From: Fred Bloggs
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Subject: Re: Design for long interval timer
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Date: Wed, 04 Dec 2002 15:21:41 GMT
NNTP-Posting-Date: Wed, 04 Dec 2002 07:21:41 PST
Organization: EarthLink Inc. -- http://www.EarthLink.net
Spehro Pefhany wrote:
> On Wed, 04 Dec 2002 14:43:10 GMT, the renowned Fred Bloggs
>>I just went to Fairchild and entered MC14541 in parts search, it
>>returned 0 results...????
> Ah, you often drop the leading 1 when looking up Motorola original
> part numbers at other places (except On, of course).
This is a slightly different part. For one thing the Auto Reset works
down to 3V on this one, another difference is that Fairchild has
tightened up Vdd range for the timing accuracy by a factor of two over
ON. Notice the logic diagram! Fairchild has inserted the inverter
between MODE and the RS-latch, where ON erroneously omitted it-)
>>>I just cracked the case on a Radio Shack #23-406 NiMH charger,
>>>and it indeed contains one of these chips. The charger works fine,
>>>BTW, it's a timer plus a number of current sinks.
>>Maybe it does and maybe it doesn't.
> The 'charging' LED indicators always seem to be in the appropriate
> state, which tells me the timer is doing exactly what it should.
> It's a 4 hour charger, BTW.
>>Can you tell us how they have the
>>timer configured- there are so many options?
> Not right now, I'll try to trace it out later in the week. It's
> not a very nice construction for casual examination- flat cables
> that will fatigue off easily connecting two PCBs in rather cramped
> conditions. Designed for manual China manufacturing.
I bet it's flawed.