Author Topic: Change the voltage on battery buss  (Read 3684 times)

Offline mikeeastman

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Change the voltage on battery buss
« on: February 08, 2016, 04:10:46 AM »
I have a PI battery buss, it puts out either 12v or 5v. I need 7-9v to power my USB Regen. What would be the best way to adjust the voltage?
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Offline P.I.

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Re: Change the voltage on battery buss
« Reply #1 on: February 08, 2016, 04:37:34 PM »
Mike, the best thing is to send it back to me to install a 9VDC regulator.  Are you will ing to give up the 5VDC or do you need an additional connector?  We'll make it happen.

I will be OOT all next week on the Blues Alive at Sea Cruise, but can do this when I return.  I am pretty much caught up (for a welcome change) and can get right on it.  I can give you 9VDC @ 5A.
"A man with an experience is never at the mercy of a man with an argument." - Hilmar von Campe

Offline rollo

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Re: Change the voltage on battery buss
« Reply #2 on: February 24, 2016, 12:32:26 PM »
  BRILLIANT !!!!!!!!!!!
contact me  at rollo14@verizon.net or visit us on Facebook
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Offline Rogerdn

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Re: Change the voltage on battery buss
« Reply #3 on: April 20, 2016, 07:25:11 PM »
Dave, could mine be converted to 7vdc for a microRendu and would it be appropriate ?

Here's what John Swenson said recently in the CA thread about an optomized ps for it,

On the power supply side of things, I can tell you the technical details of what is most important, but it won't do anybody any good because nobody tests supplies for this. there is no agreement on how to run the tests, there is NO off the shelf test equipment for this, anybody who does this (and very few are ever done) has to build there own test equipment from scratch.

It is theoretically possible somebody could build the appropriate test equipment and test a whole bunch of supplies and publish it, but they would have to get all the supplies and spend a lot of time doing it. It would be a huge project, take a large amount of time and cost a lot of money. I'm not sure who is going to pay for that, the project would have to pay someone a lot of money to take it on.

So for now there is NO WAY to technically select the best supplies, the measurements simply have not been done.

That leaves people listening to things and subjectively figuring out which sounds the best.

If you really are interested in the details, here is what is needed.

For computer type digital equipment the noise coming from the supply is really not that important. Particularly for the microRendu which has ultra low noise regulators with extremely high noise rejection.

The really important part is how the supply responds to transient loads. All digital circuits do not present a constant load to the PS, the load current varies all over the place. This changing load is not slowly changing, it makes large current changes very quickly, the supply has to deal with this and keep the voltage constant even though the load is changing rapidly.

These "transient load events" can be very short duration, medium duration or long duration. The short duration events can be handled by small capacitors near the load. The caps have to be physically small in order to keep the inductance down. But physically small caps don't hold much charge, they have to be re-charged by a fast acting regulator. This part of the system is built into the microRendu board.

These regulators have to be fed by a larger cap that can handle the medium duration events. This is also on the board.

But THOSE caps have to be fed by the external power supply. It has to be fast enough to quickly recharge the first level caps. In addition it has to KEEP them charged. What happens is that the supplies that are fast enough to properly deal with the load don't have enough capacity in THIER caps to keep it up for long. When a long term transient happens the small caps handle the first little bit of it, the caps feeding the regulators take over and keep it going, the caps in the supply take over and keep on feeding them, but the AC line part doesn't react fast enough and the output caps sag before the AC part can recharge them.

This is the big challenge of power supplies for digital circuits. They need to have large capacitors, but this usually means a slow supply. This requirement leads to strange things like needing a 6A supply to properly handle a 1 A load. If you just design the supply as 1A the transformer and diodes will have too high an impedance to react fast enough, and the caps will be too small.

There are two different ways this can be measured. The most obvious is to build an adjustable load that can be programmed for different transient loads (different changes in current and different durations of the change) and run a whole bunch of these and see what the supply does. This is a lot of data that has to be looked at. One big advantage is it shows exactly what you are looking for, how the supply responds to transient loads.

The other approach is an impedance VS frequency plot. This is one test that shows everything, it is very easy to compare between supplies, but it is not so obvious how to convert this to what you really want which is the transient response. Once you learn how to interpret the results it's actually easier to use, but it takes some effort to learn what it means. Neither of these is a nice single number people like to have to compare things, there just is not such a simple thing in this space.

John S.

Roger

Offline P.I.

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Re: Change the voltage on battery buss
« Reply #4 on: April 21, 2016, 10:20:58 AM »

Roger, the short answer is yes.  I would recommend at least 7.5VDC @ 5A, though.  This will allow the Sonore to never get starved for power.

Like I have said so many times and John seems to concur, transient response (abundant low impedance supply) is absolutely essential to get the best SQ.
"A man with an experience is never at the mercy of a man with an argument." - Hilmar von Campe

Offline Rogerdn

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Re: Change the voltage on battery buss
« Reply #5 on: April 21, 2016, 12:25:12 PM »
Thks Dave, pm me the damages pls.
« Last Edit: April 21, 2016, 12:30:08 PM by Rogerdn »

Offline P.I.

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Re: Change the voltage on battery buss
« Reply #6 on: April 22, 2016, 03:26:28 PM »
Thks Dave, pm me the damages pls.
Check your email, Roger.  Thank you.

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Dave
"A man with an experience is never at the mercy of a man with an argument." - Hilmar von Campe