Using a common power supply among few time standards
I have been addicted to home brewing GPSDO, Rubidium, OCXO, and etc, etc, etc. I don't mean making of these from scratch but taking a surplus unit and encase them in ready-to-use form. Most of them are in U2 rack case.
One part of it that I really do not like is constructing a power supply for each and every unit I make. Good power supplies are essential to clean and stable timebase, I know. It is also heat generating as most of what I make use linear regulators. But it's tedious and mandane to do it every single time! So, I wanted to make a large enough power supply to provide +24V, +/- 12V, and 5V. My plan was to have independent feed line for each timebase unit.
Is this even a good idea? I have no experience in this to make a reasonable judgement. This plan would mean these power voltages will be fed to each components without any local regulation. While I do plan to put ferrite chokes and bypass capacitors at input, but since the whole point is to eliminate local power supply components, there will be nothing else in terms of isolation.
Similarly, I was also thinking of having a large battery bank for 24 volt supply. What type of battery is irrelevant and so as charging method for this question. I have heard of this being done. But for units that require 24 volts, that means there is no room for any type of regulation. Most 24V batteries output varying voltage depending on state of charging. I know 12V battery can produce as high as 13.x volt. Is anyone doing this type of thing on this list? If so, would you be willing to share details?
Appreciate any input.
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
Hi
Well, I’m sitting here plotting the stability of some eBay “frequency standards”. The one thing I can
measure is just when the power cords get bumped.
As long as you can hold sub mili-volt sorts of stability on the supplies “as delivered” it pretty much does not
matter how you get there. If you get up into the 10’s of mili-volts then it can indeed matter on some devices.
Some devices have less sensitivity than others. By the time you get to 100’s of mili-volts, you likley are impacting
most devices in a manner you can easily see in the output.
Yes, there are a lot of assumptions in all that. The first is that it is a 12V supply and not something odd like 48V.
Scale the numbers if you are using an odd voltage. The next Is that the disruption is not simply the lead drop
from the oven current. That will have an impact, but it’s going to get mixed up with temperature stability. Step /
pop / jump sort of changes will come through to the output fairly quickly. Third is that the supply is actually going
into something that matters (like an OCXO heater) and not just the supply lead for an opamp. There are a lot
more, but they get a bit fiddly ….
One alternative is to generate something like 13V and run a good LDO at the “point of use”. Depending on what
you find for LDO’s you may be able to get quite close to 12V. The power “wasted” becomes very small in that case.
Bob
On Feb 6, 2020, at 5:28 PM, Taka Kamiya via time-nuts time-nuts@lists.febo.com wrote:
I have been addicted to home brewing GPSDO, Rubidium, OCXO, and etc, etc, etc. I don't mean making of these from scratch but taking a surplus unit and encase them in ready-to-use form. Most of them are in U2 rack case.
One part of it that I really do not like is constructing a power supply for each and every unit I make. Good power supplies are essential to clean and stable timebase, I know. It is also heat generating as most of what I make use linear regulators. But it's tedious and mandane to do it every single time! So, I wanted to make a large enough power supply to provide +24V, +/- 12V, and 5V. My plan was to have independent feed line for each timebase unit.
Is this even a good idea? I have no experience in this to make a reasonable judgement. This plan would mean these power voltages will be fed to each components without any local regulation. While I do plan to put ferrite chokes and bypass capacitors at input, but since the whole point is to eliminate local power supply components, there will be nothing else in terms of isolation.
Similarly, I was also thinking of having a large battery bank for 24 volt supply. What type of battery is irrelevant and so as charging method for this question. I have heard of this being done. But for units that require 24 volts, that means there is no room for any type of regulation. Most 24V batteries output varying voltage depending on state of charging. I know 12V battery can produce as high as 13.x volt. Is anyone doing this type of thing on this list? If so, would you be willing to share details?
Appreciate any input.
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
time-nuts mailing list -- time-nuts@lists.febo.com
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and follow the instructions there.
Hi,
Usual (best?) is supply slight over voltage and use LDO/RC filtering in
each unit as Bob suggested. But that would require either supplying
24v/12v/5v/-12v (with some margin 10%?) or converting some single supply
of 24v or 48v in each unit to required voltages at each piece of
equipment. The later requires switching supplies to get all voltages.
Anybody fancy 400Hz or even higher frequency 48v AC supply?
Will
On 7/02/20 11:52 am, Bob kb8tq wrote:
Hi
Well, I’m sitting here plotting the stability of some eBay “frequency standards”. The one thing I can
measure is just when the power cords get bumped.
As long as you can hold sub mili-volt sorts of stability on the supplies “as delivered” it pretty much does not
matter how you get there. If you get up into the 10’s of mili-volts then it can indeed matter on some devices.
Some devices have less sensitivity than others. By the time you get to 100’s of mili-volts, you likley are impacting
most devices in a manner you can easily see in the output.
Yes, there are a lot of assumptions in all that. The first is that it is a 12V supply and not something odd like 48V.
Scale the numbers if you are using an odd voltage. The next Is that the disruption is not simply the lead drop
from the oven current. That will have an impact, but it’s going to get mixed up with temperature stability. Step /
pop / jump sort of changes will come through to the output fairly quickly. Third is that the supply is actually going
into something that matters (like an OCXO heater) and not just the supply lead for an opamp. There are a lot
more, but they get a bit fiddly ….
One alternative is to generate something like 13V and run a good LDO at the “point of use”. Depending on what
you find for LDO’s you may be able to get quite close to 12V. The power “wasted” becomes very small in that case.
Bob
On Feb 6, 2020, at 5:28 PM, Taka Kamiya via time-nuts time-nuts@lists.febo.com wrote:
I have been addicted to home brewing GPSDO, Rubidium, OCXO, and etc, etc, etc. I don't mean making of these from scratch but taking a surplus unit and encase them in ready-to-use form. Most of them are in U2 rack case.
One part of it that I really do not like is constructing a power supply for each and every unit I make. Good power supplies are essential to clean and stable timebase, I know. It is also heat generating as most of what I make use linear regulators. But it's tedious and mandane to do it every single time! So, I wanted to make a large enough power supply to provide +24V, +/- 12V, and 5V. My plan was to have independent feed line for each timebase unit.
Is this even a good idea? I have no experience in this to make a reasonable judgement. This plan would mean these power voltages will be fed to each components without any local regulation. While I do plan to put ferrite chokes and bypass capacitors at input, but since the whole point is to eliminate local power supply components, there will be nothing else in terms of isolation.
Similarly, I was also thinking of having a large battery bank for 24 volt supply. What type of battery is irrelevant and so as charging method for this question. I have heard of this being done. But for units that require 24 volts, that means there is no room for any type of regulation. Most 24V batteries output varying voltage depending on state of charging. I know 12V battery can produce as high as 13.x volt. Is anyone doing this type of thing on this list? If so, would you be willing to share details?
Appreciate any input.
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
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On 2/6/20 3:14 PM, Will Kimber wrote:
Hi,
Usual (best?) is supply slight over voltage and use LDO/RC filtering in
each unit as Bob suggested. But that would require either supplying
24v/12v/5v/-12v (with some margin 10%?) or converting some single supply
of 24v or 48v in each unit to required voltages at each piece of
equipment. The later requires switching supplies to get all voltages.
Well that was the strategy used on S-100 boards. Bulk 8V unregulated
supply regulated down to 5V on the board.
I recall S-100 scheme had an issue of per-board regulator failing short and dumping 8V into bus killing rest of the system....
I am thinking of making use of 28V (aircraft power supply?) regulated power supply, and have local linear regulator to created needed voltages. One concern is, should I need large amount of 5V then loss will be tremendous. I just came across an article that discussed magnetic field sensitivity of LPRO-101. The author ended up relocating the transformer off-board. (in a different case) A very timely information as this is what I am actually working on.
Further comment will be appreciatedTakaTime-nut in training
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
On Thursday, February 6, 2020, 6:51:38 PM EST, jimlux <jimlux@earthlink.net> wrote:
On 2/6/20 3:14 PM, Will Kimber wrote:
Hi,
Usual (best?) is supply slight over voltage and use LDO/RC filtering in
each unit as Bob suggested. But that would require either supplying
24v/12v/5v/-12v (with some margin 10%?) or converting some single supply
of 24v or 48v in each unit to required voltages at each piece of
equipment. The later requires switching supplies to get all voltages.
Well that was the strategy used on S-100 boards. Bulk 8V unregulated
supply regulated down to 5V on the board.
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.
On 2/7/20 7:01 PM, Taka Kamiya via time-nuts wrote:
I recall S-100 scheme had an issue of per-board regulator failing short and dumping 8V into bus killing rest of the system....
More like the 5V regulator (most likely a trusty 7805 in a TO-3 package)
shorting, applying 8V to all those TTL parts on the board, which die,
and put 8V on the address and data lines. However, I'm not sure that
was a particularly common failure. In many years of working with a lot
of S100 systems, I never had that problem.
I am thinking of making use of 28V (aircraft power supply?) regulated power supply, and have local linear regulator to created needed voltages. One concern is, should I need large amount of 5V then loss will be tremendous.
Probably a better solution is multiple bulk supplies off line AC then
regulate down. Or a DC/DC from 28V to 8V, then good linear regulator to 5V.
There's really no way around it, although you can do things like
synchronize all your PWM converters, so if you do get spurs, they're in
consistent places.
I just came across an article that discussed magnetic field
sensitivity of LPRO-101. The author ended up relocating the transformer
off-board. (in a different case) A very timely information as this is
what I am actually working on.
Further comment will be appreciatedTakaTime-nut in training
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
On Thursday, February 6, 2020, 6:51:38 PM EST, jimlux <jimlux@earthlink.net> wrote:
On 2/6/20 3:14 PM, Will Kimber wrote:
Hi,
Usual (best?) is supply slight over voltage and use LDO/RC filtering in
each unit as Bob suggested. But that would require either supplying
24v/12v/5v/-12v (with some margin 10%?) or converting some single supply
of 24v or 48v in each unit to required voltages at each piece of
equipment. The later requires switching supplies to get all voltages.
Well that was the strategy used on S-100 boards. Bulk 8V unregulated
supply regulated down to 5V on the board.
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.
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and follow the instructions there.
Hi
As you have already noted, things do die from time to time. Fuses are a good idea, along
with protection diodes. Still, none of it is 100%. The more heat / temperature you have in
a part, the quicker it is likely to fail.
One often overlooked failure mode is loosing one supply on a +/-12V pair. If you go back in
the archives (yes that’s not easy) there are reports of significant damage on things like DMTD’s
from this sort of problem. An open ground also can do the same sort of thing.
If everything is AC coupled then a cascade failure is less likely. We run stuff like PPS, serial
com, and USB that are very much DC coupled. Having a supply die and kill the entire bench
is not a good thing. Protection on these signals is worth thinking about.
The “honking big supply” comes with great big cables protected by great big fuses. Bump this
here or there and a lot of energy is involved before the fuse does its thing. Work on
trucks or aircraft and you will come up with a lot of data on the sort of damage this can do.
These days small power supplies are dirt cheap. DC/DC converter boards also can be had
for next to nothing. For a bit more money, fairly good versions can be purchased. For a lot more
money, very good ones are out there. Running a bunch of switchers has its drawbacks. Filtering
is possible.
Not every device needs a supply that is at the <1 nv / Hz level. Most devices are fairly tolerant
of supply noise. There are a lot of systems out there that run with supplies in the 10 mv (rms)
range. One size fits all is great for inventory management. It isn’t so great on the credit card.
Does a $5 board “deserve” a $500 power setup? At least around here, it’s going to get a $1
wall wart. A $5,000 device may get treated a bit better. If a shiny new / in warranty piece of
gear shows up with this or that for power …. it stays that way (at least through the warranty
period). If HP “back in the day” thought that this approach was ok for a box I power up < once
a month, it’s fine now.
The “best answer” to energy savings is still to turn things off. That’s the compelling reason
to have external reference inputs on test gear. It’s also a compelling reason to run gear that
does not take hours (or days) to warm up and stabilize. With fun stuff like controlled outlets,
you can let Alexa manage power to this or that device. Get up in the morning and tell her to
warm up the bench. Yes, setting this all up takes some thought and some planning.
You may decide you want to have a lot of sources on at the same time. Watch out for cross talk.
The more sources you have, the more trouble you will get into. Indeed this can become nearly
impossible to deal with as you get into the “many thousands” of devices all on the same frequency.
We toss around numbers like 120 db of isolation. That’s only adequate at a specific offset and
a desired impact on stability……
Lots of directions this can go and lots of choices …..
Bob
On Feb 7, 2020, at 10:01 PM, Taka Kamiya via time-nuts time-nuts@lists.febo.com wrote:
I recall S-100 scheme had an issue of per-board regulator failing short and dumping 8V into bus killing rest of the system....
I am thinking of making use of 28V (aircraft power supply?) regulated power supply, and have local linear regulator to created needed voltages. One concern is, should I need large amount of 5V then loss will be tremendous. I just came across an article that discussed magnetic field sensitivity of LPRO-101. The author ended up relocating the transformer off-board. (in a different case) A very timely information as this is what I am actually working on.
Further comment will be appreciatedTakaTime-nut in training
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
On Thursday, February 6, 2020, 6:51:38 PM EST, jimlux <jimlux@earthlink.net> wrote:
On 2/6/20 3:14 PM, Will Kimber wrote:
Hi,
Usual (best?) is supply slight over voltage and use LDO/RC filtering in
each unit as Bob suggested. But that would require either supplying
24v/12v/5v/-12v (with some margin 10%?) or converting some single supply
of 24v or 48v in each unit to required voltages at each piece of
equipment. The later requires switching supplies to get all voltages.
Well that was the strategy used on S-100 boards. Bulk 8V unregulated
supply regulated down to 5V on the board.
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.
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Right now, my problem is where to strike a reasonable yet good compromise.
I thought of using DC/DC but these are quite noisy, and noise comes from both ends. I had one powering distribution amplifiers. For an experiment, I placed a ferrite bead on the output and the whole thing oscillated rail to rail. (and killed the dist.amp) Also, these things switch at very high speed where ability of 3 terminal regulators to reduce noise is at minimum.
On the other hand, I was playing with red label T-bolt. This thing has internal DC/DC converters to take 24V and turn it into +/- 12V and 5V. Powering it with clean linear supply and a garden variety switcher, output was equally clean. (at least far below my lab's ability to observe issues) I saw no difference in output at all. Tech support at SRS demanded I use linear supply for PRS-10, and declined to discuss further. Yet, I've seen most DIY implementation uses switcher. I think /tvb uses 48V common supply. I also read a comment on this list, when one is dealing with time-nut level accuracy and stability, every milli-volt counts.
I guess I'll have to deal with this on case-by-case basis. (pun intended)
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
On Saturday, February 8, 2020, 9:11:13 AM EST, jimlux <jimlux@earthlink.net> wrote:
On 2/7/20 7:01 PM, Taka Kamiya via time-nuts wrote:
I recall S-100 scheme had an issue of per-board regulator failing short and dumping 8V into bus killing rest of the system....
More like the 5V regulator (most likely a trusty 7805 in a TO-3 package)
shorting, applying 8V to all those TTL parts on the board, which die,
and put 8V on the address and data lines. However, I'm not sure that
was a particularly common failure. In many years of working with a lot
of S100 systems, I never had that problem.
I am thinking of making use of 28V (aircraft power supply?) regulated power supply, and have local linear regulator to created needed voltages. One concern is, should I need large amount of 5V then loss will be tremendous.
Probably a better solution is multiple bulk supplies off line AC then
regulate down. Or a DC/DC from 28V to 8V, then good linear regulator to 5V.
There's really no way around it, although you can do things like
synchronize all your PWM converters, so if you do get spurs, they're in
consistent places.
I just came across an article that discussed magnetic field
sensitivity of LPRO-101. The author ended up relocating the transformer
off-board. (in a different case) A very timely information as this is
what I am actually working on.
Further comment will be appreciatedTakaTime-nut in training
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
On Thursday, February 6, 2020, 6:51:38 PM EST, jimlux jimlux@earthlink.net wrote:
On 2/6/20 3:14 PM, Will Kimber wrote:
Hi,
Usual (best?) is supply slight over voltage and use LDO/RC filtering in
each unit as Bob suggested. But that would require either supplying
24v/12v/5v/-12v (with some margin 10%?) or converting some single supply
of 24v or 48v in each unit to required voltages at each piece of
equipment. The later requires switching supplies to get all voltages.
Well that was the strategy used on S-100 boards. Bulk 8V unregulated
supply regulated down to 5V on the board.
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Hi
DC/DC converters can indeed be filtered. If you do it wrong, things will get pretty crazy. In
general, you need at least an L/C filter and may need an R/L/C design. Things like ESR
on the caps and SRF on the inductors do indeed matter. Both common mode and differential
mode filtering may be needed. With both inductors and ferrite beads, saturation performance
is important. It’s a good idea to only use parts that have detailed data.
Three terminal regulators have a wide range of PSRR profiles. Some do almost nothing
past 1 KHz, others are still doing quite well at 10 MHz. Data sheets are your friend in this
case. For best performance, app notes are often a good resource as well.
Yes, this is circuit design. There are details to it. Test / analysis / rework are all part of the
process. That’s the way it’s done ….
Bob
On Feb 8, 2020, at 9:59 AM, Taka Kamiya via time-nuts time-nuts@lists.febo.com wrote:
Right now, my problem is where to strike a reasonable yet good compromise.
I thought of using DC/DC but these are quite noisy, and noise comes from both ends. I had one powering distribution amplifiers. For an experiment, I placed a ferrite bead on the output and the whole thing oscillated rail to rail. (and killed the dist.amp) Also, these things switch at very high speed where ability of 3 terminal regulators to reduce noise is at minimum.
On the other hand, I was playing with red label T-bolt. This thing has internal DC/DC converters to take 24V and turn it into +/- 12V and 5V. Powering it with clean linear supply and a garden variety switcher, output was equally clean. (at least far below my lab's ability to observe issues) I saw no difference in output at all. Tech support at SRS demanded I use linear supply for PRS-10, and declined to discuss further. Yet, I've seen most DIY implementation uses switcher. I think /tvb uses 48V common supply. I also read a comment on this list, when one is dealing with time-nut level accuracy and stability, every milli-volt counts.
I guess I'll have to deal with this on case-by-case basis. (pun intended)
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
On Saturday, February 8, 2020, 9:11:13 AM EST, jimlux <jimlux@earthlink.net> wrote:
On 2/7/20 7:01 PM, Taka Kamiya via time-nuts wrote:
I recall S-100 scheme had an issue of per-board regulator failing short and dumping 8V into bus killing rest of the system....
More like the 5V regulator (most likely a trusty 7805 in a TO-3 package)
shorting, applying 8V to all those TTL parts on the board, which die,
and put 8V on the address and data lines. However, I'm not sure that
was a particularly common failure. In many years of working with a lot
of S100 systems, I never had that problem.
I am thinking of making use of 28V (aircraft power supply?) regulated power supply, and have local linear regulator to created needed voltages. One concern is, should I need large amount of 5V then loss will be tremendous.
Probably a better solution is multiple bulk supplies off line AC then
regulate down. Or a DC/DC from 28V to 8V, then good linear regulator to 5V.
There's really no way around it, although you can do things like
synchronize all your PWM converters, so if you do get spurs, they're in
consistent places.
I just came across an article that discussed magnetic field
sensitivity of LPRO-101. The author ended up relocating the transformer
off-board. (in a different case) A very timely information as this is
what I am actually working on.
Further comment will be appreciatedTakaTime-nut in training
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
On Thursday, February 6, 2020, 6:51:38 PM EST, jimlux <jimlux@earthlink.net> wrote:
On 2/6/20 3:14 PM, Will Kimber wrote:
Hi,
Usual (best?) is supply slight over voltage and use LDO/RC filtering in
each unit as Bob suggested. But that would require either supplying
24v/12v/5v/-12v (with some margin 10%?) or converting some single supply
of 24v or 48v in each unit to required voltages at each piece of
equipment. The later requires switching supplies to get all voltages.
Well that was the strategy used on S-100 boards. Bulk 8V unregulated
supply regulated down to 5V on the board.
time-nuts mailing list -- time-nuts@lists.febo.com
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Hi Taka,
How about using the open frame linear supplies like the ones from Power One or Lambda?
I usually pick these up when I find them, recap if needed and they're a cheap and easy way to get a supply.
Chris
KD4PBJ
On Feb 6, 2020, at 4:29 PM, Taka Kamiya via time-nuts time-nuts@lists.febo.com wrote:
I have been addicted to home brewing GPSDO, Rubidium, OCXO, and etc, etc, etc. I don't mean making of these from scratch but taking a surplus unit and encase them in ready-to-use form. Most of them are in U2 rack case.
One part of it that I really do not like is constructing a power supply for each and every unit I make. Good power supplies are essential to clean and stable timebase, I know. It is also heat generating as most of what I make use linear regulators. But it's tedious and mandane to do it every single time! So, I wanted to make a large enough power supply to provide +24V, +/- 12V, and 5V. My plan was to have independent feed line for each timebase unit.
Is this even a good idea? I have no experience in this to make a reasonable judgement. This plan would mean these power voltages will be fed to each components without any local regulation. While I do plan to put ferrite chokes and bypass capacitors at input, but since the whole point is to eliminate local power supply components, there will be nothing else in terms of isolation.
Similarly, I was also thinking of having a large battery bank for 24 volt supply. What type of battery is irrelevant and so as charging method for this question. I have heard of this being done. But for units that require 24 volts, that means there is no room for any type of regulation. Most 24V batteries output varying voltage depending on state of charging. I know 12V battery can produce as high as 13.x volt. Is anyone doing this type of thing on this list? If so, would you be willing to share details?
Appreciate any input.
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
time-nuts mailing list -- time-nuts@lists.febo.com
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and follow the instructions there.