasable.

As for the blue things... yeah, they're the (heavy duty... 3A @ 230V) switches... is there a problem with switching the primaries???   :shock:

My amp did this, and other amp schems i've browsed do this...  I also read this post by RG describing how to correctly wire something with a three-pronged power cord... hot->fuse->switch->primary ... is there something im missing?  If a comment like that doesn't suck the wind outta my sails, i dunno what will... confidence level declining  

The reason for wanting to have an on/off switch for each individual supply is i guess, to save power, and, so i don't have to go around disconnecting cords to cut power to everything.  So if i use dc jack battery-switching AND stereo jack power switching in my pedals, I can leave the dc jacks connected (keeping battery power off), and leave all the patches connected, and be able to power up and power down certain things with a few switches.

K... i thinks that's all i have for now...  get back to me please

Edit: ah, the LEDs.  well, im not sure of the values yet, since I'm using some 15mm ones i haven't used before...  but any varying brightness wouldnt concern me one bit, it might turn out to be a useful indication of how much current each supply is putting out to the pedals as it dims, if it does...  we'll see.  It's *regulated* power, so im hoping it'll be *somewhat* consistent with the voltage... so the only reason it should dim is an overloaded supply

[object88]

Oh, crap.  I entirely misunderstood your wiring diagram.  Nevermind the dribble that I posted before.  

[niftydog]

is there a problem with switching the primaries???

no, not so much that. I think I was just thrown by the LEDs. You are switching the mains power to the primary - that's fine. But why do you need to also switch the LEDs? If you just hang the LED across the supply it will light up when the mains is switched to the primary. Save using a DPDT and it works the same way.

is there something im missing? If a comment like that doesn't suck the wind outta my sails, i dunno what will... confidence level declining

you shouldn't take it that way, I'm just a really safety concious kind of guy and I maybe go a bit overboard when warning people about mains power. It's just that as a kid I went close to winning the Darwin Awards on more than a few ocasions so I know how easy it is to have a whoopsie that may end your life!!!

Trust me, you've obviously researched this a lot more than many others who've breezed through here recently.  :shock:

without knowing the specifics of the rectifier/regulator part of the circuit, it looks fine with the exception of the LED/switch arrangement. It's not dangerous, it's just unnecessary.

Seems like the resistances at each output jack will be quite variable. Wouldn't that give you varying LED brightness?

Provided the regulator keeps the output voltage at 9VDC, and the LED and it's current limiting resistor are simply wired across the output, the LED will remain constant.

[NaBo]

OHHH!  duhh!!!

That IS unnecessary...  thanks for pointing that out!  It's actually the same 'mistake' i made while building my first project... planning to use the unused lugs of a power switching DPDT for the LED... shoulda known!!!  Now, since I have the DPDTs and a free row of lugs, I'll do as R.G. suggests as "not a bad idea", switching both hot and neutral.

and hey, DO NOT be apologetic about the warning...  I was kind of suprised there hadn't really been one before that!  I was sorta kidding about it discouraging me... just threw me for a loop a bit!

Anyway, thanks for the help nifty!  For the actual boards, I think I'll go with two GGG "regulated power supply" ones, and an LM317-based supply with that 'dying battery' feature.  They'll be on the next slab of copper clad I etch... which might be a while cuz i have about 15 etched and drilled boards to populate sometime soon and starting 2 jobs this week... summer is fun

[ethrbunny]

Provided the regulator keeps the output voltage at 9VDC, and the LED and it's current limiting resistor are simply wired across the output, the LED will remain constant.

Im a bit puzzled about this. Im going to build a new power box v similar to this (the parts have been ordered) and wanted to have LEDs showing which lines were active. Id love to put an ampmeter on it too but thats another story.


Lets say the LED needs 25 mA to be happy. If the pedal needs 5 then how can the LED light? I can see where the resistor will keep the LED protected if the pedal is drawing 100mA.

[object88]

Now, since I have the DPDTs and a free row of lugs, I'll do as R.G. suggests as "not a bad idea", switching both hot and neutral.

Woah, wait, no!!  I would highly recommend against this.  Maybe I'm talking out of my ass here (and I hope someone will correct me if I'm wrong), but there are good reasons NOT to switch both hot and neutral.

Here's what I perceive as being wrong with switching both neutral and hot: you're playing directly with AC and you've got twice as many failure points.  With a SPDT, you are switching hot or neutral, and the worse that could happen if the switch fails is that the circuit will either stay open or closed.  With a DPTP, if the switch fails, either hot or neutral will stay open or closed, or both will stay open or closed, or the switch may short hot to neutral.  Un-fun.  

IIRC, Kevin O'Connor warns against this in the section on PSUs in The Ultimate Tone, and household AC wiring (as in wall switches for lighting) is done (effectively) with SPDT, and I think for good reason.  OK, you've got that fuse there, but still, color me skeptical.

I'm not an electrician, and I'm a pretty poor electrical engineer, but I think that sticking with SPDTs (or SPSTs?) is just a better way to go.

[davebungo]

Call me old fashioned and perhaps it's because in the UK our AC supply at 220V is a lot more dangerous, but I think the idea of having mains supply on one half of a switch and the 9V LED circuit on the other side (even if the switches are mains rated) is a really BAD idea.

With the utmost respect to you I would not suggest that method of wiring to anyone.  I'm sorry but I do not agree that this is good practice...

Also, I would always connect my DC gnd to earth at a star point.  You'll probably find that your amp's input is earthed anyway so I don't see any point in isolating it.

On a less important note, I would have just one mains switch and one transformer.  With decent wiring/earthing practice I wouldn't have thought this would cause you any serious problems.  If you do earth the DC gnds, then your separate supplies are not isolated anyway.  This would also be the case if you connect pedals fed by the separate DC supplies together - again your interconnecting signal leads will common your separate DC supply circuit gnds.