timer/counter

[Qwerty]

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

 

[dmm]

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

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.

 

[Qwerty]

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

 

[Dac]

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).

 

[Brenden]

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

 

[Qwerty]

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

 

[jasen]

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.

Is this is for an "N days since last accident" sign ?

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')

stick it behind glass?

Bye.
Jasen

 

[Brenden]

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

 

[Qwerty]

that is one of the possible applications.