200 Minute Timer Circuit Design Help – 8A 120VAC Load.

[PCB.Wiz]

As PCB.Wiz points out, using a 74HC4060 (or two) even a CD4060, will give you a 14 stage binary divider (1/16384), a simple cmos gate oscillator and a clear input, all in one chip. Your RC time constants then become a lot more sensible. I've used them before for very basic battery charger timers. The datasheet should give you all you need.

Thank you for that.  I looked at the data sheet for the Texas Instruments.   Maybe I will order one and play around with it.

Another part well matched to your problem is the 74HC5555.  Now EOL but some still available.
That is a 2^24 divider + monostable, so needs 1398.1013Hz for 200 minutes pulse, when /2^24
It has 4 divider choice pins, so you can pick faster test times.  eg a 2^17 choice would give 93.75s test times, for 200 minute setting.

Or, on a pre-built MCU side, AliExpress have LCD versions of the venerable relay-timers

https://www.aliexpress.com/item/1005001800364875.html
The LCD ones seem to all use Nuvoton N76E003, which is a 16K 1T 8051 core.

Addit : here is a relay timer based on the CD4541
https://www.aliexpress.com/item/1005006185622775.html?

[Uunoctium]

I prefer using Omron timing relays
H3CR-A8 dial wheel, 1,2s-300h: starting at $9,50
H3CA-A 306 LCD, pushbutton preset, 99,9s-9999h: starting at $25

! both versions need the matching base/socket !

above prices are for bay items from Hong-Kong labelled ‚made in PRC‘, so i can't guarantee, if they are not fake
(I own many from the U.S.A. and they have worked accurately for years)

[JJ_023]

A microcontroller is what I currently use as I stated in the opening post.  An Arduino would work as well.   I was just looking to expand my knowledge and see if anything could be improved upon or be made aware of something I was not.  Thank you.

You can use the smallest, simplest, 6-pin  microcontroller you can find and program it in assembly, rather than C.

That is a great suggestion.  I can code in C not assembly.   Thank you.

[JJ_023]

I am  working on a separate "hardware" watchdog timer to stop ham sdr radio transmitter in event of cpu hang.
The timer I selected is "DC 12V FRM01 Timer" one of the generic modules available on Amazon, $17 for (2).

It has 18 modes, 0.1 s to 270 h  and  a 14 page programming manual that can be downloaded separately.
 The c/o contact is rated 125V AC 10 Amp, but recommended rating is 1/2 for resistive  or 1/3 for inductive/capacitive.
The AC contacts look well sized, separate from circuit and surrounded by ground plane
The modes are programmed with onboard buttons and led numeric display. There is a terminal for 1 20 ms pull up/pulse contact.

This timer comes in versions for 5V, 12V  and 24VDC supply, and there are a number of similar ones to this part number.

I am familiar with those  particular timers.   I usually avoid them because it's just the board and then you  have to figure out some sort of enclosure.   When I use off-the-shelf components like that I actually look to the home automation space.  Those devices are super simple to configure as a timer and enable you remote access to the device both to monitor and control.

[JJ_023]

Also, trying to use a monostable with such high resistance and capacitance values will be far too sensitive to board leakages, contamination, atmospheric humidity even. I'd consider that a non-starter.

Might check out the "C005" timer COB module which can produce delays from "5 seconds to over 40 days."

https://westsideelectronics.com/delay-timer-ic/

Thank you so much.  That C005 chip is pretty neat.   I read a few articles on it as well as the TPL5111 and variant from Texas instrument.

The problem with the C005 that I see with this application is from the following.

"The chip is not repeatedly triggered, meaning that in the time between it is triggered and resets, it will not respond or keep track of any other falling signals from the external controller."   https://westsideelectronics.com/delay-timer-ic/

https://www.ti.com/lit/ds/symlink/tpl5111.pdf?ts=1715637205537
https://www.ti.com/lit/ds/symlink/tpl5110.pdf?ts=1715617409200

 So this would prevent the user from stopping the cycle if that need arose.  Unless I am misinterpreting something.

[JJ_023]

...
Or... thinking cassette tapes ... have a cassette tape run at slow speed so that the tape ends at exactly 200 minutes... you can detect tape end with an optical sensor (tape becomes transparent at the end)

I sense a competition coming on. 

How about a narrow throated funnel, filled with fine sand, which drops on a plate below which is attached to a strain gage? 

Now seriously , the CD4541 or other similar long range counter is actually your best bet, as previously suggested.

I will have to look into how to implement that particular chip.  Thank you for the suggestion.

[JJ_023]

Timer needs to be fine-tuned once and then left as is.
The timer is going to be roughly 200 minutes.

Questions here are how much fine-tune and for what values of 'roughly' ?

So the timer event would be about 200 minutes ± 20 minutes.  Once the correct time was figured out it would never be changed.  Accuracy is fairly loose ± 1 minute.

Digital dividers are very simple, and you can get very accurate binary multiples, from any frequency. (mains, or 32.768kHz)
With a programmable divider, like a 40103, you can get finer digital control

  Unfortunately I don't have a lot of experience using dividers.  I will have to look into this further.

A small MCU would need to have some ADC ability, to allow for the adjust side.

  The adjustability would be done during build time and the end user should not have the option to adjust.

Thank you so much for the suggestions.

[JJ_023]

As PCB.Wiz points out, using a 74HC4060 (or two) even a CD4060, will give you a 14 stage binary divider (1/16384), a simple cmos gate oscillator and a clear input, all in one chip. Your RC time constants then become a lot more sensible. I've used them before for very basic battery charger timers. The datasheet should give you all you need.

Thank you for that.  I looked at the data sheet for the Texas Instruments.   Maybe I will order one and play around with it.

Another part well matched to your problem is the 74HC5555.  Now EOL but some still available.
That is a 2^24 divider + monostable, so needs 1398.1013Hz for 200 minutes pulse, when /2^24
It has 4 divider choice pins, so you can pick faster test times.  eg a 2^17 choice would give 93.75s test times, for 200 minute setting.

Or, on a pre-built MCU side, AliExpress have LCD versions of the venerable relay-timers

https://www.aliexpress.com/item/1005001800364875.html
The LCD ones seem to all use Nuvoton N76E003, which is a 16K 1T 8051 core.

Addit : here is a relay timer based on the CD4541
https://www.aliexpress.com/item/1005006185622775.html?

Those timers that you are showing I am very familiar with.   I prefer not to use them.   In a previous post I stated that I think there are better options available in the home automation section that not only enable you to control the device but to monitor it remotely.   They also come in finished cases and are very small and compact in nature.  Most of these types of home  automation devices are actually rated for 10 A. I however never connect them directly without something in the middle like a SSR.

Thank you for the suggestion on 74HC4060.  I tried to look it up but almost every place is out of stock.  I try to avoid EOL chips.

[JJ_023]

I prefer using Omron timing relays
H3CR-A8 dial wheel, 1,2s-300h: starting at $9,50
H3CA-A 306 LCD, pushbutton preset, 99,9s-9999h: starting at $25

! both versions need the matching base/socket !

above prices are for bay items from Hong-Kong labelled ‚made in PRC‘, so i can't guarantee, if they are not fake
(I own many from the U.S.A. and they have worked accurately for years)

Those I think would definitely work.  I prefer my current solution that I described in the opening post.  But thank you for a great suggestion.

[PCB.Wiz]

Thank you for the suggestion on 74HC4060.  I tried to look it up but almost every place is out of stock.  I try to avoid EOL chips.

The 4060 should be very much alive from multiple sources.
You may have meant the 74hc5555, which is single sourced, and now EOL? (Tho Rochester show ~500,000)
The 74hc5555 has good data, and is operationally very close to what you ask for.

"The chip is not repeatedly triggered, meaning that in the time between it is triggered and resets, it will not respond or keep track of any other falling signals from the external controller."

 So this would prevent the user from stopping the cycle if that need arose.  Unless I am misinterpreting something.

The stop on same button feature is rare, so you would need to do that in separate hardware.
Most common would be a simple RC from the trigger button to reset, so a long press would stop.

If you want a true toggle button,  you would use a D-FF with Schmitt clock, and probably a RC POR reset and the timer reset.

TI have a new family of 74HCSxx parts, that document Schmitt on every pin.
Nexperia 74LVC parts also mention Schmitt pins.

Release of new logic families shows MCU’s have not entirely replaced logic.
 

[temperance]

Run's on two lemons.

Adjustable Wake-Up Period: 250ms to 39 Days

https://www.analog.com/media/en/technical-documentation/data-sheets/2956fa.pdf

[PCB.Wiz]

Run's on two lemons.

Adjustable Wake-Up Period: 250ms to 39 Days

https://www.analog.com/media/en/technical-documentation/data-sheets/2956fa.pdf

That looks to be a pulsed-wakeup design timer ?  (period = time between pulses?)

There are a few niche parts like that, tho I'm not sure who buys them in volume, in 2024, at those premium prices  ?

Analog Devices LTC2956IM  1  $6.9000  10  $6.2320  1000  $2.8700

Maybe those who really need the edge features, like 36V max, or sub 1uA timing, or small size ?
It could allow designers using bigger MCU/MPU to focus on features other than deep sleep.

[mikeselectricstuff]

Divider off the mains frequency perhaps - more accurate than RC. 200 mins = 12000 secs. CD4020 & a couple of diodes to stop when bits 12 and 13 go high ( 12,288)

[temperance]

There are a few niche parts like that, tho I'm not sure who buys them in volume, in 2024, at those premium prices  ?

I have no idea who might be using those. But there must be a market for them because TI has something similar.

[JJ_023]

Thank you for the suggestion on 74HC4060.  I tried to look it up but almost every place is out of stock.  I try to avoid EOL chips.

The 4060 should be very much alive from multiple sources.
You may have meant the 74hc5555, which is single sourced, and now EOL? (Tho Rochester show ~500,000)
The 74hc5555 has good data, and is operationally very close to what you ask for.

"The chip is not repeatedly triggered, meaning that in the time between it is triggered and resets, it will not respond or keep track of any other falling signals from the external controller."

 So this would prevent the user from stopping the cycle if that need arose.  Unless I am misinterpreting something.

The stop on same button feature is rare, so you would need to do that in separate hardware.
Most common would be a simple RC from the trigger button to reset, so a long press would stop.

If you want a true toggle button,  you would use a D-FF with Schmitt clock, and probably a RC POR reset and the timer reset.

TI have a new family of 74HCSxx parts, that document Schmitt on every pin.
Nexperia 74LVC parts also mention Schmitt pins.

Release of new logic families shows MCU’s have not entirely replaced logic.

I probably made a mistake and looked at the wrong chip.   I just looked at the chip again and see that a bunch of it is in stock.   Thank you for pointing that out.

All the suggestions that you make as well as other community members really open up the possibilities for me and expand my knowledge as to what is out there.   For that I am truly grateful. 

[JJ_023]

Run's on two lemons.

Adjustable Wake-Up Period: 250ms to 39 Days

https://www.analog.com/media/en/technical-documentation/data-sheets/2956fa.pdf

Definitely a neat little chip thank you.

[JJ_023]

Divider off the mains frequency perhaps - more accurate than RC. 200 mins = 12000 secs. CD4020 & a couple of diodes to stop when bits 12 and 13 go high ( 12,288)

Keep in mind I am still somewhat of a beginner.   The way I understand what you wrote is that you would use the 60 Hz mains as a clock that you would then use a counter to keep track of time.   When it reached  12000 it would stop.  This is a great solution for this part of the equation.

 Is this correct?

The part I don't get is how do you use a couple of diodes to stop.  I don't have any real experience with counters or dividers.

Thank you in advance.

[themadhippy]

The part I don't get is how do you use a couple of diodes to stop.  I don't have any real experience with counters or dividers.

have a look at  https://tinyurl.com/23jvjxtj the top counter just keep counting from 0 to 15 ,the bottom one gets to 9 (q0 and q3 high),on the next clock pulse outputs q1 and q3 are the next to go high,causing the and output to go high which resets the counter back to 0

[exmadscientist]

There are a few niche parts like that, tho I'm not sure who buys them in volume, in 2024, at those premium prices  ?

I have no idea who might be using those. But there must be a market for them because TI has something similar.

The people who buy them are the people who don't want their critical functionality (watchdogs, life-critical timing, etc) done in software. Basically people who don't want software supervising software. Or people who have no programmed parts on a board and don't want to add a programming step just for that one little function. (This used to be more common, but most designs now have some kind of programmed part, and it's gotten much cheaper to do either way.)

The 6995 is also probably an option here but would need some glue gates to muck with RST.

I love these little guys and would buy tons of them if they were priced sanely. Alas, they're not. So no sales.

[Smokey]

...
How about a narrow throated funnel, filled with fine sand, which drops on a plate below which is attached to a strain gage? 
...

Even better would be if the strain gauge was being measured by a microcontroller that had an ADC timer set to take a reading every 200 minutes...

[PCB.Wiz]

Keep in mind I am still somewhat of a beginner.   The way I understand what you wrote is that you would use the 60 Hz mains as a clock that you would then use a counter to keep track of time.   When it reached  12000 it would stop.  This is a great solution for this part of the equation.

You can get close, but you do need a bit more than a single 4020 divider.

If you have 60Hz mains, that's  /720000, and most long counters are binary. 
Thus log2(720000) is 19.45763738 binary bits

The closest binary taps for your target of 200 are
 2^19/60/60  = 145.635 minutes
 2^20/60/60  = 291.271 minutes

If we assume you have outputs available on all binary counters, you can wait a bit longer, for more than one output to be HIGH.
 thus

 (2^19+2^17+2^16)/60/60 = 200.248 minutes - ie an AND gate combining counter taps at 19,17,16 will first pulse high at 200.48 minutes.

You wanted some adjustment, so you could for example pick taps at 19 and 17..14 for 16 choices (4 switches or jumpers), next longest is 204.8 mins or a ~2.2% step size.
More taps give finer digital settings, eg 5 taps/switches or jumpers is ~ 1.1% step size.

Or, if you like analog, you can use weighted resistors and a RRIO comparator and trim pot, to 'pick a step'.

[quadtech]

Divider off the mains frequency perhaps - more accurate than RC. 200 mins = 12000 secs. CD4020 & a couple of diodes to stop when bits 12 and 13 go high ( 12,288)

Here is an example for this -

https://www.electroniq.net/other-projects/power-supply-connection-delay-circuit.html

The timing chart is based on 50Hz. For 60Hz, the timing increments will be in 4.25 seconds instead of 5.1

[soldar]

https://www.ebay.com/itm/176152872783

[Gyro]

Divider off the mains frequency perhaps - more accurate than RC. 200 mins = 12000 secs. CD4020 & a couple of diodes to stop when bits 12 and 13 go high ( 12,288)

Here is an example for this -

https://www.electroniq.net/other-projects/power-supply-connection-delay-circuit.html

The timing chart is based on 50Hz. For 60Hz, the timing increments will be in 4.25 seconds instead of 5.1

Note that Elektor (the original diagram source) were sometimes not very careful with their mains circuit schematics. The whole circuit is at mains potential, so should not be grounded or connected to the case (which needs to be double insulated, or grounded if metal). See attached...

EDIT: Input mains ground should also be carried through to the load of course.

[BILLPOD]

Good Morning JJ, yet another ready-made option:
http://www.paragoncontrol.com/timer.html