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'[EE] Significance of +s and -s terminals on regula'
2005\08\13@230517 by Tom Wrighton

picon face
Hello all,

I recently acquired a surplus regulated DC power supply and haven't
been able to trace the model number to any definitive information on the
net.  I'm hoping to use it as a bench supply for various learning projects
including Pics etc.  It is a LAMBDA LCS-A-04; and I only get Chinese
text at the LAMBDA site.  The input is 105 - 132V, 57-63 Hz, 0-60VDC.
The terminals are: 1 AC, 2 AC, 3 -s, 4 -V, 5 ND, 6 +V, 7 +s, 8 PO.
My question is can someone give me a simple explanation on the
significance of the '-s', '+s' and 'PO' terminals.  The 'PO' terminal doesn't
look used.  the '-s' and the '+s' seem to be bridged to the '-V' and '+V'
terminals respectively.  There is a VDC ADJ hole on the side which is
fairly logical.  The '1 AC' and the '2 AC' terminals are obvious.

Any enlightenment you can offer will be greatly appreciated.
Thanks very much in advance.

Regards,

Tom




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2005\08\13@233746 by Denny Esterline

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The 's' terminals are for remote voltage sense, allows the supply to
overcome losses in the cable losses. For 95% of applications bridging them
as you describe is fine. If you need better regulation, connect the sense
terminals closer to the load.

-Denny


> Hello all,
>
> I recently acquired a surplus regulated DC power supply and haven't
> been able to trace the model number to any definitive information on the
> net.  I'm hoping to use it as a bench supply for various learning projects
> including Pics etc.  It is a LAMBDA LCS-A-04; and I only get Chinese
> text at the LAMBDA site.  The input is 105 - 132V, 57-63 Hz, 0-60VDC.
> The terminals are: 1 AC, 2 AC, 3 -s, 4 -V, 5 ND, 6 +V, 7 +s, 8 PO.
> My question is can someone give me a simple explanation on the
> significance of the '-s', '+s' and 'PO' terminals.  The 'PO' terminal
doesn't
{Quote hidden}

> --

2005\08\13@233931 by Spehro Pefhany

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At 08:05 PM 8/13/2005 -0700, you wrote:
{Quote hidden}

Hi, Tom:-

Sounds like "sense" terminals for measuring the output voltage-- used to
compensate for the voltage drop due to series resistance of wiring.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
spam_OUTspeffTakeThisOuTspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
->> Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff


2005\08\14@074038 by Gerhard Fiedler

picon face
Denny Esterline wrote:

>> The terminals are: 1 AC, 2 AC, 3 -s, 4 -V, 5 ND, 6 +V, 7 +s, 8 PO. My
>> question is can someone give me a simple explanation on the
>> significance of the '-s', '+s' and 'PO' terminals.  The 'PO' terminal
>> doesn't look used.  the '-s' and the '+s' seem to be bridged to the
>> '-V' and '+V' terminals respectively.  
>
> The 's' terminals are for remote voltage sense, allows the supply to
> overcome losses in the cable losses. For 95% of applications bridging
> them as you describe is fine. If you need better regulation, connect the
> sense terminals closer to the load.

You can use them for adding current measurement without losing the stiff
output voltage: add a current sense resistor to the output, and connect the
sense input after the current sense resistor.

You will measure both the load current and the sense current, but the sense
current is presumably small.

Gerhard

2005\08\14@091120 by olin piclist

face picon face
Tom Wrighton wrote:
> The terminals are: 1 AC, 2 AC, 3 -s, 4 -V, 5 ND, 6 +V, 7 +s, 8 PO.

S refers to "sense".  These are the voltage feedback inputs for the
regulated outputs.  They are shorted to the outputs at the power supply for
the default case.  That means the supply regulates the output voltage at the
output terminals.  For most hobby applications, that's good enough.

The reason for the separate sense terminals is to overcome a small voltage
drop in a feed wire.  Disconnect the S inputs from their respective outputs
at the power supply, then run a separate wire from the load ends of the feed
cable back to the sense inputs.  This causes the supply to regulate the
voltage at the load, not at the supply.

Usually supplies have limits built in on how much the sense inputs can cause
the outputs to rise above the specified limit.  The sense inputs are usually
connected to the outputs internally via a resistor so that the output
voltage doesn't go crazy if the sense line falls off.  However, I wouldn't
count on any of this.  If using separate sense lines, be very careful and
assume a failure could cause the output voltage to damage something.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

2005\08\14@102119 by Tom Wrighton

picon face
Hello Again,

This is to thank Denny, Sphero, Gerhard and Olin for your responses
to my query.  Since I intend to use this as a hobbyist bench supply
I'll leave the connections as found and use relatively short leads.
I appreciate the explanations and feel I understand them quite well.
You can be assured that you have added to my education (and fun).

Thanks Again,

Tom


               
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2005\08\14@104607 by Russell McMahon

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flavicon
face
>Since I intend to use this as a hobbyist bench supply
> I'll leave the connections as found and use relatively short leads.
> I appreciate the explanations and feel I understand them quite well.
> You can be assured that you have added to my education (and fun).

Note that the sense leads can be much lighter than the main power
leads. You can run main leads for some distance from the supply and
include thin sense wires eg taped to them and connected only at the
far ends. Even in a hobby application this can be very useful.

The use for bypassing a current meter that someone mentioned may be
more useful than you may expect. A multimeter set to eg 200 mA range
may have a resistance of say 15 ohms. So it would drop 0.200 x 15 = 3
volts !!!! at full scale. Having the sense leads connected beyond the
meter would eliminate the effect of this unknown and potentially (no
pun intended) very awkward resistance.


       RM

2005\08\14@133427 by Paul Hutchinson

picon face
> -----Original Message-----
> From: .....piclist-bouncesKILLspamspam@spam@mit.edu On Behalf Of Tom Wrighton
> Sent: Saturday, August 13, 2005 11:05 PM
>
> Hello all,
>
> I recently acquired a surplus regulated DC power supply and haven't
> been able to trace the model number to any definitive information on the
> net.  I'm hoping to use it as a bench supply for various learning projects
> including Pics etc.  It is a LAMBDA LCS-A-04; and I only get Chinese

The English site for LAMBDA is: http://www.lambdapower.com.

The 1985 and 1992 catalog pages for your LC series supply are available from
the older models page:
http://www.lambdapower.com/products/legacy_products.htm

Hope this helps,
Paul Hutch

{Quote hidden}

2005\08\14@211738 by Tom Wrighton

picon face
Hello Again Again,

This is to thank Paul and Russell for your responses to my query.
Paul, I tried to track down my unit at that website, but couldn't find
any reference to the 'LCS' series of supplys.  By GOOGLING I can
find a number of hits, but again nothing that will give me any chance
of information.  I think I will follow the comments of a few others and
not worry about altering the configuration.  I admit at this point
though, that Russell's comments will probably have me investigating
the principals of operation a little more.  Whether I use the sensing
concept or not, it won't hurt me to learn what it's about.

Again thanks for the responses,

Tom


               
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2005\08\14@223101 by Paul Hutchinson

picon face
> -----Original Message-----
> From: piclist-bouncesspamKILLspammit.edu On Behalf Of Tom Wrighton
> Sent: Sunday, August 14, 2005 9:17 PM
>
> Hello Again Again,
>
> This is to thank Paul and Russell for your responses to my query.
> Paul, I tried to track down my unit at that website, but couldn't find
> any reference to the 'LCS' series of supplys.  By GOOGLING I can

The LCS is a sub series of the LC series, here are direct links to the two
LC series catalog pages I had mentioned. The LCS-A-04 specs are in these old
catalog pages.
www.lambdapower.com/ftp/catalog/lc_fall85.pdf
http://www.lambdapower.com/ftp/catalog/lc_fall92.pdf

There are no datasheets on the LAMBDA site for obsolete products probably
because they don't have electronic versions. If you contact them and ask
nicely they might mail you a copy of the data sheet.

Paul

{Quote hidden}

2005\08\14@235554 by Tom Wrighton

picon face

> Paul Hutchinson <.....paullhutchinsonKILLspamspam.....yahoo.com> wrote:

> There are no datasheets on the LAMBDA site for obsolete products probably
> because they don't have electronic versions. If you contact them and ask
> nicely they might mail you a copy of the data sheet.

Paul,

That's an great suggestion.  I did that once before, about a year ago, for
another piece of donated equipment and I got excellent results; schematics
and all.  Thanks and much appreciated.

Regards,

Tom

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