need to drop battery voltage in a very confined space, eg. a watch

[ZOT]

from 1.5v to 1.35 or so. Is a 1.35v zener feasible and where would I
get one? Can't seem to find one.

 

[James T. White]

from 1.5v to 1.35 or so. Is a 1.35v zener feasible and where would I
get one? Can't seem to find one.

I'm not aware of any real zeners with Vz less than 3V. Have you
considered using a variable zener like the LMV431? Minimum voltage for
it is 1.24V.

 

[Mike Harrison]

I'm not aware of any real zeners with Vz less than 3V. Have you
considered using a variable zener like the LMV431? Minimum voltage for
it is 1.24V.

LEDs make good low-voltage zeners - choose colour according to required voltage, however for this
application I doubt a shunt regulator like a zener would be appropriate.
A Schottky diode (e.g. BAT42) in series would probably get you close to the voltage you want.

 

[Geo]

from 1.5v to 1.35 or so. Is a 1.35v zener feasible and where would I
get one? Can't seem to find one.

How much battery current have you available to divert down through the zener and
how much current does your 1.35v device require?

Geo

 

[[email protected]]

Why not simply place the battery in series with a conventional silicon
diode, which should drop the voltage into the desired ballpark?

If you're going to screw around with what I suspect is a disposable
watch, the simple solution is to purchase the correct battery for the
watch, or purchase a new watch.

Damn, you newbies seem to delight in making simple and obvious
solutions so complex!

Harry C.

 

[ZOT]

How do you propose to do that? The Vf of a silicon diode is roughly
.7V, and the OP needs to drop only .15V.

The original battery was a 1.35v MERCURY. The closest I can come with a
silver oxide battery is 1.5v. Although, some watches of this design
work fine with the SO battery, some run fast because the mechanical
oscillator (360hz) is over-driven, larger amplitude. You may have heard
of them, Bulova Accutron. The are very collectible and some models
bring more than a few grand.
ben

 

[[email protected]]

from 1.5v to 1.35 or so. Is a 1.35v zener feasible and where would I
get one? Can't seem to find one.

Instead of a shunt, would a series element work, even simply a resistor?

 

[ZOT]

Yes, I'm well aware of them. My dad had one in the early 70's, but he
traded it to my uncle for something or other. I suggest you ask the
group in alt.horology. I assume you have a 214 so, rather than risk
damaging/destroying a valuable watch, why don't you just shell out the
$15 for a real SO battery? A four pack can be had for "only" $50 here:
http://www.oldfathertime.com/accutron_parts.htm

A truly amazing timepiece. I wish I had one.

Silver oxide batteries work in most Accutrons and can be bought at
Walmart for a few bucks. It is the case that when the watch does not
work with the 1.5v SO batt, usually the 214. The 218 is less sensitive.
Resistors as suggested have been tried and the batts do not last as
long. Most in my collection run fine. Just a few stragglers that need
attention, or a complete and expensive "rephasing", ie, adjusting the
stroke of the pawl and possibly increasing downward pressure on the
secondary pawl.
Yahoo has an accutron group if anyone is interested.
ben

 

[default]

from 1.5v to 1.35 or so. Is a 1.35v zener feasible and where would I
get one? Can't seem to find one.

Neat circuit to build a regulator to take 1.5 and output 1.35 (nominal
mercury battery voltage) at:

http://ludens.cl/Electron/mercreg/mercreg.html

 

[3T39]

Hello, ZOT!
You wrote on Thu, 23 Mar 2006 08:19:38 -0600:

The original battery was a 1.35v MERCURY. The closest I can come with a
silver oxide battery is 1.5v. Although, some watches of this design
work fine with the SO battery, some run fast because the mechanical
oscillator (360hz) is over-driven, larger amplitude. You may have heard
of them, Bulova Accutron. The are very collectible and some models
bring more than a few grand.
ben


Here's my tuppence worth,
The Accutron used a "tuning fork " arrangement for timekeeping. The basic
principle is that the "tuning fork" has a natural resonant frequency similar
in many ways to a bell or even a crytal oscillator, the point being, you
can't change the resonant frequency of the tuning fork by varying the
voltage. Only physically changing the mass will do it. Consequently as long
as the oscillator starts and runs on the supplied voltage then the watch
should keep good time. In those days the electronics were a bit more rugged
than todays metal oxide stuff so I think the coil should stand up to the
increased .15v without a problem.
Pete



With best regards, 3T39. E-mail: [email protected]