[Nut-upsdev] How do I approach this problem?

[Jeff Cunningham]

Robert Woodcock wrote:
> On Mon, Nov 10, 2008 at 07:23:58AM -0800, Jeff Cunningham wrote:
>   
>> Is there any way to have the UPS restart my computers once it knows its
>> back on live power?
>>     
>
> Most BIOSs have a setting for this - it's usually set to "Last State", which
> unfortunately doesn't really work on some motherboards - "Always On" will
> work.
>
> There's (at least) two other hardware routes you can take:
>
> 1. On the ATX motherboard power header, short the green wire to a black
> wire. This forces the power supply on.
>
> 2. Rig up a relay to momentarily short the motherboard's power switch when
> power returns, toggling the power on. I have not actually tested the
> following circuit in a PC, but it's simple enough, and it should act a
> little nicer than the first method:
>
>                                           ____________
>                       100ohm             |  12V relay |
> 12VDC+ ------->|------/\/\/-------+------|+           |
> (yellow)     diode   resistor     |      |C       N/C |---------- To mobo
>                                   |      |o           |           soft
>            very large capacitor =====    |i         C |---------- power
>                                   |      |l           |           switch
> GND    ---------------------------+------|+       N/O |
> (black)                                  |____________|
>
>
> Basically, when everything is off, the N/C and C pins will be shorted
> together (like you're pressing the power button). When power returns, this
> will turn on the computer. Once the computer's 12VDC+ line puts out power
> long enough to charge the capacitor and energize the relay, the relay
> switches and the short is removed (like you had released the power button).
>
> If you attempt to turn off a computer with such a circuit attached, the
> capacitor will temporarily power the relay (the diode prevents it from
> attempting to power the rest of the computer) and give the disks a chance to
> spin down. Then the relay contacts will close and the computer will turn
> back on.
>
> I did go so far as to test how long a capacitor would power a relay - with
> the relay I had (which was 380 ohms across the coil), a 15000uF cap would
> power it for about 6 seconds, and a 25000uF cap would power it for about 10
> seconds.
>
> The resistor will see about 1.5 watts peak, but since that's only for a
> second or two, a 1/4 watt resistor won't even get warm.
>
> If you actually use this, please let me know how it works for you.
>   
Your solution #2 is very clever and could probably be made to work if 
that were my problem. But my BIOSes do have settings that will cause 
them to restart on resumption of power to the computer.  But this is 
what I think is happening in both cases (one a tripplite using nut-ups, 
the other an APS using their software):

1. Power goes out
2. UPS goes on battery power
3. UPS monitoring software waits until it thinks battery is about half 
gone then tells both computer and UPS to shut down
4. Computer shuts down, thus its last state is "off"
5. UPS shuts down.
6. Power comes back on.
7. UPS comes back on.
8. Computer stays down.

Does that make any sense?

Regards,
Jeff