Skip to Content

Wiki source code of Sensor Module

Version 58.1 by Heimir Thordarson on 2026/02/09 19:56
Hide last authors
Heimir Thordarson 47.1 1 {{wikibox title="Sensor Module" image="https://wiki.alignracing.no/bin/download/Electrical/Sensor%20Module/WebHome/ASM_AR26.png?rev=1.1" caption="3D model of the Sensor Module from Altium Designer" width="30" labelWidth="50"}}
Heimir Thordarson 9.3 2 Voltage = 4.5V - 40V
Heimir Thordarson 11.1 3 Fuse Current = 125mA
Heimir Thordarson 9.3 4 Sensor Inputs = 13
5 Voltage divider Inputs = 2
6 3V3 Thermistor Inputs = 7
7 5V Pressure Inputs = 4
Heimir Thordarson 55.1 8 Communication Protocol = CAN FD
9 Max Data rate = 1 Mbps
10
Heimir Thordarson 2.1 11 {{/wikibox}}
12
Heimir Thordarson 52.1 13 = Table of Contents =
14
Heimir Thordarson 48.2 15 {{content}}
16 {{content}}
17 {{content}}
Heimir Thordarson 51.1 18 {{toc reference="Electrical.Sensor Module.WebHome"/}}
Heimir Thordarson 48.2 19 {{/content}}
20 {{/content}}
21 {{/content}}
Heimir Thordarson 48.1 22
Heimir Thordarson 3.1 23 = Description =
24
Heimir Thordarson 9.1 25 The Sensor module is designed to measure any extra analog signals rear of the firewall. For AR26, the module is designed to measure two suspension displacement sensors, two oil temperature, four water pressure, four water temperature, and one air temperature sensor. All of the measurements are then transmitted to a CAN network, which there are two of.
Heimir Thordarson 1.5 26
Heimir Thordarson 1.2 27 = Wiring Diagram =
28
Heimir Thordarson 11.3 29 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
Heimir Thordarson 9.4 30
Heimir Thordarson 55.1 31 [[image:AR26_ASM pinout.png||height="287" width="616"]]
Heimir Thordarson 10.2 32
Heimir Thordarson 11.4 33 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.
Heimir Thordarson 10.2 34
Mads Pedersen 12.4 35
Heimir Thordarson 12.9 36 (% style="width:1058.6px" %)
Heimir Thordarson 13.1 37 |=(% style="width: 71px;" %)Pin Number|=(% style="width: 164px;" %)Pin Name|=(% style="width: 124px;" %)Type|=(% style="width: 70px;" %)(((
Heimir Thordarson 12.8 38 Pin
39 Number
Heimir Thordarson 13.1 40 )))|=(% style="width: 218px;" %)Pin name|=(% style="width: 58px;" %)(((
Heimir Thordarson 12.8 41 Type
Heimir Thordarson 13.1 42 )))|=(% style="width: 32px;" %)Pin Number|=(% style="width: 192px;" %)Pin Name|=(% style="width: 90px;" %)Pin Type
Heimir Thordarson 12.9 43 |(% style="width:71px" %)(((
Heimir Thordarson 11.5 44 1
Heimir Thordarson 14.1 45 )))|(% style="width:164px" %)Air Temperature|(% style="width:124px" %)Analog (0-3.3V)|(% style="width:70px" %)16|(% style="width:218px" %)Air Temperature|(% style="width:58px" %)GND|(% style="width:32px" %)31|(% style="width:192px" %)Suspension Displacement Left|(% style="width:90px" %)GND
46 |(% style="width:71px" %)2|(% style="width:164px" %)Suspension Displacement Left|(% style="width:124px" %)Analog (0-3.3V)|(% style="width:70px" %)17|(% style="width:218px" %)Suspension Displacement Left|(% style="width:58px" %)3V3|(% style="width:32px" %)32|(% style="width:192px" %)Suspension Displacement Right|(% style="width:90px" %)GND
Heimir Thordarson 13.1 47 |(% style="width:71px" %)3|(% style="width:164px" %)Suspension Displacement Right|(% style="width:124px" %)Analog (0-3.3V)|(% style="width:70px" %)18|(% style="width:218px" %)Suspension Displacement Right|(% style="width:58px" %)(((
48 3V3
49 )))|(% style="width:32px" %)33|(% style="width:192px" %) |(% style="width:90px" %)
50 |(% style="width:71px" %)4|(% style="width:164px" %)Oil Temperature Right|(% style="width:124px" %)Analog (0-3.3V)|(% style="width:70px" %)19|(% style="width:218px" %)Oil Temperature Right|(% style="width:58px" %)3V3|(% style="width:32px" %)34|(% style="width:192px" %) |(% style="width:90px" %)
51 |(% style="width:71px" %)5|(% style="width:164px" %)Oil Temperature Left|(% style="width:124px" %)Analog (0-3.3V)|(% style="width:70px" %)20|(% style="width:218px" %)Oil Temperature Left|(% style="width:58px" %)3V3|(% style="width:32px" %)35|(% style="width:192px" %) |(% style="width:90px" %)
52 |(% style="width:71px" %)6|(% style="width:164px" %)Cooling Temperature 4|(% style="width:124px" %)Analog (0-3.3V)|(% style="width:70px" %)21|(% style="width:218px" %)Cooling Sensor 4|(% style="width:58px" %)GND|(% style="width:32px" %)36|(% style="width:192px" %) |(% style="width:90px" %)
53 |(% style="width:71px" %)7|(% style="width:164px" %)Cooling Pressure 4|(% style="width:124px" %)Analog (0-5V)|(% style="width:70px" %)22|(% style="width:218px" %)Cooling Sensor 4|(% style="width:58px" %)3V3|(% style="width:32px" %)37|(% style="width:192px" %) |(% style="width:90px" %)
54 |(% style="width:71px" %)8|(% style="width:164px" %)Cooling Temperature 3|(% style="width:124px" %)Analog (0-3.3V)|(% style="width:70px" %)23|(% style="width:218px" %)(((
55 Cooling Sensor 3
56 )))|(% style="width:58px" %)GND|(% style="width:32px" %)38|(% style="width:192px" %) |(% style="width:90px" %)
57 |(% style="width:71px" %)9|(% style="width:164px" %)Cooling Pressure 3|(% style="width:124px" %)Analog (0-5V)|(% style="width:70px" %)24|(% style="width:218px" %)(((
58 Cooling Sensor 3
59 )))|(% style="width:58px" %)3V3|(% style="width:32px" %)39|(% style="width:192px" %) |(% style="width:90px" %)
60 |(% style="width:71px" %)10|(% style="width:164px" %)Cooling Temperature 2|(% style="width:124px" %)Analog (0-3.3V)|(% style="width:70px" %)25|(% style="width:218px" %)Cooling Sensor 2|(% style="width:58px" %)GND|(% style="width:32px" %)40|(% style="width:192px" %) |(% style="width:90px" %)
61 |(% style="width:71px" %)11|(% style="width:164px" %)Cooling Pressure 2|(% style="width:124px" %)Analog (0-5V)|(% style="width:70px" %)26|(% style="width:218px" %)Cooling Sensor 2|(% style="width:58px" %)3V3|(% style="width:32px" %)41|(% style="width:192px" %) |(% style="width:90px" %)
62 |(% style="width:71px" %)12|(% style="width:164px" %)Cooling Temperature 1|(% style="width:124px" %)Analog (0-3.3V)|(% style="width:70px" %)27|(% style="width:218px" %)Cooling Sensor 1|(% style="width:58px" %)GND|(% style="width:32px" %)42|(% style="width:192px" %) |(% style="width:90px" %)
63 |(% style="width:71px" %)13|(% style="width:164px" %)Cooling Pressure 1|(% style="width:124px" %)Analog (0-5V)|(% style="width:70px" %)28|(% style="width:218px" %)(((
64 Cooling Sensor 1
65 )))|(% style="width:58px" %)3V3|(% style="width:32px" %)43|(% style="width:192px" %)Main Power|(% style="width:90px" %)GND
66 |(% style="width:71px" %)14|(% style="width:164px" %)CAN High 1|(% style="width:124px" %)CAN|(% style="width:70px" %)29|(% style="width:218px" %)CAN Low 2|(% style="width:58px" %)CAN|(% style="width:32px" %)44|(% style="width:192px" %)Main Power|(% style="width:90px" %)+24V
67 |(% style="width:71px" %)15|(% style="width:164px" %)CAN Low 1|(% style="width:124px" %)CAN|(% style="width:70px" %)30|(% style="width:218px" %)CAN High 2|(% style="width:58px" %)CAN|(% style="width:32px" %) |(% style="width:192px" %) |(% style="width:90px" %)
Heimir Thordarson 11.4 68
Heimir Thordarson 41.4 69 == Air Temperature Sensor ==
Heimir Thordarson 12.1 70
Heimir Thordarson 16.12 71 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.
Heimir Thordarson 16.4 72
Heimir Thordarson 42.4 73 [[image:circuit with marks.png||height="237" width="566"]]
Heimir Thordarson 17.2 74
75 (% class="wikigeneratedid" %)
Heimir Thordarson 35.6 76 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.
Heimir Thordarson 17.2 77
Heimir Thordarson 27.2 78 (% style="font-size: 1.5em;" %)
79 (((
80 {{mathjax}}
Heimir Thordarson 17.6 81 $$
82 R_T = R_f \frac{V_{out}}{V_{in} - V_{out}}
83 $$
Heimir Thordarson 27.2 84 {{/mathjax}}
85 )))
Heimir Thordarson 26.2 86
Heimir Thordarson 27.2 87 Where:
Heimir Thordarson 26.2 88
Heimir Thordarson 35.6 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}}
Heimir Thordarson 35.7 90 * {{mathjax}}\(V_{out}\){{/mathjax}} = The voltage over the thermistor, and the voltage that the microcontroller will measure.
Heimir Thordarson 36.1 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
Heimir Thordarson 27.2 93
Heimir Thordarson 36.2 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.
Heimir Thordarson 36.1 95
96 (% style="font-size: 1.5em;" %)
97 (((
98 {{mathjax}}
99 $$
100 T = \frac{1}{\frac{1}{T_0} + \frac{1}{\beta} \ln\left(\frac{R_T}{R_0}\right)}
101 $$
102 {{/mathjax}}
103 )))
Heimir Thordarson 36.2 104
Heimir Thordarson 39.3 105 where:
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.**//
Heimir Thordarson 38.3 108 * {{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.
Heimir Thordarson 58.1 110 * {{mathjax}}\(R_T\){{/mathjax}} = The live resistance of the thermistor.
Heimir Thordarson 39.2 111
Heimir Thordarson 41.4 112 === Filtering ===
Heimir Thordarson 39.2 113
Heimir Thordarson 39.3 114 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.
115
116 (% style="font-size: 1.5em;" %)
117 (((
118 {{mathjax}}
119 $$
Heimir Thordarson 41.1 120 F_c = \frac{1}{2 \pi R C}
Heimir Thordarson 39.3 121 $$
122 {{/mathjax}}
123 )))
Heimir Thordarson 41.2 124
125 Where:
126
Heimir Thordarson 41.3 127 * {{mathjax}}\(F_c\){{/mathjax}} = Cut-off frequency of the filter. Any noise with a frequency above this will be filtered out.
Heimir Thordarson 42.3 128 * {{mathjax}}\(R\){{/mathjax}} = Resistance of the resistor in low-pass filter.
129 * {{mathjax}}\(C\){{/mathjax}} = Capacitance of the capacitor in the low-pass filter.
Heimir Thordarson 41.4 130
Heimir Thordarson 46.4 131 Using a resistor with 1k {{mathjax}}\(\Omega\){{/mathjax}} and a capacitor with 100 **nF **in capacitance, the cut-off frequency will be 1592 **Hz.**
Heimir Thordarson 41.4 132
133 == Suspension Displacement Sensor ==
134
Heimir Thordarson 43.1 135 For AR26, the same sensors from AR25 is reused. These are the [[Texense RSL-A-50-P>>https://cdn.shopify.com/s/files/1/0368/1989/files/technical_datasheet_RSL.pdf?413]] which can be connected as the entire voltage divider when using each end as supply and ground. The output of the sensor will then be the throw of the potentiometer.
Heimir Thordarson 41.4 136
Heimir Thordarson 42.3 137 [[image:Suspension Displacement Circuit.png]]
Heimir Thordarson 41.5 138
Heimir Thordarson 43.4 139 The sensor has a measurable range of 50mm with electrical range of 51mm, meaning that the electrical range will in practice be 1960 {{mathjax}}\(\Omega\){{/mathjax}} with 40 {{mathjax}}\(\Omega\){{/mathjax}} in total on each end.
Heimir Thordarson 42.2 140
Heimir Thordarson 44.2 141 [[image:Actual Representation of Linear Potmeter.png||height="195" width="309"]]
Heimir Thordarson 42.3 142
Heimir Thordarson 44.3 143 This can then be used to create the length of the sensor based on the input voltage.
Heimir Thordarson 43.4 144
Heimir Thordarson 45.1 145 (% style="font-size: 1.5em;" %)
146 (((
147 {{mathjax}}
148 $$
149 x = \frac{50}{1960} \left( \frac{2000\,V_{\text{out}}}{V_s} - 20 \right)
150 $$
151 {{/mathjax}}
152 )))
Heimir Thordarson 44.2 153
Heimir Thordarson 45.2 154 where:
155
Heimir Thordarson 46.6 156 * {{mathjax}}\(x\){{/mathjax}} = The mechanical placement excluding the dead length (178mm).
Heimir Thordarson 46.1 157 * {{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}}.
Heimir Thordarson 46.2 159
160 === Filtering ===
161
Heimir Thordarson 46.8 162 The sensors output latency can be expected to be a lot shorter than the air 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 air temperature sensor acceptable with a cut-off frequency of 1591 Hz.
163
Heimir Thordarson 55.2 164 == Gearbox Temperature Sensor ==
Heimir Thordarson 46.8 165
Heimir Thordarson 55.7 166 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
Heimir Thordarson 56.3 168 [[image:Oil_Temp_schematic.png||height="271" width="632"]]
Heimir Thordarson 56.2 169
Heimir Thordarson 57.1 170 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.
Heimir Thordarson 57.2 171
Heimir Thordarson 57.1 172 (% 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
Heimir Thordarson 57.2 183 * {{mathjax}}\(R_f\){{/mathjax}} = The upper resistor in the voltage divider which stays fixed, which in this case is 1k {{mathjax}}\(\Omega\){{/mathjax}}
Heimir Thordarson 57.1 184 * {{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
Heimir Thordarson 57.2 201 * {{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.**//
Heimir Thordarson 57.1 202 * {{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.
Heimir Thordarson 57.3 204 * {{mathjax}}\(R_T\){{/mathjax}} = The live resistance of the thermistor.