how to reduce speed/ amplitude of electronic pendulum??

B

Bill Walston

Guest
I recently purchased an electronic pendulum to be used in a clock I
recently digitized:

http://www.klockit.com/products/dept-356__sku-20071.html

The pendulum take a single AA battery. I used a lithium battery which
didn't last very long. I have several goals I want to try and implement:

a) I would like the battery to last much longer. What's the best way
to make this happen? I was thinking that resistance inserted between
the battery and circuit might do the trick, but unsure.

b) The pendulum runs too fast and has too much amplitude, with the
latter so much so that it keeps hitting the insides of the clock. It's
not a loud sound, but far from your typical "tick-tock" which is
desired. I'm thinking an added resistance might reduce both battery
drain as above and reduce the pendulum amplitude, but what about
frequency?

Thanks in advance for any help.

Bill
 
On 10/11/2012 10:22 AM, Bill Walston wrote:
I recently purchased an electronic pendulum to be used in a clock I
recently digitized:

http://www.klockit.com/products/dept-356__sku-20071.html

The pendulum take a single AA battery. I used a lithium battery which
didn't last very long. I have several goals I want to try and implement:

a) I would like the battery to last much longer. What's the best way to
make this happen? I was thinking that resistance inserted between the
battery and circuit might do the trick, but unsure.

b) The pendulum runs too fast and has too much amplitude, with the
latter so much so that it keeps hitting the insides of the clock. It's
not a loud sound, but far from your typical "tick-tock" which is
desired. I'm thinking an added resistance might reduce both battery
drain as above and reduce the pendulum amplitude, but what about frequency?

Thanks in advance for any help.

Bill
First thing to do is state the problem.
Click to expand...
"very long"
"much longer"
We talking minutes? years?

Can't tell from the link.
You make a pendulum slower by making it longer.
But google would have told you that in the first hit.
You make it more efficient by reducing drag.
You probably don't want to use a vacuum enclosure,
but you might be able to reduce bearing friction.
Then you "kick" it in resonance to reduce the battery drain.
The link doesn't say how the "kicker" works.
You reduce the energy "kick" to the point that the energy
in balances the pendulum losses at the amplitude you want.
Resistor might help the amplitude, but may not help the
battery drain. Unless the "kicker" is designed for it,
the amplitude will change with the battery age.
 
On Thu, 11 Oct 2012 13:22:02 -0400, Bill Walston <bill@aol.net> wrote:

I recently purchased an electronic pendulum to be used in a clock I
recently digitized:

http://www.klockit.com/products/dept-356__sku-20071.html

The pendulum take a single AA battery. I used a lithium battery which
didn't last very long. I have several goals I want to try and implement:

a) I would like the battery to last much longer. What's the best way
to make this happen? I was thinking that resistance inserted between
the battery and circuit might do the trick, but unsure.

b) The pendulum runs too fast and has too much amplitude, with the
latter so much so that it keeps hitting the insides of the clock. It's
not a loud sound, but far from your typical "tick-tock" which is
desired. I'm thinking an added resistance might reduce both battery
drain as above and reduce the pendulum amplitude, but what about
frequency?

Thanks in advance for any help.

Bill
Frequency is dependent on the length of the pendulum and the strength
Click to expand...
of the gravitational field. To slow the pendulum down either increase
the length of the pendulum or reduce the strength of the gravitational
field. Either use a D cell or an external power supply to increase
the battey life.

PlainBill
 
Frequency is dependent on the length of the pendulum
and the strength of the gravitational field.
Click to expand...
Point... As this pendulum is designed for a clock (I assume), wouldn't it
have a specified period appropriate for a clock?
 
On 10/11/2012 03:01 PM, mike wrote:
On 10/11/2012 10:22 AM, Bill Walston wrote:
I recently purchased an electronic pendulum to be used in a clock I
recently digitized:

http://www.klockit.com/products/dept-356__sku-20071.html

The pendulum take a single AA battery. I used a lithium battery which
didn't last very long. I have several goals I want to try and implement:

a) I would like the battery to last much longer. What's the best way to
make this happen? I was thinking that resistance inserted between the
battery and circuit might do the trick, but unsure.

b) The pendulum runs too fast and has too much amplitude, with the
latter so much so that it keeps hitting the insides of the clock. It's
not a loud sound, but far from your typical "tick-tock" which is
desired. I'm thinking an added resistance might reduce both battery
drain as above and reduce the pendulum amplitude, but what about
frequency?

Thanks in advance for any help.

Bill
First thing to do is state the problem.
"very long"
"much longer"
We talking minutes? years?
Click to expand...
Well, the former lithium 1.5V battery powered it for maybe 4-5 months.
I'd like to stretch this out to a year at least.

Can't tell from the link.
You make a pendulum slower by making it longer.
But google would have told you that in the first hit.
You make it more efficient by reducing drag.
You probably don't want to use a vacuum enclosure,
but you might be able to reduce bearing friction.
Then you "kick" it in resonance to reduce the battery drain.
The link doesn't say how the "kicker" works.
You reduce the energy "kick" to the point that the energy
in balances the pendulum losses at the amplitude you want.
Resistor might help the amplitude, but may not help the
battery drain. Unless the "kicker" is designed for it,
the amplitude will change with the battery age.
Click to expand...
The circuit is a 2 transistor design with resistors, capacitors and of
course the coil. I didn't try to map it out, but it looks similar to
the 2 transistor pendulum circuits on the web.

I know we can change the frequency by increasing pendulum length, but
there's no room in the enclosure. Why wouldn't a simple capacitor
change in the circuit accomplish the same goal? Isn't the coil just
part of a resonant LC circuit?

Bill
 
Bill Walston wrote:
On 10/11/2012 03:01 PM, mike wrote:
On 10/11/2012 10:22 AM, Bill Walston wrote:
I recently purchased an electronic pendulum to be used in a clock I
recently digitized:

http://www.klockit.com/products/dept-356__sku-20071.html

The pendulum take a single AA battery. I used a lithium battery which
didn't last very long. I have several goals I want to try and implement:

a) I would like the battery to last much longer. What's the best way to
make this happen? I was thinking that resistance inserted between the
battery and circuit might do the trick, but unsure.

b) The pendulum runs too fast and has too much amplitude, with the
latter so much so that it keeps hitting the insides of the clock. It's
not a loud sound, but far from your typical "tick-tock" which is
desired. I'm thinking an added resistance might reduce both battery
drain as above and reduce the pendulum amplitude, but what about
frequency?

Thanks in advance for any help.

Bill
First thing to do is state the problem.
"very long"
"much longer"
We talking minutes? years?

Well, the former lithium 1.5V battery powered it for maybe 4-5 months.
I'd like to stretch this out to a year at least.

Can't tell from the link.
You make a pendulum slower by making it longer.
But google would have told you that in the first hit.
You make it more efficient by reducing drag.
You probably don't want to use a vacuum enclosure,
but you might be able to reduce bearing friction.
Then you "kick" it in resonance to reduce the battery drain.
The link doesn't say how the "kicker" works.
You reduce the energy "kick" to the point that the energy
in balances the pendulum losses at the amplitude you want.
Resistor might help the amplitude, but may not help the
battery drain. Unless the "kicker" is designed for it,
the amplitude will change with the battery age.

The circuit is a 2 transistor design with resistors, capacitors and of
course the coil. I didn't try to map it out, but it looks similar to
the 2 transistor pendulum circuits on the web.

I know we can change the frequency by increasing pendulum length, but
there's no room in the enclosure. Why wouldn't a simple capacitor
change in the circuit accomplish the same goal? Isn't the coil just
part of a resonant LC circuit?
Click to expand...

No. The resonance is mechanical, the coil just applies a little
energy to overcome friction and keep it moving. All changing the
circuit's frequency will do is waste the battery's life as heat.
 
Bill Walston wrote:


I know we can change the frequency by increasing pendulum length, but
there's no room in the enclosure. Why wouldn't a simple capacitor
change in the circuit accomplish the same goal? Isn't the coil just
part of a resonant LC circuit?
No, the RC or LC timer in the circuit does not set the pendulum swing
Click to expand...
rate. it really can't, the pendulum is WAY too massive for a tiny,
battery-powered circuit. So, first, you need to fix the pendulum.

Second, you need to reduce the kick the circuit applies to the pendulum each
swing. That might be done by adding turns to the coil that provides the
kick. Or, the RC timer is leaving the coil current on too long, so
reducing the cap value might reduce the energy imparted, as well as preserve
battery life.

Jon
 
I recently purchased an electronic pendulum to be used in a clock I recently
digitized:

http://www.klockit.com/products/dept-356__sku-20071.html

The pendulum take a single AA battery. I used a lithium battery which didn't
last very long. I have several goals I want to try and implement:

a) I would like the battery to last much longer. What's the best way to
make this happen? I was thinking that resistance inserted between the
battery and circuit might do the trick, but unsure.

b) The pendulum runs too fast and has too much amplitude, with the latter so
much so that it keeps hitting the insides of the clock. It's not a loud
sound, but far from your typical "tick-tock" which is desired. I'm thinking
an added resistance might reduce both battery drain as above and reduce the
pendulum amplitude, but what about frequency?

Thanks in advance for any help.

Bill
Click to expand...
Cut out the sides of the clock to allow it full swing.
If this is a pendulum designed to tick at the correct rate then you
have to modify the cabinet structure to accomodate it not the other way
around.
So when you cut out the sides of the clock cabinet you will have a more
unique conversation piece. Put up a photo after you get it working.
 
On Thu, 11 Oct 2012 13:22:02 -0400, Bill Walston <bill@aol.net> put
finger to keyboard and composed:

I recently purchased an electronic pendulum to be used in a clock I
recently digitized:

http://www.klockit.com/products/dept-356__sku-20071.html

The pendulum take a single AA battery. I used a lithium battery which
didn't last very long. I have several goals I want to try and implement:

a) I would like the battery to last much longer. What's the best way
to make this happen? I was thinking that resistan
Click to expand...
Would there be any way to utilise a solar panel and a NiCad or NiMH
battery, or maybe a super capacitor? For example, you could
cannibalise a cheap solar garden light.

Excuse my ignorance, but how does your circuit know when to apply a
kick? If the kick were to come when the pendulum is on the rise, then
that would work against it. Therefore the circuit would need to know
when the pendulum has begun its descent and apply the kick at that
time.

Furthermore, if the pendulum's amplitude is growing too large, then
the circuit would need to refrain from kicking it until the amplitude
subsides, if only to conserve the battery.

Therefore ISTM that the circuit must be sensing the pendulum's
position, in which case you would need to adjust the sensor in order
to set your desired amplitude. Or am I way off?

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
 
Excuse my ignorance, but how does your circuit
know when to apply a kick?
Click to expand...
It doesn't.

Assume the pendulum is supposed to have a period of one second. You design
it to be a little bit longer, then make the driver circuit operate at
exactly one second. The pendulum will eventually sync with the driver.

Remember when TVs had hold controls? The principle is the same. The
most-stable operation is obtained when the oscillator runs a tiny bit slower
than it should, with the sync signals "kicking" it at the right frequency.
 
On Thu, 11 Oct 2012 12:10:30 -0700, "William Sommerwerck"
<grizzledgeezer@comcast.net> wrote:

Frequency is dependent on the length of the pendulum
and the strength of the gravitational field.

Point... As this pendulum is designed for a clock (I assume), wouldn't it
have a specified period appropriate for a clock?

The specific product he identifies is designed as an add-on for a
Click to expand...
quartz movement and comes with a pendulum with an adjustable length
arm. I'm unsure of the correlation between pendulum length and
amplitude of the swing, but I would expect a shorter pendulum to swing
through a wider angle.

PlainBill
 
On Oct 12, 6:00 pm, PlainB...@yawhoo.com wrote:
On Thu, 11 Oct 2012 12:10:30 -0700, "William Sommerwerck"

grizzledgee...@comcast.net> wrote:
Frequency is dependent on the length of the pendulum
and the strength of the gravitational field.

Point... As this pendulum is designed for a clock (I assume), wouldn't it
have a specified period appropriate for a clock?

The specific product he identifies is designed as an add-on for a
quartz movement and comes with a pendulum with an adjustable length
arm.  I'm unsure of the correlation between pendulum length and
amplitude of the swing, but I would expect a shorter pendulum to swing
through a wider angle.

PlainBill
Click to expand...
If I remember correctly, a larger weight on the pendulum will also
slow it down.
 
William Sommerwerck <grizzledgeezer@comcast.net> wrote in message
news:k5a0hr$64d$1@dont-email.me...
Excuse my ignorance, but how does your circuit
know when to apply a kick?

It doesn't.

Assume the pendulum is supposed to have a period of one second. You design
it to be a little bit longer, then make the driver circuit operate at
exactly one second. The pendulum will eventually sync with the driver.

Remember when TVs had hold controls? The principle is the same. The
most-stable operation is obtained when the oscillator runs a tiny bit
slower
than it should, with the sync signals "kicking" it at the right frequency.
Click to expand...
Human clocks are the same. Put a human in a cave, out of touch with the
outside world, and his natural day-length reverts to about 24.5 to 25 hour
days, requires the sun etc to sync him to 24 hour days
 
On Fri, 12 Oct 2012 20:55:56 -0700 (PDT), "hr(bob) hofmann@att.net"
<hrhofmann@att.net> wrote:

On Oct 12, 6:00 pm, PlainB...@yawhoo.com wrote:
On Thu, 11 Oct 2012 12:10:30 -0700, "William Sommerwerck"

grizzledgee...@comcast.net> wrote:
Frequency is dependent on the length of the pendulum
and the strength of the gravitational field.

Point... As this pendulum is designed for a clock (I assume), wouldn't it
have a specified period appropriate for a clock?

The specific product he identifies is designed as an add-on for a
quartz movement and comes with a pendulum with an adjustable length
arm.  I'm unsure of the correlation between pendulum length and
amplitude of the swing, but I would expect a shorter pendulum to swing
through a wider angle.

PlainBill

If I remember correctly, a larger weight on the pendulum will also
slow it down.
You don't. The effective length of the pendulum (distance between the
Click to expand...
pivot and the center of the mass) and the gravitational force are the
only things that affect the speed. Remember the experiment Galileo
did a few years before he turned his eye to the heavens.

PlainBill
 
On Fri, 12 Oct 2012 14:02:31 -0700, "William Sommerwerck"
<grizzledgeezer@comcast.net> put finger to keyboard and composed:

Excuse my ignorance, but how does your circuit
know when to apply a kick?

It doesn't.

Assume the pendulum is supposed to have a period of one second. You design
it to be a little bit longer, then make the driver circuit operate at
exactly one second. The pendulum will eventually sync with the driver.

Remember when TVs had hold controls? The principle is the same. The
most-stable operation is obtained when the oscillator runs a tiny bit slower
than it should, with the sync signals "kicking" it at the right frequency.
Click to expand...
Thanks. I'm still trying to understand how it syncs, though.

I'm trying to envision an equilibrium where the kick comes at a
regular point in the swing. Does the pendulum sync so that it gets a
kick at the beginning of the downswing, or does it come at the end of
the upswing, or can it come at any point in the arc?

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
 
Franc Zabkar wrote:
On Fri, 12 Oct 2012 14:02:31 -0700, "William Sommerwerck"
grizzledgeezer@comcast.net> put finger to keyboard and composed:

Excuse my ignorance, but how does your circuit
know when to apply a kick?

It doesn't.

Assume the pendulum is supposed to have a period of one second. You design
it to be a little bit longer, then make the driver circuit operate at
exactly one second. The pendulum will eventually sync with the driver.

Remember when TVs had hold controls? The principle is the same. The
most-stable operation is obtained when the oscillator runs a tiny bit slower
than it should, with the sync signals "kicking" it at the right frequency.

Thanks. I'm still trying to understand how it syncs, though.

I'm trying to envision an equilibrium where the kick comes at a
regular point in the swing. Does the pendulum sync so that it gets a
kick at the beginning of the downswing, or does it come at the end of
the upswing, or can it come at any point in the arc?
Click to expand...

I've only seen one electronic pendulum. it used a sensing coil to
detect the approach of the pendulum, and fired a pulse to add to the
stored energy.
 
Assume the pendulum is supposed to have a period of one second.
You design it to be a little bit longer, then make the driver circuit
operate at exactly one second. The pendulum will eventually sync
with the driver.

Remember when TVs had hold controls? The principle is the same.
The most-stable operation is obtained when the oscillator runs a bit
slower than it should, with the sync signals "kicking" it at the right
frequency.

Thanks. I'm still trying to understand how it syncs, though.
Click to expand...
There is no "intelligence" to the synchronization process. Because the
pendulum swings at a different frequency with respect to the drive circuit,
it has a continually varying phase relationship with it. So, at some point
the kick will occur when the pendulum is near the energized drive
electromagnet. The cycle starts at this point.

On the next swing, the pendulum will be slightly "late". But if it's "close
enough" to the energized electromagnet, it will receive another kick. And so
on, and so on...

I'm trying to envision an equilibrium where the kick comes at a
regular point in the swing. Does the pendulum sync so that it gets
a kick at the beginning of the downswing, or does it come at the
end of the upswing, or can it come at any point in the arc?
Click to expand...
I assume at the end of the upswing.
 
I've only seen one electronic pendulum. it used a sensing coil
to detect the approach of the pendulum, and fired a pulse to
add to the stored energy.
Click to expand...
I'm not sure that would work correctly. You want the drive coil to fire at a
fixed frequency. Otherwise, the pendulum would be synched at its lower
native frequency.
 
hr(bob) hofmann@att.net <hrhofmann@att.net> wrote in message
news:af704917-f8c2-4fda-a217-79fa751611b5@z8g2000yql.googlegroups.com...
On Oct 12, 6:00 pm, PlainB...@yawhoo.com wrote:
On Thu, 11 Oct 2012 12:10:30 -0700, "William Sommerwerck"

grizzledgee...@comcast.net> wrote:
Frequency is dependent on the length of the pendulum
and the strength of the gravitational field.

Point... As this pendulum is designed for a clock (I assume), wouldn't it
have a specified period appropriate for a clock?

The specific product he identifies is designed as an add-on for a
quartz movement and comes with a pendulum with an adjustable length
arm. I'm unsure of the correlation between pendulum length and
amplitude of the swing, but I would expect a shorter pendulum to swing
through a wider angle.

PlainBill
Click to expand...
If I remember correctly, a larger weight on the pendulum will also
slow it down.


from http://www.adam-hart-davis.org/odd_but_interesting.htm

Q. Why do the people who regulate "Big Ben's clock use adding or
subtracting old pennies to the weight on the bottom?
- John Gifford, London

A. Yes the period of pendulum is governed by its length and is independent
of the mass at the end. But if you add an old penny to the bob of the
pendulum of Big Ben, then you slightly alter its length; in fact you make it
a bit shorter, because the centre of mass of the bob is slightly raised.
Similarly if you take pennies off, you will in effect slightly lengthen the
pendulum. This seems an odd way to do it, but it is obviously very
convenient, and simpler than winding the bob up and down by a minute amount.
 
If I remember correctly, a larger weight on the pendulum will also
slow it down.
Click to expand...
Nope. The period depends on the length of the pendulum and the acceleration
of gravity.

Physics courses often include units analysis. * Such an analysis shows --
without even performing an experiment -- that length and the strength of the
gravitational field are the factors that matter.

* That probably isn't the right term, but I can't think of what it is.
 
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