MOTM

I am running a single HAA15-0.8-A power supply in my middle cabinet 
connected to two MOTM-960 distributions boards, one on each side.  I 
have been having problems with the power supply current limiting on 
power up.  My total load on this supply is 480 mA nearly balanced on 
both +/- 15 volts.

What have others done to deal with this?  I've moved some modules 
around trying to change the loading but it never really fixes it.

I've been thinking of adding a small sequencer to enable one of the 
960 distribution boards after a small delay.

Would some bulk inductance in series help?

Thanks in advance. - Dave

It's not the steady-state load, it's charging up all the caps on the boards. The 
current in the first 100ms is probably 1A or so.

No real easy solution.....power sequencing is the best.

Paul S.



----- Original Message ----- 

From: "djbrow54" <davebr@...>
To: <motm@yahoogroups.com>
Sent: Tuesday, November 22, 2005 4:40 PM
Subject: [motm] Power Supply Crowbar


>I am running a single HAA15-0.8-A power supply in my middle cabinet
> connected to two MOTM-960 distributions boards, one on each side.  I
> have been having problems with the power supply current limiting on
> power up.  My total load on this supply is 480 mA nearly balanced on
> both +/- 15 volts.
>
> What have others done to deal with this?  I've moved some modules
> around trying to change the loading but it never really fixes it.
>
> I've been thinking of adding a small sequencer to enable one of the
> 960 distribution boards after a small delay.
>
> Would some bulk inductance in series help?
>
> Thanks in advance. - Dave
>
>
>
>
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>
>

Or add a second power supply...

--- In motm@yahoogroups.com, "Paul Schreiber" <synth1@a...> wrote:
>
> It's not the steady-state load, it's charging up all the caps on 
the boards. The 
> current in the first 100ms is probably 1A or so.
> 
> No real easy solution.....power sequencing is the best.
> 
> Paul S.
> 
> 
> 
> ----- Original Message ----- 
> From: "djbrow54" <davebr@e...>
> To: <motm@yahoogroups.com>
> Sent: Tuesday, November 22, 2005 4:40 PM
> Subject: [motm] Power Supply Crowbar
> 
> 
> >I am running a single HAA15-0.8-A power supply in my middle cabinet
> > connected to two MOTM-960 distributions boards, one on each 
side.  I
> > have been having problems with the power supply current limiting 
on
> > power up.  My total load on this supply is 480 mA nearly balanced 
on
> > both +/- 15 volts.
> >
> > What have others done to deal with this?  I've moved some modules
> > around trying to change the loading but it never really fixes it.
> >
> > I've been thinking of adding a small sequencer to enable one of 
the

> > 960 distribution boards after a small delay.
> >
> > Would some bulk inductance in series help?
> >
> > Thanks in advance. - Dave
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
>

Or modify the power supply.

The Power One dual linear supplies suffer from what is called common 
mode latch up. As Paul says this is to do with the largish amount of 
capacitance that the supply has to charge up.

Power One were initially very secretive about this when I contacted them 
about that, but a little while later my e-mail managed to get to someone 
who was a little more sympathetic to our needs.

He suggested [in caps]:

1) JUST TURN UP THE CURRENT LIMIT SLIGHTLY.  THIS SHOULD WORK IF YOU ARE 
EXPERIENCING BOARDER LINE TURN ON CURRENT.

This is the trimmer that usually has a little gunk on it to stop it 
being moved.

2) ADD CAP AND RESISTOR IN SERIES FROM U1 PIN TWO TO U1 PIN THREE.  CAP 
VALUE TO BE BETWEEN 10\ufffdF TO 47\ufffdF WITH A 16VDC RATING OR HIGHER. 
RESISTOR VALUE TO BE BETWEEN 150ohms TO 220ohms.

I didn't find that this worked that well.

But what I did eventually was much more drastic. I removed many of the 
components around the LM723s and rebuilt the it as the datasheet shows 
[you can look in Horowitz and Hill and also the Elektor Formant too]. I 
used a standard current foldback method, with current limit set to 0.8A 
as before but with a foldback limit of 0.4A.

This worked very well. But it should be noted that this its about a half 
an hours work and you need to know what you are doing. The trimmer will 
need to be removed, as will a few resistors including the main current 
limiter.

I'm saying no more now. If you can do the calculations needed to get the 
values right you should be able to do the job. If you can't then you 
shouldn't be playing with a power supply.

Needless to say that if you mess it up you could fry your whole modular 
or worse, yourself.

If in any doubt at all, buy another supply.

Tony

I ran into this same problem, and solved it by adding a second power supply.
(Ultimately I added a third, but that was because I didn't plan well when I
bought the second.) However, I wonder whether the simplest solution would be
a nice, hefty double-pole switch between the two distribution boards. No
fancy sequencer needed--just turn on the AC switch first, then turn on the
switch between the two distribution boards a few seconds later after the
caps on the first set of modules have charged up. Of course you have to
remember to turn off that switch, too, but after latching up your supply a
few times you'll learn. :-)

--Adam

> -----Original Message-----
> From: Mike Marsh [mailto:michael_marsh@...]
> Sent: Tuesday, November 22, 2005 8:35 PM
> To: motm@yahoogroups.com
> Subject: [motm] Re: Power Supply Crowbar
> 
> 
> Or add a second power supply...
> 
> --- In motm@yahoogroups.com, "Paul Schreiber" <synth1@a...> wrote:
> >
> > It's not the steady-state load, it's charging up all the caps on
> the boards. The
> > current in the first 100ms is probably 1A or so.
> >
> > No real easy solution.....power sequencing is the best.
> >
> > Paul S.
> >
> >
> >
> > ----- Original Message -----
> > From: "djbrow54" <davebr@e...>
> > To: <motm@yahoogroups.com>
> > Sent: Tuesday, November 22, 2005 4:40 PM
> > Subject: [motm] Power Supply Crowbar
> >
> >
> > >I am running a single HAA15-0.8-A power supply in my middle cabinet
> > > connected to two MOTM-960 distributions boards, one on each
> side.  I
> > > have been having problems with the power supply current limiting
> on
> > > power up.  My total load on this supply is 480 mA nearly balanced
> on
> > > both +/- 15 volts.
> > >
> > > What have others done to deal with this?  I've moved some modules
> > > around trying to change the loading but it never really fixes it.
> > >
> > > I've been thinking of adding a small sequencer to enable one of
> the
> > > 960 distribution boards after a small delay.
> > >
> > > Would some bulk inductance in series help?
> > >
> > > Thanks in advance. - Dave
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > Yahoo! Groups Links
> > >
> > >
> > >
> > >
> > >
> > >
> >
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Yahoo! Groups Links
> 
> 
> 
> 
> 
> 
>

Thanks for the replies.  I moved some modules around some more and 
seemed to find a configuration that hasn't current limited yet.  I 
don't want to add another power supply as I'm limited for room.  I 
started designing a voltage sequencer but decided to monitor it for a 
while and see how it does.

Interestingly, though, I measured all four power supplies.  The one 
that current limits has the -15V coming up nearly 25 mS later than the 
+15V.  I put a photo in the DJB's System folder.  The one that current 
limits is the upper right. - Dave

--- In motm@yahoogroups.com, "djbrow54" <davebr@e...> wrote:

>
> I am running a single HAA15-0.8-A power supply in my middle cabinet 
> connected to two MOTM-960 distributions boards, one on each side.  I 
> have been having problems with the power supply current limiting on 
> power up.  My total load on this supply is 480 mA nearly balanced on 
> both +/- 15 volts.
> 
> What have others done to deal with this? - Dave

>It's not the steady-state load, it's charging up all the caps on the 
>boards. The
>current in the first 100ms is probably 1A or so.
>
>No real easy solution.....power sequencing is the best.

An overkill solution might be some kind of relay circuit with 
pseudo-random delay times (using different resistor values to charge 
up the caps) on each of the MTA connectors. Like on a Yammy TX816 
when power is applied and then a second later you hear 8 relays 
click, but not all at the same time.

I put together a small circuit out of spare parts to sequence
the second MOTM-960 distribution board.  A simple DPST relay and
a LMC555 timer delays power 1~2 seconds to half of the modules.
Just have it running on the bench so far. - Dave

DJB Power Sequencer
http://modularsynthesis.com/modules/modules.htm


--- In motm@yahoogroups.com, Scott Juskiw <scott@t...> wrote:

>>It's not the steady-state load, it's charging up all the caps
>>on the boards. The current in the first 100ms is probably 1A
>>or so.
>>
>>No real easy solution.....power sequencing is the best.
> 
>An overkill solution might be some kind of relay circuit with 
>pseudo-random delay times (using different resistor values to charge 
>up the caps) on each of the MTA connectors. Like on a Yammy TX816 
>when power is applied and then a second later you hear 8 relays 
>click, but not all at the same time.

>An overkill solution might be some kind of relay circuit with 
>pseudo-random delay times (using different resistor values to charge 
>up the caps) on each of the MTA connectors. Like on a Yammy TX816 
>when power is applied and then a second later you hear 8 relays 
>click, but not all at the same time.

I'm doing a PCB for something similar at the moment - it's away getting
etched. It's a distro board with a relay and an adjustable delay. There is
no need to have relays for each module. One per "bank" should be adequate.
Just add modules until you get problems, then remove one. Add that module to
the next bank. It's the inrush that's the issue. It's similar to an old hard
drive problem, where staring current is so high that a bank of them would
require a starting supply that can deliver twice what running requires, so
each drive is delayed for 10 seconds times its ID number. That way the
supply only needs supply the starting current for a single drive at any time.

Ken
_______________________________________________________________________
Ken Stone   sasami@... or sasami@...
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

I just finished building and installing a power delay in my 
cabinet.  I have two MOTM-960 distribution boards so I just delay 
turning one of them on by a second.  I was amazed at what a 
difference this made.  It really cleaned up the power on voltage and 
I can tell a difference by watching the LEDs on these modules.  I 
took scope photos and documented it at:
http://modularsynthesis.com/modules/DJB-Power/djbpower.htm

Dave


--- In motm@yahoogroups.com, sasami@h... wrote:
>
> 
> >An overkill solution might be some kind of relay circuit with 
> >pseudo-random delay times (using different resistor values to 
charge 
> >up the caps) on each of the MTA connectors. Like on a Yammy TX816 
> >when power is applied and then a second later you hear 8 relays 
> >click, but not all at the same time.
> 
> I'm doing a PCB for something similar at the moment - it's away 
getting
> etched. It's a distro board with a relay and an adjustable delay. 
There is
> no need to have relays for each module. One per "bank" should be 
adequate.
> Just add modules until you get problems, then remove one. Add that 
module to
> the next bank. It's the inrush that's the issue. It's similar to 
an old hard
> drive problem, where staring current is so high that a bank of 
them would
> require a starting supply that can deliver twice what running 
requires, so
> each drive is delayed for 10 seconds times its ID number. That way 
the
> supply only needs supply the starting current for a single drive 
at any time.
> 
> Ken
> 
_____________________________________________________________________
__
> Ken Stone   sasami@h... or sasami@c...
> Modular Synth PCBs for sale 
<http://www.blaze.net.au/~sasami/synth/>
> Australian Miniature Horses & Ponies 
<http://www.blaze.net.au/~sasami/>
>