Need a 5min.timer circuit

[Norm]

calculator? .....

I've just finished detailing how to tap into the

  button so you can hook up a reed switch, it

would be nice if I could make a timer for it to

keep it from shutting off after 5 minutes.

   complete details here:

http://www2.suite224.net/~peppysue/Projects.html

         Thanks for any help.

                    ( :>) Norm.

[Big All]

Or maybe what part of the board to short around to keep it from turning off.

I'm gonna stop by the dollar store tonight so I have a spare calc to futz with.

[Norm]

Yep...they're fun amazing what you get for a buck! Get the one with dual power...LeWorld, cost

the same as the cheap ink coated printed circuit,

maybe that ColdHeat solder gun would work on printed circuits the copper etched ones that is.

                Have Fun!

                   ( :>) Norm.

[Ungrounded Lightning Rod]

maybe that ColdHeat solder gun would work on printed circuits the copper etched ones that is.

Be careful with that one on boards with semiconductors on them.  It works by putting a large current in the wire to be heated.  Bridge it across a gap and it might electrocute a part.

Low voltage, granted.  But inductance could turn an interruption of its current into a high-voltage spike, and modern ICs are REALLY low voltage and VERY voltage sensitive - just a few volts can fry 'em - and an amp up the wrong lead can turn them back into sand.

[johnlm]

Norm,

I think a basic 555 timer ckt will serve your timer needs.  Do a search on hobby electronic ckts, they are all over the place out there.  There was a link to one of these hobby ckt sites on a post about a week to 10 days ago that had 555 timer ckts on it.

John

[Norm]

   Okay thanks for the reminder...in other words

scrap that idea and use regular small solder pencil for doing this type work as per Forrest M. Mims,III. or else cold connect like the unetched printed circuits, if you're not sure what you're doing? Might be the best way for real novices like me anyway.

   Wonder how many will try that 'tho....that one ad on TV shows that you can solder small

parts with it, so others might jump to the same

conclusion...hope they only try it on a $1 calculator.

                  Again Thanks for the warning.

                ( :>) Norm.

[Norm]

Or maybe what part of the board to short around to keep it from turning off.

  No I don't think that part is on the board

that is probably in the 'brain'.. part the Eprom?

  I guess I'll just look around on the internet

or unless someone here can tell me how... a capacitor and a resistor and maybe a 555?

                   ( :>) Norm            

[Norm]

 Whoops almost missed you there....thanks!

                  ( :>) Norm.

[ghurd]

Pushing "+0" is how I do it, but it would reset the automatic "+1".

Maybe electronicly push "+0, -1, +1" every 4 minutes?

G-

[Norm]

   Well if you were using it to count turns on a

coil, you wouldn't need it...but I was thinking

about counting the revolutions of a anemometer

in an hour at a time. An =  once every 4 minutes

would result in 15 extra 1's in an hour which

you could subtract afterwards.

           Fun!

            ( :>) Norm.

[Nando]

NORM:

 You could use 3 cmos devices = 4060 in series, the first set as an oscillator and the final output after 14 stages feeds a second one and the third gives a lower divison ratio, this way the oscillator can be set to around 1.11 or so miliseconds for 5 minutes = 300 second = 300 million microseconds

Let me know if interested

Regards

Nando

[Norm]

   Yes...I'm interested so give me some more detail....

   On second thought if it would make it just a

little less complicated and more economical even

a minute timer would work, if it would make for

less power consumtion....

   Well anyway let's see what happens eh?  

   Tried it out on my little windmill yesterday

, it had got up to 9748 last time I looked, went

back about hour later and it was blank evidently

the wind must have stopped blowing for a few

minutes.....

  Too bad those cheap little calculators had to

have a auto-shut off feature..

               Thanks for replying,

                   ( :>) Norm.

[ghurd]

""+0, -1, +1""

That should come out even.

G-