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74HC123 and long pulse

M

Marco Trapanese

Jan 1, 1970
0
Hi,

I'm looking for a dual (quad) monostable retriggerable multivirbrators
with minimal components count.

I need:

* +5V single power supply
* THT technology as well SMD
* "long" pulse width (> 500 ms - the 74HC123 doesn't seem to reach that)
* best would be one RC for all parts

Could you suggest me some products?

Thank you
Marco
 
J

Jan Panteltje

Jan 1, 1970
0
Hi,

I'm looking for a dual (quad) monostable retriggerable multivirbrators
with minimal components count.

I need:

* +5V single power supply
* THT technology as well SMD
* "long" pulse width (> 500 ms - the 74HC123 doesn't seem to reach that)
* best would be one RC for all parts

Could you suggest me some products?

Thank you
Marco

PIC
LOL
 
T

TTman

Jan 1, 1970
0
Marco Trapanese said:
Hi,

I'm looking for a dual (quad) monostable retriggerable multivirbrators
with minimal components count.

I need:

* +5V single power supply
* THT technology as well SMD
* "long" pulse width (> 500 ms - the 74HC123 doesn't seem to reach that)
* best would be one RC for all parts

Could you suggest me some products?

Thank you
Marco

MC14538 will do 20 seconds easy. 2u2+10M so 100N+512K will do
500mS.....tolerance/accuracy is up to you.
 
M

Marco Trapanese

Jan 1, 1970
0
TTman ha scritto:
MC14538 will do 20 seconds easy. 2u2+10M so 100N+512K will do
500mS.....tolerance/accuracy is up to you.


Great! That's what I was looking for.

Marco
 
N

Nico Coesel

Jan 1, 1970
0
Marco Trapanese said:
Hi,

I'm looking for a dual (quad) monostable retriggerable multivirbrators
with minimal components count.

I need:

* +5V single power supply
* THT technology as well SMD
* "long" pulse width (> 500 ms - the 74HC123 doesn't seem to reach that)
* best would be one RC for all parts

Could you suggest me some products?

NE555 NE556 NE558
 
J

Jim Thompson

Jan 1, 1970
0
LM555 or mc1455

Cheers

I prefer 'HC4538 for such long-time-constant tasks.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Stormy on the East Coast today... due to Bush's failed policies.
 
J

Jan Panteltje

Jan 1, 1970
0
LM555 or mc1455

Yes those will work, but then require 4 caps and 4 resistors at least.
With 4 inputs, 4 outputs, 2 power, a 14 Ppin PIC will do, and have prosessing
to spare that could possibly be used for something too.
Like for example a 16F505
http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en020096
NO external components needed, use internal RC oscillaor.
You can use 4 port interrupts and look in the interrupt routine which
one it was, and start a counter.
Main routine can do software increment of the counters and set outputs
after so many ms, with quite a high accuray.
There are many other ways to do it too.

Why keep all that antique analog stuff around?
 
J

Jan Panteltje

Jan 1, 1970
0
Yes those will work, but then require 4 caps and 4 resistors at least.
With 4 inputs, 4 outputs, 2 power, a 14 Ppin PIC will do, and have prosessing
to spare that could possibly be used for something too.
Like for example a 16F505
http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en020096
NO external components needed, use internal RC oscillaor.
You can use 4 port interrupts and look in the interrupt routine which
one it was, and start a counter.
Main routine can do software increment of the counters and set outputs
after so many ms, with quite a high accuray.
There are many other ways to do it too.

Why keep all that antique analog stuff around?

PS and PIC16F505 is 61 Euro cents for 1 piece,
can you buy 4 555, 4 caps, 4 resistors for that?
Plus the board space?
 
M

Marco Trapanese

Jan 1, 1970
0
Jan Panteltje ha scritto:
Main routine can do software increment of the counters and set outputs
after so many ms, with quite a high accuray.
There are many other ways to do it too.

Why keep all that antique analog stuff around?


I bet a PIC couldn't update outputs after 20 ns...

Marco
 
J

Jan Panteltje

Jan 1, 1970
0
Because it doesn't need a dev system, doesn't need to have code
written and debugged, doesn't need chips to be programmed on a
production basis, doesn't need a JTAG header, isn't threatened by
parts going obsolete, doesn't need reprogramming to change delays, and
generally has less jitter?

Oh, yes, almost all true.
Obsolete? PIC has been around as long as any other suff, in more variants.
So you included trimpots too?
Hope you are not still using those papper caps ;-)
 
J

Jan Panteltje

Jan 1, 1970
0
Jan Panteltje ha scritto:



I bet a PIC couldn't update outputs after 20 ns...

No, but you could add some 74HC [D]flops for that part.

Still no caps and resistors.
 
M

Martin Riddle

Jan 1, 1970
0
Jim Thompson said:
I prefer 'HC4538 for such long-time-constant tasks.

...Jim Thompson

I use that part often, nice non retriggable dual one shot.

Cheers
 
J

Jan Panteltje

Jan 1, 1970
0
What's the lifetime of a given PIC chip? Variants don't help much if
you have to re-do everything when a chip goes EOL.

In my experience pic compatibility is really good.
Even beyond PICs generations, I have used a PIC to replace dedicated chips.

If adjustable delays are useful, maybe so. How do you change or adjust
the delays on an embedded PIC?

If the PIC has EEPROM, RS232: just bring out one pin for Rx at TTL level,
it only has to listen, you can of course bring out the TX too, and read status.



Bit of overkill for this application :)


It can store lists of delay and width settings, and advance to the
next set every trigger. So it does delay hops, sweeps, patterns, stuff
like that.

Woodstock: Let us do the hop - remember that ? -
 
T

Tim Williams

Jan 1, 1970
0
   Has anyone made paper caps in the last 20 years?

I sincerely hope not! I just got through recapping a Philco TV set
from 1952. Replaced all capacitors and a few faulty tubes and it
sprang back to life, good as new. (Most of the original carbon comp
resistors are even in tolerance!)

Incidentially, I discovered that not all of the box shaped, dot-
labelled capacitors are mica. The bigger ones (>1nF) are paper
inside.

Tim
 
N

Nico Coesel

Jan 1, 1970
0
Jan Panteltje said:
Yes those will work, but then require 4 caps and 4 resistors at least.
With 4 inputs, 4 outputs, 2 power, a 14 Ppin PIC will do, and have prosessing
to spare that could possibly be used for something too.
Like for example a 16F505
http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en020096
NO external components needed, use internal RC oscillaor.
You can use 4 port interrupts and look in the interrupt routine which
one it was, and start a counter.
Main routine can do software increment of the counters and set outputs
after so many ms, with quite a high accuray.
There are many other ways to do it too.

Why keep all that antique analog stuff around?

Because it works? OTOH, changing the timing in an analog circuit is
difficult if it means modifying a lot of components on a lot of
boards. If you go analog, you must be sure it is right before going
into production. Which is not necessarely a bad thing because it
forces you to really think about what you're doing.

I recall designing a device and using a GAL16V8 for some simple logic
functions (including some timing). I used an extra 74HC14 to have
schmit-trigger inputs for the RC timing networks. Having something
programmable in a circuit can help to implement those last-minute
changes some customers like to make.

But... using a PIC is a really bad idea. I never was a fan of PIC
controllers based on what I've seen being made with PICs and the specs
from Microchip. Unfortunately one of my customers has a product for
which the PIC 16Fxxx firmware needs to be rewritten by me. Throwing
out the stock is just too expensive. The PIC processor's architecture
is even worse than I thought. Multiple memory banks, weak instruction
set. I need to jump through a lot of hoops to write C code for it and
work around the flaws in the hi-tech compiler. Can't even re-use
existing C code because pointers don't work well with multiple memory
banks. Having all data global is the most convenient. Altogether it
costs a lot of extra development time (=money). I start to wish they
had used an 8051! The PIC really is a dead-end around the next corner
if you want to get some serious work done.
 
S

Spehro Pefhany

Jan 1, 1970
0
What's the lifetime of a given PIC chip? Variants don't help much if
you have to re-do everything when a chip goes EOL.


More than 10 years seems to be okay if you don't mind minor changes
(like from OTP to flash), at least for the simpler chips. I don't
think they're any worse than any other part.
If adjustable delays are useful, maybe so. How do you change or adjust
the delays on an embedded PIC?

Tripot across Vdd-Vss and read it with a 10-bit ADC, you could have
the range from 0.5 to 0.6 seconds or whatever you like.

I just stuck a low end micro (happened to be a PIC) in as a 5-second
monostable to protect a sensor against idiotic^H^H^H^H buggy software.
No external components (power gets cycled every time it operates). I
think the code took less time than it would have to do a worst-case
calculation of analog timer periods.

And low end dev kits capable of doing debugging cost less than a cheap
PCB turn, so that's no longer an excuse. ;-)


Best regards,
Spehro Pefhany
 
D

David L. Jones

Jan 1, 1970
0
Martin said:
LM555 or mc1455

The OP asked for minimal component count.
A micro (PIC or whatever) is best for that

Dave.
 
N

Nobody

Jan 1, 1970
0
But... using a PIC is a really bad idea. I never was a fan of PIC
controllers based on what I've seen being made with PICs and the specs
from Microchip. Unfortunately one of my customers has a product for
which the PIC 16Fxxx firmware needs to be rewritten by me. Throwing
out the stock is just too expensive. The PIC processor's architecture
is even worse than I thought. Multiple memory banks, weak instruction
set. I need to jump through a lot of hoops to write C code for it and
work around the flaws in the hi-tech compiler. Can't even re-use
existing C code because pointers don't work well with multiple memory
banks. Having all data global is the most convenient. Altogether it
costs a lot of extra development time (=money). I start to wish they
had used an 8051! The PIC really is a dead-end around the next corner
if you want to get some serious work done.

You're comparing a PIC to a real CPU. This thread was comparing a PIC to
74-series logic. Do you actually need to use C (with pointers, relocatable
code etc) to write the firmware for a quad monostable?
 
D

David L. Jones

Jan 1, 1970
0
Nico said:
Because it works? OTOH, changing the timing in an analog circuit is
difficult if it means modifying a lot of components on a lot of
boards. If you go analog, you must be sure it is right before going
into production. Which is not necessarely a bad thing because it
forces you to really think about what you're doing.

I recall designing a device and using a GAL16V8 for some simple logic
functions (including some timing). I used an extra 74HC14 to have
schmit-trigger inputs for the RC timing networks. Having something
programmable in a circuit can help to implement those last-minute
changes some customers like to make.

But... using a PIC is a really bad idea.

Tell that to the countless manufacturers who use PIC's in almost every
conceivable embedded device on the market.
They didn't make it to the #1 position in 8 bit micros at one stage for no
reason.

Dave.
 
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