Re: 24Hr/7 Day Timer


"Bob" <noemail@xxxxxxxxxx> schreef in bericht
news:dlg8og$o62$1@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> "John Fields" <jfields@xxxxxxxxxxxxxxxxxxxxx> wrote in message
> news:plfmn15hnqc2tf2jq87m1jh889tevpf9ci@xxxxxxxxxx
>> On Wed, 16 Nov 2005 04:46:49 +0000 (UTC), "Bob" <noemail@xxxxxxxxxx>
>> 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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