4017 chip won't behave!

[[email protected]]

Very good point- one of the most accurate long duration timebases available for applications like this is the power line. You should get +/- a few seconds accuracy over a seven day interval. The OP really needs something like this:

http://www.intersil.com/en/products/timing-and-digital/rtcs/real-time-clocks/ISL12032.html

There he has provisions for battery backup and external crystal timebase to coast through black/brown-outs. It can't miss. The drawback is it needs a controller, but it's worth the effort for the vastly improved performance over what he has now.

Thanks, but it's way too much for my modest requirements. JF's design should do nicely if I can get it up and running.

 

[[email protected]]

---



I tried to simulate the circuit and it seems that something is very

wrong.



I'll see if I can find out what the problem is and post back when I

do.



Sorry 'bout that. :-(

Thanks very much, John. I'm sure a man of your caliber won't struggle too much to get to the root of the problem, whatever it is. I've already orderedthe NAND gat chip but haven't laid out a new board yet, so no harm done!
I'll be interested to read your findings in due course...

 

[[email protected]]

---



I tried to simulate the circuit and it seems that something is very

wrong.



I'll see if I can find out what the problem is and post back when I

do.

You want to use Q0 of each counter to clock the succeeding stage and not Q9.. A rising edge on Q0 of any single stage means it has received ten clocks,so that is the time to increment the next decade by one. You probably wantto include a manual MR input too. Maybe not a bad idea to add some filtering to the 555 trigger to avoid false triggering due to decoding hazards by the '30.

 

[[email protected]]

You want to use Q0 of each counter to clock the succeeding stage and not Q9. A rising edge on Q0 of any single stage means it has received ten clocks, so that is the time to increment the next decade by one. You probably want to include a manual MR input too. Maybe not a bad idea to add some filtering to the 555 trigger to avoid false triggering due to decoding hazards by the '30.

You could use the CARRY_OUT too, same difference, the leading edges are coincident.

 

[[email protected]]

You could use the CARRY_OUT too, same difference, the leading edges are coincident.

Thank you for your interest, Fred. The more the merrier.
John, if you could post the LTSpice netlist for your suggested circuit thatwould be very helpful to my understanding at this end. Thanks again.

 

[josephkk]

On Tuesday, 11 December 2012 15:36:58 UTC+1, John Fields wrote:

OK. Thanks for the datasheet link. The sheets I've seen up until now have been very terse affairs, badly photocopied and hard to see. This oneis way more informative.
I'm not in a position to post a schematic at this time, but from what you said in your last post it wouldn't assist much if the chips I'm usingare wrong.

Basically all I want to do is make up a time-lock for a cash safe. Aftera 7 day delay during which the safe remains locked shut, one timed pulseof 1 second releases its electromagnetic lock and the safe can be opened. Obviously that pulse if it's from CMOS will need to be beefed up to actuate the lock, but that's the easy bit.
Why are 4017s not suitable for the timing part of the application?

Oh my. Hitting a one second window once a week is very difficult in human
operated systems. Perhaps you may wish to be more thoughtful about your
design requirements.

All in all this application begs for a micro-controller based solution.

?-)

 

[Jasen Betts]

Basically all I want to do is make up a time-lock for a cash safe. After a 7 day delay during which the safe remains locked shut, one timed pulse of 1 second releases its electromagnetic lock and the safe can be opened. Obviously that pulse if it's from CMOS will need to be beefed up to actuate the lock, but that's the easy bit.
Why are 4017s not suitable for the timing part of the application?

For large counts chips like 4060 and 4040 may be easier to use

A 4060 running with the oscillator running at 16Hz will produce
1hz pulses on pin 7 and a period of 1024 seconds on pin 3

A week is 604800 seconds so you need to divide that rate by 590

Which can probably be done using a diode-and and a 4040 counter.

A D-type flip-flop to mix that with the 1hz rate to get the 1 second
pulse and another flip-flop to halt the circuit after that.

If you can live with slightly wider pulses to the output you can use
a divide bt 512 instead of 590 which is easier to arrange using these
binary counters.

if you need more precision than the R-C oscillator at the input can
provide perhaps you can use the frequency of the AC supply.

 

[[email protected]]

All in all this application begs for a micro-controller based solution.

Too unnecessarily complicated for my modest purposes, I'd say. That's why I'd like to stick to something close to the original concept. The circuit John Fields posted, if it can be fixed-up, would be close to ideal for me.

 

[[email protected]]

if you need more precision than the R-C oscillator at the input can

provide perhaps you can use the frequency of the AC supply.

I had considered this. Sniff some mains inductively, then pass it through arectifier and an inverter/Schmidt trigger to convert it to a square wave and then count the pulses up to a pre-determined limit. Accurate for sure, but not being terribly au fait with what chips are out there I don't know ofan IC that could count up to 604,800 decimal and put out a signal pulse when that target has been reached. I'd still rather stick with JF's design...

 

[[email protected]]

I had considered this. Sniff some mains inductively, then pass it througha rectifier and an inverter/Schmidt trigger to convert it to a square waveand then count the pulses up to a pre-determined limit. Accurate for sure,but not being terribly au fait with what chips are out there I don't know,of an IC that could count up to 604,800 decimal and put out a signal pulsewhen that target has been reached. I'd still rather stick with JF's design....

Sorry, that should have been 604,800 x 50 from a 50Hz mains source...

 

[[email protected]]

Thanks for the update, John. Nice to hear you didn't have to do any furthermods on it. After a great deal of fruitless searching my ISP has informed me they no longer provide access to alt.binaries hierarchy and couldn't or wouldn't give me a reason! The netlist is just ascii so could you post it here, perhaps?
TIA.

 

[[email protected]]

---

Yes, but it uses different parts than those supplied with LTspice so

you couldn't see the schematic properly, or run it.



If you email me your email address I'll get the files to you that way.

You're a gentleman, sir.

 

[[email protected]]

Too unnecessarily complicated for my modest purposes, I'd say. That's whyI'd like to stick to something close to the original concept. The circuit John Fields posted, if it can be fixed-up, would be close to ideal for me.

complicated? it is an 8pin part and a few lines of code

-Lasse

 

[[email protected]]

complicated? it is an 8pin part and a few lines of code

Yes. Complicated for *my* modest needs. I don't require a Raspberry Pi or even a mere PIC for a 7 day timer!

 

[[email protected]]

Yes. Complicated for *my* modest needs. I don't require a Raspberry Pi oreven a mere PIC for a 7 day timer!

guess there's different kinds of complicated there': a 50cent pic/avr
etc. with everything including the oscillator in a 8 pin package and
then there's a whole gaggle of logic ic's and some sort of oscillator

-Lasse

 

[Ralph Barone]

Sorry, that should have been 604,800 x 50 from a 50Hz mains source...

So divide it twice. 30,240,000 must have two factors that make the design
simple. Choose one to be a large power of two for elegance and just brute
force the other divider.

 

[Jeroen Belleman]

guess there's different kinds of complicated there': a 50cent
pic/avr etc. with everything including the oscillator in a 8 pin
package and then there's a whole gaggle of logic ic's and some sort
of oscillator

You know quite well that the hardware complexity of a micro-
controller solution has nothing in common with that of wired
logic.

The hassle of installing the software, learning the chip's
structure and language, getting to grips with flashing the
thing, etc. is a good deal more involved than wiring a few
CD4017s together. Of course, once you've mastered all that,
the project becomes immensely easier and blows most slow
discrete logic designs completely out of the water.

It's a hurdle, to be sure, but it's worth the investment.

Jeroen Belleman

 

[[email protected]]

---
Actually, it's a little more complicated than that since to get the
timing exactly right, going that way, one needs to consider the
instruction execution time.

Have you considered that?

have you? where, in counting the number of timer ticks until you
reach 7 days,
does instruction time enter the equation?

you are concerned about the few nanonseconds it takes to set an output
when
the 7 days has passed?

-Lasse

 

[[email protected]]

uP's are the "solution" to all problems... and generally also the
failure mechanism.

so are transistors ic's etc. I don't see the difference

-Lasse

 

[Jasen Betts]

complicated? it is an 8pin part and a few lines of code

Do you now of a cheap usb pic programmer with linux support?