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Forum Index : Microcontroller and PC projects : Great Real Time Clock Module
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Geoffg Guru  Joined: 06/06/2011 Location: AustraliaPosts: 3292 |
This is probably not news to many people but if you need an accurate clock in your Micromite project this has to be one of the best: http://www.ebay.com/sch/i.html?_nkw=DS3231 
I bought a bunch of them for a project and they are incredibly cheap (less than $3), VERY accurate (+/- one minute per year) and best of all just work. As a bonus they include a 4KB EEPROM and the ability to measure temperature. About the only thing to watch out for is that some sellers do not include the battery (check the description). Recommended. Geoff Graham - http://geoffg.net |
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atmega8 Guru Joined: 19/11/2013 Location: GermanyPosts: 724 |
Hello, i have the same good Experience with this Modules, cheap, accurate and they work out of the Box with mmbasic. They will be shiped without battery because of security rules and flight regulatories. |
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| PicFan Senior Member  Joined: 18/03/2014 Location: AustriaPosts: 133 |
Hello ! I have the same good Experience with this Module !! DS-3231 RTC Modul |
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Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9610 |
I've started using these ones. No EEPROM on these, but they are TINY, which is great for a small PCB. I also have some of the ones Geoff has Smoke makes things work. When the smoke gets out, it stops! |
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Zonker Guru Joined: 18/08/2012 Location: United StatesPosts: 767 |
Yep Grogs... I got a 10 pack of those... Plugged the first one in and had no problems so far... |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9610 |
You can get this module with a different battery fitted(smaller), which makes the module a couple of bucks cheaper still, but I hear that those ones suffer a very high battery failure rate.... The ones with the yellow plastic-wrap on the battery don't seem to give any issues. Smoke makes things work. When the smoke gets out, it stops! |
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TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6283 |
But even though the photo clearly shows the battery with yellow plastic wrap, don't be surprised if there is no battery when the modules arrive. Jim VK7JH MMedit |
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| trevoz Newbie  Joined: 03/05/2014 Location: AustraliaPosts: 8 |
+1 |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9610 |
Mine always arrived with the battery fitted. I expect that they don't fit it sometimes, as any electronic device with battery fitted is an airplane no-no these days - and I can understand their reasons, unfortunately.  Smoke makes things work. When the smoke gets out, it stops! |
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centrex Guru Joined: 13/11/2011 Location: AustraliaPosts: 320 |
Hi all The rtc modules that Geoff pointed to come with a charging circuit for LRI2032 chargeable lithium cells. What effect this circuit would have on a standard cr2032 cell I no not. If you have used this module with the cr2032 I would like know if there is a problem or not. Cliff Cliff |
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BobD Guru Joined: 07/12/2011 Location: AustraliaPosts: 935 |
Cliff The battery is an LIR2032. I'm correcting you to make it easier if you search. There is some mods around to remove the charge from the battery. Check out this link and read the first user comment on the second page. http://www.banggood.com/DS3231-AT24C32-IIC-High-Precision-Real-Time-Clock-Module-For-Arduino-p-81066.html also this one has a manual available. Don't know how useful it is. http://www.dx.com/p/ds3231-high-precision-real-time-clock-module-blue-3-3-5-5v-222910#.Vnkiv3mR8-U Bob |
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| robert.rozee Guru Joined: 31/12/2012 Location: New ZealandPosts: 2442 |
the user manual (an archive containing a collection of documents) does provide a useful schematic which matches the PCB i bought on ebay. direct link here: http://m5.img.dxcdn.com/CDDriver/CD/sku.222910.rar it appears that the battery is fed from Vcc via a diode and 200 ohm resistor for charging purposes. it is therefore NOT a good idea to fit a CR2032 cell UNLESS either the diode or 200 ohm resistor is removed. at the same time, removing the LED and/or 1k series resistor may be prudent to save on 2mA of Vcc current. 
indeed, there is no real need for a rechargable battery to have been designed for in the first place, as in standby mode (Vcc off, no signals applied to SDA or SCL) the DS3231 draws an average of less than 3uA from the battery. cheers, rob :-) |
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| centrex Guru Joined: 13/11/2011 Location: AustraliaPosts: 320 |
As noted above there is some info on the web...... https://edwardmallon.wordpress.com/2014/05/21/using-a-cheap-3-ds3231-rtc-at24c32-eeprom-from-ebay/ the above gives a great deal of information including a complete circuit of the device. Cliff 
Cliff |
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