PC/electronics help needed

[Daniel J Beardsall]

Greetings all.

Assume for a moment that I have no knowledge of electronics (not true,
but I only know what I've picked up and that's rather patchy). I'm
looking to make a little addon for my PC and I need a little help. I'm
after making 3 time/date displays using 7-segment (numbers) and
10-segment (letters) LED displays. One of them should actually show the
correct time, the others I'd like to show other static times, preferably
with the option to change them occasionally. The latter parts should be
within my reach but the actual clock is a bit more of a problem, our
school was a bit crap and didn't actually teach us how to do that.

I'd rather make it from scratch but I'll butcher an alarm clock if I
have to.

The other thing is that it needs to be powered from the PC's power
supply, so it'll need to run on either 5V or 12V, with some form of
battery backup to power just the real clock when the machine is switched
off. If somehow it could be made to display the system's internal time
that would be wonderful, but not necessary.

Any help at all would be vastly appreciated.

DjBx

 

[John Doe]

...I'm looking to make a little addon for my PC and I need a little help. I'm
after making 3 time/date displays using 7-segment (numbers) and
10-segment (letters) LED displays. One of them should actually show the
correct time, the others I'd like to show other static times, preferably
with the option to change them occasionally. The latter parts should be
within my reach but the actual clock is a bit more of a problem, our
school was a bit crap and didn't actually teach us how to do that.

I would ask in the electronics groups.
sci.electronics...

Good luck.

 

[sdeyoreo]

Not sure what you want but:
first, 5 or 12 from the PC is not problem, even get 5 vdc from the USB
port,
second: you want the system time thats displayed in the task bar on
the bottom right of your monitor displayed on your gadget? Then would
it be connected to the computer thru the parallel port or serial or
USB? When computer shuts down, does this display keep going, like
automatically switching to an internal clock, then back to computer
when its turned on again? You could write a program to send any number
you want out the parallel port, read he system time, send out the
hoy=urs, then send out the minutes.

 

[w_tom]

The problem with an alarm clock is that the chip is
completely contained. The only information coming out would
be seven segment displays - multiplexed. You would have to
convert that back to some usable form OR build a memory device
to store those multiplexed seven segment outputs and then
drive the other displays. Four digits times seven segments
plus AM/PM is 29 D flipflop latches and LED display drivers.

What type of time do you want to store? For example, if
time of day, then the alarm clock solution is better. AC
powered clocks synchronize with the 60 Hz power line - whose
accuracy is traceable to the National Bureau of Standards. To
avoid the complexity of same, the alarm clock would be a good
foundation to start construction. You would probably have to
beef up or supplement the alarm clock's power supply to power
your latching registers and two additional displays.

Another alternative is to start from scrap with a single
chip computer. Again, your timing crystal accuracy is just
another consideration. But a single chip computer affords you
great flexibility to enhance your design.

 

[Daniel J Beardsall]

Not sure what you want but:

first, 5 or 12 from the PC is not problem, even get 5 vdc from the USB
port,

Yes I know, I intend to run it off one of the internal Molex connectors.

second: you want the system time thats displayed in the task bar on
the bottom right of your monitor displayed on your gadget? Then would
it be connected to the computer thru the parallel port or serial or
USB?

Yes. Any of those, whichever turns out to be easiest. Which from what
I've gathered would be parallel.

When computer shuts down, does this display keep going, like
automatically switching to an internal clock, then back to computer
when its turned on again? You could write a program to send any number
you want out the parallel port, read he system time, send out the
hoy=urs, then send out the minutes.

Yes, I'd like the clock to be sort of independent with occasional
updates from the PC clock (mostly to save the hassle of setting it
manually). The program isn't the problem, I could knock something up in
VB, it's getting something that can translate my outputs and display it
that's the problem.

DjBx

 

[Daniel J Beardsall]

The problem with an alarm clock is that the chip is

completely contained. The only information coming out would
be seven segment displays - multiplexed. You would have to
convert that back to some usable form OR build a memory device
to store those multiplexed seven segment outputs and then
drive the other displays. Four digits times seven segments
plus AM/PM is 29 D flipflop latches and LED display drivers.

The other displays would be independent of the actual clock, if that's
what you mean. And yes, when I mentioned butchering an alarm clock that
was mostly as a last-resort kind of option.

What type of time do you want to store? For example, if
time of day, then the alarm clock solution is better. AC
powered clocks synchronize with the 60 Hz power line - whose
accuracy is traceable to the National Bureau of Standards. To
avoid the complexity of same, the alarm clock would be a good
foundation to start construction. You would probably have to
beef up or supplement the alarm clock's power supply to power
your latching registers and two additional displays.

The problem there is that I'm not in the US, I'm in the UK, and our
electrical supply isn't quite so simple. It's mostly 50Hz but can
fluctuate wildly, which often interferes with clocks. Besides, I'm not
looking to run it off direct mains, I'm looking to run it off computer
power, so a battery-powered alarm clock was more what I had in mind.

Another alternative is to start from scrap with a single
chip computer. Again, your timing crystal accuracy is just
another consideration. But a single chip computer affords you
great flexibility to enhance your design.

Now you're talking. But I wouldn't know where to start hooking something
like that into something capable of driving LED segment displays. Which
I suppose is ultimately the help I'm after.

Thankyou for your response.

DjBx

 

[David Maynard]

The other displays would be independent of the actual clock, if that's
what you mean. And yes, when I mentioned butchering an alarm clock that
was mostly as a last-resort kind of option.



The problem there is that I'm not in the US, I'm in the UK, and our
electrical supply isn't quite so simple. It's mostly 50Hz but can
fluctuate wildly, which often interferes with clocks. Besides, I'm not
looking to run it off direct mains, I'm looking to run it off computer
power, so a battery-powered alarm clock was more what I had in mind.



Now you're talking. But I wouldn't know where to start hooking something
like that into something capable of driving LED segment displays. Which
I suppose is ultimately the help I'm after.

Thankyou for your response.

DjBx

I'm still not sure what you're trying to do, precisely, but maybe this will
stimulate some ideas.

http://www.rentron.com/Products/SLED4C.htm

 

[User N]

[snip description of clock project]

It is likely that there are commerically available and assembled
products that either do exactly what you want or something similar.
I've come across clock/timing devices with PC interfaces, as
well as general purpose displays with PC interfaces. It would be
worth investigating.

Various companies make "electronic kits", "hobby kits", "learning
kits", or whatever you want to call them... kits with all the parts and
instructions you need to assemble some simple electronic device.
If you google hard you'll find led clocks, timers, programmable
displays, displays that interface with PC ports, etc. One or more
of those kits might provide a starting point.

There are many websites where people document their school or
hobby projects. You should be able to find some websites that
contain usefull information on projects that have something in
common with yours. For example, people have interfaced all sorts
of things to their PC, and over the years I've run across quite a few
sites with detailed directions, schematics, parts lists, source code, etc.
If you find something close you can lift part of the HW design and/or
SW.

If there is a good library and/or bookstore near you, you should
be able to find not only books on electronic design basics, but
electronic "cookbooks" that have schematics for all sorts of basic
circuits.

Having said all that, the suggestion that you take this discussion to
an electronics newsgroup or web forum was truly the best one. For
there you are likely to find a higher percentage of people who have
the required experience, and hopefully interest and willingness to
guide you. When you introduce yourself, be sure to talk a little
about what hardware experience you have. Have you ever designed
something with integrated circuits and discrete components? Have
you ever selected and purchased all the parts, and wired them up on
a breadboard? Have you done board layout/routing, and made or
purchased a PCB? Also talk a little about what software development
experience you have. That way people can steer you in the best
direction.

Have fun.

 

[sdeyoreo]

It's real easy in VB.net, but remember, XP will not allow you to
program the ports, you need a "kernal driver" that runs in a special
mode. This link explains it: http://www.logix4u.net/inpout32.htm My
I/O programs start by calling ShellExec to run a script that puts you
into the proper user mode.

 

[w_tom]

AC electric cannot vary wildly because all grid generators
must match up perfectly with all others - or the entire grid
collapses. To find a clock that varies wildly, visit a PC
clock. That clock is way too inaccurate to control the 50 Hz
grid - where timing accuracy is essential.

Use a PC as the timing source. Therefore you only need
write special software to write to displays- ie driven through
parallel ports. But then why bother with fancy hardware
displays? You can put up clock displays in Windows on the
monitor.

Previously posted was using an alarm clock 'kludge' - every
other display is independent of the actual clock - except when
the display number is first latched from a master display.
Appreciate everything posted up to now is perfectly matching
your request - because details are missing. What are the
details? For example, the grid 50 Hz remains a most accurate
source of timing which is why AC electric clocks remain on
time every day - without resetting every week. If 50 Hz AC is
not accurate enough, then anything in a PC or in the embedded
processor is even worse. IOW you did not provide a necessary
detail such as the number for timing accuracy. You did not
say where those other displays get their numbers.

Are you trying to display a time of day, or time of event.
For that matter, what is wrong with a controller from a
defective microwave oven?

How to connect to a display? First select the display.
Then find the driver chip for that type of display. IOW
download datasheets. Read some 3 or eight pages chock full of
information (assume something like 15+ minutes per page).

If that example (rentron.com) is what you want, then why not
buy it? I remain completely confused by what you are trying
to do. If 50 Hz AC power is not accurate enough, then this
example is even worse. Just more little contradictory details
that completely confused me.

It is possible that you have not yet learned an engineer's
mentality. This project is how you learn so much. Same
reason why to teach why the military want people educated in
the temperament of reality. Notice what you may have
perceived as a simple project might take weeks. Something
that would become obvious once you first list those details.
The military teaches their future officers to be engineers.
To learn that reality is not as simplistic as taught in
secondary school. To learn temperament that comes from putting
initial ideas into reality. Making ideas into reality is
rarely taught in general education. We learn it by doing what
you are trying to accomplish here. Currently, you have starve
your request for information with insufficient details.

 

[David Maynard]

AC electric cannot vary wildly because all grid generators
must match up perfectly with all others - or the entire grid
collapses. To find a clock that varies wildly, visit a PC
clock. That clock is way too inaccurate to control the 50 Hz
grid - where timing accuracy is essential.

Power grid frequency varies automatically with the difference between
supply and demand and is controlled by opening and closing the steam
valves of the turbines that drive the generators. In the continental
European grid (UCTE), the spec says that the time-scale defined by the
rotating grid phase vector must remain within +/- 30 seconds of UTC. The
UCTE control center in Laufenbourg, Switzerland sends out instructions
every 24 hours to shift the nominal frequency of 50.0 Hz, if necessary, to
either 49.99 or 50.01 Hz (+/- 10 mHz) if the network clock starts to drift
away from UTC too far. For comparison: the measured frequency deviation
from the nominal frequency is not supposed to be more than 40 mHz for more
than 10% of the time and not more than 60 mHz for more than 1% of time.

As such, at any moment in time the AC grid can 'vary wildly' (subjective)
compared to the tolerances of a PC clock (typical RTC 32.768 kHz crystal
being 20ppm @ 25C, which can accumulate to being off 52s after a month).
The difference is that the power grid is routinely (24 hours) 'corrected'
to bring it back so, over the long term, it remains within tolerance
whereas a PC clock's error just keeps accumulating, unless one does a
similar thing and syncs it with a more accurate time reference.

 

[Overlord]

Power grid frequency varies automatically with the difference between
supply and demand and is controlled by opening and closing the steam
valves of the turbines that drive the generators. In the continental
European grid (UCTE), the spec says that the time-scale defined by the
rotating grid phase vector must remain within +/- 30 seconds of UTC. The
UCTE control center in Laufenbourg, Switzerland sends out instructions
every 24 hours to shift the nominal frequency of 50.0 Hz, if necessary, to
either 49.99 or 50.01 Hz (+/- 10 mHz) if the network clock starts to drift
away from UTC too far. For comparison: the measured frequency deviation
from the nominal frequency is not supposed to be more than 40 mHz for more
than 10% of the time and not more than 60 mHz for more than 1% of time.

As such, at any moment in time the AC grid can 'vary wildly' (subjective)
compared to the tolerances of a PC clock (typical RTC 32.768 kHz crystal
being 20ppm @ 25C, which can accumulate to being off 52s after a month).
The difference is that the power grid is routinely (24 hours) 'corrected'
to bring it back so, over the long term, it remains within tolerance
whereas a PC clock's error just keeps accumulating, unless one does a
similar thing and syncs it with a more accurate time reference.

I believe I know pretty much what you're after. However I have no real hard
fast wiring recommendations. There are many software programs out there
to link with atomic clocks to fix your PC's inaccuracy. I run AtomTime myself
and it's nice to be able to set the PC to within a fraction of a second without
relying on your power main's fluctuating frequency(heh).
If you buy one of the programs, several have options to check/reset the PC
time against the atomic clock on a schedule every so many hours, when the
PC boots up, etc. I fix people's computers (which is more spyware removal
and Winders settings screwups anymore than strictly hardware upgrades) and
am horrified by some of the times (and dates!) I see on some of the systems.

Alternatively you might buy a standalone clock that syncs to the radio signals
transmitted by atomic clocks so it would be totally independant from the PC.
I am assuming they do that in England or Europe. The clock constantly
monitors the broadcasts and updates itself no matter how badly the mains
freq screws with it.

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[David Maynard]

I believe I know pretty much what you're after. However I have no real hard
fast wiring recommendations. There are many software programs out there
to link with atomic clocks to fix your PC's inaccuracy. I run AtomTime myself
and it's nice to be able to set the PC to within a fraction of a second without
relying on your power main's fluctuating frequency(heh).
If you buy one of the programs, several have options to check/reset the PC
time against the atomic clock on a schedule every so many hours, when the
PC boots up, etc. I fix people's computers (which is more spyware removal
and Winders settings screwups anymore than strictly hardware upgrades) and
am horrified by some of the times (and dates!) I see on some of the systems.

Alternatively you might buy a standalone clock that syncs to the radio signals
transmitted by atomic clocks so it would be totally independant from the PC.
I am assuming they do that in England or Europe. The clock constantly
monitors the broadcasts and updates itself no matter how badly the mains
freq screws with it.

Thanks. That's good information but I was just commenting on the power line
frequency and am not the one looking to make the external clock, for what
reason I don't know.

I already sync all my local machines to tick.usno.navy.mil. Or, rather, my
domain controller does and the rest sync with the DC.