help me about 555

[E.persia]

hi
I have a project that is connected with the famous 555 timer
I want ask you if you know a newwer chip with the better feature ...
this is very urgent to me
thank you all!

 

[Yukio YANO]

E.persia wrote:

hi
I have a project that is connected with the famous 555 timer
I want ask you if you know a newwer chip with the better feature ...
this is very urgent to me
thank you all!

I came across a 555 chip with an on board programmable divider ! This
increased the range and accuracy !

Part of a Timer I disassembled about 25 years ago don't remember the
Chip # ?

Yukio YANO

 

[Bill]

On Thu, 04 Sep 2008 22:13:11 GMT, Yukio YANO <yano@shaw.ca> wrote:

I came across a 555 chip with an on board programmable divider ! This
increased the range and accuracy !

A divider would increase the range and resolution, but not the
accuracy, which is determined by the oscillator (R, C, threshold
variance, etc). If the oscillator is 5 % accurate to generate a 50 ms
pulse, it is also 5 % accurate to generate a 5 minute pulse.

Best,

 

[Rich Grise]

On Thu, 04 Sep 2008 21:09:14 +0100, Electronworks.co.uk wrote:

The 7555 is a lower power version.

Apart from that, the 555 hits the nail on the head for most low cost designs
(ie consumer electronics) applications I ever come across.

What are you looking for in the newer chip that the 555 does not do?

His homework.

Cheers!
Rich

 

[Michael Black]

On Thu, 4 Sep 2008, Yukio YANO wrote:

E.persia wrote:
hi
I have a project that is connected with the famous 555 timer
I want ask you if you know a newwer chip with the better feature ...
this is very urgent to me
thank you all!

I came across a 555 chip with an on board programmable divider ! This
increased the range and accuracy !

Part of a Timer I disassembled about 25 years ago don't remember the Chip # ?

The XR-2240. Put a ripple counter in the same package as an RC timer.

But, the thing about the 555 was that it was general enough to find
lots of use. You could use it as a monostable, or an astable, you could
use it as a latch, you could use it as a driver when more current was
needed, you could use it for all kinds of things. Because while it
was designed as a timer, it brought enough out to the pins to make
it versatile. It came out at a time when CMOS was barely available,
and TTL was king, yet here was a device that could do some logic functions
yet run over a wider voltage range than TTL.

It was succesful, because of that versatility. The early datasheet
and application note were full of things you could use it for that
wasn't about "timing". And as soon as it was out of the gate, other
people cooked up things to use it for.

The success brought other IC timers. Walter Jung's IC Timer Cookbook
from about 1977 is full of various things you could do, and the also
rans that came along in the wake of the 555. Quad timers like the 558.
Things like the XR-2240. "Precision timers", the numbers I can't
remember.

Yet those also rans are vague to most, because they never
had the success of the 555. They undoubtedly were good for what
they did, but they didn't do much beyond what they were good for.
It was much easier to stock the 555, and add a counter or whatever,
than to have all those different types of IC timers around, which
much of the time wouldn't have a use.

Michael

 

[Michael Black]

On Fri, 5 Sep 2008, Bill wrote:

On Thu, 04 Sep 2008 22:13:11 GMT, Yukio YANO <yano@shaw.ca> wrote:

I came across a 555 chip with an on board programmable divider ! This
increased the range and accuracy !

A divider would increase the range and resolution, but not the
accuracy, which is determined by the oscillator (R, C, threshold
variance, etc). If the oscillator is 5 % accurate to generate a 50 ms
pulse, it is also 5 % accurate to generate a 5 minute pulse.

But, if you've got a really long time period, it's far easier to

adjust a clock running much faster than waiting all that time to
see if the output matches the desired time. You can adjust and
see the results almost immediately, whereas if you've got a 555
with a 5 minute cycle, you have to wait five minutes between
any adjustment.

Plus, it's easier to get better tolerance capacitors in small
values than cheap electrolytics, which is what a lot of people
would end up using if they needed long time periods. Likewise
the resistors become reasonably valued, rather than tens of megohms
where external factors may add resistance in parallel to the
timing resistor.

It's not that the XR-2240 makes things more accurate, but the
arrangement makes it easier. Of course, you can do the same
thing with a 555 and a separate divider.

Michael

 

[E.persia]

hi every body
I think you are right
may be my explaination make the subject more obvious
I'm gonna make a moisture capacitive sensor for a specific oilseed ...
the moisture will be checked by the capacity that will change respect
to the dielectric beetween the plates(the oil seed)
I use this capacitive as the C in unstable multivibrator to make
square waves with diffrent T that a micro going to read it and so on
but my problem is :because of the C range (50 to 100 pf) I have to use
very big R to have a better T and in that way it can't feed the
current for 555 to be in the ideal range of work
so it's my complete problem
is ther any ic for me
is there any way to sove this problem

thank you all!

 

[gs]

E.persia wrote:

hi
I have a project that is connected with the famous 555 timer
I want ask you if you know a newwer chip with the better feature ...
this is very urgent to me
thank you all!

Well there came a nice LM3905 with some neat features, then
they got rid of it.

greg

 

[Jamie]

E.persia wrote:

hi every body
I think you are right
may be my explaination make the subject more obvious
I'm gonna make a moisture capacitive sensor for a specific oilseed ...
the moisture will be checked by the capacity that will change respect
to the dielectric beetween the plates(the oil seed)
I use this capacitive as the C in unstable multivibrator to make
square waves with diffrent T that a micro going to read it and so on
but my problem is :because of the C range (50 to 100 pf) I have to use
very big R to have a better T and in that way it can't feed the
current for 555 to be in the ideal range of work
so it's my complete problem
is ther any ic for me
is there any way to sove this problem

thank you all!
Use a dual 555 (556) system and gate the outputs as mixer effect.

you set one at a standard with a null pot and the other will
be attached to the capacitor plates.

With that, you can select a much higher range of frequency to
work with and product a lower freq offset. etc..

http://webpages.charter.net/jamie_5"