[sdiy] Powering a second bit of kit from same PSU (wiring options)

[random variate]

Thanks again - your review of the PSU is appreciated - datasheet here:

http://www.xppower.com/pdfs/SF_PCM50.pdf


What do you think having perused the datasheet?

Cheers

Tim

----------------------------------------
> Subject: Re: [sdiy] Powering a second bit of kit from same PSU (wiring options)
> From: tom at electricdruid.net
> Date: Wed, 18 Feb 2015 16:45:07 +0000
> CC: nate at paperproductsmusic.com; chris at chrismusic.de; synth-diy at dropmix.xs4all.nl
> To: randomvariate at hotmail.co.uk
>
> Does it give you a *maximum* per rail? That'd be more useful.
>
> But yeah, it sounds enough to me. If they're drawing between 0.35A and 0.5A, then you can still run two of them off a 1A supply - just. That negative rail will be the limiting factor, since the 3A positive side is going to have plenty of grunt for the job.
>
> In practice, I'd hope that the current draw isn't quite as symmetrical as they make out, and that the negative side won't be quite as tight as 0.7-1A makes out.
>
> If the supply is ok up to 42W, that should be ok. 0.35A x 12V = 4.2W, so each SynthDriver is 8.4W or so (two rails). That would put two units somewhere around 15-20W, which sounds safe enough.
>
>
> On 18 Feb 2015, at 16:29, random variate <randomvariate at hotmail.co.uk> wrote:
>
>> Thanks for the replies.
>>
>> So, the SynthDrivers need a minimum of 0.35A per rail (+12v/-12v).
>>
>> The PSU I bought is the XP Power PCM50UD07, which delivers 3A and 1A respectively on each output, to 42W max power output.
>>
>> Do you think that has enough oomph to drive two Synth Driver Units?
>>
>> Cheers
>>
>> Tim
>>
>>
>>
>>
>>
>>
>>
>>
>> ----------------------------------------
>>> Date: Wed, 18 Feb 2015 10:14:21 -0500
>>> From: nate at paperproductsmusic.com
>>> To: chris at chrismusic.de
>>> CC: synth-diy at dropmix.xs4all.nl
>>> Subject: [sdiy] Powering a second bit of kit from same PSU (wiring options)
>>>
>>>> (Well, I'm assuming a simple 2 pin PSU - if you have a "real" PSU with
>>>> +/GND/-, things are looking much more benign.)
>>>
>>> If the proposed power supply has plenty of current for two boxes, it's
>>> probably not a wall-wart :)
>>>
>>> Besides, if:
>>> "Say for example, both units use a voltage regulator for an artificial
>>> center ground between both power pins, and use that as a signal ground.
>>> If both centers are not at the same voltage, you may have kind of a
>>> short circuit via signal ground."
>>>
>>> That would be done in the individual boxes/units/synths/etc and the
>>> only thing that would be affected would be overall current draw. The
>>> grounds are otherwise inherently isolated by the voltage dividers and
>>> regulators. Well, not isolated, but drawing current back through the
>>> supplies. This is the whole reason NOT to use a DC wall-wart, because
>>> the power is usually dirty, and hard to calculate overall current draw
>>> (and therefore supply voltage). At least with an AC wall-wart, the
>>> supplies are symmetrical. So, as you draw more current the supply
>>> voltages decrease equivalent amounts.
>>>
>>> As you said, this is all besides the point because if it's a
>>> legitimate power supply (linear transformer based design) it should be
>>> capable of driving anything you want. As long as you don't exceed it's
>>> current specifications, of course.
>>>
>>> I say go for it. I'd run the other box power cord separately with
>>> similar gauge wire. If your individual boxes aren't equipped with a
>>> fuse, that might be a good idea.
>>>
>>> Nate
>>> _______________________________________________
>>> Synth-diy mailing list
>>> Synth-diy at dropmix.xs4all.nl
>>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>>
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at dropmix.xs4all.nl
>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>