| Author |
Message |
stefanv
Guest
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 Posted:
Tue Dec 06, 2005 5:35 pm Post subject:
1 second UPS |
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Hi, I’m new to this forum, impressed to see there are still a lot o
people out there who love to play with electronics and do not mind sharin
some good ideas. So here’s my situation;
Dealing with a cabin with a lot of power outages. I have a trace inverte
system providing DC from 12 volts batteries. I also have a deskto
computer. When the grid power falls (or comes back) the inverter switches
Most often not fast enough and the computer reboots :( I tried a simple UP
(after the inverter) but it doesn’t recognized the modified sine wave fro
the Trace as “clean” power, so it just runs its battery dead after abou
20 minutes without consider the Trace is there take over.
My search is to find an “UPS” that that will bridge the half a second
need for the Trace inverter to kick in. Time being so short, I figure
don’t need clean power, both voltage and frequency don’t need to b
stable, just something half a second to fool my computer’s power supply A
is still on.
I was thinking along following lines:
- feed power to computer using a NO contacts on a DPDT relay 110v AC tha
goes on when AC (Trace) is present.
- charge (before this relay)through a rectifier a 680uf 200v cap up.
- create a 20ma 12v power using a rc bridge and a zenner over the cap t
run a 555 at about 60hz
- feed this frequency straight to an n-mosfet 200v 15amps switching th
capacitors charge to the NC contacts of the relay .
- put a resistor in series with the relay to run it at about 80V (so i
still goes on at regular 110 supply, but falls faster when the powe
starts going down.)
- so when the power falls, the relay switches the line AC off and feeds
straight square wave at 60 hz for as long as the cap will discharge.
Again this is ugly power, but I only need it for half a second or less
When the Trace inverter kicks in the relay will switch back on and regula
power restored.
Figuring charge in a cap is CV2/2 in watts/sec, a 680 uf cap should hold
watts/sec. A computer power supply being approx 250 watts/hr, this is 0.0
watts/sec. No I’m not expecting my cap to give me a full minute, tha
would likely make something explode :)
Comments? Better ideas? I like the challenge of doing this without
transformer!
Sorry for the long post.
StefanV
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Noway2
Guest
|
| Posted:
Tue Dec 06, 2005 5:35 pm Post subject:
Re: 1 second UPS |
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|
You may be able to find a transfer switch that will detect the power
loss and transfer to an alternate source in a short enough period of
time to keep your computer (or other loads) alive. The impression I
have recieved is that computer power supplies have changed over the
years, lengthening the time period that they withstand a power loss
condition. The reason behind these changes, being to reduce the
complexity and hence cost of the upstream transfer switches.
I would suggest starting your search at the Asco website. I believe
that they make relatively inexepensive devices, though the term
inexpensive may be subjective.. |
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Dan Hollands
Guest
|
| Posted:
Tue Dec 06, 2005 5:35 pm Post subject:
Re: 1 second UPS |
|
|
"stefanv" <stefan@maximasa.com> wrote in message
news:TZGdnYWjG5qZDQjeRVn_vA@giganews.com...
| Quote: | Hi, I'm new to this forum, impressed to see there are still a lot of
people out there who love to play with electronics and do not mind sharing
some good ideas. So here's my situation;
Dealing with a cabin with a lot of power outages. I have a trace inverter
system providing DC from 12 volts batteries. I also have a desktop
computer. When the grid power falls (or comes back) the inverter switches.
Most often not fast enough and the computer reboots :( I tried a simple
UPS
(after the inverter) but it doesn't recognized the modified sine wave from
the Trace as "clean" power, so it just runs its battery dead after about
20 minutes without consider the Trace is there take over.
My search is to find an "UPS" that that will bridge the half a second I
need for the Trace inverter to kick in. Time being so short, I figure I
don't need clean power, both voltage and frequency don't need to be
stable, just something half a second to fool my computer's power supply AC
is still on.
I was thinking along following lines:
- feed power to computer using a NO contacts on a DPDT relay 110v AC that
goes on when AC (Trace) is present.
- charge (before this relay)through a rectifier a 680uf 200v cap up.
- create a 20ma 12v power using a rc bridge and a zenner over the cap to
run a 555 at about 60hz
- feed this frequency straight to an n-mosfet 200v 15amps switching the
capacitors charge to the NC contacts of the relay .
- put a resistor in series with the relay to run it at about 80V (so it
still goes on at regular 110 supply, but falls faster when the power
starts going down.)
- so when the power falls, the relay switches the line AC off and feeds a
straight square wave at 60 hz for as long as the cap will discharge.
Again this is ugly power, but I only need it for half a second or less.
When the Trace inverter kicks in the relay will switch back on and regular
power restored.
Figuring charge in a cap is CV2/2 in watts/sec, a 680 uf cap should hold 4
watts/sec. A computer power supply being approx 250 watts/hr, this is 0.07
watts/sec. No I'm not expecting my cap to give me a full minute, that
would likely make something explode :)
Comments? Better ideas? I like the challenge of doing this without a
transformer!
Sorry for the long post.
StefanV
|
If you still have the "simple" UPS system that works, why not connect your
big battery in place of the battery in the UPS - assuming the voltages are
compatible.
--
Dan Hollands
1120 S Creek Dr
Webster NY 14580
585-872-2606
dhollan3@rochester.rr.com
www.QuickScoreRace.com
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Ted Edwards
Guest
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| Posted:
Wed Dec 07, 2005 1:35 am Post subject:
Re: 1 second UPS |
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stefanv wrote:
| Quote: | Dealing with a cabin with a lot of power outages. I have a trace inverter
system providing DC from 12 volts batteries. I also have a desktop
computer. When the grid power falls (or comes back) the inverter switches.
|
The only 100% reliable system I've ever built for this sort of thing
used a regulated switching supply to float charge a SLA 12V battery
which powered an inverter which ran the computer. Since the first
supply is regulated, the batteries are just sitting there being floated
until the power fails. When this happens, The secondary inverter simply
keeps going off the batteries. No relays, no switches, no glitches. I
built that system back in the '70s.
Ted |
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Jim Thompson
Guest
|
| Posted:
Wed Dec 07, 2005 1:35 am Post subject:
Re: 1 second UPS |
|
|
On Tue, 06 Dec 2005 07:20:04 -0600, "stefanv" <stefan@maximasa.com>
wrote:
| Quote: | Hi, I’m new to this forum, impressed to see there are still a lot of
people out there who love to play with electronics and do not mind sharing
some good ideas. So here’s my situation;
Dealing with a cabin with a lot of power outages. I have a trace inverter
system providing DC from 12 volts batteries. I also have a desktop
computer. When the grid power falls (or comes back) the inverter switches.
Most often not fast enough and the computer reboots :( I tried a simple UPS
(after the inverter) but it doesn’t recognized the modified sine wave from
the Trace as “clean” power, so it just runs its battery dead after about
20 minutes without consider the Trace is there take over.
[snip] |
A lot of UPS's (APS for example) have an output that signals "Your
computer must shut down in x minutes".
Why not use said signal to start an inverter?
Here, in Arizona, I've contemplated such a signal system to start a
motor-generator set (I have a very expensive reef tank that wouldn't
do well with any sustained power outage :)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food. |
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Mark
Guest
|
| Posted:
Wed Dec 07, 2005 1:35 am Post subject:
Re: 1 second UPS |
|
|
another problem with relays...
I tried something like this for a sump pump...
the pump connected to the DPDT relay wipers,
the power line to one set of contacts
an inverter to the other set of contacts...
I first tested this with a lamp load and when the relay switched, my
inverter blew up...
I suspect the relay contacts.... when opening at the peak of a cycle
.....,can arc for a short while and the arc actually bridges the
inverter to the power line which promply destroys it...
I decided I would need complex time delays and two relays to absolulty
prevent this...
In my case I didn't care if the pump was off for a few seconds during
the switch over, but I didn't like my inverter blowing up when the
realys switched...
So in your case, a realy may not do the trick....
I agree with the other poster, get a big set of batteries for the UPS
and just use it directly... it's already desgined to do the
switchover... thats what I ended up doing for the sump pump...
Mark |
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petrus bitbyter
Guest
|
| Posted:
Wed Dec 07, 2005 1:35 am Post subject:
Re: 1 second UPS |
|
|
"stefanv" <stefan@maximasa.com> schreef in bericht
news:TZGdnYWjG5qZDQjeRVn_vA@giganews.com...
| Quote: | Hi, I’m new to this forum, impressed to see there are still a lot of
people out there who love to play with electronics and do not mind sharing
some good ideas. So here’s my situation;
Dealing with a cabin with a lot of power outages. I have a trace inverter
system providing DC from 12 volts batteries. I also have a desktop
computer. When the grid power falls (or comes back) the inverter switches.
Most often not fast enough and the computer reboots :( I tried a simple
UPS
(after the inverter) but it doesn’t recognized the modified sine wave from
the Trace as “clean” power, so it just runs its battery dead after about
20 minutes without consider the Trace is there take over.
My search is to find an “UPS” that that will bridge the half a second I
need for the Trace inverter to kick in. Time being so short, I figure I
don’t need clean power, both voltage and frequency don’t need to be
stable, just something half a second to fool my computer’s power supply AC
is still on.
I was thinking along following lines:
- feed power to computer using a NO contacts on a DPDT relay 110v AC that
goes on when AC (Trace) is present.
- charge (before this relay)through a rectifier a 680uf 200v cap up.
- create a 20ma 12v power using a rc bridge and a zenner over the cap to
run a 555 at about 60hz
- feed this frequency straight to an n-mosfet 200v 15amps switching the
capacitors charge to the NC contacts of the relay .
- put a resistor in series with the relay to run it at about 80V (so it
still goes on at regular 110 supply, but falls faster when the power
starts going down.)
- so when the power falls, the relay switches the line AC off and feeds a
straight square wave at 60 hz for as long as the cap will discharge.
Again this is ugly power, but I only need it for half a second or less.
When the Trace inverter kicks in the relay will switch back on and regular
power restored.
Figuring charge in a cap is CV2/2 in watts/sec, a 680 uf cap should hold 4
watts/sec. A computer power supply being approx 250 watts/hr, this is 0.07
watts/sec. No I’m not expecting my cap to give me a full minute, that
would likely make something explode :)
Comments? Better ideas? I like the challenge of doing this without a
transformer!
Sorry for the long post.
StefanV
|
Stefan,
Guess you have to refresh your basics on electricity. The energy stored in a
capacitor is CV/2 in J(oules) or W(att)s(econds). The energy required to
power the PC for half a second is 250 * 0.5 = 125Ws, which is much, much
more then your capacitor can hold.
petrus bitbyter |
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w_tom
Guest
|
| Posted:
Wed Dec 07, 2005 1:35 am Post subject:
Re: 1 second UPS |
|
|
Once upon a time, some power supplies were made with an
internal battery (sealed lead acid) so that power supply could
continue to run for minutes after a power loss. Did not sell
well because consumers need to see the big and separate UPS.
Don't know if these power supplies are still available. But
it is what you seek.
Computer power supplies will normally maintain power output
for a few tens of milliseconds of power loss. You need it to
maintain power for hundreds of milliseconds. That typically
means some type of battery as part of the computer's power
supply. It was not a big battery - maybe about the size of
six size D batteries. Once designed a 'PC' wall controller
with that battery inside so that power loss left the PC
working. They were becoming harder to find even back then.
Otherwise the UPS needs power from some big ass line filter
so that UPS does not confuse dirty power with a power loss.
Such line filters will weight tens of pounds and cost a few
$hundred. But it will (probably) solve the problem of using
external UPS until the backup power kicks in. Have seen them
used in factories where equipment had defective internal power
supply; was crashing system for the most trivial of electrical
problems.
stefanv wrote:
| Quote: | Hi, I’m new to this forum, impressed to see there are still a lot
of people out there who love to play with electronics and do not
mind sharing some good ideas. So here’s my situation;
Dealing with a cabin with a lot of power outages. I have a trace
inverter system providing DC from 12 volts batteries. I also have
a desktop computer. When the grid power falls (or comes back) the
inverter switches. Most often not fast enough and the computer
reboots :( I tried a simple UPS (after the inverter) but it
doesn’t recognized the modified sine wave from the Trace as
“clean” power, so it just runs its battery dead after about
20 minutes without consider the Trace is there take over.
My search is to find an “UPS” that that will bridge the half a
second I need for the Trace inverter to kick in. Time being so
short, I figure I don’t need clean power, both voltage and
frequency don’t need to be stable, just something half a second
to fool my computer’s power supply AC is still on.
I was thinking along following lines:
- feed power to computer using a NO contacts on a DPDT relay 110v
AC that goes on when AC (Trace) is present.
- charge (before this relay)through a rectifier a 680uf 200v cap up.
- create a 20ma 12v power using a rc bridge and a zenner over the
cap to run a 555 at about 60hz
- feed this frequency straight to an n-mosfet 200v 15amps switching
the capacitors charge to the NC contacts of the relay .
- put a resistor in series with the relay to run it at about 80V (so
it still goes on at regular 110 supply, but falls faster when the
power starts going down.)
- so when the power falls, the relay switches the line AC off and
feeds a straight square wave at 60 hz for as long as the cap will
discharge.
Again this is ugly power, but I only need it for half a second or
less. When the Trace inverter kicks in the relay will switch back
on and regular power restored.
Figuring charge in a cap is CV2/2 in watts/sec, a 680 uf cap should
hold 4 watts/sec. A computer power supply being approx 250 watts/hr,
this is 0.07 watts/sec. No I’m not expecting my cap to give me a
full minute, that would likely make something explode :)
Comments? Better ideas? I like the challenge of doing this without
a transformer! |
|
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| Back to top |
|
|
Ken Taylor
Guest
|
| Posted:
Wed Dec 07, 2005 1:35 am Post subject:
Re: 1 second UPS |
|
|
Mark wrote:
| Quote: | another problem with relays...
I tried something like this for a sump pump...
the pump connected to the DPDT relay wipers,
the power line to one set of contacts
an inverter to the other set of contacts...
I first tested this with a lamp load and when the relay switched, my
inverter blew up...
I suspect the relay contacts.... when opening at the peak of a cycle
....,can arc for a short while and the arc actually bridges the
inverter to the power line which promply destroys it...
I decided I would need complex time delays and two relays to absolulty
prevent this...
In my case I didn't care if the pump was off for a few seconds during
the switch over, but I didn't like my inverter blowing up when the
realys switched...
So in your case, a realy may not do the trick....
I agree with the other poster, get a big set of batteries for the UPS
and just use it directly... it's already desgined to do the
switchover... thats what I ended up doing for the sump pump...
Mark
You need to make sure you use a make-before-break relay for that |
application. There are actual mains cut-over contactors which are made
for the job.
A satellite station I worked on previously had a big cut-over switch for
the mains to generator. In auto-mode it was guaranteed to cut across
within a cycle of the mains supply. Apparently the *really* big versions
of this (ours was only 20kVA) would break your arm if you got in the way!
Cheers.
Ken |
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Guest
|
| Posted:
Wed Dec 07, 2005 1:35 am Post subject:
Re: 1 second UPS |
|
|
UPS are commonly availble for FREE with bad batteries, which are
frequently 12 volts.
So just put your computer on a surplus UPS, go oversize, and use
seperate battery/s
I say go oversize because the design run time isnt just battery
capacity, its also about component heating.
Oversize is cheap and effective.... |
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Mark
Guest
|
| Posted:
Wed Dec 07, 2005 9:02 am Post subject:
Re: 1 second UPS |
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|
make before break will connect the inverter to the power line and blow
it up....
even if you use a break before make relay like I did, the arc will jump
across sometimes and still blow up the inveter
Mark |
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Ken Taylor
Guest
|
| Posted:
Wed Dec 07, 2005 9:35 am Post subject:
Re: 1 second UPS |
|
|
"Mark" <makolber@yahoo.com> wrote in message
news:1133924100.304726.287960@g49g2000cwa.googlegroups.com...
| Quote: | make before break will connect the inverter to the power line and blow
it up....
even if you use a break before make relay like I did, the arc will jump
across sometimes and still blow up the inveter
Mark
I'm clearly losing it - I made double-sure I wrote the right thing coz I |
suspected I'd get it arse-about.
Ken |
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stefanv
Guest
|
| Posted:
Thu Dec 08, 2005 8:43 am Post subject:
Re: 1 second UPS |
|
|
| Quote: | Stefan,
Guess you have to refresh your basics on electricity. The energy store
in a
capacitor is CV/2 in J(oules) or W(att)s(econds). The energy required t
power the PC for half a second is 250 * 0.5 = 125Ws, which is much, muc
more then your capacitor can hold.
petrus bitbyter
|
Petrus,
To my knowledge a 250watts power rating are watts per hr. To make sure
checked last months electric bill :) I used less than 400 kw/hr for th
month. This is 400,000 Watt/hr. At your claim for a computer supply at 25
watts /sec, 1 computer alone would run that in 1600 seconds or 27 minute
per month. I think you are mixing up W/hr with w/sec. J are w/sec indeed
I'm sure I won't get a long time, but 1/2 second is more than likely if
get the rest of the circuit to run :)
A computer uses "only" 0.07w/s
StefanV |
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stefanv
Guest
|
| Posted:
Thu Dec 08, 2005 9:15 am Post subject:
Re: 1 second UPS |
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|
So I tried it
I haven't gotten to the relay yet as I have another problem to solv
first.
I build the circuit and made a schematic a
http://www.maximasa.com/cnc/1secUPS.jpg
As expected I get a bad quality square wave that actually runs
transformer really hot in a minute :) but as I need only 1/2 a sec of it
I'm not to worried. But, while I have 135v DC loaded in the capacitor,
only get a 78v "AC" after the mosfet. Any sugestions why and how I ca
crank this up?
Then I'll try the relay,...
StefanV |
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ehsjr
Guest
|
| Posted:
Thu Dec 08, 2005 9:35 am Post subject:
Re: 1 second UPS |
|
|
stefanv wrote:
| Quote: | Stefan,
Guess you have to refresh your basics on electricity. The energy stored
in a
capacitor is CV/2 in J(oules) or W(att)s(econds). The energy required to
power the PC for half a second is 250 * 0.5 = 125Ws, which is much, much
more then your capacitor can hold.
petrus bitbyter
Petrus,
To my knowledge a 250watts power rating are watts per hr. To make sure I
checked last months electric bill :) I used less than 400 kw/hr for the
month. This is 400,000 Watt/hr. At your claim for a computer supply at 250
watts /sec, 1 computer alone would run that in 1600 seconds or 27 minutes
per month. I think you are mixing up W/hr with w/sec. J are w/sec indeed.
I'm sure I won't get a long time, but 1/2 second is more than likely if I
get the rest of the circuit to run :)
A computer uses "only" 0.07w/s
StefanV
|
Well ----- your computer uses ~250 watts every instant it is on.
If it is on for one hour, it uses 250 watt_hours. If it is on
for 1 second, it uses 250 watt_seconds.
Your posted circuit would give you only about 30 mS (if that),
and you need 500 mS. Look at the RC time constant: the PC
draws 2.5 amps every instant it is on. At 110V, that's an
equivalent resistance of 44 ohms. Your RC is .000680 * 44
or .02992 seconds, at which time the cap will have discharged
to about 85 volts and the PC will shut down. (At least, I assume
they shut down at around that voltage. Maybe it's higher.)
Ed |
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