555 mono (restriction on Resistance value)

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vinodquilon

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Find the attachment (https://www.scribd.com/doc/27157788) . The purpose of the circuit is to turn on reed relay for 60sec, when
first ring_signal occurs. For that I have to use C= 100 uF & R= 560 K. But somewhere I have
read, in the design of 555 mono take R= 10 K to limit current through the internal transistor
to 1 mA.
Is it correct ? Can I use 560 K ?

It is my first time experience with Eagle to draw schematic. If someone notice any drawing faults
in my schematic, pls inform me to improve my drawing skill with Eagle.....
 

shouldn't be a problem,
I recall long time ago experimenting with long term delay, ie > 1hr and using > 1MOhm+ and 1000uF for C.
repeatable accuracy is not so great the longer the delay is.

You might prefer to do this with the CMOS version of 555, ie 7555.
Its an improved product.

the 555 must be the most ubitious IC of all time
 


Thanks xaccto,
It is first time I heard about 7555. Thanks a lot.....
 

Hi,
CMOS version as 7555 is surly a possibility, but in my opinion is more reliable if you take a CMOS counter with oscillator (I think CD4040 or 4060?) and you have the needed low frequency signal on the output.
It has very low current need too.
K.
 

karesz said:
Hi,
CMOS version as 7555 is surly a possibility, but in my opinion is more reliable if you take a CMOS counter with oscillator (I think CD4040 or 4060?) and you have the needed low frequency signal on the output.
It has very low current need too.
K.
Click to expand...

The CD4040 don't have built-in oscillators so forget about using them for this application.
The CD4060 is too old because the CD4541 does its job much better.
 

For jobs like that you may consider PICAXE08 ..
Some times it is called the new millennium 555 ..
Not only you don’t need to worry about R or C, and triggering the 555-timer on power-on can cause some problems ..
Nothing like that with PICAXE, if you need to change time, or delay, or generate slow or fast wave – everything is done in the BASIC language and PICAXE-BASIC is probably the simplest dialect of all of BASIC dialects ..

Foe example: 1s delay
WAIT 1000
That’s all ..

There are tons of publications on the web, just GOOGLE for PICAXE ..

Rgds,
IanP

https://www.technologystudent.com/pics/picax1.htm
**broken link removed**
 

Simple PICAXE-08 program to create accurate 60 sec output time delay when first ring trigger occurs.

start:
if pin3=1 then holdoff
goto start

holdoff:
high 2
wait 60
low 2
goto start


See the attachment. Opto-couplers' output goes to IP 3 (pin no.4) of PICAXE-08.
I will connect IP/OP 2 (pin no.5) of PICAXE-08 to base of relay driving transistor BC547.
Thus I can accurately turn on relay for 60 sec when first ring signal comes.

I am newbie in the field of PIC microcontroller. Thanks for all help by IanP of edaboard.

I couldn't find any eagle libraries for PICAXE-08 on cadsoft. Does anyone have ?
 

vinodquilon said:
..The CD4040 don't have built-in oscillators so forget about using them for this application.
The CD4060 is too old because the CD4541 does its job much better.
Click to expand...
My friend,
I had a "?" setted...
Otherwise; if you knows all things so good: what do you wished with your questioning pls; it exist in moderner versions too as 74HCxxx...
Sorry, I think nobody need a "jobtherapy" from you her.
K.
btw, I agree with JanP, the PICAXE08 (& some others too) is better for thes job.
 

 

The point is, once you start using something like PICAXE you will (most likely) never look back at 555-s and co. because of versatility and easiness ..
It’s just sentiment of old-school engineers ..

BTW, PICAXE can operate from 3V to 5.5V and for 1s delay (my mistake) one uses PAUSE 1000 (or WAIT 1) command ..
Max. current (sunk or sourced) by any I/O pin is 25 mA ..

Rgds,
IanP
 

Hi xacto,
Im an old schol type, but in some projets are from me too (if it was better/neede) PICs/MSPs.. applied...
Iou should not so rash tell some thing over inpossibilities pls!
Long time delay begins usual at 1--10 sec, in from so long timing is usual better to apply some speeder oscillator & a counter_maybe programmable; thes isnt modernst circuit technique!
Over 30-40 yeras means "s the solution" for delays/timings for i.e. minutes/hours...
A PIC nowadays is only a moderner & compacter version of that!...
If you needs more as 25 mA a transistor is really nothing today! You need as developer of reliables so & so a driver after your intelligent circuit...
I think nobody other has some problem with a 5V circuit, even with relay outputs not.
"in are" so & so the 3V3 or less power systems
Greatings!
K.
 

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