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-   -   Real Time Clock? (http://www.homebrewtalk.com/f235/real-time-clock-346674/)

SMc0724 08-09-2012 06:09 PM

Real Time Clock?
 
So what is your opinion about the need for a Real Time Clock on an AutoBrew system? Mine is Arduino, which does not come with one. Software can be used to create real time, but needs to be updated.

mendesm 08-09-2012 06:23 PM

I'm not sure you'd need such accurate time keeping.

What are you doing with the controller that you think you need, or could use, an RTC?

SMc0724 08-09-2012 07:07 PM

Mainly as a timer in case of power loss or surge, that is about all I can think would be needed. In a power loss, I would need to take over the brew anyway.

Battery backup might be a better use of resources.

jpalarchio 08-09-2012 11:07 PM

Probably not necessary but I have one (http://macetech.com/store/index.php?...&products_id=8).

It's I2C, easy to work with.

If you decide to get one, pay attention to the chip; there seems to be a many cheaper models different than the DS3231 which don't have great accuracy.

crane 08-17-2012 02:32 PM

Quote:

Originally Posted by SMc0724
Mainly as a timer in case of power loss or surge, that is about all I can think would be needed. In a power loss, I would need to take over the brew anyway.

Battery backup might be a better use of resources.

I don't quite understand what an RTC is going to help you with. So you have a power loss and the system comes back on then what. Are you going to have it log with time stamps periodically in which case you could look at the log and have it recognize that it wasn't done with the previous brew session and pick up where it left off? If you want to do this then you will still need battery backup for the RTC itself to not loose track of time. If you are talking about a battery backup for the arduino I don't know how that will work as you will still need power to turn on your pumps, valves and heating elements.

To handle a power loss I would think it would be more effective and easier to code by allowing you to restart a brew profile at step number x rather than intelligently trying to pick up where it left off.

audger 08-17-2012 03:45 PM

its probably not intended for a power loss. the internal clock on the arduino isnt fantastic and drifts considerably. however i dont think the drift will be more than a second here or there over the course of a 6-8 horu brew day, which shouldnt be much of an issue. it only becomes noticable if you are logging over the course of a few weeks or more.

SMc0724 08-17-2012 08:18 PM

Quote:

Originally Posted by crane
Are you going to have it log with time stamps ...andy pick up where it left off? If you want to do this then you will still need battery backup for the RTC itself to not loose track of time.

Yes that is what I was thinking. I planned for the RTC to have it's own battery.

Quote:

Originally Posted by crane
you will still need power to turn on your pumps, valves and heating elements..

I'm thinking that the battery backup would be for the Arduino and possibly the RTC to keep track of where the process stopped, how long it's off, and then allow an intelligent restart.

Quote:

Originally Posted by crane
To handle a power loss I would think it would be more effective and easier to code by allowing you to restart a brew profile at step number x rather than intelligently trying to pick up where it left off.

How would that work? Just log the events, then what happens at restart?

Alternately I could just put a WiFi network connection and use it to log times.

jpalarchio 08-17-2012 11:56 PM

Quote:

Originally Posted by SMc0724 (Post 4339715)
Yes that is what I was thinking. I planned for the RTC to have it's own battery.

The ChronoDot RTC in my link above has a battery.

SMc0724 08-19-2012 04:45 PM

jpalarchio,
How do you use the RTC?

jpalarchio 08-19-2012 11:33 PM

Quote:

Originally Posted by SMc0724 (Post 4344001)
jpalarchio,
How do you use the RTC?

I don't currently. I had it from something else and I don't know that it'll be included in my setup. I plan to log externally so I can just timestamp entries when I insert them into the database.

For the relatively short amount of time a brew session lasts, I can't see it being necessary unless you want to do some kind of timed start like heating up an electric HLT before your day starts.

If you look at the BrewTroller code, they do some nice stuff that maintains the timer during a power fail without a battery or RTC.


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