Home > Prototyping, Tech geeks, Temperature monitoring > Wireless Fermenter Temperature Monitoring (Part 2)

Wireless Fermenter Temperature Monitoring (Part 2)

Prototype20140712 notedToday I spent a good amount of time tinkering with the components for my wireless fermenter temperature design – perhaps to the detriment of everything else I was supposed to be doing, but that’s how it usually goes for me. I’ll hammer and hammer and hammer on something until I either am frustrated beyond coping or I have it to a place I am happy with. I think I am finally at that “happy” point, for now.

As things turned out, my intended path of using the 3.3V Arduino Pro Mini wasn’t working due to the one critical detail I mentioned almost as an afterthought in my previous post… the need to integrate a Real-Time Clock (RTC) into the mix so I could accurately timestamp the data. There are quite a few RTCs out there, but very few that both work at 3.3V and are reasonably priced. The DS1307 can send its signals at 3.3V, but it has to be powered by 5V – which left me either having to have a dedicated 5V bus for just the DS1307 and bringing in a 3.3V regulator circuit, or just swapping everything out to 5V. Both the SD card breakout board and my Bluetooth breakout down-convert to 3.3V, so it was the easier path to just replace the Pro Mini with it’s 5V brother.

WirelessTemps20140712After many hours of fiddling and cursing, and countless uploads from the Arduino IDE – My serial output looks pretty good. I’ve got several “commands” from the PC to the Arduino working as well. Currently implemented are:

  • s – Sends all data in the datalog
  • sd – Sends all data in the datalog and purges it (erases it) from the SD card
  • f – Forces the Arduino to take a sample immediately
  • r – sets the sample rate, such as “r300” for every 300 seconds
  • t – sets the clock time, such as “t20140712220000” for 12-Jul-14 11pm

The sample rate is stored and retrieved from non-volatile RAM in the DS1307, so it should survive power-downs / power-up cycles just fine. I need to find some 3V coin cell holders and integrate a battery backup for the DS1307 so the time information isn’t lost as well.

Where is the Bluetooth stuff? Yeah, I know. Remember my previous statement about hammering on something until I can’t cope with the frustration? That’s what happened first thing this morning. After about an hour of getting absolutely nowhere with it, I decided to bypass the Bluetooth and get to the good stuff shown above. Essentially I can’t get the stupid Bluetooth module to behave like a wireless serial port yet. I can pair it with the PC Bluetooth dongle, and it seems like I can even get it into config mode, but nothing comes back on the terminal window to tell me the configuration is working. I have little doubt it is from something I am doing wrong… and I will return to battle with it some other day. All the data is stored as a text file as well, so right now you could also pop out the MicroSD card and plug it into the PC and read the file directly, if you wanted.

My next step will probably be implementing the PC-side interface. It’ll be a relatively simple custom-tailored VB.NET application that allows you to connect to the Arduino, download the datalog file, and set the time and sample interval. Once I’ve got the Bluetooth stuff figured out all that can happen wirelessly without any real change in the code.

Until next time…

Advertisements
  1. No comments yet.
  1. No trackbacks yet.

Leave a Reply

Please log in using one of these methods to post your comment:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: