Re: [Server-devel] 12 Volt power system for School Servers
I'd be interested in ddwrt on tp-link 2030's, primarily because of the Nepali data, that they can handle 25 clients, and because they run on 5v. Add to that a DC-DC buck converter to 5v at the remote end of poe. I'm testing http://www.amazon.com/gp/product/B00A71CMDU/ref=oh_details_o07_s00_i00?ie=UTF8&psc=1which in the spec has 8-23v input capability, and 3A output ($8) Let's analyze the worst case for an ethernet cable at maximum distance. (24 awg wire at 70C has resistance of 29 ohms/1000 feet, poe has 2 wires per leg, but we have drop in each leg. So my guess is worst case loop resistance of 300 feet * 29 ohms/1000 feet * 2 legs / 2 wires/leg = 8.7 ohms loop resistance. If the minimum input voltage for the DC-DC is 8, then we only have 3 volts of drop to play with. The current input spec for the tp-link is 1A. So if 300 at 1A would dorp 8.7 volts, and we can only afford 3 v drop, we can only extend the AP 100 feet from the server. I suspect that the current draw is much less than the spec, worst case battery discharge,ambient temperature, are not likely, so more than 100 feet is likely. This solution, would probably work for 3 or 4 adjacent classrooms, and 75-150 students -- but needs to be reality tested. George On Thu, May 30, 2013 at 12:47 AM, wrote: > Send Server-devel mailing list submissions to > server-devel@lists.laptop.org > > To subscribe or unsubscribe via the World Wide Web, visit > http://lists.laptop.org/listinfo/server-devel > or, via email, send a message with subject or body 'help' to > server-devel-requ...@lists.laptop.org > > You can reach the person managing the list at > server-devel-ow...@lists.laptop.org > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Server-devel digest..." > > > Today's Topics: > >1. Re: 12 Volt power system for School Servers. (James Cameron) >2. Re: 12 Volt power system for School Servers. (Sameer Verma) >3. Re: 12 Volt power system for School Servers. (David Farning) >4. Re: 12 Volt power system for School Servers. (Anna) >5. Re: 12 Volt power system for School Servers. (Adam Holt) >6. Re: 12 Volt power system for School Servers. (Tony Anderson) > > > -- > > Message: 1 > Date: Thu, 30 May 2013 08:26:32 +1000 > From: James Cameron > To: David Farning > Cc: server-devel , Tony Anderson > > Subject: Re: [Server-devel] 12 Volt power system for School Servers. > Message-ID: <20130529222631.gb20...@us.netrek.org> > Content-Type: text/plain; charset=iso-8859-1 > > On Wed, May 29, 2013 at 04:51:47PM -0500, David Farning wrote: > > Any thoughts on powering the AP?? > > They are all different. > > First, select an AP that says it has a 12V input. > > I would record the voltage without load emitted by the power supply > supplied by the manufacturer. This is a known maximum voltage that > the AP can take. > > Then I would record the voltage on load. This is a known minimum > voltage. > > Then I would record the input voltage specifications of the access > point using the manufacturer's documentation. This is usually a > typical voltage, but sometimes they include a maximum or minimum. If > there was no documentation, I'd ask them, though perhaps with no great > expectation of success. > > Taking the minimum and maximum of those three values, I'd compare them > to the lead-acid battery charge cycle operating range of 10V to 15V. > > If there remains any doubt (e.g. they haven't specified a maximum), I > would attach the AP to a variable power supply and gradually ramp it > up to 15V, checking for sudden drop of current (a blown fuse), or > excessive operating heat. > > Once I'm happy, I would cut the cable as far from the device as > possible, and reterminate it there. Before cutting, I would discharge > the power supply capacitors ... saves wear and tear on wire cutters. > > If the AP was USB powered Wifi dongle, the problem goes away. > > -- > James Cameron > http://quozl.linux.org.au/ > > > -- > > Message: 2 > Date: Wed, 29 May 2013 15:48:48 -0700 > From: Sameer Verma > To: James Cameron , David Farning > , Jerry Vonau < > jvo...@shaw.ca>, > server-devel , Tony Anderson > > Subject: Re: [Server-devel] 12 Volt power system for School Servers. > Message-ID: > putnsch5+7b4levahwr-zsxbb...@mail.gmail.com> > Content-Type: text/plain; charset=ISO-8859-1 > > On Wed, May 29, 2013 at 3:26 PM, James Cameron wrote: > > On Wed, May 29
Re: [Server-devel] 12 Volt power system for School Servers.
We have a primary school in PNG with school server driving 9 wireless access points with PoE to cover a 200 laptop deployment with 7 classrooms http://wikieducator.org/OLPC_PNGSDP/Kisap Powered by 12V solar using the excellent Sundaya kits. The wiring looks untidy, I know, but they have worked very reliably over 2-3 years. Also the integrated batteries and proprietary DC connectors make it difficult to misuse the power (a common cause of early demise of batteries) http://www.sundaya.com/welcomeEN.php The Mikrotik GrooveA range of outdoor wireless access points are really good. They will work on 9-27V so even with 12V, you can get very long cable runs, and you can screw in a vertical omni or your antenna of choice. We didn't use them in the deployment above but I would do in the future. David Leeming Solomon Islands -Original Message- From: server-devel-boun...@lists.laptop.org [mailto:server-devel-boun...@lists.laptop.org] On Behalf Of James Cameron Sent: Thursday, 30 May 2013 4:17 p.m. To: Tony Anderson Cc: server-devel Subject: Re: [Server-devel] 12 Volt power system for School Servers. Tony makes an interesting point that may be new to some: On Thu, May 30, 2013 at 06:47:26AM +0200, Tony Anderson wrote: > This discussion is relevant because 12vdc does not travel well over > long distances. It may be necessary in a school with multiple > classrooms to use an inverter to provide 110 or 220vac to the > routers via PoE. As the distance between the battery bank and the access point increases, so too does the required _diameter_ of copper cable. Copper cable is quite valuable, and easily traded. It can be a good security practice to avoid installing too much of it. If the cable is too thin, the power demand by an access point causes too much of a voltage drop. For instance, one might put 12V DC in one end, and get 10V DC out the other end. The access point may still work fine. But some of the power will be lost as heat in the cable, lowering efficiency. At some point, depending on cost, reliability, and availability of equipment, it is worth operating at a higher voltage. The options would seem to be Power over Ethernet (PoE), which will yield 12.95W (IEEE 802.3af-2003) or 25.5W (IEEE 802.3at-2009), or an inverter with a separate power circuit. My best guess is that PoE will be cheaper, because a power circuit installed to meet electrical regulations would tend to be designed for the minimum domestic power standard of the country. For example, in Australia the minimum is 10A at 240V, or 2400W. The mass of copper is far more than what PoE would require. Then there's the cost of a 12V input PoE power sourcing equipment (PSE). -- James Cameron http://quozl.linux.org.au/ ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
Re: [Server-devel] 12 Volt power system for School Servers.
Tony makes an interesting point that may be new to some: On Thu, May 30, 2013 at 06:47:26AM +0200, Tony Anderson wrote: > This discussion is relevant because 12vdc does not travel well over > long distances. It may be necessary in a school with multiple > classrooms to use an inverter to provide 110 or 220vac to the > routers via PoE. As the distance between the battery bank and the access point increases, so too does the required _diameter_ of copper cable. Copper cable is quite valuable, and easily traded. It can be a good security practice to avoid installing too much of it. If the cable is too thin, the power demand by an access point causes too much of a voltage drop. For instance, one might put 12V DC in one end, and get 10V DC out the other end. The access point may still work fine. But some of the power will be lost as heat in the cable, lowering efficiency. At some point, depending on cost, reliability, and availability of equipment, it is worth operating at a higher voltage. The options would seem to be Power over Ethernet (PoE), which will yield 12.95W (IEEE 802.3af-2003) or 25.5W (IEEE 802.3at-2009), or an inverter with a separate power circuit. My best guess is that PoE will be cheaper, because a power circuit installed to meet electrical regulations would tend to be designed for the minimum domestic power standard of the country. For example, in Australia the minimum is 10A at 240V, or 2400W. The mass of copper is far more than what PoE would require. Then there's the cost of a 12V input PoE power sourcing equipment (PSE). -- James Cameron http://quozl.linux.org.au/ ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
Re: [Server-devel] 12 Volt power system for School Servers.
Hi, The setup at the Kokobe Primary school in Lesotho has a small solar panel (too small) which attempts to charge two car batteries (deep cycle would be better but not available). The router (Belkin) runs directly from the battery (we cut the cable). Linksys and other routers I have used all run on 12vdc at 1A. The MSI server does not run on 12vdc because of the design of it's power supply which requires a higher voltage (15vdc works). I purchased a Zotac which also uses an Atom processor but houses a 2.5in drive. It requires 19vdc. Most standard laptops require 19vdc at 3.2A (maximum) to charge the batteries. I suspect the MSI and Zotac simply use laptop hardware for the power supply even though no battery is involved. The router problem is that most home routers ($30 variety) can handle a limited number of connections (less than a classroom of XOs). OLE Nepal has found that a TP-Link router with DDWRT handles 25 connections (15 with the delivered firmware). In any case, a school really should have a router per classroom to provide enough connections (not to increase signal strength). OLE Nepal powers all of the routers in a school from the same UPS that powers the server so that the network will continue to operate in a power failure. Since the routers are also connected by an ethernet cable, PoE would be quite useful. This discussion is relevant because 12vdc does not travel well over long distances. It may be necessary in a school with multiple classrooms to use an inverter to provide 110 or 220vac to the routers via PoE. So far in Lesotho, the laptops have been used in a single classroom next to the server and router so I don't have live experience in distributing routers. We will face that problem next year at the Nohana school which has two classroom buildings about 50m apart and where the teachers want to use the laptops in their own classroom. Tony ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
Re: [Server-devel] 12 Volt power system for School Servers.
Just a reminder to include po...@lists.laptop.org if this discussion advances, the tightly focused electrical/energy list run by Richard Smith for many years to come God willing =) http://lists.laptop.org/listinfo/power On Wed, May 29, 2013 at 8:46 PM, Anna wrote: > On Wed, May 29, 2013 at 5:26 PM, James Cameron wrote: > >> >> If the AP was USB powered Wifi dongle, the problem goes away. >> >> > Speaking of, and this would only be appropriate for extremely small > deployments, but I started messing around on the XSCE with hostapd with a > wifi dongle this very afternoon. It's been on my wishlist for a long time, > but earlier kernels didn't have support and it is such a PITA to compile > the XO kernel. > > Anna > > ___ > Server-devel mailing list > Server-devel@lists.laptop.org > http://lists.laptop.org/listinfo/server-devel > > ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
Re: [Server-devel] 12 Volt power system for School Servers.
On Wed, May 29, 2013 at 5:26 PM, James Cameron wrote: > > If the AP was USB powered Wifi dongle, the problem goes away. > > Speaking of, and this would only be appropriate for extremely small deployments, but I started messing around on the XSCE with hostapd with a wifi dongle this very afternoon. It's been on my wishlist for a long time, but earlier kernels didn't have support and it is such a PITA to compile the XO kernel. Anna ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
Re: [Server-devel] 12 Volt power system for School Servers.
Thanks guys, I'll start playing tonight. On Wed, May 29, 2013 at 5:48 PM, Sameer Verma wrote: > On Wed, May 29, 2013 at 3:26 PM, James Cameron wrote: > > On Wed, May 29, 2013 at 04:51:47PM -0500, David Farning wrote: > >> Any thoughts on powering the AP? > > > > They are all different. > > > > Yep. The one we use in Bhagmalpur (India) and in Jamaica is the > Ubiquiti Picostation2 unit that runs off a PoE injector. Ours run off > 110/220V AC, but an AP that can run over 48V PoE can use a DC-to-DC > PoE unit to power it from a 12V battery source. > > cheers, > Sameer > > > First, select an AP that says it has a 12V input. > > > > I would record the voltage without load emitted by the power supply > > supplied by the manufacturer. This is a known maximum voltage that > > the AP can take. > > > > Then I would record the voltage on load. This is a known minimum > > voltage. > > > > Then I would record the input voltage specifications of the access > > point using the manufacturer's documentation. This is usually a > > typical voltage, but sometimes they include a maximum or minimum. If > > there was no documentation, I'd ask them, though perhaps with no great > > expectation of success. > > > > Taking the minimum and maximum of those three values, I'd compare them > > to the lead-acid battery charge cycle operating range of 10V to 15V. > > > > If there remains any doubt (e.g. they haven't specified a maximum), I > > would attach the AP to a variable power supply and gradually ramp it > > up to 15V, checking for sudden drop of current (a blown fuse), or > > excessive operating heat. > > > > Once I'm happy, I would cut the cable as far from the device as > > possible, and reterminate it there. Before cutting, I would discharge > > the power supply capacitors ... saves wear and tear on wire cutters. > > > > If the AP was USB powered Wifi dongle, the problem goes away. > > > > -- > > James Cameron > > http://quozl.linux.org.au/ > > ___ > > Server-devel mailing list > > Server-devel@lists.laptop.org > > http://lists.laptop.org/listinfo/server-devel > > > > > -- David Farning Activity Central: http://www.activitycentral.com ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
Re: [Server-devel] 12 Volt power system for School Servers.
On Wed, May 29, 2013 at 3:26 PM, James Cameron wrote: > On Wed, May 29, 2013 at 04:51:47PM -0500, David Farning wrote: >> Any thoughts on powering the AP? > > They are all different. > Yep. The one we use in Bhagmalpur (India) and in Jamaica is the Ubiquiti Picostation2 unit that runs off a PoE injector. Ours run off 110/220V AC, but an AP that can run over 48V PoE can use a DC-to-DC PoE unit to power it from a 12V battery source. cheers, Sameer > First, select an AP that says it has a 12V input. > > I would record the voltage without load emitted by the power supply > supplied by the manufacturer. This is a known maximum voltage that > the AP can take. > > Then I would record the voltage on load. This is a known minimum > voltage. > > Then I would record the input voltage specifications of the access > point using the manufacturer's documentation. This is usually a > typical voltage, but sometimes they include a maximum or minimum. If > there was no documentation, I'd ask them, though perhaps with no great > expectation of success. > > Taking the minimum and maximum of those three values, I'd compare them > to the lead-acid battery charge cycle operating range of 10V to 15V. > > If there remains any doubt (e.g. they haven't specified a maximum), I > would attach the AP to a variable power supply and gradually ramp it > up to 15V, checking for sudden drop of current (a blown fuse), or > excessive operating heat. > > Once I'm happy, I would cut the cable as far from the device as > possible, and reterminate it there. Before cutting, I would discharge > the power supply capacitors ... saves wear and tear on wire cutters. > > If the AP was USB powered Wifi dongle, the problem goes away. > > -- > James Cameron > http://quozl.linux.org.au/ > ___ > Server-devel mailing list > Server-devel@lists.laptop.org > http://lists.laptop.org/listinfo/server-devel > > ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
Re: [Server-devel] 12 Volt power system for School Servers.
On Wed, May 29, 2013 at 04:51:47PM -0500, David Farning wrote: > Any thoughts on powering the AP? They are all different. First, select an AP that says it has a 12V input. I would record the voltage without load emitted by the power supply supplied by the manufacturer. This is a known maximum voltage that the AP can take. Then I would record the voltage on load. This is a known minimum voltage. Then I would record the input voltage specifications of the access point using the manufacturer's documentation. This is usually a typical voltage, but sometimes they include a maximum or minimum. If there was no documentation, I'd ask them, though perhaps with no great expectation of success. Taking the minimum and maximum of those three values, I'd compare them to the lead-acid battery charge cycle operating range of 10V to 15V. If there remains any doubt (e.g. they haven't specified a maximum), I would attach the AP to a variable power supply and gradually ramp it up to 15V, checking for sudden drop of current (a blown fuse), or excessive operating heat. Once I'm happy, I would cut the cable as far from the device as possible, and reterminate it there. Before cutting, I would discharge the power supply capacitors ... saves wear and tear on wire cutters. If the AP was USB powered Wifi dongle, the problem goes away. -- James Cameron http://quozl.linux.org.au/ ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
Re: [Server-devel] 12 Volt power system for School Servers.
Thanks james, Any thoughts on powering the AP? On Wed, May 29, 2013 at 4:45 PM, James Cameron wrote: > On Wed, May 29, 2013 at 04:38:06PM -0500, Jerry Vonau wrote: > > Is the inverter really needed for a XO? The step-down transformer used > > on the XO puts out 13.5v but the XOs only need 11 volts to charge[1]. > > Therefore I believe you could run and/or charge the XOs directly from a > > 12v source like a storage battery, perhaps though a regulator. I just > > don't want to cut the cord off of a working power supply to find > > out. > > Cut the cord about 20cm from the power supply, and fit a screw > terminal, so the cord can be reassembled if needed. > > Yes, the XO will safely run direct from any 12V lead-acid storage > battery. The battery will not permit the voltage to exceed what the > XO can accept. > > (It isn't technically a step-down transformer, but a switch-mode power > supply, but no matter.) > > -- > James Cameron > http://quozl.linux.org.au/ > -- David Farning Activity Central: http://www.activitycentral.com ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
Re: [Server-devel] 12 Volt power system for School Servers.
On Wed, May 29, 2013 at 04:38:06PM -0500, Jerry Vonau wrote: > Is the inverter really needed for a XO? The step-down transformer used > on the XO puts out 13.5v but the XOs only need 11 volts to charge[1]. > Therefore I believe you could run and/or charge the XOs directly from a > 12v source like a storage battery, perhaps though a regulator. I just > don't want to cut the cord off of a working power supply to find > out. Cut the cord about 20cm from the power supply, and fit a screw terminal, so the cord can be reassembled if needed. Yes, the XO will safely run direct from any 12V lead-acid storage battery. The battery will not permit the voltage to exceed what the XO can accept. (It isn't technically a step-down transformer, but a switch-mode power supply, but no matter.) -- James Cameron http://quozl.linux.org.au/ ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
Re: [Server-devel] 12 Volt power system for School Servers.
On Wed, 2013-05-29 at 15:42 -0500, David Farning wrote: > The piece I am looking at is reducing the losses between the battery > and the server/AP. > See my earlier response. > > Several systems have a 12V Battery which is inverted to 120AC which is > then transformed back to low voltage DC for input to the server/AP. > That doesn't seem very efficient. > +1 Jerry > > Dave > > > On Wed, May 29, 2013 at 3:29 PM, Sameer Verma wrote: > On Wed, May 29, 2013 at 1:03 PM, David Farning > wrote: > > Tony could you share more information about your work on 12 > Volt power > > supplies for School Servers? > > > > Whenever I see a School Server setup containing a 12V > Battery, an inverter, > > a power strip, and a couple of 120V to 12V power supplies to > provide power > > for the server and the AP... my eyes start to tear up:( > > > > The situation I am looking at has power part of the day so > we can recharge > > the battery. To keep things simple we would like to use a > Trimslice or XO-4 > > and off the shelf AP. > > > > Ideally we would like to have 'kit' that contained > everything except that > > battery that can be set up and tested before arriving at the > deployment. > > > > Thanks > > > > -- > > David Farning > > Activity Central: http://www.activitycentral.com > > > > > ___ > > Server-devel mailing list > > Server-devel@lists.laptop.org > > http://lists.laptop.org/listinfo/server-devel > > > > What about an off-the-shelf SoHo UPS unit? > > cheers, > Sameer > > > > > -- > David Farning > Activity Central: http://www.activitycentral.com > ___ > Server-devel mailing list > Server-devel@lists.laptop.org > http://lists.laptop.org/listinfo/server-devel ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
Re: [Server-devel] 12 Volt power system for School Servers.
On Wed, 2013-05-29 at 15:03 -0500, David Farning wrote: > Tony could you share more information about your work on 12 Volt power > supplies for School Servers? > > > Whenever I see a School Server setup containing a 12V Battery, an > inverter, a power strip, and a couple of 120V to 12V power supplies to > provide power for the server and the AP... my eyes start to tear up:( > > Is the inverter really needed for a XO? The step-down transformer used on the XO puts out 13.5v but the XOs only need 11 volts to charge[1]. Therefore I believe you could run and/or charge the XOs directly from a 12v source like a storage battery, perhaps though a regulator. I just don't want to cut the cord off of a working power supply to find out. > The situation I am looking at has power part of the day so we can > recharge the battery. To keep things simple we would like to use a > Trimslice or XO-4 and off the shelf AP. > > Most of the networking devices use a transformer also but with perhaps a different voltage rating, with a regulator that takes 12 DC in we can output the voltage needed for the lower (<12v) voltage DC devices. If they run on usb power or < 12v dc this should be do-able. > Ideally we would like to have 'kit' that contained everything except > that battery that can be set up and tested before arriving at the > deployment. > > > Thanks > Recharging the storage battery is limited by the means that are available to recharge the storage battery perhaps via solar or wind, and is the related to the issue of how many XOs are in use that need charging. Jerry 1. http://wiki.laptop.org/index.php?title=Battery_and_power > > -- > David Farning > Activity Central: http://www.activitycentral.com > ___ > Server-devel mailing list > Server-devel@lists.laptop.org > http://lists.laptop.org/listinfo/server-devel ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
Re: [Server-devel] 12 Volt power system for School Servers.
The piece I am looking at is reducing the losses between the battery and the server/AP. Several systems have a 12V Battery which is inverted to 120AC which is then transformed back to low voltage DC for input to the server/AP. That doesn't seem very efficient. Dave On Wed, May 29, 2013 at 3:29 PM, Sameer Verma wrote: > On Wed, May 29, 2013 at 1:03 PM, David Farning > wrote: > > Tony could you share more information about your work on 12 Volt power > > supplies for School Servers? > > > > Whenever I see a School Server setup containing a 12V Battery, an > inverter, > > a power strip, and a couple of 120V to 12V power supplies to provide > power > > for the server and the AP... my eyes start to tear up:( > > > > The situation I am looking at has power part of the day so we can > recharge > > the battery. To keep things simple we would like to use a Trimslice or > XO-4 > > and off the shelf AP. > > > > Ideally we would like to have 'kit' that contained everything except that > > battery that can be set up and tested before arriving at the deployment. > > > > Thanks > > > > -- > > David Farning > > Activity Central: http://www.activitycentral.com > > > > ___ > > Server-devel mailing list > > Server-devel@lists.laptop.org > > http://lists.laptop.org/listinfo/server-devel > > > > What about an off-the-shelf SoHo UPS unit? > > cheers, > Sameer > -- David Farning Activity Central: http://www.activitycentral.com ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
Re: [Server-devel] 12 Volt power system for School Servers.
On Wed, May 29, 2013 at 1:03 PM, David Farning wrote: > Tony could you share more information about your work on 12 Volt power > supplies for School Servers? > > Whenever I see a School Server setup containing a 12V Battery, an inverter, > a power strip, and a couple of 120V to 12V power supplies to provide power > for the server and the AP... my eyes start to tear up:( > > The situation I am looking at has power part of the day so we can recharge > the battery. To keep things simple we would like to use a Trimslice or XO-4 > and off the shelf AP. > > Ideally we would like to have 'kit' that contained everything except that > battery that can be set up and tested before arriving at the deployment. > > Thanks > > -- > David Farning > Activity Central: http://www.activitycentral.com > > ___ > Server-devel mailing list > Server-devel@lists.laptop.org > http://lists.laptop.org/listinfo/server-devel > What about an off-the-shelf SoHo UPS unit? cheers, Sameer ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
[Server-devel] 12 Volt power system for School Servers.
Tony could you share more information about your work on 12 Volt power supplies for School Servers? Whenever I see a School Server setup containing a 12V Battery, an inverter, a power strip, and a couple of 120V to 12V power supplies to provide power for the server and the AP... my eyes start to tear up:( The situation I am looking at has power part of the day so we can recharge the battery. To keep things simple we would like to use a Trimslice or XO-4 and off the shelf AP. Ideally we would like to have 'kit' that contained everything except that battery that can be set up and tested before arriving at the deployment. Thanks -- David Farning Activity Central: http://www.activitycentral.com ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
