Re: [time-nuts] 24 hr clock movements...
On 1/20/14 10:06 AM, Jim Lux wrote: On 1/19/14 1:51 PM, Tom Van Baak wrote: Use 24h clocks for best results. They can be had from www.clockkit.com, an excellent source of DIY quartz clock parts. I couldn't find 24hr movements on the clockkit.com site.. where are they? http://www.klockit.com/depts/SpecialtyClockMovements/dept-379.html ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 24 hr clock movements...
Hi So really it boils down to : http://www.klockit.com/products/dept-379__sku-bbbii.html Since that already has a full driver on it (battery / oscillator / chip) - you will need to do some surgery to get directly at the stepper motor. (or am I missing something?) Bob On Jan 20, 2014, at 1:17 PM, Jim Lux jim...@earthlink.net wrote: On 1/20/14 10:06 AM, Jim Lux wrote: On 1/19/14 1:51 PM, Tom Van Baak wrote: Use 24h clocks for best results. They can be had from www.clockkit.com, an excellent source of DIY quartz clock parts. I couldn't find 24hr movements on the clockkit.com site.. where are they? http://www.klockit.com/depts/SpecialtyClockMovements/dept-379.html ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 24 hr clock movements...
That listing is a bit vague about if it has a second hand. For the kind of pulse drive that has been discussed here, it seems you would want a definite second capability and step vs. smooth second hand drive. I know nothing except a little web searching, but this one seems to have the right features... http://www.clockparts.com/clock-part/24-hour-high-torque-movement/ but, although they mention a 24-hour dial available, the page for it on the site has no content. Searching eBay gave some hits, but most of what I saw for 24-hour movements seemed to have smooth second hand (not step). On 1/20/2014 10:17 AM, Jim Lux wrote: On 1/20/14 10:06 AM, Jim Lux wrote: On 1/19/14 1:51 PM, Tom Van Baak wrote: Use 24h clocks for best results. They can be had from www.clockkit.com, an excellent source of DIY quartz clock parts. I couldn't find 24hr movements on the clockkit.com site.. where are they? http://www.klockit.com/depts/SpecialtyClockMovements/dept-379.html ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 24 hr clock movements...
On 1/20/14 3:32 PM, Rex wrote: That listing is a bit vague about if it has a second hand. For the kind of pulse drive that has been discussed here, it seems you would want a definite second capability and step vs. smooth second hand drive. I know nothing except a little web searching, but this one seems to have the right features... http://www.clockparts.com/clock-part/24-hour-high-torque-movement/ but, although they mention a 24-hour dial available, the page for it on the site has no content. it is very much a matter of buying a few and trying them. If you don't install a second hand, then that solves the inertia of the secondhand problem. The challenge is that because the motor for these things is basically a step at a time, if the hand has too much inertia, then the hand will either not move enough to get to the next tep (dying battery syndrome we've all seen), or, it will move past (because the braking torque isn't high enough. It's sort of the torsional resonance effect that afflicts stepper motors in another form. The magnetic impulse is basically driving a spring (the magnetic field) with a mass on it. These things are always highly idiosyncratic. I would imagine that fiddling with the duration and magnitude of the step pulses (or, for that matter the shape of the pulse) could have a huge effect if one wanted to optimize it. A couple decades ago we built a large (5-6 foot diameter) stopwatch prop with a stepper motor, and we had to play with the drive voltage, the capacitance and resistance in the step channels to make it work right. Today, you'd do microstepping, or use a clever algorithm to customize the step waveform. Generally you want a voltage profile that's sort of a spike (to get the current flowing in the winding) with a back porch, and then a reverse polarity at the end (to stop the motion). (I note that this problem is not unique to AA powered clocks. The hands of the clock on the UC Berkeley Campanile are wood for a similar reason.) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 24 hr clock movements...
Since most of those cheapo movements are a simple single-coil motor, energized with alternating polarity short pulses, it would seem that there is no need for a 24 hour movement. You can just have your micro pulse it twice the normal period, but with the same as normal pulse width(s). Check out the movement teardown in lunchtime clock at Instructables.com - http://www.instructables.com/id/Lunchtime-Clock/ Bob LaJeunesse From: Jim Lux jim...@earthlink.net To: time-nuts@febo.com Sent: Monday, January 20, 2014 7:04 PM Subject: Re: [time-nuts] 24 hr clock movements... On 1/20/14 3:32 PM, Rex wrote: That listing is a bit vague about if it has a second hand. For the kind of pulse drive that has been discussed here, it seems you would want a definite second capability and step vs. smooth second hand drive. I know nothing except a little web searching, but this one seems to have the right features... http://www.clockparts.com/clock-part/24-hour-high-torque-movement/ but, although they mention a 24-hour dial available, the page for it on the site has no content. it is very much a matter of buying a few and trying them. If you don't install a second hand, then that solves the inertia of the secondhand problem. The challenge is that because the motor for these things is basically a step at a time, if the hand has too much inertia, then the hand will either not move enough to get to the next tep (dying battery syndrome we've all seen), or, it will move past (because the braking torque isn't high enough. It's sort of the torsional resonance effect that afflicts stepper motors in another form. The magnetic impulse is basically driving a spring (the magnetic field) with a mass on it. These things are always highly idiosyncratic. I would imagine that fiddling with the duration and magnitude of the step pulses (or, for that matter the shape of the pulse) could have a huge effect if one wanted to optimize it. A couple decades ago we built a large (5-6 foot diameter) stopwatch prop with a stepper motor, and we had to play with the drive voltage, the capacitance and resistance in the step channels to make it work right. Today, you'd do microstepping, or use a clever algorithm to customize the step waveform. Generally you want a voltage profile that's sort of a spike (to get the current flowing in the winding) with a back porch, and then a reverse polarity at the end (to stop the motion). (I note that this problem is not unique to AA powered clocks. The hands of the clock on the UC Berkeley Campanile are wood for a similar reason.) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 24 hr clock movements...
I think there is a slight flaw in slowing the drive to half rate. The hour hand could then go around once in 24 hours, but the minute and second hand movement is halved too. Rather non-intuitive to read unless you only put on the hour hand and make a new 24-hour dial face. On 1/20/2014 5:57 PM, Robert LaJeunesse wrote: Since most of those cheapo movements are a simple single-coil motor, energized with alternating polarity short pulses, it would seem that there is no need for a 24 hour movement. You can just have your micro pulse it twice the normal period, but with the same as normal pulse width(s). Check out the movement teardown in lunchtime clock at Instructables.com - http://www.instructables.com/id/Lunchtime-Clock/ Bob LaJeunesse ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 24 hr clock movements...
Jim, I think you missed the main point I was trying to address. It seems that many of the newer quartz movements do not move the second hand in one-second steps. They move it in some way that appears smooth to a human observer. (Even if there is no actual second hand, the same motive issues need to be looked at.) I assume the smooth motor is still some kind of stepper but being driven by pulses at a much higher rate than a one-second rate. If you receive one of these versions, you will have a more difficult job to drive it. You'd need to figure out what rate is driving it and generate that. The 1-second step versions would be easier for us to generically interface with. The description on the Klockit page wasn't very clear about which type it is (also it was somewhat ambiguous about using a secondhand, at all, if desired -- there is a footnote that I couldn't quite decipher). On 1/20/2014 4:04 PM, Jim Lux wrote: On 1/20/14 3:32 PM, Rex wrote: That listing is a bit vague about if it has a second hand. For the kind of pulse drive that has been discussed here, it seems you would want a definite second capability and step vs. smooth second hand drive. I know nothing except a little web searching, but this one seems to have the right features... http://www.clockparts.com/clock-part/24-hour-high-torque-movement/ but, although they mention a 24-hour dial available, the page for it on the site has no content. it is very much a matter of buying a few and trying them. If you don't install a second hand, then that solves the inertia of the secondhand problem. The challenge is that because the motor for these things is basically a step at a time, if the hand has too much inertia, then the hand will either not move enough to get to the next tep (dying battery syndrome we've all seen), or, it will move past (because the braking torque isn't high enough. It's sort of the torsional resonance effect that afflicts stepper motors in another form. The magnetic impulse is basically driving a spring (the magnetic field) with a mass on it. These things are always highly idiosyncratic. I would imagine that fiddling with the duration and magnitude of the step pulses (or, for that matter the shape of the pulse) could have a huge effect if one wanted to optimize it. A couple decades ago we built a large (5-6 foot diameter) stopwatch prop with a stepper motor, and we had to play with the drive voltage, the capacitance and resistance in the step channels to make it work right. Today, you'd do microstepping, or use a clever algorithm to customize the step waveform. Generally you want a voltage profile that's sort of a spike (to get the current flowing in the winding) with a back porch, and then a reverse polarity at the end (to stop the motion). (I note that this problem is not unique to AA powered clocks. The hands of the clock on the UC Berkeley Campanile are wood for a similar reason.) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 24 hr clock movements...
On 1/20/14 5:57 PM, Robert LaJeunesse wrote: Since most of those cheapo movements are a simple single-coil motor, energized with alternating polarity short pulses, it would seem that there is no need for a 24 hour movement. You can just have your micro pulse it twice the normal period, but with the same as normal pulse width(s). Check out the movement teardown in lunchtime clock at Instructables.com - http://www.instructables.com/id/Lunchtime-Clock/ The difference is that a 24 hr clock has a 24:1 gear ratio between minute and hour hands, and a 12 hr clock has 12:1. If you're doing hour hand only, yep, any movement will do. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
