Newbie Circuit Design Help

[Stanislaw Flatto]

Don,

I trust your assessment of my mental stability in this area, but I do
not have PIC programming capabilities, nor do I have the resources, or
time to learn how to program a PIC.

Is there really now way to do this using off the shelf parts?
Justin

[sarcastic?]
Have you looked around your kitchen, if it is 21 century model there
should be a wonder called "micro-oven" which includes exactly what you
describe.
[/sarcastic?]

HTH

Stanislaw

 

[linnix]

Ed,
So if we nixed the display - can this be done off the shelf?

Depends on how accurate you want the timer be.

Seriously, if you are rejecting any micro solution,
you are asking for more cost and complexity.

A $5 micro can do the job with or without display.

If you don't want to program the micro, we (or somebody else)
would be more than happy to sell you 25 pre-programmed chips.

 

[Homer J Simpson]

Intended use:
A start button to begin counting
A red Led lit while counting
At the end of the 180 minutes the red Led should go off, green led on
Hit a reset to turn all leds off
Circuit sits idle until start pressed again.

What's it for?




--
..
..
..
..
..
..
..
..

 

[Joerg]

Ed,
So if we nixed the display - can this be done off the shelf?

Yes, Justin, with a CD4060. This is "the" chip for long timers, no need
for a uC but also no display. This link might provide some ideas:

http://www.coolcircuit.com/circuit/timer_4060/index.html

Oh, and please post your relpies below the text, not above. Makes it
easier to read and increases your chances for a useful response ;-)

 

[Rich Grise]

I tried sci.electronics.basic

That list is only available via archive and the last post was in 2004.

Maybe you're not looking in the right place. I go to http://www.google.com
and click "More/Groups", then search for group "sci.electronics.basics",
and it comes right up.

What you really need to do is call your ISP or go to their website, and
find the name of your news server, and use a real newsreader.

I don't need anyone to give me the complete answer, just point me in the
right direction.

Try a 4060:
http://www.fairchildsemi.com/ds/CD/CD4060BC.pdf
with a 32.678 KHz watch crystal - that should give you 2 Hz. Then,
a flip-flop and three decade counters with 7-segment decoder/drivers.
Use another flip-flop for start, and the end count of 180, which you
decode with some gates, resets the "run" flip-flop. Another button for
"clear", and you're done.

Nothing to it!

Good Luck!
Rich

Also, please bottom-post.

 

[EdV]

Ed,
So if we nixed the display - can this be done off the shelf?

Justin

Some other posters beat me to it but I also recommend using the 4060.
Here ia link you might find useful:

http://uk.geocities.com/ronj_1217/al1/24t.html

 

[Joerg]

Some other posters beat me to it but I also recommend using the 4060.
Here ia link you might find useful:

http://uk.geocities.com/ronj_1217/al1/24t.html

Ah, the good old days. Haven't seen a Veroboard layout suggestion in
years. Thanks. Those were the days when you could actually see the parts
on a circuit board without a microscope.

 

[Rich Grise]

Don,

I trust your assessment of my mental stability in this area, but I do
not have PIC programming capabilities, nor do I have the resources, or
time to learn how to program a PIC.

Is there really now way to do this using off the shelf parts?
Justin

Of course not! There are billions and billions of ways. Did you
miss my answer? It's really not hard at all.

And please learn to bottom-post, and trim judiciously.

And Don seems to be getting cranky in his old age - when he was
your age, he published a book or three that had all of this stuff
laid out for you.

Good Luck!
Rich

 

[Joel Kolstad]

And Don seems to be getting cranky in his old age - when he was
your age, he published a book or three that had all of this stuff
laid out for you.

I suspect he was really hoping he could convince the OP to write it in
PostScript.

 

[DJ Delorie]

And please learn to bottom-post, and trim judiciously.

But... you didn't.

 

[C F Page]

I need help designing a timing circuit.

The circuit should not use a PIC, and an IC is preferable.

The circuit needs to countdown from 180 minutes to zero.

Intended use:
A start button to begin counting
A red Led lit while counting
At the end of the 180 minutes the red Led should go off, green led on
Hit a reset to turn all leds off
Circuit sits idle until start pressed again.

I also need the "countdown" displayed on 3 seven segment leds.

Any help appreciated!

Thanks,
Justin

Just out of curiosity to see if it could be done with an 8-pin PIC
and what amounts to homebrewed SPI, I excavated a PICkit1 Flash
Starter Kit that's been waiting to be tried for some months now,
put it up under Win98SE, and did a design study, the results of
which are attached.

The design uses a 12F675 as system controller and three octal DFF
chips connected as a shift register to interface to the three LED
displays and two discrete LEDs; I won't have time to debug the
software on the target hardware until at least the weekend, but I
thought you might like to see the initial study to at least get a
feel for the possibilities.

If you would like to play with the code, all you need is that starter
kit, which can be had from either Microchip or Digi-Key for $35 plus
shipping: it has all the hardware and software needed to compile the
code and program it into a 12F675 (supplied) using nothing but a USB
connection to a WinDoze box.

The "study" part of it was as much of the formatting and documentation
of the source code as of the algorithmic and implementation details.
The source code is meant to be completely self-contained and self-
explanatory; I would be most grateful for any opinions as to how well
the document succeeds in attaining this objective.

Finally, continuing with an observation others have made: you can
get a "digital kitchen timer" which does most of what you want for
about $15 off the Web; I imagine that its guts could be used as a
"component" to which your own peripherals could be interfaced,
leaving little more than mechanical design to be done.

COTS, anyone?