MSP430 Temperature Logger

My family has started incubating eggs, and it has been a real struggle to keep the temperature in the right range. Perhaps it is the incubator, perhaps user error. At any rate, I wanted to lend a hand with my technical know how, so I have begun working on a project. The basic concept is that I want to create a temperature logger to store data for the entire period of incubation, and also an alarm or buzzer for when the temperature is out of bounds. Here are the results for three days of incubating.

Three Days of Logging

Three Days of Logging

The temperature is in F multiplied by 100. Basically 98.00 degrees equals 9800.

For the project I’m using the MSP430 with factory calibrated temperatures. The ADC in the MSP430 is a 10 bit ADC, but is only sensitive to about 0.5 degrees C. To increase the sensitivity, I’m using oversampling to get about 13 bits of accuracy. I then use Integer math to convert the temp to F with two decimal places. I check the temperature every 10 seconds and alarm if the temp is to high or too low.

Right now the data logger is storing temperature at about 15 minute intervals. I need to add a crystal so that I can measure this more precisely, as the times right now are approximate.

The buzzer / alarm is proving a bit problematic for me. Right now, I have a 70 dB buzzer, but it seems to quiet.

The other problem I have is battery life. I’m currently using one or two CR2032s( http://en.wikipedia.org/wiki/CR2032_battery ). When I’m using one battery should last two or maybe three incubations. When I’m using two batteries I need to regulate the voltage, but the current voltage regulator I’m using uses too much power, so battery life is estimated to be roughly 30 hours. The two battery approach may be needed to keep the buzzer well powered. I’m looking at a new LDO voltage regulator, and that should take care of the problem.

I’ll put some pictures up of my temperature logger as I progress. Right now it is in the prototype stages on a breadboard.

Kim

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