Temperature Logger and Buzzer

[kim27]

After doing further testing, I've encountered one more major problem. The following is data logging overnight. If you notice, there is a sudden spike in the temperature, followed by a big whole in the data.



The whole in the data is caused by the device being under powered. One of the batteries I've been using to test with has finally exceeded its usefulness, and can no longer provide enough volts to write the temperature to the flash.

So what is with the spike in temperature? Well, when the device resets, it looks for the next memory location that has not been written to, and attempts to write to that memory location. Really, those values should be at the end of the graph, not in the middle.

The problem could be solved in a few different ways. The first method I could use to solve the problem is to detect when the power is to low to be useful for writing to flash. From observing the voltage when running, it appears that the voltage drop tends to occur when I'm using the LED. I may be able to wire up an input pin to interrupt the CPU when the voltage drops below a specific voltage.

Another option is to use the ADC to monitor the battery voltage, but this may use more power than I would like.

Thoughts?

 

[Mister B]

Have you thought of a wall wart? 5v ones are fairly common. Would it be too much voltage? I haven't seen any 3v ones, but there probably are some.

 

[kim27]

I haven't ruled out using a wall wart, but I was hoping to make it a battery powered. Maybe stick it in one of the easter eggs the kids got.

If I went with the wall wart I can just use a Voltage Regulator the like the L78L33ACZ ( http://www.st.com/web/en/resource/technical/document/datasheet/CD00000446.pdf ) and that will bring it down to a reasonable voltage.

 

[kim27]

And the first version is wired up! Going to try it out next Monday with some Icelandic eggs.

 

[Mister B]

Good luck! I never would have gotten that to work. I would have had to go Arduino on it. My teaching buddy and I are working on an Arduino temp and humidity probe. It is supposed to turn on a light when the temp goes down, off when it goes up. It will also open and close a vent to keep the humidity constant. So far, we have LEDs to come on when something is supposed to happen. All we have to do is get the servo and the relay to work. Our next project is to put a stepper motor on a timer to turn the eggs. I think we can do it all with the same Arduino.

 

[kim27]

Good luck! I never would have gotten that to work. I would have had to go Arduino on it. My teaching buddy and I are working on an Arduino temp and humidity probe. It is supposed to turn on a light when the temp goes down, off when it goes up. It will also open and close a vent to keep the humidity constant. So far, we have LEDs to come on when something is supposed to happen. All we have to do is get the servo and the relay to work. Our next project is to put a stepper motor on a timer to turn the eggs. I think we can do it all with the same Arduino.

Awesome. Have you done anything to calibrate your thermostat? What add-ons are you using to monitor temps and humidity?

 

[Mister B]

No calibration yet, we are just getting it to work. I'll have to look when we get back to school to see what the temp and humidity sensor is. It is one that senses both, though. Most of our time was getting it to print out to a LCD panel.

 

[kim27]

So we've started incubating a new batch of eggs.



As you can see the temperature logger / buzzer made it into the incubator this time; however, there are some weird behaviors going on with the temperature logger.

As you can see below there is a weird sea-saw behavior going on with the temperature according to the temperature logger. The non-digital thermometers seem to stay at a nice 99.5 - 100.0 degrees. I understand if my reading was just higher, or just lower, but this pattern does seem kinda weird. I wonder if the digital is just more sensitive to the heat changes? Or if there is some extra digital noise at the higher temperatures?



When the temperature logger is running at lower temps, I don't get any weird patterns.



I've had to turn off the buzzer feature off until I figure out what is going on. Now life turns into which thermometer to trust, and with digital one being the new kid on the block, not that one.

 

[kim27]

The following is roughly another 9 days with recording data at fifteen minute intervals. Notice how we still have the wave going on through out the data.



Well, after a lot of logging, it seems that we still have a problem. Now I decided, lets record more data, but let us record extra data points. So now instead of just storing the over sampled value, we will also store the average of the over sampled value, the non over sampled value, and the average of non over sampled value. The averages will be from four sequential readings. Here are the results from storing them once every fifteen minutes(so far all the temperature recordings have been taken at 15 minute intervals in hopes of storing an entire incubation period worth of data).



This new set of data seems to rule out problems with the oversampling; however, it does show that using averaging appears to provide some better results. This still leaves the question, are we still just getting ADC noise? To rule out getting a group of bad readings, let us try recording the temperature every minute and see what that looks like.





This appears to rule out getting noise on the ADC line; however, it does leave a few questions unresolved. Why do the other thermometers not report the same type of behavior? Is this just an problem of observing the analog thermometers at the right time? Is this a sensitivity issue? Perhaps the MSP430 calibration is off?

It looks like I'll have to dig deeper.

 

[kim27]

Finally, a picture of some of the hatched eggs!