‫Welcome to the temperature sensor interface demonstration on the art development board for this demonstration
‫we're using two four digit seven segment displays on the breadboard where each of the segment of the
‫7:7 displays are tied together through a 56 ohm resistor and then is fed back into the JMB PMA port
‫of the Arti development board.
‫We also have each of the digits selects for all eight digits on the 7:7 display are controlled through
‫eight different two and thirty four transistors with 470 ohm resistor connected to the base.
‫And these are controlled through the J.C p.m. on port of the Ardie development board.
‫And we also have our external temperature sensor that we have on a separate circuit board that is controlled
‫with we have a power in the ground coming in and we're feeding the output of the temperature sensor
‫into the 8:0 of the chip kit.
‫Slash Arduino port on the arm on board.
‫We also have reusing switches zero to determine whether recalculate or temperature and Fahrenheit or
‫Celsius and our switch 3 which enables or disables the temperature collection.
‫So in order to show you switch three to set to enable right now we have it enabled if I pull high will
‫disable it.
‫You'll see we have all zeros across the board and two eights.
‫That's because with the micro BLAYSE processor we have running in there our default values for the output
‫ports that we're writing to our sign and our degree symbol whether it's C or F they go to all ones.
‫So they all they show up here.
‫They go all of those excuse me they go to all zeros.
‫So we're going to be pulling on those and we're in display in eight.
‫So if I pull it back down will display the temperature which currently the sensor is reading a temperature
‫of fifty six point seven fifty six point five nine degrees Fahrenheit.
‫And if I switch my switch down it'll turn to Celsius.
‫Now you notice there's a little bit of a delay.
‫That's because in the software we have a delay after we take that reading we wait a half second and
‫then we take another temperature reading and then update the temperature display because temperatures
‫typically do not change fast enough within a half a second.
‫They don't change that fast so every half second is plenty enough you could probably make it slower
‫but in order to show you how this actually works so I'm going to switch to Fahrenheit again.
‫So you know this is a little bit of a delay that's because we just took a reading.
‫And when updates now at fifty seven point seventy five degrees Fahrenheit.
‫Now in order to verify this is actually working one you could have a thermometer and get a reading of
‫the temperature in your house the thermometer in my house says it's approximately 58 degrees.
‫So we're within one degree and that's exactly what the data sheet says on this part is that it's accurate
‫within two degrees.
‫So if you take and put your finger over the sensor and see we're at 59 degrees and once we get the reading
‫you should see it jump up.
‫That's because my hand is warmer than the sensor itself.
‫And so it jumped it up went from 58 to almost 67 10 degrees in one second.
‫And from here on out it's going to slowly creep up until eventually through thermodynamics the temperature
‫sensor reaches the temperature of my hand.
‫So I get to sit here and hold it and keep warming it up but I'm going to let it go.
‫And you'll see here in a moment that the temperature will start or continue to drop so are 66 and it's
‫going to continue to drop.
‫And what you will notice sometimes there may be an erroneous reading if you will.
‫So it'll be at 64 It may jump down to 54 and then come right back up.
‫That is because we don't have I don't have any filtering or any sort of averaging.
‫I take one sample we take one sample and then we go ahead and make a calculation off of it in order
‫to make this more robust.
‫If you're doing like a critical design you would most likely want to do something where you take three
‫or four samples and get the average of them and use that value as opposed to taking one.
‫But this is just to show you that you can use external analog temperature sensors to actually display
‫a digital temperature and that is the temperature interface demonstration running on the already built
‫inboard.