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neandrewthal
Joined: May 11, 2007
Posts: 672
Location: Canada
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 Posted: Fri Nov 09, 2007 9:02 pm Post subject:
Power supply wiring. |
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I`ve got pretty much everything figured out for my modular except how to wire mains to the power supply. I found this diagram on google:
http://sound.westhost.com/psu-wiring.htm#2.2
Would this be appropriate for wiring a synth power supply? How do I know which of the two terminals on my AC jack goes to which point on the supply? What switch/wire/fuse/fuse holder would you recommend? How do you ground the AC when you use a wooden case, right onto one of the front panels? Thanks. |
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RF
Joined: Mar 23, 2007
Posts: 1502
Location: Northern Minnesota, USA
Audio files: 28
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| Posted: Sat Nov 10, 2007 1:28 pm Post subject:
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Hi Neandrewthal,
People seem a bit hesitant to answer questions on wiring mains...42 views, no answers 
From what I see that page does just fine.
Use caution & think it through and you'll be OK.
For the three wires from the mains, Green is ground, White neutral and Black is hot. (I like to use computer power supply cords and the matching recepticle - if you do that the recepticle is often labled and sometimes has some bypassing built in)
Depending on the power supply you have, it will likely specify which transformer connection is for the hot. Fuse the hot lead, I like to use panel mount fuse holders. For the switch, pretty much your choice - but check the voltage and current ratings - they are often printed on the side of the switch. The larger toggle switches often have larger terminals and more room to solder your line wires onto. Heat shrink line any connections that might be exposed to an unexpected finger, including switch terminals and fuse holder connections...
Fuse size depends on your requirements - probably less than 1 amp...
Your line ground probably goes right to your power supply chassis if this is a commercial supply.
Good luck...
bruce |
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Clack
Joined: Aug 08, 2005
Posts: 438
Location: Walthamstow - london
Audio files: 5
G2 patch files: 1
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| Posted: Mon Nov 12, 2007 1:57 am Post subject:
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I would like to know this too, I have a 500mA Power supply ( pre-built )
should I use a quick blow fuse? At how many amps above the max current?
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Clacktronics.co.uk |
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Randaleem
Joined: May 17, 2007
Posts: 456
Location: Northern CA, USA
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| Posted: Mon Nov 12, 2007 2:39 am Post subject:
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| RF wrote: | Use caution & think it through and you'll be OK.
For the three wires from the mains, Green is ground, White neutral and Black is hot. |
Hi neandrewthal,
RF has given you some good advice here, but I'd like to clarify a couple points?
The BLK,WH, GR colors he's listed are okay for American electrical code rules. Most of the rest of the world uses the so-called "harmonised" color scheme for power cords. For this standard the GND will be green with a yellow stripe, the hot will be brown, and the neutral will be blue.
Growing up in the USA, I used to have a problem remembering which of the harmonised colors was HOT. A helpful Aussie spelled it out in a way I'll never forget! Brown is hot because that's the color your drawers will be if you touch it   (smiley pun intended; read em  )
| Quote: | | (I like to use computer power supply cords and the matching recepticle - if you do that the recepticle is often labled and sometimes has some bypassing built in) |
This is great advice too; especially for a synth. The silver colored block that the IEC connector is attached to (or part of) is a line filter. It is designed to both keep the synth electrical noise from being placed on the power grid it is plugged into, and also to filter the incoming AC going to your synth PSU. Many different types are available but every one I've ever seen was shiny metal housed. If you have only a black plastic IEC housing it is probably not a line filter and is only a connection for the AC cord.
PC power supplies often use the non line filtered IEC connector because they have line filter components on their PCB.
FWIW, Line filters are available which are separate from an IEC input (power cord) connector. I think it is a good idea to include one of these in your synth power supply setup.
Manufacturers are required to use some form of line filter to meet part 15 of the FCC radiation rules. You may not care about that from a "rules standpoint", but in a studio environment anything you can do to help in keeping your DIY project a "good neighbor" on the Mains power can be useful in keeping overall audible noise out of your mix. Especially if you have vintage synths sharing the mains circuits.
A very common and therefore inexpensive size IEC integrated line filter is 3Amps; which will be more than enough for any synth less than room wall size. Google "line filter" and you'll see dozens of examples.
Kind regards, Randal |
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Randaleem
Joined: May 17, 2007
Posts: 456
Location: Northern CA, USA
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| Posted: Mon Nov 12, 2007 2:47 am Post subject:
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| Mr Clack wrote: | | I would like to know this too, I have a 500mA Power supply ( pre-built ) should I use a quick blow fuse? At how many amps above the max current? |
Hi Clack!
Typically fuses 1-1/2 to 2 times the max INPUT load are used.
Whether to use fast or slow depends upon the type of Power supply circuit you are using. For a typical linear supply with capacitor filtering, you can probably use either. But sometimes if the capacitors are large there will be a large inrush current which will blow the fast type fuse, requiring a slo-blo instead be used.
OTOH decent PSU's with a high inrush will often have built in limiting of this startup current or recommend specific add-on current limiting devices in their spec sheets. So it's really pretty hard to say which you'd need. In cases like this, the best thing is to ask the mfr. or check the product docs to be advised.
Barring that, start with the "safest" (1-1/2 times, fast style) and work your way towards the slower ones from there.
Kind regards, Randal |
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neandrewthal
Joined: May 11, 2007
Posts: 672
Location: Canada
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| Posted: Mon Nov 12, 2007 9:44 am Post subject:
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Thanks muchly guys
I do have a PC power connector which is labeled but my power supply(Power one 5A btw) just says "apply AC at 1 and 4" Is there any way of figuring out which one of these gets the lead? Also it says the max fuse rating is 3A. Does that mean this is what I should use, or lower? |
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Randaleem
Joined: May 17, 2007
Posts: 456
Location: Northern CA, USA
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| Posted: Mon Nov 12, 2007 3:17 pm Post subject:
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| neandrewthal wrote: | | I do have a PC power connector which is labeled but my power supply(Power one 5A btw) just says "apply AC at 1 and 4" Is there any way of figuring out which one of these gets the lead? |
YOU will make this distinction when you place the AC power switch in place and wire iot to either p1 or p4!. The power switch (in America) needs to be in the HOT line path. So you will then "choose" the hot pin as being 1 or 4 depending upon which you use for this wire. IOW, from an electrical standpoint, the PSU inputs don't care or distinguish between "hot" and "neutral". But there ARE some commonly applied choices. Personally, I'd look at the physical layout of the PSU input pins. Which ever of P1 or P4 is closer physically to the pin(s) for GND I would wire as the neutral. The remaining one which is further from the GND pin(s) would then become the HOT and have the power switch in its path.
BTW, Many European and international electrical codes require that BOTH the hot and neutral be switched by a mains power switch. This requires a more expensive two-pole switch, but it is a worthwhile addition in many cases.
What all this is trying to avoid is having current being consumed by the device even when it is "off". And also to prevent current flow if there is a short to GND and the switch is off. With America's less strict code you could have an improperly wired wall outlet senmnding hot up the supposedly neutral line. If a short between hot or neutral and GND develops in your device, you have a complete circuit even with the single pole mains switch off. And a Fire hazard. The Intl. style dual pole switch prevents this.
If everyting is wired correctly in an American system there is no problem because the wider neutral blade of the plug polarises the wall connection allowing the single pole switch to effectively prevent any current flow.
If you're going to be gigging with your synth, I'd use a two-pole switch because you cannot rely on the correct-ness of local power wiring at your performance venues.
| Quote: | | Also it says the max fuse rating is 3A. Does that mean this is what I should use, or lower? |
You want to use the lowest fuse rating that accomodates your current draw through the PSU as this offers th ebest protection to your connected circuits.
Since these PSU's are made "universal", the mfr. cannot know how much amperage you intend to draw and therefore cannot decide for you which size fuse to use. All they can do is to assume that you may draw the maximum their PSU is capable of providing. This is the source of the 3A rating you've mentioned. It means that if you use the PSU to its full capacity, this is the fuse size to use.
Kind regards, Randal |
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neandrewthal
Joined: May 11, 2007
Posts: 672
Location: Canada
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| Posted: Mon Nov 12, 2007 10:45 pm Post subject:
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| Thanks, I don't plan on gigging in the near future but I'll go with a double pole switch just to be safe. For the fuse I guess about 500ma should be alright for 14 modules plus a Paia MIDI 2 CV. |
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etaoin
Joined: Jun 30, 2005
Posts: 761
Location: Utrecht, NL
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| Posted: Tue Nov 13, 2007 12:45 am Post subject:
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| Quote: | | BTW, Many European and international electrical codes require that BOTH the hot and neutral be switched by a mains power switch. This requires a more expensive two-pole switch, but it is a worthwhile addition in many cases. |
Indeed. I've been hit by mains power that I thought was switched off on more than one occassion...
And especially with the flat euro style plug that can be plugged in either way, you never know which wire is hot.
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http://www.casia.org/modular/ |
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blue hell
Site Admin
Joined: Apr 03, 2004
Posts: 24085
Location: The Netherlands, Enschede
Audio files: 278
G2 patch files: 320
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| Posted: Tue Nov 13, 2007 5:26 am Post subject:
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| Etaoin wrote: | | And especially with the flat euro style plug that can be plugged in either way, you never know which wire is hot. |
Some places in the Netherlands, inner city Amsterdam f.i., still have a modified 127V system in which both wires are hot. Apart from that outlets over here are always symmetrical so you never know what wire will end up as hot.
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Jan
also .. could someone please turn down the thermostat a bit.
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