5 min precision countdown timer

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Bountyhunter

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Jun 12, 2005, 9:34:23 AM6/12/05
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Hi! an anybody please help me. I was looking for a electronic kit but
cant find one anyware. I want to make it myself but need help with the
design. I must be able to preset the time from 30 sec to 5 min with the
time desplayed. When the preset time reaches 0 it must switch on a
buzzer or switch a relay. I've seen some 5 x 8 dot matrix displays
(ELM-2081EWA) that i was thinking of using. Can someone please help!!!!

DaveM

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Jun 12, 2005, 12:18:55 PM6/12/05
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"Bountyhunter" <ja...@fronthosting.com> wrote in message
news:1118583263.8...@f14g2000cwb.googlegroups.com...

What you're after is a "Presettable Down Counter" with an accurate time
base. But you didn't fully define the project.
You mentioned "precision" in the subject. How much precision do you need
(how many minutes/seconds/milliseconds/etc)? How accurate does the timer
need to be (within seconds/milliseconds/etc)?
How do you wish to preset the time into the timer (potentiometer/thumbwheel
switches/etc)?

Do you want to build this using discrete components, or can you program a
PIC (a PIC would be marvelously suited for this task)?

Do you specifically want to build this item, or buy off-the-shelf? Look in
the kitchen appliance section of Walmart or Target for cooking timers. They
will perform everything you asked for except for the relay output. However,
you can probably hack the unit and find a point inside that changes state
when the timer expires, and use that to trigger your relay.

--
Dave M
MasonDG44 at comcast dot net (Just subsitute the appropriate characters in
the address)

Never take a laxative and a sleeping pill at the same time!!


Bountyhunter

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Jun 12, 2005, 12:47:01 PM6/12/05
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Thanks! the timer need not be that accurat and need only have min and
sec indicators from 5 min down to 30 sec. I want to use discrete
componants and i realy want to build it myself. I would like to set the
min and sec separatly but two push buttons, one for up and one for down
will olso do.

Thanks

DaveM

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Jun 12, 2005, 7:27:09 PM6/12/05
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"Bountyhunter" <ja...@fronthosting.com> wrote in message
news:1118583263.8...@f14g2000cwb.googlegroups.com...
> Hi! an anybody please help me. I was looking for a electronic kit but
> cant find one anyware. I want to make it myself but need help with the
> design. I must be able to preset the time from 30 sec to 5 min with the
> time desplayed. When the preset time reaches 0 it must switch on a
> buzzer or switch a relay. I've seen some 5 x 8 dot matrix displays
> (ELM-2081EWA) that i was thinking of using. Can someone please help!!!!


"Bountyhunter" <ja...@fronthosting.com> wrote in message

news:1118594821....@f14g2000cwb.googlegroups.com...


A few counter kits that might interest you:

http://www.montek.com/cart/product.php?productid=27115
http://www.hobbyengineering.com/SectionEK.html
http://www.hobbytron.net/CE-CK1613.html?AID=10289758&PID=1374120
http://electronickits.com/kit/complete/elec/ck1612.htm
http://electronickits.com/kit/complete/elec/ck1613.htm

Ken Smith

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Jun 12, 2005, 7:32:52 PM6/12/05
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In article <1118594821....@f14g2000cwb.googlegroups.com>,


If not take a look at the CD4511 datasheet.

Basically you need 3 up/down counters.

The LSD of the seconds is a divide by 10.
The MSD of the seconds is a divide by 6.
The Minutes is a divide by 5.
--
--
kens...@rahul.net forging knowledge

Bountyhunter

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Jun 13, 2005, 12:24:23 PM6/13/05
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Thanks Dave.

I've had a lok around on those sites and seen a couple of
timers/counters, but I'm in Cape Town South Africa and the local
suppleir of those kits informed me that they can order it for me if I
take a minimum of 5. WHAT A LOAD OF CROC!!!!!!! I.m not that good
with electronics that i can figure out and design one on my own but can
read diagrams and put a little thinking like how a decade counter goes
with a 7 seg display ect. When it comes to the 5 x 8 dot matric
display, it a whole new balpark to me.

Thanks

Bountyhunter

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Jun 13, 2005, 12:27:34 PM6/13/05
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Hi Ken. I'm not that good at this game so you will have to explain a
little more
Thanks

John Fields

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Jun 13, 2005, 1:12:58 PM6/13/05
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On 13 Jun 2005 09:24:23 -0700, "Bountyhunter" <ja...@fronthosting.com>
wrote:

---
I'll be happy to help you out, but why do you want to use 5X8 matrix
displays?

--
John Fields
Professional Circuit Designer

JeffM

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Jun 13, 2005, 4:11:54 PM6/13/05
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>I'm not that good at this game
> Bountyhunter
>
It's obvious that you're new to Usenet too:
http://groups-beta.google.com/groups?scoring=d&filter=0&enc_author=uxGTLhYAAABxpKtgdtezs9xrngGNzqy_xtQP97naGHx3rA6c0Sncig
More below.

>so you will have to explain a little more
>

http://www.google.com/search?q=CD4511+datasheet


FYI, Google Groups is not Usenet; it is but one way of accessing
Usenet.

Most folks use a "newsreader" to read the groups.
http://www.google.com/search?&q=gravity+forte+xnews+40tude+mozilla
That means that the vast majority of people don't see what you see on
Google.

See how I went back and added a bit of your previous post to this post?
That is called **context**.
To get context the easy way:
(hint: Don't click the Reply link that is in plain sight),
click the **show options** link, then click THAT Reply link.

You don't have to re-post **everything** from the previous post;
feel free to snip out as much from the automated blockquote as you
wish.
I only leave enough to show what part I'm referencing ("context").
See above.

Read some threads and observe how others post, then do likewise.
.
.
Rich Grise (pointedly) remarks on context here:
http://groups-beta.google.com/group/sci.electronics.design/browse_frm/thread/3e13158594651a47/1569906f59f22fb6?q=include-context-when-you-post-from-google-groups+are-universally-hated+include-context

The guidelines for Usenet are here:
http://66.102.7.104/search?q=cache:8PaSp2kKbWoJ:www.faqs.org/rfcs/rfc1855.html+just-enough+at-*-top-*-*-message+do-not-*-*-*-original
(Worth scanning--especially the parts I've highlighted.)

Bountyhunter

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Jun 14, 2005, 2:14:13 AM6/14/05
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John Fields wrote:
> >
> ---
> I'll be happy to help you out, but why do you want to use 5X8 matrix
> displays?
>
> --
> John Fields
> Professional Circuit Designer

Thanks John,

The 5 x 8 is something that i've seen in a shop on display an it showed
up brighter than any other display in the shop, also then because of
the price of the that display is a tenth of the price of the same size
seven segment LED display.

Spehro Pefhany

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Jun 14, 2005, 6:58:42 AM6/14/05
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On 13 Jun 2005 23:14:13 -0700, the renowned "Bountyhunter"
<ja...@fronthosting.com> wrote:

They are more of a hassle to drive. Although you *could* make it work
without a micro, it would be even more hassle. Almost invariably they
are internally multiplexed so you have to generate the scan signals,
and you need a few hundred bits of ROM to store the characters (which
could be done with a generous handful of diodes, but it wouldn't be
pretty at all).

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
sp...@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

John Fields

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Jun 14, 2005, 9:31:38 AM6/14/05
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On 13 Jun 2005 23:14:13 -0700, "Bountyhunter" <ja...@fronthosting.com>
wrote:

---
As Spehro noted, if those are multiplexed displays, the job gets to
be much more of a hassle. What more can you find out about them? Are
they just 40 LEDs with 80 leads coming out the back or are there a lot
fewer leads? (Like 13 or 41?) Do you have or can you get their
manufacturer's name and their part number?

Ken Smith

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Jun 14, 2005, 9:46:22 AM6/14/05
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In article <1118680054....@g14g2000cwa.googlegroups.com>,

Feed: CD4511 datasheet into google to get the data sheet for the CD4511.

From elsewhere in the thread, I have learned that you want to drive a
matrix display. The CD4511 helps the most if you have a 7 segment
display.

Bountyhunter

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Jun 14, 2005, 1:23:14 PM6/14/05
to

> ---
> As Spehro noted, if those are multiplexed displays, the job gets to
> be much more of a hassle. What more can you find out about them? Are
> they just 40 LEDs with 80 leads coming out the back or are there a lot
> fewer leads? (Like 13 or 41?) Do you have or can you get their
> manufacturer's name and their part number?
>
>
> --
> John Fields
> Professional Circuit Designer

John!

This is a 14 pin matrix display. (ELM-2081EWA) If this display is that
big a problem, can I can make my own seven segment LED display with a
couple of super bright LED's? This will give me the same dislpay
brightness as the 5 x 8 matrix display but wil connect the same as an
common cathode seven segment display. As i dont need the timer to time
down for more than 5 min, i can make 3 of these units
Thanks
Edward

John Fields

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Jun 14, 2005, 4:30:18 PM6/14/05
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On 14 Jun 2005 10:23:14 -0700, "Bountyhunter" <ja...@fronthosting.com>
wrote:

>John!
>
>This is a 14 pin matrix display. (ELM-2081EWA) If this display is that
>big a problem, can I can make my own seven segment LED display with a
>couple of super bright LED's? This will give me the same dislpay
>brightness as the 5 x 8 matrix display but wil connect the same as an
>common cathode seven segment display. As i dont need the timer to time
>down for more than 5 min, i can make 3 of these units

---
You might be able to, but you'd wind up with some ugly characters.
Try it. Lay out a 5X7 array made out of circles (LEDs) and see what
it looks like. Don't forget that the LEDs you assign to a segment
have to stay there no matter what the character is.

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