Maker Pro
Maker Pro

Answering Machine - Power Backup?

L

Len Krauss

Jan 1, 1970
0
I have a phone answering machine / cordless phone combo unit which has no
backup battery. My area has a fair number of short power interruptions. When
they occur and power is later restored, the unit's day & time-stamp clock
(for subsequent messages) is inaccurate. There is no function available to
reset it remotely. So, if I'm away for a month, and there've been several
power blips, the day&time stamp on messages I retreive remotely is
meaningless.

The unit is powered by AC to DC converter block. Input: 120v, 60hz, 8.5w.
Output: 9vdc, 500ma.

Seeking ideas on possible ways to have backup power to overcome this
problem.

Thanks,
Len
 
J

Jim Thompson

Jan 1, 1970
0
I have a phone answering machine / cordless phone combo unit which has no
backup battery. My area has a fair number of short power interruptions. When
they occur and power is later restored, the unit's day & time-stamp clock
(for subsequent messages) is inaccurate. There is no function available to
reset it remotely. So, if I'm away for a month, and there've been several
power blips, the day&time stamp on messages I retreive remotely is
meaningless.

The unit is powered by AC to DC converter block. Input: 120v, 60hz, 8.5w.
Output: 9vdc, 500ma.

Seeking ideas on possible ways to have backup power to overcome this
problem.

Thanks,
Len

APC has some really cheap UPS's. I use their ES-350 to backup my home
wireless phone system.

...Jim Thompson
 
J

John Popelish

Jan 1, 1970
0
Len said:
I have a phone answering machine / cordless phone combo unit which has no
backup battery. My area has a fair number of short power interruptions. When
they occur and power is later restored, the unit's day & time-stamp clock
(for subsequent messages) is inaccurate. There is no function available to
reset it remotely. So, if I'm away for a month, and there've been several
power blips, the day&time stamp on messages I retreive remotely is
meaningless.

The unit is powered by AC to DC converter block. Input: 120v, 60hz, 8.5w.
Output: 9vdc, 500ma.

Seeking ideas on possible ways to have backup power to overcome this
problem.

Thanks,
Len
For something that small, you should be able to hang a rechargeable
battery across the supply's DC output. Since it will be always
charging, you want it to supply a low charging current so the
batteries don't overcharge. That implys a resistor in series with the
battery would be a good ides. But then you need to parallel the
resistor with a diode, so that at power failure, the battery can power
answering machine through the diode with little voltage drop.

I think an experiment is in order, to determine how low the voltage
can go and still have the machine operate correctly, to decide if you
need 6 or 8 cells.

You might look for some low cost AA rechargables and one of these
battery holders:
http://www.batteryholders.com/BH48AAL.pdf
http://www.batteryholders.com/BH26AAL.pdf
 
I

Ignoramus26315

Jan 1, 1970
0
How about buying an uninterruptible power supply...

i

I have a phone answering machine / cordless phone combo unit which has no
backup battery. My area has a fair number of short power interruptions. When
they occur and power is later restored, the unit's day & time-stamp clock
(for subsequent messages) is inaccurate. There is no function available to
reset it remotely. So, if I'm away for a month, and there've been several
power blips, the day&time stamp on messages I retreive remotely is
meaningless.

The unit is powered by AC to DC converter block. Input: 120v, 60hz, 8.5w.
Output: 9vdc, 500ma.

Seeking ideas on possible ways to have backup power to overcome this
problem.

Thanks,
Len


--
 
P

Pooh Bear

Jan 1, 1970
0
Len said:
I have a phone answering machine / cordless phone combo unit which has no
backup battery. My area has a fair number of short power interruptions. When
they occur and power is later restored, the unit's day & time-stamp clock
(for subsequent messages) is inaccurate. There is no function available to
reset it remotely. So, if I'm away for a month, and there've been several
power blips, the day&time stamp on messages I retreive remotely is
meaningless.

The unit is powered by AC to DC converter block. Input: 120v, 60hz, 8.5w.
Output: 9vdc, 500ma.

Seeking ideas on possible ways to have backup power to overcome this
problem.

The most cost effective answer is to buy an answering machine that does what you
need.

Graham
 
P

Pooh Bear

Jan 1, 1970
0
Ignoramus26315 said:
How about buying an uninterruptible power supply...

At several times the price of a decent answering machine with internal backup ?

Graham
 
I

Ian Stirling

Jan 1, 1970
0
Len Krauss said:
I have a phone answering machine / cordless phone combo unit which has no
backup battery. My area has a fair number of short power interruptions. When
they occur and power is later restored, the unit's day & time-stamp clock
(for subsequent messages) is inaccurate. There is no function available to
reset it remotely. So, if I'm away for a month, and there've been several
power blips, the day&time stamp on messages I retreive remotely is
meaningless.

The unit is powered by AC to DC converter block. Input: 120v, 60hz, 8.5w.
Output: 9vdc, 500ma.

Seeking ideas on possible ways to have backup power to overcome this
problem.

Do you have a soldering iron and clue?
My first attempt would be to take 5 D cells (7.5V) and two diodes.
Put the diode in series with the 5 D cells and the power supply, with the
other ends of the diodes going to the plug.

This should last several hours downtime.
 
K

keith

Jan 1, 1970
0
At several times the price of a decent answering machine with internal backup ?

If one's worried about it, have the telco take care of it. I've
disconnected from land-lines, so my cell carrier takes care of such
trivia.
 
K

kell

Jan 1, 1970
0
The unit is powered by AC to DC converter block. Input: 120v, 60hz, 8.5w.
Output: 9vdc, 500ma.

Seeking ideas on possible ways to have backup power to overcome this
problem.



positive from
power supply
_______________________
|
\/diode
-
|_________________positive to machine
|
-
/\diode
|
five or six alkaline
D cells in series
|
_______________________|__________________negative to machine
negative from
power supply

the cathode (striped end) of the upper diode in the diagram connects to
the cathode of the lower diode in the diagram. Sterling suggested five
cells (7.5 volts) to make sure the battery voltage is lower than the
power supply, so that the batteries won't direct current into the
machine during normal operation. But your machine needs to be able to
run on less than 7 volts in that case. If you find you need six cells
to get the machine to run, an extra diode or two at the positive
battery pole might be called for to drop the battery output to below
that of the power supply.
For John Popelish's circuit using rechargeable batteries, omit the
upper diode and put a resistor in parallel with the lower diode.

If you are using google, hit the show original option to see the
diagram in a non-proportional font.
 
P

Paul Hovnanian P.E.

Jan 1, 1970
0
kell said:
positive from
power supply
_______________________
|
\/diode
-
|_________________positive to machine
|
-
/\diode
|
five or six alkaline
D cells in series
|
_______________________|__________________negative to machine
negative from
power supply

the cathode (striped end) of the upper diode in the diagram connects to
the cathode of the lower diode in the diagram. Sterling suggested five
cells (7.5 volts) to make sure the battery voltage is lower than the
power supply, so that the batteries won't direct current into the
machine during normal operation. But your machine needs to be able to
run on less than 7 volts in that case. If you find you need six cells
to get the machine to run, an extra diode or two at the positive
battery pole might be called for to drop the battery output to below
that of the power supply.
For John Popelish's circuit using rechargeable batteries, omit the
upper diode and put a resistor in parallel with the lower diode.

If you are using google, hit the show original option to see the
diagram in a non-proportional font.

If you want to go 'first class', Maxim (and others, I'm sure) make
controller chips that handle switchover between adapter input and
battery. They handle battery state monitoring, charger control (if you
want to make it a NiCad or NiMH). The p/n I have handy is a Maxim
MAX1538. This might be overkill (it handles two batteries), but they
might have a similar controller for a single battery.
 
A

Al

Jan 1, 1970
0
Jim Thompson said:
APC has some really cheap UPS's. I use their ES-350 to backup my home
wireless phone system.

...Jim Thompson

All but one of my UPSs come from my town's recycling center for free. Of
course I test them before I use them. I even replace the batteries in
some of them. The latest one I got, is good for 200VA for about 5
minutes. Should keep a phone happy for a long time.


Al
 
R

Rich Grise

Jan 1, 1970
0
All but one of my UPSs come from my town's recycling center for free. Of
some of them. The latest one I got, is good for 200VA for about 5
minutes. Should keep a phone happy for a long time.

Al

A whole UPS, for a telephone? Since the output of the wall wart is
nominally 9V, I'd just stick an ordinary 9V "transistor" battery
in parallel with it, with a blocking diode. I'd think an alkaline would
last almost its shelf life in that kind of application. (after having
plunked down fifteen bucks for a set of NiMHs, and having to recharge them
almost weekly, I'm seriously impressed with the lifetime of alkalines!)

Good Luck!
Rich
 
J

Jim Thompson

Jan 1, 1970
0
A whole UPS, for a telephone? Since the output of the wall wart is
nominally 9V, I'd just stick an ordinary 9V "transistor" battery
in parallel with it, with a blocking diode. I'd think an alkaline would
last almost its shelf life in that kind of application. (after having
plunked down fifteen bucks for a set of NiMHs, and having to recharge them
almost weekly, I'm seriously impressed with the lifetime of alkalines!)

Good Luck!
Rich

It's a wireless system, so the base station is of significant power.
I also run the cell phone chargers at that desk location.

They're rare, but AZ down-times have been known to be as long as 24
hours :-(

...Jim Thompson
 
S

Spajky

Jan 1, 1970
0
I have a phone answering machine / cordless phone combo unit which has no
backup battery. My area has a fair number of short power interruptions.
The unit is powered by AC to DC converter block. Input: 120v, 60hz, 8.5w.
Output: 9vdc, 500ma.

IMHO those AC to DC converter block gives around 16V
unregulated output w/o load (if not switching type already
regulated!); when such a device is connected to it, it drops few V &
appliance has internal voltage stabilizer to 9V. I had a case with
similar setup @ my neighbour years ago I solved so:

I fixed a pack of Ni-Cd acu batteries 7x1,2V/800mAh nominal
(when charged fully gives 10V) to the AC to DC converter block &
supplied the "pack" thru a 1N4007 & 68ohm/1W resistor in series from
that AC/DC converter (it was an ordinary one, not switching type!), so
it was charging the pack with max.80mA long term (half of that took
the appliance when on hook, so constant charging was only other 40mA)
The power for apliance than was taken from the battery pack ... it was
an analog Panasonic answering machine (cassette type) with home
wireless phone ...

It was working Ok for years ...
 
Len Krauss said:
My area has a fair number of short power interruptions.

How short is short? If you're in the house when one of these happens,
do the lights go out for less than a second, or do they stay off for
longer than that? If it's less than a second, you might try hanging a
big electrolytic capacitor across the power input to the answering
machine. Use one of a few thousand microfards (uF) with at least a
25 V voltage rating. The capacitor is polarized and usually the
negative lead is marked - make sure you hook it up the right way. This
is the same idea as hanging a rechargeable battery on the power input,
except the "battery" has much lower capacity.

If the above doesn't make any sense, buy one of the "fat power strip"
APC UPSes for about $30 or so and plug the answering machine into that.

Matt Roberds
 
L

Len Krauss

Jan 1, 1970
0
Some great ideas here guys. Thanks!

I should have been clear that there are some less frequent but longer power
outages (a few hours) as well as blips. For that reason, I'm leaning towards
a UPS. I can get an low cost APC BK280 refurb with specs as follows:

Output power capacity 280 VA, 180 Watts
Replacement battery cartridge RBC2
Typical backup time at half load 18.2 minutes
Typical backup time at full load 6.7 minutes

On the assumption that the cordless phone's batteries are fully charged when
a long outage begins, I'm thinking that even less than the indicated power
(see below) would be drawn to keep the answering base alive until the
batteries get weak, a which point more power would be drawn for charging.

What's your guesstimate of backup time given the very light load I've
indicated ???

Thanks,
Len
 
Len Krauss said:
I should have been clear that there are some less frequent but longer power
outages (a few hours) as well as blips. For that reason, I'm leaning towards
a UPS. I can get an low cost APC BK280 refurb with specs as follows:

Output power capacity 280 VA, 180 Watts
Replacement battery cartridge RBC2
Typical backup time at half load 18.2 minutes
Typical backup time at full load 6.7 minutes

Since this involves rechargeable batteries, all "marketing" numbers can
be halved, making the half load number something like 9 minutes. The
phone's power supply takes 8.5 W, so you'd expect something like (90 W /
8.5 W) * 9 or about 90 minutes. In reality it will be a bit longer than
this. Make sure nothing else gets plugged into the battery-backed
outlets on the UPS.

Matt Roberds
 
Top