Maker Pro
Maker Pro

1 second UPS

S

stefanv

Jan 1, 1970
0
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
 
N

Noway2

Jan 1, 1970
0
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..
 
D

Dan Hollands

Jan 1, 1970
0
stefanv said:
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
[email protected]
www.QuickScoreRace.com
 
W

w_tom

Jan 1, 1970
0
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.
 
T

Ted Edwards

Jan 1, 1970
0
stefanv said:
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
 
P

petrus bitbyter

Jan 1, 1970
0
stefanv said:
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
 
M

Mark

Jan 1, 1970
0
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
 
J

Jim Thompson

Jan 1, 1970
0
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
 
K

Ken Taylor

Jan 1, 1970
0
Mark said:
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
 
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....
 
M

Mark

Jan 1, 1970
0
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
 
K

Ken Taylor

Jan 1, 1970
0
Mark said:
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
 
J

James D. Veale

Jan 1, 1970
0
Your electric bill is in kilowatt-hours, not kilowatts per second.

Your 250 watt computer would run for 1600 hours (not seconds) to equal
your 400 kilowatt hour electric bill.

Watts are joules per second. No hours involved.

Joules are watt-seconds, not watts per second.
 
S

stefanv

Jan 1, 1970
0
I see your point and my mix-up between watts-second and watts per second.
will have to go back to my school books and refresh.

Re my schematic at http://www.maximasa.com/cnc/1secUPS.jpg could I brin
up the voltage using an H-bridge?

Re transfering AC to DC, back to AC and back to DC. Indeed, it sound
crazy, but it's a combination of 2 things.
First the chalenge of making an idea work once it's in your head!
Next, I know of many people with the same problem who wouldn't mind havin
one of these (if it ever works) The luxury of just plugging in a devic
in-line and having the problem fixed, is worth more to them than openin
up computers, changing power supplies, opening up UPS, hooking externa
batteries or buying overtock items and rebuilding them to fit the purpose

The value for them is in an easy, off-the shelf, plug and play device.
Yes, if ever, I would probably build 50 of them and sell them just abov
cost. I love building things and I like the idea of a compact in-lin
device vs a bulky one.

It's a chalenge, I appreciate your advice!

StefanV
 
stefanv said:
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

Maybe get yourself some nicads and run the LT rails off those during
power down. Perhaps monitor the 5&12v rails, and when they get close to
min V spec, switch on your nicads, using a solid state switch. This
could sit in a spare pci slot, making it nice and neat. It would be a
UPS as well as a glitch coverer.

NT
 
P

Pat Ford

Jan 1, 1970
0
Maybe get yourself some nicads and run the LT rails off those during
power down. Perhaps monitor the 5&12v rails, and when they get close to
min V spec, switch on your nicads, using a solid state switch. This
could sit in a spare pci slot, making it nice and neat. It would be a
UPS as well as a glitch coverer.

NT

What about getting a 12V computer power supply, running that off the
battries and charger the batteries with a charger?

Pat
 
W

w_tom

Jan 1, 1970
0
Why is "converting dc to ac then back to dc again" crazy
when that is exactly what a computer power supply does?
Computer power supplies that contain a 12 volt battery use
that 'converting' feature to integrate a rechargeable battery
into a non-interruptable computer power supply.

Capacitors could accomplish same. Then we temper the theory
with the reality of numbers. Some manufacturers made computer
power supplies that includes a rechargeable battery.

Meanwhile, we also call that a laptop computer.
 
P

petrus bitbyter

Jan 1, 1970
0
stefanv said:
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

Stefan,

This is exactly why I advised to refresh your basics. Maybe the confusion
comes from the word "power". AFAIK it's used meaning both "force" and
"energy" which are two different things. If you have 110V on your outlet and
a fuse of lets say 16A then you have 110*16=1760W available. But that's not
what you pay for. (Unless you have a minimum contribution.) You have to pay
for the part of that 1760W * the time you use it. That's what you find on
your bill.

400kWh = 400,000Wh = 1440,000,000 Ws. Which directly shows why they use kWh
on the bills. (If they really put kw/hr on the bill they do definitly wrong.
Maybe you can even sue them for it. I would not be very astonished if they
do, as bills are often made by bookkeepers that may have some knowledge of
money but no knowledge at all of the products they sell.)

So if you need 250W for half a second, you need 125Ws. (What's that in kWh?
:) That's not much energy compared to the amount on your bill. Even a small
battery can produce it - but not within half a second. To store it in a
capacitor on the other hand requires quite a huge capacitor. Calculate for
your own, using the CV/2 rule.

To summerize the lecture :)

Energy = Force * Time -> [J] = [W] * (or [Ws] but not [W/s] !)

petrus bitbyter
 
C

Chris Jones

Jan 1, 1970
0
petrus said:
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

No, the energy is 0.5 times the capacitance times the voltage squared.
or C*V*V/2

It is practical to power a computer for a second from a large capacitor, but
that capacitor would be perhaps somewhat larger than a normal PC power
supply.

Chris
 
C

Chris Jones

Jan 1, 1970
0
w_tom said:
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.


I think if you open up the PC power supply and find the terminals of the
main input capacitor, these terminals could be brought to a shrouded
(finger proof) insulated connector on the back of the power supply. You
could then build a grounded box containing a bank of capacitors which would
be connected essentially in parallel with the internal capacitor of the PC
power supply. The larger capacitor could keep the supply running for a
second or more. In order to avoid very large surge currents when the PC is
first turned on, a high-power series resistor should be inserted so that
the external capacitor charges gently. A diode across the charging
resistor would allow the fairly large current to flow out of the capacitor
when powering the PC.

5Amp 400V
--------|<|-------
| |
.-----/\/\/------.
| 10kOhm |
| .-----------
| + | + |
----- ------------- \
----- ------------- /
| PC cap | external \ 100kOhm
| | cap / Bleed resistor
| | |
-----------------.-----------

There are numerous safety considerations when building something like this,
and if you don't understand the risks involved then it is better to learn
about the dangers before considering building it.

Chris
 
Top