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 Forum index » DIY Hardware and Software » YuSynth
Hello, and psu question
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cloudberry



Joined: Jun 30, 2009
Posts: 19
Location: uk

PostPosted: Fri Jul 03, 2009 2:43 pm    Post subject: Hello, and psu question Reply with quote  Mark this post and the followings unread

Hello!

I've started to take my first steps in synth diy, and am building yusynth's minimoog filter, with a pcb from bridechamber. I'm pretty much a newbie in electronics too...

My question is about a psu. I'd like to eventually run several modules off one psu (perhaps all in one box) that I can plug straight into the mains. (i'd prefer not to get involved with wal-warts etc..) Looking around on Farnell's site I came across this: http://cpc.farnell.com/jsp/search/productdetail.jsp?sku=PW02245

However, looking at Oakley Sound, or the MOTM psu, for example, seemed to discourage this idea.

Can anyone enlighten me please? Is the Farnell one suitable?

Many thanks,


Cloudberry
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magman



Joined: Feb 04, 2009
Posts: 361
Location: Liverpool, UK

PostPosted: Fri Jul 03, 2009 4:02 pm    Post subject: Reply with quote  Mark this post and the followings unread

The key thing with modules like this one is connecting them to the mains and doing it safely.

This module looks like it should be mounted to a PCB (I would suggest that it has pins coming out of the base of the module) then connected to the mains electric via fuse(s) and a mains switch. That's just a brief overview, there will be a lot more details around the electrical safety aspects that should be taken into account when installing this kind of module.

My favourite saying for this kind of thing is "Treat it with the respect that you would treat anything that can kill you". If you aren't confident about being able to cope with these aspects of electrical safety, follow the MOTM route and use an intrinsically safe route.

Apart from this, the module looks quite useful and isn't bad value. By the way, this is from CPC, which is a member of the Farnell group of companies, but isn't actually Farnell itself (CPC is in Preston, Farnell is based in Leeds). Newark in the US is yet another part of the Farnell Group by the way.

I'm currently building an MOTM style case (literally this weekend) and I will be taking very great care with fuses, switches, cabling and earth bonding as a part of this construction, but then I have the experience and knowledge of what needs to be used and where.

Hope that helps.

Magman
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Uncle Krunkus
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PostPosted: Sat Jul 04, 2009 5:36 am    Post subject: Reply with quote  Mark this post and the followings unread

Yeah, I agree with magman,
generally I would say that if you don't know exactly what's what when it comes to mains stuff, then get advice and help.
Probably the best idea would be to get a complete and ready to run PSU. You'll know when you've got enough experience to put one together yourself.

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yusynth



Joined: Nov 24, 2005
Posts: 1221
Location: France

PostPosted: Sat Jul 04, 2009 6:48 am    Post subject: Reply with quote  Mark this post and the followings unread

The PSU you pointed to on farnell's site is not suitable for using within a modular synth because this one is of the switched type while it is HIGHLY recommanded to use a linear power supply.

If you want to buy one choose a Power One or a similar (check on this forum, this has been addressed many time).

If you wish to build one yourself I would recommand this one :

http://www.cgs.synth.net/modules/cgs66_psu.html

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cloudberry



Joined: Jun 30, 2009
Posts: 19
Location: uk

PostPosted: Sun Jul 05, 2009 10:32 am    Post subject: Reply with quote  Mark this post and the followings unread

Many thanks for the replies!
Yes, not long after posting I discovered that linear rather than switching is better for this build. But as regards an encapsulated psu is concerned, if I can get one that also has a pcb I can attach it to then this may be the way to go.
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magman



Joined: Feb 04, 2009
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Location: Liverpool, UK

PostPosted: Sun Jul 05, 2009 4:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

Cloudberry,

Actually, if you go to CPC's parents website at Farnell, there are a few PSU's that get close to fitting this bill.

First there is this Lascar PSU which gives +/- 15V at 200mA:

http://uk.farnell.com/lascar/psu203/psu-pcb-2-output/dp/1183258

Then you have the VXI power supply modules, like this one:

http://uk.farnell.com/vxi-power/14442-000/psu-15v-0-2a-epsd-15-200c/dp/1186402

which have corresponding PCB's for one or two of these modules. Again, these modules peak at 200mA (so 2 would give you 400mA).

I've just bought one of these Calex PSU's from Farnell myself:

http://uk.farnell.com/calex/32212b/psu-open-frame-12v-15v-1-7a/dp/4893864

This PSU appears to be similar to the Power One units mentioned earlier (and quite often on this forum), has more than 8 times the power of the encapsulated supplies and will need the mains input connecting properly (switched and fused), but I'm planning on building quite a big modular so this fits for me and the price was right.

Hope this helps

Regards

Magman
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cloudberry



Joined: Jun 30, 2009
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PostPosted: Mon Jul 13, 2009 10:21 am    Post subject: Reply with quote  Mark this post and the followings unread

Many thanks Magman! I'll have a look.

I also found this:

http://gb.mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMu0oxGuRuNKH8MNxSrv1EW6orsleSixYcM%3d
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Ali M



Joined: Sep 01, 2009
Posts: 88
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PostPosted: Wed Sep 30, 2009 5:40 am    Post subject: Reply with quote  Mark this post and the followings unread

question for magman,

I just want to know more about the calex PSU, do you have to wire a mains socket to it? And is it particularly dangerous to connect up?

more noob questions from me!!

thanks
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magman



Joined: Feb 04, 2009
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PostPosted: Wed Sep 30, 2009 9:39 am    Post subject: Reply with quote  Mark this post and the followings unread

Ali M,

This is not an easy one to answer, as I don't know your current level of electronics knowledge.

The Calex PSU is a bare chassis linear PSU, and all connections to it have to be soldered. With the one I bought, I installed an IEC mains socket, a mains fuse and a mains switch. You have to pay particular attention to having a good earth connection and all exposed connections (IEC, Socket, etc) should use insulated connections (Heat shrink or insulated crimps), you don't want to be able to touch any exposed mains connections inside your synth case (This is definately not a nice experience, BTDTGTT). All cabling should be mains rated on the mains side of the PSU (I actually stripped a mains cable to get the correct wire).

On the DC side, I used an Oakley Dizzy - distribution board.

Wiring mains power needs to be treated the way you would treat anything that can kill you.

If you don't feel competent, don't do it!!

Buy a ready made synth PSU like the MOTM 900 or 950 instead.

Hope this helps

Magman


Calex PSU Installation.JPG
 Description:
Overall view of the PSU installation - Mains input on the left, Calex PSU, then Oakley Dizzy
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Calex PSU Installation.JPG



Mains Wiring.JPG
 Description:
Mains wiring, including power switch and a DC output DIN connector.
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Mains Wiring.JPG



Mains Wiring Detail.JPG
 Description:
This gives a bit more detail. Earth bonding at the top, fuse in the middle and IEC inlet at the bottom.
Notice the lack of any visible connections, everything is shrouded or insulated.
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Mains Wiring Detail.JPG


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Ali M



Joined: Sep 01, 2009
Posts: 88
Location: uk

PostPosted: Wed Sep 30, 2009 1:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks magman,

You answered my question exactly.
Im not going to buy a MOTM PSU as they are a bit expensive for my budget.
I think I will go with the calex, as it will power a lot more modules. For less money.
Your pictures and notes help loads aswell. thanks
I have a fair bit of electronics knowledge, but obviously not enough! I just want to confirm what I already think.

On the dc side, do i have to use a power distrubution board? Are the voltages at this stage dangerous?

thanks
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magman



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PostPosted: Wed Sep 30, 2009 4:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ali M,

The voltages on the DC side are not that dangerous (if you treat it stupidly, you could get a nasty burn, 30V rail to rail at 1.5A is a low power welding current), but some form of distribution system will make connections a lot easier.

Even if you just use a screw terminal block or chocolate block with common connections on one side back to the power supply. it will make things a lot easier to connect up your synth modules. You don't want to be soldering lots of wires onto the PSU connections if you can avoid it, even if this kind of wiring - star wiring - is the optimal connection method.

There are quite a few distribution boards available, apart from the Oakley, such as MOTM and CGS. I chose the Oakley Dizzy as it has a form of connection that is closer to star wiring than some of the other distribution boards. As a low cost alternative, you could also use Veroboard, especially if you use 0.1" pitch connectors, like Molex KK. Another plus for a distribution boards is that it is easier to disconnect modules for testing and calibration - or moving to a different rack.

Hope that helps

Magman
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Ali M



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PostPosted: Thu Oct 01, 2009 1:05 am    Post subject: Reply with quote  Mark this post and the followings unread

Ideal! thanks magman,

I was more concerned about the DC side, I think I will be ok with the mains. As long as I am not touching it while it is on.
Im feeling quite confident about doing it now.

I may have a few more questions when I get to that stage. If you dont mind answering them?

thanks for your help tho, you are a star

cheers bud!
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Uncle Krunkus
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PostPosted: Thu Oct 01, 2009 1:22 am    Post subject: Reply with quote  Mark this post and the followings unread

Ali,
be 1000 times more worried about the mains side, and you should be okay. Wink

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magman



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PostPosted: Thu Oct 01, 2009 2:23 am    Post subject: Reply with quote  Mark this post and the followings unread

Ali M wrote:
I was more concerned about the DC side, I think I will be ok with the mains. As long as I am not touching it while it is on.
Im feeling quite confident about doing it now.

Ali

Just to reinforce this point, you shouldn't be able to touch anything mains related whilst its on. Insulate and protect any place where mains connections are used so that a finger can't inadvertently touch mains anywhere in your equipment.

One other point its worth making. Make sure you have ground connections to all metalwork in you synth. As it will have a mains power supply in the case (the reason for this discussion), you have to have an earth in the mains lead and ground any metalwork that someone can touch. This is one of the reasons I decided to put a common earthing point in my cabinet, then all rack rails and panels are connected back to this earthing point. The Oakley Dizzy also has a connection for routing a ground to front panels on the modules as well (have a look at the Dizzy documentation on the Oakley website).

Play it safe and stay alive to enjoy making music.

Regards

Magman
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Ali M



Joined: Sep 01, 2009
Posts: 88
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PostPosted: Thu Oct 01, 2009 3:47 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi magman,

I meant that i dont intend to fiddle with the psu once its set up. And I will cover all bear mains connections.
It was just the DC output....

thanks for your help, and you uncle krunkus!

Now that you mention metal case....would using wood be a problem? heat wise? Obviously I wont ground the wood! But it wont burn the wood will it?

thanks again

ali
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magman



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PostPosted: Thu Oct 01, 2009 6:14 am    Post subject: Reply with quote  Mark this post and the followings unread

Ali,

Wood cases are no problem. The total output of the PSU is around 50W when fully loaded, so I doubt you will have any problems.

If you are using metal front panels, these still need to be grounded, even in a wooden case. It's to protect anyone touching the metal panels if you get a fault in the mains connections somewhere.

Regards

Magman
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