timer/counter

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I am looking for a circuit that will activate a trigger every 24 hrs and count
the pulses and
display the count using 3 or 4 7 segment led displays (the display will need to
be resetable).

I need something that is fairly power efficient as it would probably be battery
operated. Any suggestions??

TIA



Re: timer/counter



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the pulses and
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be resetable).
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operated. Any suggestions??
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There are several microcontrollers that have very low current usage. Texas
Instruments MSP430 series,
some Atmel AVRs, and Microchip PICs, etc.

7 segment led displays are great users of current, so an LCD would be my
preference.

The AVR Butterfly is a cheap (~$30) development tool that has on-board an
ATMega169 microcontroller,
4Mbit dataflash, 32KHz crystal, speaker, 100 segment lcd, light and temperature
sensors and a battery,
all on one credit card sized board. I think Soanar handle it.

Dontronics has a MSP430F2131 (8K program flash, 256 bytes data and 256 bytes
data flash) header
board for about $20. Just add a cheap off-the-shelf 16x2 LCD and some buttons.
Those should be
banging around in any engineer's or technician's box-o-bits. Code examples for
the MSP430 series
are freely available on the 'net, and it's supported by the Yahoo MSP430 group.

For such a simple application, tools such as the Butterfly or the 'F2131 might
be considered an overkill,
but when you have all (or nearly all) the hardware on one small cheap board, it
makes it difficult to
ignore them, especially if there won't be many units in the field.

One thing you didn't mention, is how many pulses per 24 hour period you are
expecting.


Re: timer/counter


Thanks for the reply.

Pulses, well the way I was originally thinking was to use the pulse to trigger
the LED display - so that would
be 1 pulse per 24 hours time frame.

Basically I need a timer that will count and displays days that have past. My
original post was not all that clear -
teached me to avoid posting when not feeling so great.

The display has to be visiable from 10' away which is why I was thinking LED's
(not above using an external
power supply if have to, I know solar cells are not enough to drive a LED
display). Exploring all options right now.

thanks again,
Tim

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the pulses and
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to be resetable).
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battery operated. Any suggestions??
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Instruments MSP430 series,
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preference.
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ATMega169 microcontroller,
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sensors and a battery,
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data flash) header
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Those should be
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the MSP430 series
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be considered an overkill,
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makes it difficult to
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expecting.


Re: timer/counter


May I ask what application this is for and what you want to spend? How
accurate does the 24 hours have to be? We have literally $50 units that have
2.5 inch 7 segments displays running ATMEL Cpus with realtime clocks. They
would raw a few microamp in sleep mode. You would have to toggle a switch to
turn on the LED display, otherwise you would pulse it and its brightness
would be really low (unless you get a giant battery of course).

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Re: timer/counter


Information purposes of the number of days past since an certain event. They
almost need
to be displaying info almost constantly (external power supply may have to be
used). It needs
to count to probably 999 days.

How big are the units (mostly interested in depth) and can an external source be
applied? It
will also need to be modifiable (ie: key switch installed for the reset - so as
it can only
be reset via 'authorized person') :)

Direct contact info?

Thanks,
Tim

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Re: timer/counter


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almost need
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used). It needs
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Is this is for an "N days since last accident" sign ?

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be applied? It
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as it can only
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stick it behind glass?

Bye.
   Jasen

Re: timer/counter


You could use mechanical flip over segment type displays, this way power
would only be needed for a brief period once a day to change the digits,
and when the unit was reset.

Is solar power an option, with some small cells and a rechargable
battery (or supercap) to keep it running at night?

Otherwise, Large LCD units are available from selected sources.

Dallas makes a 32KHz temp compensated oscillator module the DS32KHz
which gives 4 minutes a year accuracy over a pretty good temperature
range. This could be fed into any microcontroller you like to run the
clock accurately without a lot of messing about with calibration.


Regards,
         Brenden Ede


jasen wrote:
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almost need
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used). It needs
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be applied? It
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as it can only
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Re: timer/counter


that is one of the possible applications. ;)
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Re: timer/counter


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the LED display - so that would
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original post was not all that clear -
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(not above using an external
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display). Exploring all options right now.

a large (eg 30mm high) LCD would be readable from that distance.
the sort of thing that's used for LCD wall clocks)

--

Bye.
   Jasen

Re: timer/counter



How many days do you need to count to?

Perhaps you could just have 1 low duty cycle blinking LED for each day
that has elapsed. This would only work if the number of days was less
than 20 or so or else the unit would be impractically large.

There's heaps of micros that could do the function and you could power
it from 2 Alkaline cells if you kept the power use low.

Regards,
        Brenden Ede




jasen wrote:
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the LED display - so that would
Quoted text here. Click to load it
original post was not all that clear -
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(not above using an external
Quoted text here. Click to load it
display). Exploring all options right now.
Quoted text here. Click to load it

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