[sdiy] Prebuilt bipolar 15v supply?

[John Luciani]

On 10/12/07, Sam Ecoff <secoff at execpc.com> wrote:
> Hi John,
>
> On Oct 12, 2007, at 1:43 PM, John Luciani wrote:
>
> > I am assuming that the power supply meets your voltage/current
> > requirements.
>
> Voltage, absolutely... Ray says the sequencer will run successfully
> on anything from 9-15 volts. For most of his designs, he has posted
> typical current requirements, but not for the sequencer.

With such a wide operating range you should't have a trim or regulation issue.

> So... this raises two additional newbie questions: 1. how does one go about
> figuring out the current requirement from looking at the schematic?
> 2. Would it be reasonable to just purchase one of the supplies I
> think I'm going to use and try it and see if it works? (Given that I
> know the voltage is correct and the current is enough to power a
> typical module, is there a potential for damaging the unit? I don't
> think so, but then again, I'm still too new to really know....)

You would have to look at the specifications for each IC and estimate the
the amount of power dissipated in the resistive elements. I would do a rough
estimate and then measure the current drawn by the circuit.

> > A couple more things to look at ---  Is there a minimum load?
> > What is the response to faults like a short circuit. Make sure you
> > select protection
> > based upon the amount of current your circuit will draw.
>
> Again, newbie mode <<on>>. Given a power supply like this,  http://
> tinyurl.com/2238oa, how does one tell? Some of that info appears on
> the catalog page that links from the main page about this supply, but
> sadly, that supply isn't listed on that page.

That information is not shown in the datasheet. You would have to call the
manufacturer. I hate to assume but since the min load specification is
not listed there probably isn't a minimum load.

> O.k..... just called Jameco, I have some answers. First, the catalog
> # shouldn't be listed on that page since it's a web only item which
> doesn't appear in the catalog. Second, the person I spoke to was able
> to give me the minimum load info: 1 amp on the +12v line, 500 mA on
> the 12v line, and 3 amps on the +5v line. Given that I wouldn't be
> using the 5v line, this suddenly seems like a no go. Also... I don't
> know much about this, but it seems highly unlikely to me given what
> typical modules draw that the sequencer would draw 1 amp on the
> positive line.
>
> So.... it seems like I'm sort of back to square one... phooey.

The person on the phone gave you *maximum* load specifiations not
the minimum.  It is unlikely you will get detailed specification data from any
of the distributors. You would need to talk to the manufacturer.
If you are not going to use the +5V you should buy a supply
without it.

(* jcl *)



-- 
http://www.luciani.org