Serial port control of an ATX power supply

Hi,

It's been 20+ years since I did any kind of circuit design, so I'm struggling quite a bit with this. Here's what I'm trying to do:

I have a server sitting in a remote location (actually a cell block...) that occaisionally hangs. While I'm trying to determine the reason it hangs, I need a way to remotely toggle the power.

My thought is to run a piece of CAT 5 from the troublesome server up to a server that is reachable via the Internet. I would connect that CAT

5 cable to a spare serial port on the good server. Using the DTR/RTS pins I would come up with a way to raise those pins to high giving me enough power to activate a reed relay located at the far end. The other side of the reed relay would be connected to the power on circuit of the ATX power supply in the circuit. The relay would be Normally Open and when closed would be closed until my code releases it or minimally 10 seconds.

I need help identifying the current needs and what components would work; any help would be gratefully appreciated and I'll be happy to share whatever circuit comes out of this.

Thanks!

Pat

Reply to
pjhealy
Loading thread data ...

To restart it? That seems very cruel - and may trash the OS.

Reply to
Homer J Simpson

Given that the system is completely hung; there is no other option than recycling power... Besides, I'm a heartless bastard anyway.... *8-)

Reply to
pjhealy

I would use a 5V wall wart at the remote location for power. Use the DTR to drive a transistor to power the relay. Dave

Reply to
CheapscateDave

Use the POE concept? Use the spares in the CAT5 to drive a relay thats connected to the PC RESET button.

Cheers

Reply to
Martine Riddle

I'm thinking along these lines:

---(+)DTR--------+ +------------------------------+ 8 \\ | (relay) 8 * (ATX PSON) 8 | |

---(-)TXD--------+ +------------------------------+

When DTR is pulled high, that should be enough to energize the coil on a low curren reed relay. When energized it should close the switch on the otherside of the reed relay and hold long enough for the ATX power supply to shut down.

What I'm looking for is specific suggestions on a model of reed relay or SSR that will do the trick. Do I need any resistors on the serial side?

Thanks!

Pat

Reply to
pjhealy

Y-Face: ?)Aw4rXwN5u0~$nqKj`xPz>xHCwgi^q+^?Ri*+R(&uv2=E1Q0Zk(>h!~o2ID@6{uf8s;a+M[5[U[QT7xFN%^gR"=tuJw%TXXR'Fp~W;(T"1(739R%m0Yyyv*gkGoPA.$b,D.w:z+ Hi,

It doesn't need to be cat5. door-bell wire would do the task. but if there's cat5 there already there's no point wasting it.

That's marginal. I measure about 10.5mA short-circuit current on a serial port pin so you're going to need something like a 5V relay with a 1K resistance.

or maybe you could parallel two (or all three) of the output pins together to drive a 500 ohm relay (you can drive the txd pin high by setting the break bit, or almost high by writing sequence of zero bytes)

ATX switch current is only a few milliamps at about 5V. the contacts in any reed relay will be able to handle that.

Bye. Jasen

Reply to
jasen

?)Aw4rXwN5u0~$nqKj`xPz>xHCwgi^q+^?Ri*+R(&uv2=E1Q0Zk(>h!~o2ID@6{uf8s;a+M[5[U[QT7xFN%^gR"=tuJw%TXXR'Fp~W;(T"1(739R%m0Yyyv*gkGoPA.$b,D.w:z+ User-Agent: slrn/0.9.8.1 (Debian)

task.

10.5mA short-circuit current on a serial port

Jasen - Just what I was looking for thanks; Can you recommend an on-line source for the parts?

Thanks!

Pat

Reply to
pjhealy

If you can run wire to the room, why not just put a power relay in the AC input and drop power the easy way? If you use a normally-closed relay, the brief application of a battery to two wires will drop AC power for you.

For that matter, X-10 modules with remote control by transmitter or computer-control plugin cards are an easily available item. Maybe you can lose the wire.

For other folk with remote requirements, there are boxes available that will answer the phone and take a request to toggle power, but that seems too elaborate. We used the PowerKey products from Sophisticated Circuits, years ago.

You might also consider the builtin capabilities of UPS boxes, which often have serial control.

Reply to
whit3rd

Whit3rd - thanks for the thought; I hadn't thought about the X10 stuff; but since it's a commercial building, I suspect the 3phase power would throw off the X10 communication (maybe not, I'm not sure...). I thought about using some type of 120V relay but came to the conclusion it would be cheaper to get a low voltage relay instead and not worry about finding one that can handle the current and wattage needs of the

120 line.
Reply to
pjhealy

One comment. One of the things that can help make a computer reliable, is a smooth power rail. Brownouts of more than a very few mSec, can cause computer lockups. Now a small UPS, would provide this, and most such units, offer a serial interface, as mentioned by the poster above, allowing shutdown control. You should also change the bootup of the OS, to _default_ to performing a FSCK, whatever system you use.

Best Wishes

Reply to
Roger Hamlett

Roger; thanks for the the thought - I agree, it's likely a power supply issue. The system is a PC based PBX and the problem started when I plugged in a TDM card that requires a power directly from the power supply (similar to video SLI cards).

The system is on a UPS, but the shutdown control expects that system to be up so that a daemon on that machine can be signalled when the UPS is on battery and can perform a normal safe shutdown. Since the system is hung, the daemon won't respond to anything the UPS tells it to do. Now, if I could hook to the UPS serial port from another computer and instruct the UPS to shutdown that power port, then I might have something. However, my experience is that the UPS will issue commands from the serial port but has limited ability to listen and act on commands (ie. it will respond to status commands, but not "shutdown AC plug 1", etc.).

The system is also Linux based, and will do an auto FSCK upon reboot if necessary. I also plan on replacing the internal power supply sometime tonight, but since the system is a PBX, it will need to be up all the time. So even if the replacement power supply fixes the problem, I'd like to have the ability to have another machine monitor its status and be able to reboot it...

Thanks for taking the time to read these messages; I'm picking up a lot of useful information.

I'm looking for an online retailer who'll sell the reed relays along with components like a PC slot cover with a printed circuit board on the back (but no PCI-like interface) and small componenents like the connectors that would be able to connect to the motherboards PSON jumper as well as the male that would provide connection to the UPS. Any suggestions on a source for these would be greatly appreciated.

Thanks!

Pat

Reply to
pjhealy

Except for larger units, they do not normally have the ability to shutdown an individual plug, but full on/off control is normally available, on units like the APC 'smart' devices. The problem is that APC, require you to sign a full 'non disclosure' agreement, before they will give you data about the extended command set... However their UPS's are controllable by the hardware interface, and this is published. On this, pin 8, is a 24v output, that remains on, even when the unit is switched off (useful - however only rated at 40mA). Pin 4 is the 'common', and pin 1, is 'shutdown'. Normally this pin is connected to DTR on the PC, which switches off the unit, when shutdown has completed. A couple of diodes, and a resistor, would allow you to operate this pin without interfering with PC operation. One other suggestion, why not consider adding a watchdog to the unit?. A simple external box, connected to the reset switch, with either a PIC, or a simple monostable multivibrator, triggered from one line off a serial port. If the line does not have an 'edge' in it for say 30 seconds, it resets the PC. Have a small program running a timer event, that every ten seconds or so, sends a character out this serial port. If the program stops, the system will be reset. Such units are available off the shelf, and some even allow normal serial 'pass throgh' on the unit. This way, you don't have to be fiddling around resetting the unit yourself... :-)

Best Wishes

Reply to
Roger Hamlett

Roger - that's great info; there's a non-APC model attached, but I have the source code to their Unix scripts; so maybe I can dope that out. I'm interested in the PIC; can you point to a source that I could look at?

Thanks!

Reply to
pjhealy

Save yourself all the messy wiring trouble + code writing and check if your computer supports Wake on LAN in the Bios Power management section. WOL is an old standard that has been around since 1997 and lets you remotely switch on or shut off your computer remotely. All computers I've used have it so you may be lucky... if you use a separate Network card then you'd have to check that its also compliant otherwise for 10-20 bucks you'd get one. Otherwise you could also check for WOM (Wake on Modem) an old standard that powers on/off your computer by phone. If the latter is absent you'd probably spend as much time modding your Bios with it as writing the serial port code though excluding all the messy wiring.

lemonjuice

Reply to
lemonjuice

If I was doing this on a PIC, I'd just write the code myself. I have done similar units in the past. What these did, was simply watch the serial port, resetting a timer whenever a particular character was received. If the character did not arrive in a particular time, and the timer overflows, they issue a single reset pulse. The timer then starts again, but for a longer time (usually a couple of minutes). This allows time for the system to start. However there are dozens of off the shelf watchdog units now. Look at (for example):

formatting link
This one has Linux drivers. Or for something different (assuming your application does disk I/O):
formatting link

Best Wishes

Reply to
Roger Hamlett

Roger - I like the trinity-electronics device; seems to be just the item. I'll check into the cost of that... Thanks again! Pat

Reply to
pjhealy

The mother board is an AM2 based system; I suspect the WOL is there. Do you have any links to where I can read up on how to control the WOL feature remotely?

Thanks!

Reply to
pjhealy

Unless things have changed recently, Wake On LAN only lets you wake a computer remotely, it doesn't support remote shutdowns. I'm not sure I'd even want my machines able to be shut down by a wildly insecure protocol like WOL. It doesn't much matter that it's insecure because all it can do is start a machine which is off, which will usually only cost some electricity.

Tim

Reply to
Tim Auton

Search for Magic Packet on the AMD site or LAN Desk manager by Intel. The following websites have some nice info

formatting link
formatting link
formatting link

Best wishes

lemonjuice

Reply to
lemonjuice

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.