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1 hour ON/23 hours OFF?

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MikeMl

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I need a simple (preferably one CMOS chip) timer/counter which puts out a logic high for about 1 hour out of every 24 hours for a battery charger circuit. Does not need crystal accuracy; a R-C oscillator is good enough. Does not need to be settable or resettable; it will run continuously and I don't care what time of day/night the output will be active.

I have an old Motorala CMOS manual which shows a MC14451 which would work for this, but this part appears to be obsolete, and is only available as NOS. I could cobble something with CMOS hex inverter used as an oscillator, a string of counters, and some and gates to create the output period, but I'm hoping that someone has a single chip solution for me?
 

john1

Active Member
Hi Mike,

How about a daylight sensor,
feeding a 1 hour single shot FET timer.

The FET timer is a simple RC circuit with i think 3 components.

John :)
 

tcmtech

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There are 86400 seconds in a day so what if you used a 555 timer that had a .86 second cycle that fed into 5 divide by ten IC's in series. for a total of a divide by 100000 count. Then use the 1 in 100000 pulse output to trigger another one shot 555 timer that does a roughly 1 hour time out.

All analog and crude but still a interesting design challenge.
 

MikeMl

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Any small microcontroller and a 32,768Hz crystal is probably the only 1 chip solution you're likely to find.

Starting from 32kHz, it would take a 22 bit counter to get to 24 hours. The Capture counter in a PIC is 16 bits, so I could use software to count overflows from the 16 bit counter which is counting the 32kHz crystal. Which small PIC has the counter hardware?
 

blueroomelectronics

Well-Known Member
They all have counters, you can do a counter of enormous length in software. If it's got an AC source you can feed it 50/60Hz instead of the crystal.
 

crutschow

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The CD4060 is a 14-bit binary counter with a built in oscillator circuit that can be connected as an RC (or crystal) type oscillator. A 5.27Hz oscillator design would give you a 24-hour cycle. You would need another chip enabled by the 24-hour cycle to give you the 1 hour period.
 

MikeMl

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Thanks Carl. That one looks like it might work. If I AND Q14, Q13, Q12, Q10 (unfortunately they didn't make Q11 available) I would get two 45min periods in a 24hour cycle, 45 min apart? Q14 would be high for 12 hours, Q13 for 6h; ... Q10 for 0.75h (45 min).
 

ericgibbs

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Thanks Carl. That one looks like it might work. If I AND Q14, Q13, Q12, Q10 (unfortunately they didn't make Q11 available) I would get two 45min periods in a 24hour cycle, 45 min apart? Q14 would be high for 12 hours, Q13 for 6h; ... Q10 for 0.75h (45 min).

hi Mike,
This device will give long time delays.
Attached d/s and a couple of circuits I did for a poster, which are up and running.

EDIT:
This HEF4521 has an internal osc driver.
 

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BrownOut

Banned
hi Mike,
This device will give long time delays.
Attached d/s and a couple of circuits I did for a poster, which are up and running.

EDIT:
This HEF4521 has an internal osc driver.

This is the sort of thing I see here from time to time, and think I might want to come back to it. Then, the thread eventually rolls off the page, and I can't find it when I want it. Is there a bank where these can be stored?
 

ericgibbs

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Most Helpful Member
This is the sort of thing I see here from time to time, and think I might want to come back to it. Then, the thread eventually rolls off the page, and I can't find it when I want it. Is there a bank where these can be stored?

hi,
Why dont you copy any images or data that you want to archive to Your CP Albums.??:)
 

Pommie

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Most Helpful Member
You can also subscribe to the thread. See Thread Tools on the first post and then you can see it in User CP.

Mike.
 

marcbarker

New Member
This is a single-IC solution, uses a PIC12F508. Uses mains frequency as timebase. Has an output that goes on and off the same time(s) every 24 hrs. The original application was for an applicance that learned a daily routine, in real time. You program the required on and off times by being there at the right time and pressing the button.

It's my code I'd wrote, I pass it into the public domain with no warranty or support.

It's an "electronic version" of this common
8245-315Zdy7fkZL._SL75_SS50_.jpg
mechanical timer, complete with the Pegs (you know, the motor thingy with the pegs round the wheel that goes round each day)

Sorry the picture is so big
 

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tcmtech

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A simple way to get a programmable 24 hour timer is to take an old digital alarm clock radio and tie a relay into the circuit that powered the radio part. Use it to turn on the device in question.

I did that to one in high school for an experiment in order to get my boom box to work off of a timer. I also set up one that way for a friend of mine years ago so he could use it as a engine heater timer in the winter.

Most alarm clocks automatically shut off the alarm after an hour or so.

Its just a thought.
 

MikeMl

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Most Helpful Member
hi Mike,
This device will give long time delays.
....

I looked up both. the 2240CN is no longer on TI's page, and I can only find NOS. The 4521 looks good. It is still in stock at DigiKey.

Here is what I came up with using the 4521:

(almost a single-chip solution)
 

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ericgibbs

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I looked up both. the 2240CN is no longer on TI's page, and I can only find NOS. The 4521 looks good. It is still in stock at DigiKey.

Here is what I came up with using the 4521:

(almost a single-chip solution)

hi,
In the CD4000 lib of LTS is the CD4040 [ 12stage] you could cascade two of the these to give the 24 stage, just for development.
 

MikeMl

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hi,
In the CD4000 lib of LTS is the CD4040 [ 12stage] you could cascade two of the these to give the 24 stage, just for development.

Do you think I could wait for LTS to simulate 16,777,216 cycles of the RC oscillator :D
 

ericgibbs

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Do you think I could wait for LTS to simulate 16,777,216 cycles of the RC oscillator :D

LOL,
I was thinking along the lines of say a 'bumped up' clock rate for simulation.:)
 

k7elp60

Active Member
Do you think I could wait for LTS to simulate 16,777,216 cycles of the RC oscillator :D
I don't have a simulator program, but on occasion have had to due long time periods. I set the divider to where I think it should be and then use a faster clock than needed, and then measure the output time on my frequency counter that also measures period. If the divide is correct then I use the intended clock. I have used the 4541,4060, and 4040 many times.
 
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