| Author |
Message |
Bob
Guest
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 Posted:
Wed Nov 16, 2005 4:46 am Post subject:
24Hr/7 Day Timer |
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I have a project that requires turning a plastic disc (about the same size
as a CD) through 360 degrees in 7 days or 24 hours using a battery powered
system of some sort. The smaller and cheaper the better! Can anyone suggest
the best way I should approach this problem?
Thanks
Bob
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Chris
Guest
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| Posted:
Wed Nov 16, 2005 5:35 pm Post subject:
Re: 24Hr/7 Day Timer |
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Bob wrote:
| Quote: | I have a project that requires turning a plastic disc (about the same size
as a CD) through 360 degrees in 7 days or 24 hours using a battery powered
system of some sort. The smaller and cheaper the better! Can anyone suggest
the best way I should approach this problem?
Thanks
Bob
|
Hi, Bob. The ideal solution for this would be a small AC gearmotor.
They're made for this kind of service, and they're inexpensive.
But if you need a battery-operated solution and the moment of inertia
of your disc isn't too great, an "easy button" relatively cheap
solution for one day rotation might be a 24-hour ham wall clock:
http://www.eham.net/reviews/detail/2794
It might be worth picking one up on ebay and just trying it. You only
need the clock movement -- the clock face itself isn't necessary. The
bigger clocks would probably have enough torque on the movement hour
hand to pull a CD-sized piece of plastic around with no problem, at
least while the battery was fresh. To get more torque, you may want to
wire up a "D"-sized battery to replace the AA. It would last longer,
too.
For a 7-day movement, some kind of gearing might be in order.
Another inexpensive solution which might give you more "oompfh" would
be to use a small 5V stepper motor, 3 or 4 "D" batteries or a 6V
lantern battery, and a PIC with some logic level FETs or darlington
transistors. It would be trivial to program in the long time delay
between steps. You could also use a switch to differentiate between
1-day and 7-day movement. The trick would be to pulse the stepper
coils for only a fraction of a second each time there's movement, like
the battery-operated clocks, to reduce long term power dissipation.
If you'd like to use a cheapie 4000-series CMOS and 555 solution to
replace the PIC, it would actually be quite a bit bigger and more
expensive, due to board space, number of ICs and construction hassles.
Also, a PIC with a ceramic resonator (+/- 0.5%) would be more accurate
and stable than the R-C oscillator of a 555 or CD4060 with a tweaker
pot. If you needed even more accuracy, you could use a crystal for the
PIC.
If you're looking for that type of solution, or if this isn't enough,
you should post again with more detail on your project requirements.
Good luck
Chris |
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John Fields
Guest
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| Posted:
Wed Nov 16, 2005 5:35 pm Post subject:
Re: 24Hr/7 Day Timer |
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On Wed, 16 Nov 2005 04:46:49 +0000 (UTC), "Bob" <noemail@nospam.com>
wrote:
| Quote: | I have a project that requires turning a plastic disc (about the same size
as a CD) through 360 degrees in 7 days or 24 hours using a battery powered
system of some sort. The smaller and cheaper the better! Can anyone suggest
the best way I should approach this problem?
|
---
I replied to your post in another newsgroup, but I'm not going to
reply to it again as I did there. In the future, please crosspost
since it makes life simpler for all of us.
--
John Fields
Professional Circuit Designer
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Bob
Guest
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| Posted:
Wed Nov 16, 2005 9:36 pm Post subject:
Re: 24Hr/7 Day Timer |
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Thanks very much for the suggestions, only I am not clear whether a PIC
solution would be best since the two posts seem to contradict each other. Do
you know of a circuit/PIC program on the internet that you could recommend
this?
I like the clock idea but I guess I would need to have a gearbox as well as
the disc must rotate very slowly to give an almost continuous but slow
rotation during the period.
A selector switch to operate the unit in either period would be ideal but
the alternative of making two units is ok.
Do you think it would be possible to put an invertor on a12V battery to
power an AC gearmotor? I'm open to all possibilities!
Bob
"John Fields" <jfields@austininstruments.com> wrote in message
news:plfmn15hnqc2tf2jq87m1jh889tevpf9ci@4ax.com...
| Quote: | On Wed, 16 Nov 2005 04:46:49 +0000 (UTC), "Bob" <noemail@nospam.com
wrote:
I have a project that requires turning a plastic disc (about the same
size
as a CD) through 360 degrees in 7 days or 24 hours using a battery
powered
system of some sort. The smaller and cheaper the better! Can anyone
suggest
the best way I should approach this problem?
---
I replied to your post in another newsgroup, but I'm not going to
reply to it again as I did there. In the future, please crosspost
since it makes life simpler for all of us.
--
John Fields
Professional Circuit Designer |
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Ben Jackson
Guest
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| Posted:
Thu Nov 17, 2005 1:35 am Post subject:
Re: 24Hr/7 Day Timer |
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On 2005-11-16, Bob <noemail@nospam.com> wrote:
| Quote: | I have a project that requires turning a plastic disc (about the same size
as a CD) through 360 degrees in 7 days or 24 hours using a battery powered
system of some sort. The smaller and cheaper the better! Can anyone suggest
the best way I should approach this problem?
|
Do you mean switchable 24h or 7d? Also, you need to specify how many
steps you need. You could sleep for 23:59:59 and turn the disc one
turn at 60rpm in the final second! An AC timing motor could probably
do it in zillions of tiny steps. A solution with a PIC and a hobby
servo might only give you 1000 steps (1/3rd of a degree accuracy...)
--
Ben Jackson
<ben@ben.com>
http://www.ben.com/ |
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petrus bitbyter
Guest
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| Posted:
Thu Nov 17, 2005 5:35 pm Post subject:
Re: 24Hr/7 Day Timer |
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"Bob" <noemail@nospam.com> schreef in bericht
news:dlg8og$o62$1@nwrdmz03.dmz.ncs.ea.ibs-infra.bt.com...
| Quote: | "John Fields" <jfields@austininstruments.com> wrote in message
news:plfmn15hnqc2tf2jq87m1jh889tevpf9ci@4ax.com...
On Wed, 16 Nov 2005 04:46:49 +0000 (UTC), "Bob" <noemail@nospam.com
wrote:
I have a project that requires turning a plastic disc (about the same
size
as a CD) through 360 degrees in 7 days or 24 hours using a battery
powered
system of some sort. The smaller and cheaper the better! Can anyone
suggest
the best way I should approach this problem?
---
I replied to your post in another newsgroup, but I'm not going to
reply to it again as I did there. In the future, please crosspost
since it makes life simpler for all of us.
--
John Fields
Professional Circuit Designer
Thanks very much for the suggestions, only I am not clear whether a PIC
solution would be best since the two posts seem to contradict each other.
Do
you know of a circuit/PIC program on the internet that you could recommend
this?
I like the clock idea but I guess I would need to have a gearbox as well
as
the disc must rotate very slowly to give an almost continuous but slow
rotation during the period.
A selector switch to operate the unit in either period would be ideal but
the alternative of making two units is ok.
Do you think it would be possible to put an invertor on a12V battery to
power an AC gearmotor? I'm open to all possibilities!
Bob
|
Invertor? Highly depends on the available power. AC motors are relative
powerhungry and invertors need also some to function.
Guess the wall clock is the best option if... it only can turn your disc.
Short hands weight next to nothing and I don't know about your disc. But as
you will remove the oher hands, guess you have a good chanche. As for the
turning, you have a 12 hours rotation already. Adding mechanical gearing is
pretty expensive and requires some skills in that field. So what about
electronic delay? The quarz wall clocks I'm aware off all use a simple drive
mechanism. It's a coil in which a small piece of iron is driven to and fro.
That iron drives the wheels but it is driven by short current pulses through
the coil. The X-tal and a chip provides that pulses through two pins. One
per two seconds each pin gives a short (positive) pulse while the other is
kept low. So you get one tick/second. So the "only" thing you have to do is
putting some divide by fourteen circuit between the drive pins and the coil.
Once you got the idea, you will find out you only need one divide by seven
circuit and a capacitor. (And an amplifier/comparator to bring the 1.5V
pulses provided buy the clock chip to the level of your logic circuit.)
petrus bitbyter |
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Rich Grise
Guest
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| Posted:
Fri Nov 18, 2005 1:35 am Post subject:
Re: 24Hr/7 Day Timer |
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On Wed, 16 Nov 2005 04:46:49 +0000, Bob wrote:
| Quote: | I have a project that requires turning a plastic disc (about the same size
as a CD) through 360 degrees in 7 days or 24 hours using a battery powered
system of some sort. The smaller and cheaper the better! Can anyone suggest
the best way I should approach this problem?
|
Buy a 24-hour clock, and glue the disk to the hour hand.
Cheers!
Rich |
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ehsjr
Guest
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| Posted:
Fri Nov 18, 2005 9:35 am Post subject:
Re: 24Hr/7 Day Timer |
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Bob wrote:
| Quote: | I have a project that requires turning a plastic disc (about the same size
as a CD) through 360 degrees in 7 days or 24 hours using a battery powered
system of some sort. The smaller and cheaper the better! Can anyone suggest
the best way I should approach this problem?
Thanks
Bob
|
A 30 degree stepper motor with 100:1 external gearing would
give you .3 degrees per step. Fire it once every 504 seconds.
Doubtful you'll see the motion - .3 degrees is only 1/20
of the distance the minute hand moves in one minute.
You might even be able to get away with a 1.8 degree stepper
and no gearing, fired 200 times in 7 days, or once every
((7*24*60)/200)*60 seconds.
Ed |
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Jasen Betts
Guest
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| Posted:
Fri Nov 18, 2005 12:13 pm Post subject:
Re: 24Hr/7 Day Timer |
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On 2005-11-16, Bob <noemail@nospam.com> wrote:
| Quote: | I have a project that requires turning a plastic disc (about the same size
as a CD) through 360 degrees in 7 days or 24 hours using a battery powered
system of some sort. The smaller and cheaper the better! Can anyone suggest
the best way I should approach this problem?
|
use a cheap battery powered clock mechanism and 14:1 or 2:1 gearing on the
hour hand.
--
Bye.
Jasen |
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