Which external RTC (for timer) is better for industrial purpose?

[Saeedk9574]

Hi everyone
I have been working to create a device for industrial purpose. I need to use a timer ic in it, but I do ot know which one is better. Does anybody know that I can use ds1307 in this device or it is not approprite for industrial devices as it is one of the chippest timers. In this regard, If you think ds1307 is not suitable, should I use ds3231 or pcf8563?

 

[Pommie]

There is not enough information. If your chip (uC) has a crystal then it "might" be accurate enough to keep it's own time, assuming none loss of power. If connected to internet then an NTP server could be the answer. I have a clock with a Wemos board that connects to my WiFi and fetches the time via NTP - it's never wrong.

I normally use one of the (very cheap) RTC modules that include a CR2032 battery for backup and never had a problem assuming you have I²C available.

Mike.
Edit, and the ability to set the time.

 

[Saeedk9574]

There is not enough information. If your chip (uC) has a crystal then it "might" be accurate enough to keep it's own time, assuming none loss of power. If connected to internet then an NTP server could be the answer. I have a clock with a Wemos board that connects to my WiFi and fetches the time via NTP - it's never wrong.

I normally use one of the (very cheap) RTC modules that include a CR2032 battery for backup and never had a problem assuming you have I²C available.

Mike.
Edit, and the ability to set the time.

The device will not connected to the Internet, in addition, for accuracy I decided to use an external RTC, but I am afraid ds1307 works faulty if it gets in the exposure of severe temperature. I read this on the Internet.

 

[Ian Rogers]

The DS1307 is only accurate to 1/2 minutes a month ( depending on crystal used ) I get a big variance on timing, but I only use the time on a generic print out so I don't mind the inaccuracy. The DS3231 is far more accurate.

 

[Pommie]

depending on crystal used

Won't that be the same on all chips or is temperature a big factor?

Mike.

 

[Nigel Goodwin]

Won't that be the same on all chips or is temperature a big factor?

Mike.

Temperature is a big factor, as Ian said the DS3231 is FAR better than the DS1307 - so there's no reason not to use the DS3231.

 

[rjenkinsgb]

We've use the MCP7940N in a few things; those are readily available and cheap, automotive grade and have a calibration facility.

https://www.microchip.com/en-us/product/mcp7940n

Datasheet:

https://ww1.microchip.com/downloads/aemDocuments/documents/MPD/ProductDocuments/DataSheets/MCP7940N-Battery-Backed-I2C-RTCC-with-SRAM-20005010J.pdf

 

[danadak]

Why not use a general purpose processor with an RTC in it ?

Post #5 https://www.edaboard.com/threads/which-timer-is-better-for-industrial-purpose.408990/#post-1762635


Regards, Dana.

 

[For The Popcorn]

As Ian and Nigel said, the DS3231 is extremely accurate. I have a couple DS3231-based clocks and they are accurate to within about a minute per year.

They use an internal crystal which is temperature compensated. They cost more than the DS1307, but eliminate the need for a crystal and a couple COG (preferably) caps.

 

[sagor1]

Would a GPS module work? Would depend on location I guess. Add that with a rtc and you would have accurate time always.

 

[Nigel Goodwin]

Would a GPS module work? Would depend on location I guess. Add that with a rtc and you would have accurate time always.

Tends not to be very good indoors, if it works at all - and it takes a while to connect as well.

The DS3231 is a cheap, easy, and accurate (enough) option.

 

[schmitt trigger]

I also recommend the DS3231.
But as others mentioned, the internal registers require initialization with a I2C- capable microcontroller.

 

[Nigel Goodwin]

I also recommend the DS3231.
But as others mentioned, the internal registers require initialization with a I2C- capable microcontroller.

Any micro-controller is I2C capable, as it's simple to do in software.

An extra nice feature is that you can set one of the pins to provide a 1 second pulse, and use that to trigger an interrupt for the micro-controller.

 

[Pommie]

Looks like the DS3231 wins hands down and available cheap.
I recently posted a program to setup an RTC. Here.

Mike.