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Changes for page Sensor Module

Last modified by Heimir Thordarson on 2026/07/05 12:56
From version 56.3
edited by Heimir Thordarson
on 2026/02/09 19:51
Change comment: There is no comment for this version
To version 58.3
edited by Heimir Thordarson
on 2026/02/11 19:49
Change comment: There is no comment for this version

Summary

Details

Page properties
Content
... ... @@ -86,10 +86,10 @@
86 86  
87 87  Where:
88 88  
89 -* {{mathjax}}\(R_f\){{/mathjax}} = The upper resistor in the voltage divider which stays fixed, which in this case is 4.7k {{mathjax}}\(\Omega\){{/mathjax}}
90 -* {{mathjax}}\(V_{out}\){{/mathjax}} = The voltage over the thermistor, and the voltage that the microcontroller will measure.
91 -* {{mathjax}}\(V_{in}\){{/mathjax}} = The supply voltage of the voltage divider, which in this case is a constant 3.3 {{mathjax}}\(V\){{/mathjax}}
92 -* {{mathjax}}\(R_T\){{/mathjax}} = Resistance of the thermistor
89 +* {{mathjax}}\(R_f\){{/mathjax}}= The upper resistor in the voltage divider which stays fixed, which in this case is 4.7k {{mathjax}}\(\Omega\){{/mathjax}}
90 +* {{mathjax}}\(V_{out}\){{/mathjax}}= The voltage over the thermistor, and the voltage that the microcontroller will measure.
91 +* {{mathjax}}\(V_{in}\){{/mathjax}}= The supply voltage of the voltage divider, which in this case is a constant 3.3 {{mathjax}}\(V\){{/mathjax}}
92 +* {{mathjax}}\(R_T\){{/mathjax}}= Resistance of the thermistor
93 93  
94 94  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.
95 95  
... ... @@ -104,10 +104,10 @@
104 104  
105 105  where:
106 106  
107 -* {{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.**//
108 -* {{mathjax}}\(T_0\){{/mathjax}} = The test temperature at which the thermistor is 10k {{mathjax}}\(\Omega\){{/mathjax}}, which in this case is 25 degrees celsius.
109 -* {{mathjax}}\(R_0\){{/mathjax}} = The resistance of the thermistor when it is 25 degrees celsius.
110 -* {{mathjax}}\(R_T\){{/mathjax}} = The current resistance of the thermistor.
107 +* {{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.**//
108 +* {{mathjax}}\(T_0\){{/mathjax}}= The test temperature at which the thermistor is 10k {{mathjax}}\(\Omega\){{/mathjax}}, which in this case is 25 degrees celsius.
109 +* {{mathjax}}\(R_0\){{/mathjax}}= The resistance of the thermistor when it is 25 degrees celsius.
110 +* {{mathjax}}\(R_T\){{/mathjax}}= The live resistance of the thermistor.
111 111  
112 112  === Filtering ===
113 113  
... ... @@ -124,9 +124,9 @@
124 124  
125 125  Where:
126 126  
127 -* {{mathjax}}\(F_c\){{/mathjax}} = Cut-off frequency of the filter. Any noise with a frequency above this will be filtered out.
128 -* {{mathjax}}\(R\){{/mathjax}} = Resistance of the resistor in low-pass filter.
129 -* {{mathjax}}\(C\){{/mathjax}} = Capacitance of the capacitor in the low-pass filter.
127 +* {{mathjax}}\(F_c\){{/mathjax}}= Cut-off frequency of the filter. Any noise with a frequency above this will be filtered out.
128 +* {{mathjax}}\(R\){{/mathjax}}= Resistance of the resistor in low-pass filter.
129 +* {{mathjax}}\(C\){{/mathjax}}= Capacitance of the capacitor in the low-pass filter.
130 130  
131 131  Using a resistor with 1k {{mathjax}}\(\Omega\){{/mathjax}} and a capacitor with 100 **nF **in capacitance, the cut-off frequency will be 1592 **Hz.**
132 132  
... ... @@ -153,9 +153,9 @@
153 153  
154 154  where:
155 155  
156 -* {{mathjax}}\(x\){{/mathjax}} = The mechanical placement excluding the dead length (178mm).
157 -* {{mathjax}}\(V_s\){{/mathjax}} = The supply voltage of the linear potentiometer, in this case it is 3.3 {{mathjax}}\(V\){{/mathjax}}.
158 -* {{mathjax}}\(V_{out}\){{/mathjax}} = The output voltage of the linear potentiometer. ranging from 0.033{{mathjax}}\(V\){{/mathjax}} to 3.267{{mathjax}}\(V\){{/mathjax}}.
156 +* {{mathjax}}\(x\){{/mathjax}} = The mechanical placement excluding the dead length (178mm).
157 +* {{mathjax}}\(V_s\){{/mathjax}}= The supply voltage of the linear potentiometer, in this case it is 3.3 {{mathjax}}\(V\){{/mathjax}}.
158 +* {{mathjax}}\(V_{out}\){{/mathjax}} = The output voltage of the linear potentiometer. ranging from 0.033{{mathjax}}\(V\){{/mathjax}} to 3.267{{mathjax}}\(V\){{/mathjax}}.
159 159  
160 160  === Filtering ===
161 161  
... ... @@ -165,6 +165,46 @@
165 165  
166 166  The gearbox Temperature Sensor for AR26 will be the [[GAG10K3976B1>>https://www.te.com/en/product-GAG10K3976B1.html]], a NTC temperature probe which will be installed into a generic M5 bolt which is mounted on the upright in the wheel assembly. The thermistor will be connected in a voltage divider configuration where the thermistor is in the lower position so that the voltage lowers when the temperature increases.
167 167  
168 -[[image:Oil_Temp_schematic.png||height="271" width="632"]]
168 +[[image:Oil_Temp_schematic.png||height="208" width="486"]]
169 169  
170 -Knowing the beta constant of the thermistor, the
170 +Knowing the beta constant of the thermistor, the equation for the temperature based on the voltage measured by the ADC inside microcontroller can be derived.
171 +
172 +(% style="font-size: 1.5em;" %)
173 +(((
174 +{{mathjax}}
175 +$$
176 +R_T = R_f \frac{V_{out}}{V_{in} - V_{out}}
177 +$$
178 +{{/mathjax}}
179 +)))
180 +
181 +Where:
182 +
183 +* {{mathjax}}\(R_f\){{/mathjax}}= The upper resistor in the voltage divider which stays fixed, which in this case is 1k {{mathjax}}\(\Omega\){{/mathjax}}
184 +* {{mathjax}}\(V_{out}\){{/mathjax}}= The voltage over the thermistor, and the voltage that the microcontroller will measure.
185 +* {{mathjax}}\(V_{in}\){{/mathjax}}= The supply voltage of the voltage divider, which in this case is a constant 3.3 {{mathjax}}\(V\){{/mathjax}}
186 +* {{mathjax}}\(R_T\){{/mathjax}}= Resistance of the thermistor
187 +
188 +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.
189 +
190 +(% style="font-size: 1.5em;" %)
191 +(((
192 +{{mathjax}}
193 +$$
194 +T = \frac{1}{\frac{1}{T_0} + \frac{1}{\beta} \ln\left(\frac{R_T}{R_0}\right)}
195 +$$
196 +{{/mathjax}}
197 +)))
198 +
199 +where:
200 +
201 +* {{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 3976 //**K.**//
202 +* {{mathjax}}\(T_0\){{/mathjax}}= The test temperature at which the thermistor is 10k {{mathjax}}\(\Omega\){{/mathjax}}, which in this case is 25 degrees celsius.
203 +* {{mathjax}}\(R_0\){{/mathjax}}= The resistance of the thermistor when it is 25 degrees celsius.
204 +* {{mathjax}}\(R_T\){{/mathjax}}= The live resistance of the thermistor.
205 +
206 +=== Filtering ===
207 +
208 +The sensors output latency can be expected to be a lot shorter than the oil temperature sensor as the sensor is just a variable sensor based on placement. The limiting factor for the system which uses this information is the CAN-BUS messages from the inverters which send the information each 6.25 milliseconds. This means that the cut-off frequency cannot be any lower than 160 Hz, which will make the same type of low pass filter from the oil temperature sensor acceptable with a cut-off frequency of 1591 Hz.
209 +
210 +