Linux-Hams archive - May 1998: RE: Watchdog
RE: Watchdog
Patrick Ouellette (jjmmflk.grcgimbhm@roskapostia.tunk.net)
Fri, 8 May 1998 09:21:32 -0400
>
> Patrick Ouellette wrote in a message to Mike Bilow:
>
> PO> I've thought of a similar setup. Diodes to handle the
> PO> current can be hard to find/expensive, so I thought of using
> PO> a spdt relay with the coil connected to the AC that would
> PO> connect the battery when the ac drops out. The advantage I
> PO> see here is the circuit that connects the batteries uses no
> PO> power and has no voltage drop while you are on batteries.
>
> PO> I have been working on a similar system to keep my rig
> PO> powered when I loose AC. I use the relay to connect the
> PO> battery to the charger while the AC is on (actually while my
> PO> 12v power supply is on since the relays I am using have 12v
> PO> DC coils), and to the rig when the AC drops. The radio
> PO> doesn't seem to mind the momentary power glitch when the
> PO> relay drops.
>
> First, I think you want to float the batteries on charge, which
> means that you
> don't need much extra by way of diodes.
The diodes would need to pass the entire current required be the
UPS. I'm guessing around 10 or more amps, depending on the UPS
and what is connected to it.
>
> Second, bouncing computers up and down on relays is not a good idea.
Read the setup from previous messages in the thread - the computer
would not be bouncing up and down on relays. The relays would be
used to connect a large battery to the UPS, before it shut down from
a low battery condition. And allow the large battery to be disconnected
from the UPS and placed on a separate charger when power returned.
Pat