Convert battery powered to battery backup
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Posted by runderwo@mail.win.org on April 19, 2007, 12:59 pm
Please log in for more thread options I just installed one of those cheapo battery powered (two 1.5V AA) thermostats. It occurred to me that I could run a regulator from the 24V supply in the wall to derive the 3V needed to run the unit and use the batteries only as a backup. What would I need to do to safely wire this regulator in parallel with the batteries so that both can supply power to the unit, but so that no current from the regulator runs through the batteries? Any alternate takes on this idea? | ||||||||||||||||||||||||||||
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Posted by Homer J Simpson on April 19, 2007, 2:24 pm
Please log in for more thread options Don't. The batteries are already a backup - the device is powered off the 24 VAC line except when closed. | ||||||||||||||||||||||||||||
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Posted by runderwo@mail.win.org on April 19, 2007, 3:53 pm
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>
> > > I just installed one of those cheapo battery powered (two 1.5V AA)
> > thermostats. It occurred to me that I could run a regulator from the > > 24V supply in the wall to derive the 3V needed to run the unit and use > > the batteries only as a backup. What would I need to do to safely > > wire this regulator in parallel with the batteries so that both can > > supply power to the unit, but so that no current from the regulator > > runs through the batteries? Any alternate takes on this idea? >
> Don't. The batteries are already a backup - the device is powered off the 24 > VAC line except when closed. The manual specifically states that the device is powered only by the batteries... | ||||||||||||||||||||||||||||
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Posted by Homer J Simpson on April 19, 2007, 7:53 pm
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> The manual specifically states that the device is powered only by the
> batteries... I get two or three years out of a set of batteries. Why make the effort? | ||||||||||||||||||||||||||||
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Posted by Rich Grise on April 19, 2007, 2:47 pm
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On Thu, 19 Apr 2007 09:59:21 -0700, runderwo@mail.win.org wrote: > I just installed one of those cheapo battery powered (two 1.5V AA)
> thermostats. It occurred to me that I could run a regulator from the > 24V supply in the wall to derive the 3V needed to run the unit and use > the batteries only as a backup. What would I need to do to safely > wire this regulator in parallel with the batteries so that both can > supply power to the unit, but so that no current from the regulator > runs through the batteries? Any alternate takes on this idea? Use two diodes, say 1N400x or so: Battery + ------->|-------+
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+-------- equipment | 3V Reg. + ------->|-------+
Hope This Helps! Rich | ||||||||||||||||||||||||||||
> thermostats. It occurred to me that I could run a regulator from the
> 24V supply in the wall to derive the 3V needed to run the unit and use
> the batteries only as a backup. What would I need to do to safely
> wire this regulator in parallel with the batteries so that both can
> supply power to the unit, but so that no current from the regulator
> runs through the batteries? Any alternate takes on this idea?