Hi Fields,

I´m researching the 40103. It seems a good solution. Looking forward for the schematic.

Thanks a lot!

 

nonsense?[/QUOTE]

Yes, since if you don't specify the accuracy you need/want in the beginning, the whole thing turn seems like a massive waste of time.

Anyway, a schematic for you follows. The counter on the left is the 30 minute timer and the counter on the right is the 180 second timer and you program them by setting the broadside inputs in binary, with the MSB being on the top. once the inputs are set, S1 is pressed which will load the counters with their data and they'll start counting down to zero, one at a time. The short counter starts first, and when it times out it RESETS the RS latch, U5, which inhibits the short counter and enables the long counter. The long counter will then start counting and when it times out it'll SET the latch and start the count cycle anew. I ran the thing through LTspice and its output plot under the schematic says the thing works. If you like I can post the .asc file so you can play with the circuit.



It's designed to run using a 1 second clock, and Digi-Key has a nice one from Abracon, for about USD 2, so you can save all that hassle with endless trimming and build something that just works.

The output from U5 is HCMOS, so if you want to use it to drive a relay you should probably buffer it with a transistor to keep from hurting the gate.

Finally, I haven't minimized the logic and there are some gates left over with unused inputs which MUST be terminated to either ground or the positive rail.

 

Anyway, a schematic for you follows.

Much of the text is to small to read. What are the timer chip part numbers?

ak

 

Much of the text is to small to read. What are the timer chip part numbers?

ak

Yeah, sorry about that . I'll fix it as soon as I can get to it.

In the meantime the counters are 40103s.

 

Fields isn´t this solution a little bit to much. I mean 4 CI and one clock generator. I like the idea to make the counting very precise and the possibility to display the counter with and extra CI and extra components. But then i come back to the idea you called nonsense, to use a micro-controller.

Also, with a 16Khz crystal and one counter it is possible to assemble a very precise clock.

Well, i will play around the concept for learning purposes.

 

As i explained i dont have an osciloscope, and if i had this frequency i would have a different outcome.

If you want to use a chain of CMOS dividers - you could do worse than clock it with a 32.768kHz watch crystal.

A bit nearer to analogue is the programmable unijunction, they were developed for longer time periods than were possible with the original type unijunction. The popular 2N6027/8 are a bit scarce nowadays, but you can construct the equivalent with a complementary pair of signal transistors - its basically an SCR with the gate at the other end. Come to think of it - you can turn the circuit upside down and make the same type of pulse generator with a 2N5061 TO92 SCR.

The PUT generates narrow pulses, but you can use your CMOS monostable or wire a 555 for that function.

 

Yeah, sorry about that . I'll fix it as soon as I can get to it.

In the meantime the counters are 40103s.

Fields isn´t this solution a little bit to much. I mean 4 CI and one clock generator. I like the idea to make the counting very precise and the possibility to display the counter with and extra CI and extra components. But then i come back to the idea you called nonsense, to use a micro-controller.

As i recall, my comment regarding your content being nonsense was predicated on your total confusion with regard to asking a question which would yield something other than noise as an answer.

So far, you've progressed to the point where you've stated that you can live with an error of a second or two out of the 180 second short count timer, which is a step in the right directon.

Also, as I recall, you originally stated:

"This can be set very easily with a microcontroller, but for sake of parts and knowledge i want to try to make this with analog. Also, managing analog real-time time set with microcontroller can be tricky with potentiometer, which would lead to a complex case of HMI"

All total nonsense since you don't know what you're talking about, and what you're hoping for is that someone will give you a clue that you don't have to pay for in terms of face.



Also, with a 16Khz crystal and one counter it is possible to assemble a very precise clock.

Well, i will play around the concept for learning purposes.

 

Fields isn´t this solution a little bit to much. I mean 4 CI and one clock generator. I like the idea to make the counting very precise and the possibility to display the counter with and extra CI and extra components. But then i come back to the idea you called nonsense, to use a micro-controller.

The refusal to use one was yours, not mine.

Also, with a 16Khz crystal and one counter it is possible to assemble a very precise clock.

Indeed, but you've posted only opinon and haven't show the circuit required to prove your point .

Well, i will play around the concept for learning purposes.

How would you get 1 second clock out of a 16 kKz oscillator?

 

Yeah, sorry about that . I'll fix it as soon as I can get to it.

In the meantime the counters are 40103s.

It's fixed.

 

How would you get 1 second clock out of a 16 kKz oscillator?

http://www.hackersbench.com/Projects/1Hz/

 

http://www.hackersbench.com/Projects/1Hz/

You wrote: "Also, with a 16Khz crystal and one counter it is possible to assemble a very precise clock."

That’s just not true, since the closest you could get to 1Hz with a 16kHz crystal is 0.976Hz. Unless you know some tricks, that is, but then you’re past your one chip target.

You could do it with a 16384Hz crystal and a 4060, but you’d still need a handful of discretes to get the thing working, while with a 1Hz clock oscillator you just solder it down and you’re done.

There’s also the fact that 16kHz and 16.384kHz crystals are pretty much unobtainium unless you get them custom ground, so that $2, 1Hz off-the-shelf clock oscillator starts looking prettier all the time,