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Changes for page Sensor Module

Last modified by Heimir Thordarson on 2026/07/05 12:56
From version 35.1
edited by Heimir Thordarson
on 2026/01/22 13:57
Change comment: There is no comment for this version
To version 41.1
edited by Heimir Thordarson
on 2026/01/26 17:41
Change comment: There is no comment for this version

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15 15  
16 16  In the following section, how the sensor module is connected will be covered. The connector for the sensor module is a [[High-Density d'sub-44>>https://www.te.com/en/product-2311770-1.html]] which is directly solderen onto the circuit board. The plug needed for this system is the [[204517-3>>doc:Sandbox.TestPage3]], which uses crimps instead of solder cups which is common for the dsub connectors
17 17  
18 -[[image:AR26_ASM pinout.png||height="221" width="469"]]
18 +[[image:AR26_ASM pinout.png||height="214" width="457"]]
19 19  
20 20  In the figure above, the pinout shows how the pins are divided. Each box shows which pins belong together for each usecase, where the red box is the power input. Yellow boxes are for each canbus network, while the green box is for each sensor used in AR26.
21 21  
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63 63  
64 64  The air temperature sensor will be used to have a dynamic reference setpoint for the cooling system. This could reduce the current draw from the low voltage system compared to having a fixed reference point. This is because the regulator will not try to cool the water to a temperature lower than the ambient temperature. The sensor works as a resistor which varies depending on its temperature. Where in this case, the resistance lowers when the temperature increases (NTC). To make the microcontroller able to measure the changes in resistance, the thermistor is put into a voltage divider circuit.
65 65  
66 -[[image:circuit with marks.png||height="195" width="465"]]
66 +[[image:circuit with marks.png||height="218" width="520"]]
67 67  
68 68  (% class="wikigeneratedid" %)
69 -As shown in the figure above, the thermistor is put into a voltage divider circuit with a 4k7 ohm resistor to convert the resistance changes of the thermistor to a measurable voltage. To find the temperature of the thermistor based on the voltage measure by the analog-to-digital converter (adc), the resistance of the thermistor needs to be calculated based on the voltage from a voltage divider.
69 +As shown in the figure above, the thermistor is put into a voltage divider circuit with a 4k7 ohm resistor to convert the resistance changes of the thermistor to a measurable voltage. To find the temperature of the thermistor based on the voltage measure by the analog-to-digital converter (ADC), the resistance of the thermistor needs to be calculated based on the voltage from a voltage divider.
70 70  
71 71  (% style="font-size: 1.5em;" %)
72 72  (((
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79 79  
80 80  Where:
81 81  
82 -* {{mathjax}}\(R_f\){{/mathjax}} = the upper resistor in the voltage divider which stays fixed, which in this case is 4.7k \(\Omega\)
82 +* {{mathjax}}\(R_f\){{/mathjax}} = The upper resistor in the voltage divider which stays fixed, which in this case is 4.7k {{mathjax}}\(\Omega\){{/mathjax}}
83 +* {{mathjax}}\(V_{out}\){{/mathjax}} = The voltage over the thermistor, and the voltage that the microcontroller will measure.
84 +* {{mathjax}}\(V_{in}\){{/mathjax}} = The supply voltage of the voltage divider, which in this case is a constant 3.3 {{mathjax}}\(V\){{/mathjax}}
85 +* {{mathjax}}\(R_T\){{/mathjax}} = Resistance of the thermistor
83 83  
84 -(% class="wikigeneratedid" %)
87 +Knowing this, the resistance of the thermistor can be added into the following equation. This will determine the temperature of the thermistor based on the known resistance and the beta value of the thermistor.
88 +
89 +(% style="font-size: 1.5em;" %)
90 +(((
91 +{{mathjax}}
92 +$$
93 +T = \frac{1}{\frac{1}{T_0} + \frac{1}{\beta} \ln\left(\frac{R_T}{R_0}\right)}
94 +$$
95 +{{/mathjax}}
96 +)))
97 +
98 +where:
99 +
100 +* {{mathjax}}\(\beta\){{/mathjax}} = material constant that defines the steepness of its resistance-temperature curve between two temperature points, usually 25/85 degrees celsius. In this case it is 3694 //**K.**//
101 +* {{mathjax}}\(T_0\){{/mathjax}} = The test temperature at which the thermistor is 10k {{mathjax}}\(\Omega\){{/mathjax}}, which in this case is 25 degrees celsius.
102 +* {{mathjax}}\(R_0\){{/mathjax}} = The resistance of the thermistor when it is 25 degrees celsius.
103 +* {{mathjax}}\(R_T\){{/mathjax}} = The current resistance of the thermistor.
104 +
105 +==== Filtering ====
106 +
107 +Considering that the sensor can only promise a reaction time of 5 seconds when in water, it can be assumed that a heavy filter will not add any problematic latencies. To ensure a low cost, the filter uses common components which will filter any noise above the inverter switching noise.
108 +
109 +(% style="font-size: 1.5em;" %)
110 +(((
111 +{{mathjax}}
112 +$$
113 +F_c = \frac{1}{2 \pi R C}
114 +$$
115 +{{/mathjax}}
116 +)))
85 85