Temperature Sensor Using MSP-EXP430F5529, LM35 + LCD102x64

About the Circuit:

The connection is very basic, the sensor to VCC and GND, the signal Vout of the LM35 is connected to the analog channel A6 of the MSP.

About the Code:

To obtain the temperature we need to perform a few calculations, for example in the LM35 datasheet it tells us that Vout = 10mV / ° C, in other words 1 ° C = 10mV, for example if we have a temperature of 30 ° C we will have Vout = 300mV, another point that we should consider will be the resolution of the ADC, in this case it is 12 bits, this means that we can have values ​​from 0 to 4096, to know what voltage corresponds to a bit we can say that; 1Bit = 3.3V / 4096 = 3300mV / 4096 = 0.8056mV.

With this we can know how many bits will be present in A6 when the temperature is 30 ° C, therefore Bits30 ° C = 300mV / 0.8056mV = 372.39.

The ways of presenting the equation that describes the behavior of the temperature can be of different forms but in the end the same result is achieved, I do it in the following way, of course, considering the previous calculations.

1 Bit = 0.8056mV

1 ° C = 10mV

And applying a rule of three we have 1 Bit = 0.8056mV * ° C / 10mV = 0.08056 ° C

Then I can deduce that if this constant is multiplied by the bits in A0, I will obtain my desired temperature, for example; 0.08056 * 373.30 = 29.99 ° C, considering that we have not used all the decimals we can say that our temperature is correct.

With this constant we reduce a little the process in the code, to avoid making the divisions, I must also mention that in the code I take 32 samples (1 sample every 32mS approximately) and then I get the average value with a displacement, so I update the temperature in approximately 1 second and show it on the screen, there is also a bar where we show from 10 ° C to 45 ° C, when the temperature is less at 45 ° C the LED1 changes state every second, when it is higher the LED1 changes its status every 32 milliseconds (flashing faster).

Video:

Here a small video of the working temperature sensor:

Well, I hope this has helped you...