how to build a clock with pulse for the hours!

[dave]

Wonder if some kind person can describe how I can build a circuit that
is basically a black-box (clock) that provides a short pulse - that
outputs 1 pulse for 1 o'clcok 2 pulse for 2 o'clock etc?

I don't even need a display - but would need some means to set the
time for the pulses to be on the hour.

What I need it for is to drive a small solenoid to which is attached a
hammer that strikes a (real) metal gong. It's a novelty clock!

I can build the circuit ok but I don't have the expertise to design
the it.

Thank hopefully.

 

[Nobody]

On Fri, 05 Jun 2009 10:03:33 +0100, dave wrote:

Wonder if some kind person can describe how I can build a circuit that
is basically a black-box (clock) that provides a short pulse - that
outputs 1 pulse for 1 o'clcok 2 pulse for 2 o'clock etc?

I don't even need a display - but would need some means to set the
time for the pulses to be on the hour.

What I need it for is to drive a small solenoid to which is attached a
hammer that strikes a (real) metal gong. It's a novelty clock!

I can build the circuit ok but I don't have the expertise to design
the it.

The "stock" answer for any digital logic problem involving more than a
dozen gates is "use a PIC" (or other microcontroller). Whether that's the
right answer depends upon how many of these you're planning on making.

If it's just one or two, the cost of a programmer (~$35) and the time
taken to learn microcontroller programming will outweigh the cost and
effort of a discrete solution. Unless you're planning on making similar
projects in the future, in which case you may as well start learning
microcontrollers now.

If it's between dozens and many thousands, using a microcontroller
(whether PIC, AVR, etc) is the logical option. For very large quantities,
a custom chip will eventually win out, but I guess that you're not talking
about that kind of scale.

The main question is how you're going to adjust the time without a
display. That's a far more involved problem than generating 1-12 pulses
every hour.

 

[Robert Roland]

On Fri, 05 Jun 2009 15:26:15 +0100, Nobody <nobody@nowhere.com> wrote:

The main question is how you're going to adjust the time without a
display. That's a far more involved problem than generating 1-12 pulses
every hour.

It does not *have* to be involved at all. It depends on the
requirements. You could, for example, have one button that must be
pushed at exactly 1 o'clock. Extremely technically simple, but not
very practical.

On the other end of the scale you could use GPS or DCF77 to fully
eliminate any need for adjustments, even after a power outage.

Finding that perfect balance between simple (cheap) enough and
practical enough is the challenge. I can't come up with a better idea
than a simple 7 segment display and a couple of buttons.
--
RoRo

 

[Jon Kirwan]

On Fri, 05 Jun 2009 10:03:33 +0100, dave <dave@127.0.0.1> wrote:

Wonder if some kind person can describe how I can build a circuit that
is basically a black-box (clock) that provides a short pulse - that
outputs 1 pulse for 1 o'clcok 2 pulse for 2 o'clock etc?

I don't even need a display - but would need some means to set the
time for the pulses to be on the hour.

What I need it for is to drive a small solenoid to which is attached a
hammer that strikes a (real) metal gong. It's a novelty clock!

I can build the circuit ok but I don't have the expertise to design
the it.

The comments already made provide some range to think over. I'm going
to jump in and take a specific shot.

I'll assume that you'd really like some precision -- something on the
order you've come to expect from a common watch. That's going to be
"hard" even for a microcontroller supporting a 32kHz crystal, because
watch makers have gone to some lengths now in designing low cost means
with relatively high precision. Achieving that in a new design with a
microcontroller will take effort and equipment. In fact, doing that
with any newly designed circuit will, regardless of whether or not it
includes a microcontroller. (So that's out -- unless you can consider
something on the order of 20 seconds a day drift, or worse. If this
were on the order of some minutes a day drift, it would be cheap and
easy with a micro.)

It costs about US$10 at my local shopping store to buy a watch with
hands. You might consider doing what any decent bomb-maker may do --
modify the watch to provide an electrical contact for you. These
watches have delicate hands but I suspect that the gearing for the
hour hand is sufficient that a slight loading would be acceptable. A
fine wire, for example. To avoid bounce, relying upon a contact time
that is unknown but probably long compared to what you want, etc., you
may want to add a second point of contact for resetting a circuit -- a
flip flop, for example. And then add a one-shot to the output to give
the desired pulse duration.

The watch face cover may be glass or plastic. If plastic, you might
simply drill through it with a tiny drill bit to make a penetration
near the hour position. If glass, remove it entirely or penetrate it
with a drill, too. The fine wire might be 40 gauge, wrapped lightly
over the hour hand and arranged so that the tip extends outwards
towards the hole. Arrange another wire (any convenient diameter) so
that when the hour hand's fine wire goes by the hole that it will have
to brush across it. The tip of the hour hand wire should be just
barely long enough to be forced to brush across it in its travel.

You'd need to tweak things to get the initial timing of the hour pulse
at the right point.

Another possibility would be to use a tiny neodymium magnet on the tip
(or even midway, perhaps) of the hour hand. Use a "reed relay" in a
glass ampule and locate it near enough to the hour hand that the
magnet will be able to close the relay. This one seems good in ways,
tricky in others. Good in that you may be able to find a small magnet
with enough power that you can close the reed relay even when it is
outside the face cover. Which leaves everything sealed. Bad in that
if that idea can't work at all, you may still face difficulties
finding any magnet tiny enough, yet powerful enough to consistently
close the reed relay at any marginal distance apart. Traditionally,
the magnets used are rather large, so this would need to be a matter
of experimentation before proceeding. But there are companies on the
web selling such things. Personally, I'd tear apart a cd-rom drive
for the magnets near where the tiny coil near the optical lens is at.
They are often VERY small and yet VERY powerful. A mere fragment of
one of those may do the trick.

Jon

 

[Nobody]

On Fri, 05 Jun 2009 19:09:43 +0200, Robert Roland wrote:

Finding that perfect balance between simple (cheap) enough and
practical enough is the challenge. I can't come up with a better idea
than a simple 7 segment display and a couple of buttons.

Which is still significantly more complex than generating the pulses.

 

[John Fields]

On Fri, 05 Jun 2009 10:03:33 +0100, dave <dave@127.0.0.1> wrote:

Wonder if some kind person can describe how I can build a circuit that
is basically a black-box (clock) that provides a short pulse - that
outputs 1 pulse for 1 o'clcok 2 pulse for 2 o'clock etc?

I don't even need a display - but would need some means to set the
time for the pulses to be on the hour.

What I need it for is to drive a small solenoid to which is attached a
hammer that strikes a (real) metal gong. It's a novelty clock!

I can build the circuit ok but I don't have the expertise to design
the it.

---
1. How accurate does it have to be?

2. Can you use the AC mains as a time base?

JF

 

On Jun 5, 2:27 pm, Jon Kirwan <j...@infinitefactors.org> wrote:

includes a microcontroller.  (So that's out -- unless you can consider
something on the order of 20 seconds a day drift, or worse.  If this
were on the order of some minutes a day drift, it would be cheap and
easy with a micro.)

HUH??? With a 32k xtal and no trimming at all it is easy to achieve
<2sec/day drift on a micro like the MSP430F2013. My Babylonian clock
uses this approach and - since accuracy isn't the gimmick - you can be
sure I didn't take any particular pains to make it accurate.

<http://www.youtube.com/watch?v=tCcCAcNFRt0>

 

[Jon Kirwan]

On Fri, 5 Jun 2009 18:07:49 -0700 (PDT), zwsdotcom@gmail.com wrote:

On Jun 5, 2:27 pm, Jon Kirwan <j...@infinitefactors.org> wrote:

includes a microcontroller.  (So that's out -- unless you can consider
something on the order of 20 seconds a day drift, or worse.  If this
were on the order of some minutes a day drift, it would be cheap and
easy with a micro.)

HUH??? With a 32k xtal and no trimming at all it is easy to achieve
2sec/day drift on a micro like the MSP430F2013. My Babylonian clock
uses this approach and - since accuracy isn't the gimmick - you can be
sure I didn't take any particular pains to make it accurate.

http://www.youtube.com/watch?v=tCcCAcNFRt0

I didn't write that one _must_ get drift that bad. In practice, a few
minutes a month does happen and temperature has a particularly
noticeable impact. There are some nice data sheets on compensating in
software for temperature drift that improve this. I think Dallas also
provides a part that is a bit pricey but does pretty good, too.

Cheap watches do all this, and do it cheaply.

It was just a thought. Sorry this bothers you.

Jon

 

On Jun 5, 6:07 pm, zwsdot...@gmail.com wrote:

On Jun 5, 2:27 pm, Jon Kirwan <j...@infinitefactors.org> wrote:

includes a microcontroller.  (So that's out -- unless you can
consider
something on the order of 20 seconds a day drift, or worse.  If
this
were on the order of some minutes a day drift, it would be cheap
and
easy with a micro.)

HUH??? With a 32k xtal and no trimming at all it is easy to achieve
2sec/day drift on a micro like the MSP430F2013. My Babylonian
clock
uses this approach and - since accuracy isn't the gimmick - you can
be
sure I didn't take any particular pains to make it accurate.

http://www.youtube.com/watch?v=tCcCAcNFRt0

Or you can do what I did and use the AC line as the primary timebase
for a microcontroller and default to the processor crystal during
power failures. I'm currently finishing the software to tie in to a C-
Max WWVB receiver. The power line as a reference is 0 seconds drift
even without the WWVB but with it will auto set DST and take care of
leap seconds. The C-Max receive module with the antenna is at DigiKey
for $10.70 - single unit price.

G˛

 

[dave]

On Fri, 05 Jun 2009 20:06:29 -0500, John Fields
<jfields@austininstruments.com> wrote:

On Fri, 05 Jun 2009 10:03:33 +0100, dave <dave@127.0.0.1> wrote:

Wonder if some kind person can describe how I can build a circuit that
is basically a black-box (clock) that provides a short pulse - that
outputs 1 pulse for 1 o'clcok 2 pulse for 2 o'clock etc?

I don't even need a display - but would need some means to set the
time for the pulses to be on the hour.

What I need it for is to drive a small solenoid to which is attached a
hammer that strikes a (real) metal gong. It's a novelty clock!

I can build the circuit ok but I don't have the expertise to design
the it.

---
1. How accurate does it have to be?

2. Can you use the AC mains as a time base?

JF

Thanks for all the replies. A few things.
For me, accuarcy here is not important (it would be nice if it was
though). This is more of means to exploit the very nice sound this
gong-thing makes. Just a light tap (even with finger) makes it sound.
I would like to keep it "mechanical" as possible (someone suggested
sampling the sound etc) but would rather not go that route.
I think maybe the small magnet on a real clock hand might be the one
to have go at in the spirit of this project (as the electronics is
probably beyond me).
I thought maybe there is a some "clock chip" I could use and then
somehow (some how ) get the n pulses for each of the hours.
Thanks again.

 

[Nobody]

On Sat, 06 Jun 2009 12:11:26 +0100, dave wrote:

I thought maybe there is a some "clock chip" I could use and then
somehow (some how ) get the n pulses for each of the hours.

There are clock chips, but they're generally designed to either interface
directly to 7-segment displays, or to a CPU.

Decoding either would probably be more effort than keeping the time
with a string of binary counters.

 

[Electronworks.co.uk]

"Jon Kirwan" <jonk@infinitefactors.org> wrote in message
news:4ipj25p67cnu3u474dokhgcjeeltkgm19k@4ax.com...

On Fri, 5 Jun 2009 18:07:49 -0700 (PDT), zwsdotcom@gmail.com wrote:

On Jun 5, 2:27 pm, Jon Kirwan <j...@infinitefactors.org> wrote:

includes a microcontroller. (So that's out -- unless you can consider
something on the order of 20 seconds a day drift, or worse. If this
were on the order of some minutes a day drift, it would be cheap and
easy with a micro.)

HUH??? With a 32k xtal and no trimming at all it is easy to achieve
2sec/day drift on a micro like the MSP430F2013. My Babylonian clock
uses this approach and - since accuracy isn't the gimmick - you can be
sure I didn't take any particular pains to make it accurate.

http://www.youtube.com/watch?v=tCcCAcNFRt0

I didn't write that one _must_ get drift that bad. In practice, a few
minutes a month does happen and temperature has a particularly
noticeable impact. There are some nice data sheets on compensating in
software for temperature drift that improve this. I think Dallas also
provides a part that is a bit pricey but does pretty good, too.

Cheap watches do all this, and do it cheaply.

It was just a thought. Sorry this bothers you.

Jon

I agree with you Jon. here is the Dallas device and indeed it is pricey

precision 32kHz clock:
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2940/t/al

Most 32Khz crystal clocks are indeed only accurate to about 30ppm, so

(30/1,000,000) x 60 x 60 x 24 = 2.6 seconds per day which is 15 minutes per
year.... as long as the temperature does not change. If it does, things just
get worse.

You could always measure the drift over 1 week and compensate with a lookup
table in your software to frig the time as a rough compensation

Watches are compensated to have good accuracy at body temperature

--
Bill Naylor
www.electronworks.co.uk
Electronic Kits for Education and Fun

 

[Robert Roland]

On Sat, 06 Jun 2009 12:11:26 +0100, dave <dave@127.0.0.1> wrote:

I thought maybe there is a some "clock chip" I could use and then
somehow (some how ) get the n pulses for each of the hours.

Clock building is not an uncommon hobby. You can buy the clock
mechanics and then build the rest yourself. Maybe some of those kits
have some sort of cuckoo clock functionality. I have found some with
chime functionality, but I couldn't find any cuckoo stuff.

Alternatively, you could hack something like this:
http://www.amazon.com/Xacta-Radio-Controlled-Cuckoo-Clock/dp/B000KEYA4S
--
RoRo

 

[default]

On Fri, 05 Jun 2009 18:27:28 GMT, Jon Kirwan
<jonk@infinitefactors.org> wrote:

On Fri, 05 Jun 2009 10:03:33 +0100, dave <dave@127.0.0.1> wrote:

Wonder if some kind person can describe how I can build a circuit that
is basically a black-box (clock) that provides a short pulse - that
outputs 1 pulse for 1 o'clcok 2 pulse for 2 o'clock etc?

I don't even need a display - but would need some means to set the
time for the pulses to be on the hour.

What I need it for is to drive a small solenoid to which is attached a
hammer that strikes a (real) metal gong. It's a novelty clock!

I can build the circuit ok but I don't have the expertise to design
the it.

The comments already made provide some range to think over. I'm going
to jump in and take a specific shot.

I'll assume that you'd really like some precision -- something on the
order you've come to expect from a common watch. That's going to be
"hard" even for a microcontroller supporting a 32kHz crystal, because
watch makers have gone to some lengths now in designing low cost means
with relatively high precision. Achieving that in a new design with a
microcontroller will take effort and equipment. In fact, doing that
with any newly designed circuit will, regardless of whether or not it
includes a microcontroller. (So that's out -- unless you can consider
something on the order of 20 seconds a day drift, or worse. If this
were on the order of some minutes a day drift, it would be cheap and
easy with a micro.)

It costs about US$10 at my local shopping store to buy a watch with
hands. You might consider doing what any decent bomb-maker may do --
modify the watch to provide an electrical contact for you. These
watches have delicate hands but I suspect that the gearing for the
hour hand is sufficient that a slight loading would be acceptable. A
fine wire, for example. To avoid bounce, relying upon a contact time
that is unknown but probably long compared to what you want, etc., you
may want to add a second point of contact for resetting a circuit -- a
flip flop, for example. And then add a one-shot to the output to give
the desired pulse duration.

The watch face cover may be glass or plastic. If plastic, you might
simply drill through it with a tiny drill bit to make a penetration
near the hour position. If glass, remove it entirely or penetrate it
with a drill, too. The fine wire might be 40 gauge, wrapped lightly
over the hour hand and arranged so that the tip extends outwards
towards the hole. Arrange another wire (any convenient diameter) so
that when the hour hand's fine wire goes by the hole that it will have
to brush across it. The tip of the hour hand wire should be just
barely long enough to be forced to brush across it in its travel.

You'd need to tweak things to get the initial timing of the hour pulse
at the right point.

Another possibility would be to use a tiny neodymium magnet on the tip
(or even midway, perhaps) of the hour hand. Use a "reed relay" in a
glass ampule and locate it near enough to the hour hand that the
magnet will be able to close the relay. This one seems good in ways,
tricky in others. Good in that you may be able to find a small magnet
with enough power that you can close the reed relay even when it is
outside the face cover. Which leaves everything sealed. Bad in that
if that idea can't work at all, you may still face difficulties
finding any magnet tiny enough, yet powerful enough to consistently
close the reed relay at any marginal distance apart. Traditionally,
the magnets used are rather large, so this would need to be a matter
of experimentation before proceeding. But there are companies on the
web selling such things. Personally, I'd tear apart a cd-rom drive
for the magnets near where the tiny coil near the optical lens is at.
They are often VERY small and yet VERY powerful. A mere fragment of
one of those may do the trick.

Jon

I like your thinking. I don't know if a magnet is practical the
clock hands are relatively heavy - I notice when testing batteries
with a clock and dummy load, the clock almost always stop with the
second in the west most quadrant trying to climb past the "9."

A photo interrupter, that the hand moves through, would probably be a
better idea. A single one with some method to set the bell count
would probably be easier than trying to find both the hour and minute
hands and the 13 interrupters that might take.

Or take a digital clock and use logic or a pic to decode the display,
or just use the guts from a quartz analog clock to provide an accurate
one second pulse to a counter or pic.
--

 

[Jon Kirwan]

On Sat, 06 Jun 2009 11:13:34 -0400, default <default@defaulter.net>
wrote:

On Fri, 05 Jun 2009 18:27:28 GMT, Jon Kirwan
jonk@infinitefactors.org> wrote:

On Fri, 05 Jun 2009 10:03:33 +0100, dave <dave@127.0.0.1> wrote:

Wonder if some kind person can describe how I can build a circuit that
is basically a black-box (clock) that provides a short pulse - that
outputs 1 pulse for 1 o'clcok 2 pulse for 2 o'clock etc?

I don't even need a display - but would need some means to set the
time for the pulses to be on the hour.

What I need it for is to drive a small solenoid to which is attached a
hammer that strikes a (real) metal gong. It's a novelty clock!

I can build the circuit ok but I don't have the expertise to design
the it.

The comments already made provide some range to think over. I'm going
to jump in and take a specific shot.

I'll assume that you'd really like some precision -- something on the
order you've come to expect from a common watch. That's going to be
"hard" even for a microcontroller supporting a 32kHz crystal, because
watch makers have gone to some lengths now in designing low cost means
with relatively high precision. Achieving that in a new design with a
microcontroller will take effort and equipment. In fact, doing that
with any newly designed circuit will, regardless of whether or not it
includes a microcontroller. (So that's out -- unless you can consider
something on the order of 20 seconds a day drift, or worse. If this
were on the order of some minutes a day drift, it would be cheap and
easy with a micro.)

It costs about US$10 at my local shopping store to buy a watch with
hands. You might consider doing what any decent bomb-maker may do --
modify the watch to provide an electrical contact for you. These
watches have delicate hands but I suspect that the gearing for the
hour hand is sufficient that a slight loading would be acceptable. A
fine wire, for example. To avoid bounce, relying upon a contact time
that is unknown but probably long compared to what you want, etc., you
may want to add a second point of contact for resetting a circuit -- a
flip flop, for example. And then add a one-shot to the output to give
the desired pulse duration.

The watch face cover may be glass or plastic. If plastic, you might
simply drill through it with a tiny drill bit to make a penetration
near the hour position. If glass, remove it entirely or penetrate it
with a drill, too. The fine wire might be 40 gauge, wrapped lightly
over the hour hand and arranged so that the tip extends outwards
towards the hole. Arrange another wire (any convenient diameter) so
that when the hour hand's fine wire goes by the hole that it will have
to brush across it. The tip of the hour hand wire should be just
barely long enough to be forced to brush across it in its travel.

You'd need to tweak things to get the initial timing of the hour pulse
at the right point.

Another possibility would be to use a tiny neodymium magnet on the tip
(or even midway, perhaps) of the hour hand. Use a "reed relay" in a
glass ampule and locate it near enough to the hour hand that the
magnet will be able to close the relay. This one seems good in ways,
tricky in others. Good in that you may be able to find a small magnet
with enough power that you can close the reed relay even when it is
outside the face cover. Which leaves everything sealed. Bad in that
if that idea can't work at all, you may still face difficulties
finding any magnet tiny enough, yet powerful enough to consistently
close the reed relay at any marginal distance apart. Traditionally,
the magnets used are rather large, so this would need to be a matter
of experimentation before proceeding. But there are companies on the
web selling such things. Personally, I'd tear apart a cd-rom drive
for the magnets near where the tiny coil near the optical lens is at.
They are often VERY small and yet VERY powerful. A mere fragment of
one of those may do the trick.

Jon

I like your thinking. I don't know if a magnet is practical the
clock hands are relatively heavy - I notice when testing batteries
with a clock and dummy load, the clock almost always stop with the
second in the west most quadrant trying to climb past the "9."

I have no idea how practical it is. I imagine (and only imgaine) that
it _may_ be possible to get a small enough 'bit' of a neodymium magnet
and place it far enough back towards the axis of the hour hand that
the combination might function. I also worry that the remaining size
of it may be still too big to remain underneath the watch face cover,
so that cover may still be a problem. Besides, it just forces the
distance to the reed relay that much farther away, which is part of
all the factors that need to be optimized together. However, might be
fun to find out.

A photo interrupter, that the hand moves through, would probably be a
better idea. A single one with some method to set the bell count
would probably be easier than trying to find both the hour and minute
hands and the 13 interrupters that might take.

That's good. I have used interrupters. In this case, I might instead
paint a highly reflective spot on the hour hand and use reflection
instead of interruption. But I like this.

Or take a digital clock and use logic or a pic to decode the display,
or just use the guts from a quartz analog clock to provide an accurate
one second pulse to a counter or pic.

Yes, that crossed my mind. But then that hauls in the coding, tools,
etc. So I avoided mentioning it. Just because I have all that stuff
doesn't mean others want to buy into all that trouble.

Jon

 

[Jon Kirwan]

On Sat, 6 Jun 2009 13:31:51 +0100, "Electronworks.co.uk"
<newsgroups@electronworks.co.uk> wrote:

"Jon Kirwan" <jonk@infinitefactors.org> wrote in message
news:4ipj25p67cnu3u474dokhgcjeeltkgm19k@4ax.com...
On Fri, 5 Jun 2009 18:07:49 -0700 (PDT), zwsdotcom@gmail.com wrote:

On Jun 5, 2:27 pm, Jon Kirwan <j...@infinitefactors.org> wrote:

includes a microcontroller. (So that's out -- unless you can consider
something on the order of 20 seconds a day drift, or worse. If this
were on the order of some minutes a day drift, it would be cheap and
easy with a micro.)

HUH??? With a 32k xtal and no trimming at all it is easy to achieve
2sec/day drift on a micro like the MSP430F2013. My Babylonian clock
uses this approach and - since accuracy isn't the gimmick - you can be
sure I didn't take any particular pains to make it accurate.

http://www.youtube.com/watch?v=tCcCAcNFRt0

I didn't write that one _must_ get drift that bad. In practice, a few
minutes a month does happen and temperature has a particularly
noticeable impact. There are some nice data sheets on compensating in
software for temperature drift that improve this. I think Dallas also
provides a part that is a bit pricey but does pretty good, too.

Cheap watches do all this, and do it cheaply.

It was just a thought. Sorry this bothers you.

Jon

I agree with you Jon. here is the Dallas device and indeed it is pricey

precision 32kHz clock:
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2940/t/al

Most 32Khz crystal clocks are indeed only accurate to about 30ppm, so

(30/1,000,000) x 60 x 60 x 24 = 2.6 seconds per day which is 15 minutes per
year.... as long as the temperature does not change. If it does, things just
get worse.

You could always measure the drift over 1 week and compensate with a lookup
table in your software to frig the time as a rough compensation

Watches are compensated to have good accuracy at body temperature

And, it seems from experience now, surprisingly good measurement
accuracy even off my hand.

Years ago, I had wrist watches that were pretty good when I wore them
but if I left them off for a few months would show drift I could
quickly spot. Lately, because my autistic daughter likes watches for
reasons I don't entirely understand, I've gone out and bought all
kinds of cheap $10 watches. They are now surprisingly good, off or
on. I have one I wear (she removes it and puts it back on me, one or
two times a day) that is tied to WWVB and updates itself every night,
so that (plus my cell phone) represents my accuracy standard around
the home. Sometimes, I wear them just to "bug" her, keep them in my
coat pocket, or they just lay around the house. We tend to keep our
house open to the outside (I live on a farm), unheated and uncooled to
save money, and temperatures in the house vary widely from about 55F
to 90F. (We are very comfortable at 55F, but if it gets much below
that we will heat. We never cool.) In short, these watches
experience temperature differences over the year vastly exceeding
their assumed use. And, of course, there are pocket watches that hang
from belt hooks, which may (or may not, I don't know) assume that they
are placed _in_ the pocket, normally. (Frankly, I think they have to
assume that they will simply hang openly, though.)

I've been very much impressed with the consistency in performance of
even these cheaper watches. They have certainly improved the
technology. Very, very accurate in marking off time.

I have read a page or two getting into _some_ detail about how this is
achieved. But nothing as good as I'd like to see. I drool over
trying to understand _all_ the myriad details that have coalesced into
a modern, cheap watch. If anyone knows of something talking about all
of the manufacturing details, those that are important to control and
why, those that are not important to control for and also why, etc.,
I'd love to see it.

Jon

 

[Jon Kirwan]

On Sat, 06 Jun 2009 12:11:26 +0100, dave <dave@127.0.0.1> wrote:

On Fri, 05 Jun 2009 20:06:29 -0500, John Fields
jfields@austininstruments.com> wrote:

On Fri, 05 Jun 2009 10:03:33 +0100, dave <dave@127.0.0.1> wrote:

Wonder if some kind person can describe how I can build a circuit that
is basically a black-box (clock) that provides a short pulse - that
outputs 1 pulse for 1 o'clcok 2 pulse for 2 o'clock etc?

I don't even need a display - but would need some means to set the
time for the pulses to be on the hour.

What I need it for is to drive a small solenoid to which is attached a
hammer that strikes a (real) metal gong. It's a novelty clock!

I can build the circuit ok but I don't have the expertise to design
the it.

---
1. How accurate does it have to be?

2. Can you use the AC mains as a time base?

JF

Thanks for all the replies. A few things.
For me, accuarcy here is not important (it would be nice if it was
though). This is more of means to exploit the very nice sound this
gong-thing makes. Just a light tap (even with finger) makes it sound.
I would like to keep it "mechanical" as possible (someone suggested
sampling the sound etc) but would rather not go that route.
I think maybe the small magnet on a real clock hand might be the one
to have go at in the spirit of this project (as the electronics is
probably beyond me).
I thought maybe there is a some "clock chip" I could use and then
somehow (some how ) get the n pulses for each of the hours.
Thanks again.

The idea using a wire wrapped around the hour hand and making contact
with another wire is close to _mechanical_. The problem will be that
it makes contact for some period of time. Using it only as a simple
switch to the solenoid without something else may be a problem. You
might arrange things, also mechanically, so that the solenoid action
also disturbs the wire connection in just such a way as to move it to
the other side and break contact. But my imagination is short on
practical ideas there. Maybe someone else has a handy thought about
it.

[The problem I have with "doing up a microcontroller solution" for you
(which I'd otherwise consider doing free for a moment, at least), is
that no matter what I did you'd need some way of "setting the time."
This means an input device and some means of letting you know what the
clock thinks. Two-way communication of some kind. It's possible,
though perhaps difficult, to consider doing this using a single push
button and a single LED. Short and long LED blinks can communicate
surprising amounts of information. I've done crazier things before.
But it would require some thought about making that work well. So
that holds me back. Making the interface easier to use means more
expense and more design considerations, so that blocks me, too.]

Jon

 

[Nobody]

On Sat, 06 Jun 2009 18:53:16 +0000, Jon Kirwan wrote:

[The problem I have with "doing up a microcontroller solution" for you
(which I'd otherwise consider doing free for a moment, at least), is
that no matter what I did you'd need some way of "setting the time."
This means an input device and some means of letting you know what the
clock thinks. Two-way communication of some kind. It's possible,
though perhaps difficult, to consider doing this using a single push
button and a single LED. Short and long LED blinks can communicate
surprising amounts of information.

A piezo speaker is slightly more expensive than an LED, but still only
needs one pin, and allows for different frequency beeps. Or even speech
synthesis (but that's pushing it on a 12F508, though).

Even simpler electronically: telephone-style pulse dialling. One input,
no outputs.

 

[John Fields]

On Fri, 05 Jun 2009 10:03:33 +0100, dave <dave@127.0.0.1> wrote:

Wonder if some kind person can describe how I can build a circuit that
is basically a black-box (clock) that provides a short pulse - that
outputs 1 pulse for 1 o'clcok 2 pulse for 2 o'clock etc?

I don't even need a display - but would need some means to set the
time for the pulses to be on the hour.

What I need it for is to drive a small solenoid to which is attached a
hammer that strikes a (real) metal gong. It's a novelty clock!

I can build the circuit ok but I don't have the expertise to design
the it.

---
Just for grins, let's say you want to drive this thing from 60Hz mains.

Then you'll have a very accurate 60Hz signal that you can use for a
timebase, and you can get your gong ringing signal like this:




+----+
+----------------+--------------|S |
| +------------+ | U2 | |
| | COUNT UP | | COUNT DN | |
| | +--------+ | | +--------+ | |
| +-|LOAD TC|-+ +--|LOAD TC|--|R Q|-+
+------------+ | | | | | +----+ |
60Hz>---| DIV 216000 |--1Hr-+---|> | +--|> | U3 |
+------------+ | | | | | |
0---|D3 Q3|---|--|D3 | |
0---|D2 Q2|---|--|D2 | |
0---|D1 Q1|---|--|D1 | |
1---|D0 Q0|---|--|D0 | |
+--------+ | +--------+ |
U1 | |
| ASTABLE |
| +--------+ |
+--|OUT E|---------+
| +--------+
| U4
|
| +V
| |
| +----------+
| | |K
| [SOLENOID] [DIODE]
| | |
[R] +----------+
| |
| C
+---B Q1
E
|
GND


Here's how it works:

Initially, a switch is pressed at precisely 1 o'clock which resets the
divide-by-216000 counter, loads binary 0001 into U1 and also into U2
when the "1" ripples through U1.

The switch isn't shown because it's a PITA to do the ASCII and the
circuitry is trivial.

Anyway...

Once 0001 is loaded into U2, its Terminal Count (TC) output will go
false, allowing U3-Q to go true since its SET "S" will be true when its
RESET "R" input goes false.

Then, when U3-Q goes true it will enable U4, an astable with an "ON"
time long enough to allow Q1 to energize the solenoid and create the
desired sound from the gong and a period long enough to allow the
ringing of the gong to decay as desired before the next strike.

The astable is also used as the clock source for U2, and once U2 counts
down to zero its TC output will go true, resetting U3, which will
disable U4.

Assuming that the output of U1 was 0001 because of the pushbutton reset,
then, when the next pulse comes out of the divide-by-216000 counter, an
hour later, U1 will increment to 0010, 0010 will be loaded into U2, U3
will be set, U4 will be enabled, will issue two pulses to the solenoid
driver, and then will shut down.

When the next pulse comes in from the one-hour divider, U1 will
increment, that value will be loaded into U2, and that number of
gong-strikes will be dealt with by U2 until U2 counts down to zero.

JF

 

[Jon Kirwan]

On Sun, 07 Jun 2009 00:03:06 +0100, Nobody <nobody@nowhere.com> wrote:

On Sat, 06 Jun 2009 18:53:16 +0000, Jon Kirwan wrote:

[The problem I have with "doing up a microcontroller solution" for you
(which I'd otherwise consider doing free for a moment, at least), is
that no matter what I did you'd need some way of "setting the time."
This means an input device and some means of letting you know what the
clock thinks. Two-way communication of some kind. It's possible,
though perhaps difficult, to consider doing this using a single push
button and a single LED. Short and long LED blinks can communicate
surprising amounts of information.

A piezo speaker is slightly more expensive than an LED, but still only
needs one pin, and allows for different frequency beeps. Or even speech
synthesis (but that's pushing it on a 12F508, though).

Hehe. No, I'm not wanting to engage that kind of programming as a
one-off for no charge. I've got other stuff to do. The single LED
would be okay. Maybe two?

Even simpler electronically: telephone-style pulse dialling. One input,
no outputs.

I used to be perfectly able to dial a phone number merely using the
phone's hang-up mechanism. Yes, that can work. What I _have_ done
before is used the difference between a short press and a long one to
select different paths and used the LED to signal the user what was
happening. Kind of a press short, LED blinks in certain way to let
you know that's what it interpreted; or press and hold and the LED
would go into a different state to indicate that it had registered the
long press as a long press. Different menu systems entered either
way. Etc. While cheap and easy enough to implement, it can be
tedious to the user.

Jon