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Using a d cell battery to power a digital watch?

Hi, I am new to this group and have been playing around with unwanted
(by others) digital watches. I have been powering them with wires
soldered to the correct polarity on the watch contacts and using
battery holders bought from radio shack to power the watches with d
cell batteries (rechargeable alkaline in some cases). I have checked
and the polarity/voltage (current is easily accepted especially
compared to the special coin cell batteries these devices came with) is
correct in my situation. For some reason some of the devices will reset
or otherwise go blank. I have minimized this with one of my wanted
timers by using solid wire (for some reason it makes a big difference)
but when the wire is in certain positions the blanking still happens. I
am suspecting that this low voltage/low current situation is caused by
the battery wires acting like an antenna and the low current/low
voltage is counteracted by this phenomenon.

In summary the question is - how can I eliminate these digital devices
from going blank seemingly randomly and if not then why not?

Thanks, later!
 
R

Rich Grise

Jan 1, 1970
0
Hi, I am new to this group and have been playing around with unwanted
(by others) digital watches. I have been powering them with wires
soldered to the correct polarity on the watch contacts and using
battery holders bought from radio shack to power the watches with d
cell batteries (rechargeable alkaline in some cases). I have checked
and the polarity/voltage (current is easily accepted especially
compared to the special coin cell batteries these devices came with) is
correct in my situation. For some reason some of the devices will reset
or otherwise go blank. I have minimized this with one of my wanted
timers by using solid wire (for some reason it makes a big difference)
but when the wire is in certain positions the blanking still happens. I
am suspecting that this low voltage/low current situation is caused by
the battery wires acting like an antenna and the low current/low
voltage is counteracted by this phenomenon.

In summary the question is - how can I eliminate these digital devices
from going blank seemingly randomly and if not then why not?

It's probably intermittent solder connections. The battery clips in a
watch are either stainless or nickel plated, both of which are hard to
solder properly. I'd either go with a mechanical connection (i.e.,
two pieces of copper foil on either side of a wood or plastic slug
the size of a watch battery) or work on your soldering to those parts.
You'll probably need a more aggressive flux, but then it will have to
be cleaned completely so it doesn't corrode.

And it's very, very unlikely that anything your leads would pick up
antenna-wise would have anything to do with it - these voltages are
measured in microvolts.

Good Luck!
Rich
 
L

Larry Brasfield

Jan 1, 1970
0
Hi, I am new to this group and have been playing around with unwanted
(by others) digital watches. I have been powering them with wires
soldered to the correct polarity on the watch contacts and using
battery holders bought from radio shack to power

That battery holder could be part of the problem.
Is there any movement of or shock applied to the
battery holder when it is supposed to be helping
power the watch? Brief opens would well explain
the symptoms you report.
the watches with d
cell batteries (rechargeable alkaline in some cases). I have checked
and the polarity/voltage (current is easily accepted especially
compared to the special coin cell batteries these devices came with) is
correct in my situation. For some reason some of the devices will reset
or otherwise go blank. I have minimized this with one of my wanted
timers by using solid wire (for some reason it makes a big difference)

I am reasonably sure that your solid wire preference is an
example of the "Post Hoc" fallacy. If interested in that, see
http://www2.sjsu.edu/depts/itl/graphics/adhom/posthoc.html

If the solid wire actually did "fix" the problem, it was because
you had to change your connection technique, and the new
one works better.
but when the wire is in certain positions the blanking still happens. I
am suspecting that this low voltage/low current situation is caused by
the battery wires acting like an antenna and the low current/low
voltage is counteracted by this phenomenon.

That is conceivable if you have made some huge loop,
separating members of the wire pair. You didn't do
that, did you? If not, RFI is not the problem.
In summary the question is - how can I eliminate these digital devices
from going blank seemingly randomly and if not then why not?

I think you just need to get power to them on
a continuous basis, not even briefly interrupted.
Thanks, later!

You're welcome now.
 
B

Bob Masta

Jan 1, 1970
0
Hi, I am new to this group and have been playing around with unwanted
(by others) digital watches. I have been powering them with wires
soldered to the correct polarity on the watch contacts and using
battery holders bought from radio shack to power the watches with d
cell batteries (rechargeable alkaline in some cases). I have checked
and the polarity/voltage (current is easily accepted especially
compared to the special coin cell batteries these devices came with) is
correct in my situation. For some reason some of the devices will reset
or otherwise go blank. I have minimized this with one of my wanted
timers by using solid wire (for some reason it makes a big difference)
but when the wire is in certain positions the blanking still happens. I
am suspecting that this low voltage/low current situation is caused by
the battery wires acting like an antenna and the low current/low
voltage is counteracted by this phenomenon.

In summary the question is - how can I eliminate these digital devices
from going blank seemingly randomly and if not then why not?

Thanks, later!

Besides the good advice others have given, consider that
these watches typically use LCD displays that are not soldered
in place but are simply held against a strip of contacts.
It's pretty easy to dislodge this, and I've seen plenty of
cheap units where the watch behaves just as you describe.
I suspect that may be one reason why they are discarded
by others in the first place!

Best regards,



Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
 
Thanks guys! It's better to be a brief open in this case rather
than an antenna issue because this way I can fix it with a better
electrical connection instead of trying to shield the power conductors.
I am going to resolder the device I am most interested in so that the
wires (will use stranded) are soldered directly to the device's
internal wires instead of to the coin cell pads/connectors. My solder
connections seemed perfect but will try the previously mentioned fix.
The other devices I have can wait. I will probably post my findings
here. It will be good to know if my stranded wire is good or not.
Thanks again, later guys!
 
B

Bill Bowden

Jan 1, 1970
0
I have been powering them with wires soldered to the
I think a AAA battery will last as long or longer than a "D" cell,
since both have the same shelf life and the watch draws very little
power. Probably not enough to drain a AAA battery during it's shelf
life.

Why waste a "D" cell when you can get the same performance from a AAA
cell?

-Bill
 
D

Doug McLaren

Jan 1, 1970
0
| >> I have been powering them with wires soldered to the
| >> correct polarity on the watch contacts and using
| >> battery holders bought from radio shack to power
| >> the watches with d cell batteries (rechargeable
| >> alkaline in some cases).
|
| I think a AAA battery will last as long or longer than a "D" cell,
| since both have the same shelf life and the watch draws very little
| power. Probably not enough to drain a AAA battery during it's shelf
| life.
|
| Why waste a "D" cell when you can get the same performance from a AAA
| cell?

Agreed, a AAA cell would probably last years.

However, you mentioned a rechargable alkaline? Big waste. I don't
know what the discharge rate on those are, but a NiCd would be dead in
six months, and a NiMH cell in under 3.

I love my rechargable batteries and buy them in large quantities, but
I also know that there's applications that they don't work well for
due to their relatively high self discharge rate -- remotes, smoke
alarms, emergency flashlights, etc.
 
B

Bill Bowden

Jan 1, 1970
0
However, you mentioned a rechargable alkaline? Big waste

Actually, the OP mentioned it. But yes, recharagable batteries of any
variety are a waste for a digital clock/watch application. Alkaline
AAAs are the only way to go. Or maybe Lithium for longer shelf life,
but those are more expensive.

I ran a quartz wall clock for 3 years using 5 salt water cells in
series. I used 5 small olive jars with a strip of copper and aluminum
inside submerged in salt water. Gave me about 300 mV per cell at a
couple milliamps, but I got tired of adding water to the cells every
week or so to make up for the evaporation.

-Bill
 
B

Bob Masta

Jan 1, 1970
0
Actually, the OP mentioned it. But yes, recharagable batteries of any
variety are a waste for a digital clock/watch application. Alkaline
AAAs are the only way to go. Or maybe Lithium for longer shelf life,
but those are more expensive.

I ran a quartz wall clock for 3 years using 5 salt water cells in
series. I used 5 small olive jars with a strip of copper and aluminum
inside submerged in salt water. Gave me about 300 mV per cell at a
couple milliamps, but I got tired of adding water to the cells every
week or so to make up for the evaporation.

-Bill

On a related note, my trick is to take 9V batteries
that are "dead" at 8V, and make a tiny 3V regulator
that sits on a battery clip. I have a menagerie of
clocks, kitchen timers, calculators, etc, with 9V batteries
stapped to them. It takes a ***long*** time to drain
a "dead" 9V down below 3V... and dead 9V batteries
are free!

The regulator uses an LED with a large series resistor
as a super-sharp low-voltage Zener, plus a simple pass
transistor. Works great, and totally impractical... I love it!






Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
 
Interesting stuff. I am pretty sure a rechargeable alkaline battery has
a longer shelf (charge) life than rechargeable nicads or rechargeable
nimhs. I am using a rechargeable "d" battery simply because it is
handy. I don't like traveling across town in this tourist town risking
my life every time with those other drivers. I appreciate the answers -
especially the one about solder connections and nickel or stainless
steel contact points. I soldered directly to the power supply wires in
my aqua reminder and it works perfectly now and the same with the
bicycle odometers. So it was a poor electrical connection, good
mechanical connection that I had previously. This project is practical
to me much like my other previous project I haven't finished yet. That
was to make a rechargeable battery pack for a smoke alarm and before
you scoff and say that wouldn't be reliable keep in mind I have seen
fire alarms using that exact same method and that fire alarm was a
first alert brand. The only reason I didn't buy it when I saw it is
because it was used, I might very well do some searching right now for
new units of those and might order one. The one I saw is directly wired
to the house' power supply (~115 volts). Thanks for telling me that the
solder connection was a poor electrical connection but a good
mechanical connection when it comes to stainless steel and nickel, that
solved my problem perfectly - Later!
 

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