Microcontroller homework 3
E) RF = 10k, RL = 28k2, RH = 107k
F) Before scaling: 2.35 steps/°C. After scaling: 3.42 steps/°C
5. Some things were assumed, as they were not given.
30 = 1,13V
40 = 0,976V
So 35 should be between 40 and 30. Assuming about 1,053 V.
Same for 5 degrees... Assuming about 1,725 V.
35 degrees digital 1,053/10*1024 = 107,8272
5 degrees digital 1,725/10*1024 = 176,64
177 108 = 69 ADC counts, 30 degrees SPAN
69/30 = 2,3 ADC steps per degree
We need the tempertature 5-35 to fall between 1V 9V at the ADC. This gives us
408 counts over a range of 30 degrees. 13,6 counts per degree.
Swing of the output 0,672V must translate into 9-1=8V, this is a gain of 8/0,672, or
11,9.
1,053 * 11,9 = 12,53
1,725 * 11,9 = 20,53
20,53-12,53 = 8V The span is right. Now we need to check the offset.
12,53 1 = 11,53 V
20,53 9 = 11,53 V
Offset is fine.
Since Vref is 10V, the second equation is
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