Linux-Hams archive - May 1998: Re: Watchdog
Re: Watchdog
Charles Greene (zkjewf@sptelefilm.com.br)
Fri, 01 May 1998 11:28:17 -0400
At 01:17 PM 4/30/98 -0700, Alex Holden wrote:
>Charles Greene wrote:
><BIG snip>
>> chargers have different design criteria, as do the inverters. I'd say=
the=3D
>> battery/charger/inverter would be a misapplication of the technology=
for=3D
>> use as a UPS. The automatic UPS is pricey, but the basic, stripped=
down=3D
> ^ ^ ^ ^ ^ =20
>^ ^
>> UPS is not, so why not use a stripped down UPS and design a controller=
that=3D
> ^ ^ ^
>I disaree. Even the cheapest, low capacity ones are more than =A3100. That
>is more than I can afford, being a poor student. The idea was to design
>something which could be built on a shoestring budget, mostly from junk
>box parts. It just so happens that since at least two of us have the
>expertise to build a "smart" microcontrolled system, we may as well put
>that in at the same time. It has the added advantage that we could
>include a hardware watchdog timer (and possibly temperature monitoring
>capability) in the same unit.
>My current thinking is that we may be able to do away with the
>complexity of an inverter by supplying the low voltage DC of the PC
>directly from the UPS, possibly via a dummy ISA card, or some inline
>connectors which fit between the leads from the power supply to the
>motherboard. It would not be able to power the monitor, but most hams
>really just want their node to stay up until the mains comes back on,
>and for the system to shut down if the power cut is so long that the
>UPSs batteries start to run out.
>
>73s, Alex.
Well, Alex, powering the PC from a battery is not the same as using a UPS.=
I'm sorry I didn't understand what you were proposing. A UPS puts out 115=
AC from an inverter using an internal battery. I powered our local voice=
repeater from a battery for emergency power, and you could do something=
like that. Use a six volt battery and run the power from the battery to=
the +5v power supply through two 10 amp diodes to drop the voltage from=
full charge voltage of 6.9 volts to 5.5 volts (the drop through each diode=
is .7 amps). Or use a 10 amp 115 volt AC relay powered across the mains and=
when the AC power drops out, the relay switches the battery in. It may=
drop your computer in the meantime, so the diode approach is better in that=
respect. You could try a large capacitor across the power supply. You=
need + 12 v of about 1 amp, which you can get from a 12 volt battery, and=
-12 volts low current which you can get from a DC-DC power supply or=
another battery. Of course, you need to be concerned how to charge the=
batteries, and hopefully, the entire combination will cost less than UPS,=
if cost is the primary consideration. I can get a basic UPS for in the low=
100's, so the cost differential is different here.
-------------------
Be nice. It doesn't take any longer.
-------------------
Charles Greene
Internet=terhi.victor@logonet.com
Internet to Amprnet=wrv.izfjikpa@ctii.com
115 Aaron Avenue
Bristol, RI (On the shore of beautiful Narragansett Bay)