Re: Help me solve this design problem PLEEEZ

On Thu, 31 Mar 2005 09:21:54 -0500, Mark Jones <abuse@xxxxxxxxx>
wrote:

>bill.sloman@xxxxxxxx wrote:
>> You need an up-down counter and a slow clock - a 32,768 Hz source as
>> used in watches might serve as the clock, and counting five minutes of
>> that needs a 24-bit counter, for which you could use the LSI LS7166
>> 24-bit multimode counter (available ex-stock from Farnell). Multi-mode
>> includes up-down ....
>>
>> Of course, any single chip microcontroller could handle the job - the
>> Microchip Technology PIC series comes to mind (and Farnell have pages
>> of variants for you to chose from) though the Atmel AVR parts are
>> reputed to be nicer to work with. For this application you'd presumably
>> clock the microcontroller at 32.768kHz.
>>
>> ------------
>> Bill Sloman, Nijmegen
>>
>
>
> Or, of course he could do the dual 555 thing. One timer for "on time" and one
>for "off time", which added with some logic gates allows the first timer to work
>and produce an error condition. Sonalert module for audio alert. No 3 months
>required to learn PICs.

---
5 minutes is a little long for a 555, and 24 bits is a little much,
IMO, but a successful marriage might be a single 555 astable with a 20
second period and a 4 bit up-down counter.

--
John Fields
Professional Circuit Designer
.

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