Wiki source code of Low voltage wiring

Last modified by Lars Skullerud on 2026/09/22 16:37

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version	line-number	content
9.1	1	{{wikibox image="https://wiki.alignracing.no/bin/download/Electrical/Low%20voltage%20wiring/WebHome/wireharness.jpg?rev=1.1"}}
1.1	2	Cables=yes
	3	{{/wikibox}}
	4
	5	{{toc/}}
	6
	7	= Description =
	8
	9
	10	= Design =
	11
9.1	12	== Pinout guide ==
1.1	13
7.1	14	There are a few rules regarding designing the pinout.
5.1	15
7.1	16	1. Pins intended to be used together (eg. +3V3, GND and AI for a sensor) should be physically grouped together.
	17	1. Ground and power to the PCB should be placed in one of the "corners" of the connector.
	18	1. CANbus connection should be placed in one of the "corners " of the connector.
	19	1. For PCBs with two CANbus high/low pairs, both pairs should be grouped together.
	20
	21	Rule 1 should ALWAYS be followed, it is intended to reduce the amount of spaghetti wiring on the car.
9.2	22
7.1	23	Rule 4 should also ALWAYS be followed, this is because it allows for creating short CANbus stubs. On a serial bus like CANbus, when the waveform hits a end it generate a reflection. If the length of a stub is too long, depending on the bus speed and length these stub reflection can mess with the bus timing, degrading or completely ruining data transfer.
9.2	24
7.1	25	Rule 2 and 3 are best practice rules intended to standardize designs but can be omitted if they prohibitively affect the trace routing, delaying completion of the design.
	26
	27	[[Example pinout>>image:Electrical.Sensor Module.WebHome@AR26_ASM pinout.png]]
	28
	29	(% class="wikigeneratedid" %)
	30	Above is an example pinout demonstrating all four rules. The boxes outline groupings of pins that are used for the same component, the exact way pins are grouped is irrelevant so long as they are physically beside each other (chose a grouping which simplifies your trace routing). Both powe and CANbus interfaces are placed in corners, and the two CANBus interfaces are placed next to each other.
9.6	31
1.1	32	== Color codes ==
	33
9.3	34	\|=Color\|=Signal
9.7	35	\|(% style="--darkreader-inline-color:var(--darkreader-text-ff0000, #ff1a1a); color:red" %)Red\|Power (24V/12V)
	36	\|(% style="--darkreader-inline-color:var(--darkreader-text-000000, #e8e6e3); color:black" %)Black\|Ground
	37	\|(% style="--darkreader-inline-color:var(--darkreader-text-008000, #72ff72); color:green" %)Green\|CAN Low
	38	\|(% style="--darkreader-inline-color:var(--darkreader-text-ffff00, #ffff1a); color:yellow" %)Yellow\|CAN High
	39	\|(% style="--darkreader-inline-color:var(--darkreader-text-800080, #ff72ff); color:purple" %)Purple\|SDC
13.2	40	\|(% style="--darkreader-inline-color:var(--darkreader-text-000000, #e8e6e3); color:black" %)White\|Analogue signals
9.7	41	\|(% style="--darkreader-inline-color:var(--darkreader-text-0000ff, #337dff); color:blue" %)Blue\|Digital signals
1.1	42
9.3	43	(% class="wikigeneratedid" %)
9.7	44	Useful rule for remembering which color is for CAN LOW and HIGH: "YelLOW is HIGH because that just makes sense".
9.3	45
1.1	46	== Headers & connectors ==
	47
3.1	48	=== Reasoning ===
1.1	49
3.1	50	The connectors on the car are standardized, this eases development by removing the need for finding new products matching requirements every year. It reduces the amount of different products and tools kept in stock. The selected connectors have already been proven to work by previous members. If future members want to use different connectors than the once listed below careful consideration should be given to what benefits swapping connectors would provide and why it is necessary.
	51
	52	=== Note about "legacy" connector series ===
	53
	54	Some of the connectors on the car are "legacy" connectors. A "legacy" connector, is a connector outside of the connector series listed below. It is in use on the car due to it being part of a old system, the work needed to replace them would be too great or too costly to perform. A good example of this is the AMPSEAL connector for the [[ACCU MB>>https://wiki.alignracing.no/bin/view/Electrical/ACCU%20MB/]] from AR26. In order to replace this connector a redesign and reproduction of both the motherboard and TSAC would be necessary. So long as systems like this are used on the car the old connectors will remain in use, but it is encouraged to replace this connector with one outlined below in future designs of these systems.
	55
1.1	56	=== PCBs ===
	57
	58	==== Inside enclosures ====
	59
3.1	60	In this section, "Inside enclosure" connectors refers to headers on a PCBs that are connected to wires running inside a waterproof, sealed during operation enclosure.
1.1	61
9.10	62	\|=Series Name\|=Header\|=Mating part\|=Crimps\|=Accessories\|=Usage
	63	\|Molex Mega-Fit\|[[Header>>https://www.molex.com/en-us/part-list/0177?general.componentType=PCB%20Header&productNameList=Mega-Fit]]\|[[Mating part>>https://www.molex.com/en-us/part-list/0177??taxonomyPathValueLast=Connector%20Housings&physical.gender=Receptacle&productNameList=Mega-Fit]]\|[[Crimps>>https://www.molex.com/en-us/part-list/0177?taxonomyPathValueLast=Crimp%20Terminals&productNameList=Mega-Fit]]\|N/A\|Power
	64	\|Würth WR-MPC3\|[[Single Row>>https://www.we-online.com/en/components/products/WTB_WR_MPC3_MALE_HEADER_SINGLE_ROW]], [[Dual Row>>https://www.we-online.com/en/components/products/WTB_WR_MPC3_MALE_HEADER_DUAL_ROW]]\|[[Single Row>>https://www.we-online.com/en/components/products/WTB_WR_MPC3_RECETACLE_PLUG_SINGLE_ROW]], [[Dual Row>>https://www.we-online.com/en/components/products/WTB_WR_MPC3_RECEPTACLE_PLUG_DUAL_ROW]]\|[[Crimps>>https://www.we-online.com/en/components/products/WTB_WR_MPC3_TERMINALS]]\|N/A\|Signal
	65	\|Würth WR-MM\|[[Male>>https://www.we-online.com/en/components/products/BTB_WR-MM_MINIMODULE_THT]]\|[[Female>>https://www.we-online.com/en/components/products/BTB_WR-MM_MINIMODULE_THT]]\|N/A\|N/A\|Board to board
1.1	66
9.4	67	==== PCB inn/out of enclosure ====
2.1	68
3.1	69	In this section, "Inn/out of enclosure" connector refers to connectors/headers on a PCB that goes through an enclosure wall, bypassing the need for running cables inside the enclosure to a dedicated connector in the enclosure wall. This section is for PCB mounted series, for PCB independent series see below.
2.1	70
9.9	71	\|=Series Name\|=Header\|=Mating part\|=Crimps\|=Accessories\|=Usage
	72	\|AMPLITE HD-22\|[[Header>>https://www.te.com/en/plp/d-sub-connectors/Y30jn.html?n=539879%20924001&d=657166&type=products&inStoreWithoutPL=false&q2=]]\|[[Mating part>>https://www.te.com/en/plp/d-sub-connectors/Y30jn.html?n=539881%20924000&d=657166&type=products&inStoreWithoutPL=false&q2=]]\|[[Crimps>>https://www.te.com/en/plp/connector-contacts/Y30lv.html?n=829500%2054207&d=653859%20765006%20554900&type=products&inStoreWithoutPL=false&q2=]]\|N/A\|Signal
10.1	73	\|Amphenol D-Sub Hybrid\|[[Header>>url:http://www.amphenol-cs.com/product-series/d-sub-hybrid.html?gender%5Bfilter%5D=Header%2C20102&termination_style%5Bfilter%5D=Through+Hole%2C20099]]\|[[Mating part>>url:http://www.amphenol-cs.com/product-series/d-sub-hybrid.html?gender%5Bfilter%5D=Receptacle%2C20095&termination_style%5Bfilter%5D=Through+Hole%2C20099]]\|[[Crimps>>url:http://www.amphenol-cs.com/product-series/d-sub-hybrid.html?termination_style%5Bfilter%5D=N%2FA%2C20201]]\|N/A\|Power/Signal
2.1	74
	75	=== Inn/out of enclosures ===
	76
3.1	77	In this section, "Inn/out of enclose" connector refers to connectors that are not mounted directly on a PCB but in the wall of an enclosure, bridging the inside and outside of the enclosure. Wires from "Inside enclosure" connectors can be terminated in these to connect them to the outside world.
2.1	78
	79	==== Signal ====
	80
10.1	81	\|=Series Name\|=Header\|=Mating part\|=Crimps\|=Accessories\|=Usage
10.2	82	\|AMPLITE HD-22\|[[Header>>https://www.te.com/en/plp/d-sub-connectors/Y30jn.html?n=539880%2054207%20924000&d=657166&type=products&inStoreWithoutPL=false&q2=]]\|[[Mating part>>https://www.te.com/en/plp/d-sub-connectors/Y30jn.html?n=539880%2054207%20924000&d=657167&type=products&inStoreWithoutPL=false&q2=]]\|[[Male>>https://www.te.com/en/plp/connector-contacts/Y30lv.html?n=829500%2054207&d=653859%20765006%20554900&type=products&inStoreWithoutPL=false&q2=]], [[Female>>https://www.te.com/en/plp/connector-contacts/Y30lv.html?n=829500%2054207&d=653860%20765006%20554900&type=products&inStoreWithoutPL=false&q2=]]\|N/A\|Signal
10.1	83	\|Amphenol D-Sub Hybrid\|[[Header>>https://www.amphenol-cs.com/product-series/d-sub-hybrid.html?termination_style%5Bfilter%5D=Through+Hole%2C20099&gender%5Bfilter%5D=Header%2C20102]]\|[[Mating part>>https://www.amphenol-cs.com/product-series/d-sub-hybrid.html?gender%5Bfilter%5D=Receptacle%2C20095&termination_style%5Bfilter%5D=Through+Hole%2C20099]]\|[[Crimps>>https://www.amphenol-cs.com/product-series/d-sub-hybrid.html?termination_style%5Bfilter%5D=N%2FA%2C20201]]\|N/A\|Power/Signal
2.1	84
	85	==== Power ====
	86
	87
	88	=== Peripheral ===
	89
9.9	90	\|=Series Name\|=Header\|=Mating part\|=Crimps\|=Accessories\|=Usage
	91	\|Deutch DTM\|[[Male (unpowered)>>https://www.te.com/en/product-CAT-D485-CH8172.html?n=54304%2095191&d=568931%20568938%20681711%20659727%20545677&type=products&inStoreWithoutPL=false&q2=]]\|[[Female (powered)>>https://www.te.com/en/product-CAT-D485-CH8172.html?n=54304%2095191&d=568931%20568938%20681710%20659727%20545677&type=products&inStoreWithoutPL=false&q2=]]\|[[Male>>https://www.te.com/en/product-CAT-D48-ST273.html?r=2&compatible=DTM04-08PA&d=549868&type=products&inStoreWithoutPL=false&q2=]], [[Female>>https://www.te.com/en/product-CAT-D48-ST273.html?r=2&compatible=DTM06-08SA]]\|[[Wedgelocks>>https://www.te.com/en/product-CAT-D485-W416.html?&type=products&n=893250%2054304%2095191]]\|Signal
2.1	92
13.2	93	=== Firewall ===
2.1	94
13.2	95	For the wheel encoders cables with one D-sub style shielded connector in each end is permanently installed through a cable gland. The reason for this as opposed to using a connector installed in the firewall is because of T4.8.8 and the encoder cables needing to be shielded from end to end. The connector listed below should only be used for power, CANbus, analog and digital signals between the front and rear of the car.
2.1	96
12.1	97	\|=Series Name\|=Header\|=Mating part\|=Crimps\|=Accessories\|=Usage
13.3	98	\|Deutch DTM\|[[Header>>https://www.te.com/en/product-DTM04-12PA-L012.html]]\|[[Mating part>>https://www.te.com/en/product-CAT-D485-CH8172.html?q=deutch%20dtm&d=568931%20568938%20681710%20545398&type=products&inStoreWithoutPL=false&q2=]]\|[[Male>>https://www.te.com/en/product-CAT-D48-ST273.html?r=0&compatible=DTM04-12PA-L012]], [[Female>>https://www.te.com/en/product-CAT-D48-ST273.html?r=0&compatible=DTM06-12SA]]\|[[Wedgelock M>>https://www.te.com/en/product-CAT-D485-W416.html?r=0&compatible=DTM04-12PA-L012]], [[Wedgelock F>>https://www.te.com/en/product-CAT-D485-W416.html?r=0&compatible=DTM06-12SA]]\|Power/Signal
12.1	99
4.1	100	== Power ==
	101
13.4	102	Power is distributed to the car from the [[PDB>>doc:Electrical.Power controller.WebHome]], located in the switch panel. Each component, box or PCB in the rear of the car is supplied by its own power/gnd pair. The PDB provides several power/gnd pairs through the firewall to the front of the car, critical systems get their own dedicated pair. A single power/gnd pair is fed through the firewall and split off to all non critical systems in the front of the car. This way weight is saved by reducing the amount of long cables passed from the rear to the front of the car, and a single failure on a non critical board does affect the power supplied to a critical one.
4.1	103
13.4	104	\|=Non critical\|=Critical
	105	\| \|
	106	\| \|
	107	\| \|
	108	\| \|
	109	\| \|
	110
4.1	111	== CANbus ==
	112
13.4	113	CANbus is a serial communication protocol used to pass data between systems on the car. Being a serial buss the only topology allowed is a serial one, that being connecting the bus devices together one after the other with only a single cable splice at the connection points (see image below). Connecting this type of bus in any other type topology will prevent communication on the bus.
4.1	114
13.4	115	[[image:controller-area-network-bus-topology-3696091310.jpg]]
	116
13.6	117	The reason CANbus only can utilize this topology is due to its nature as a differential bus, when the buss state switches the waveform of the switch propagates throughout the network and reflects of any ends, these reflections can interfere with following waveform and disrupt data transmission. This is the reason for the 120 ohm resistors at each buss end, they match the impedance of the bus, causing the waveform to settle without reflections when the waveform reaches the bus end.
13.4	118
13.6	119	It is physically impossible in a practical CANbus network to have stubs with zero length, see the image above, the devices have to be connected to the bus line with wire "offshoots" from the main bus. These "offshoots" are called stubs, the waveform will reflect of any stub present on the bus. Designed incorrectly too long stubs will disrupt data transfer, too long of a bus will also have this effect.
13.5	120
13.8	121	As it is the waveform reflections that interfere with data transfer it is data rate, wave timing which determins weather or not a wave reflection will interfere with subsequent transmissions. Calculating the permissible length and stub length can be difficult, best practice based on manufacturers suggestion for 1Mb/s is bus length less than 100m and no stub longer than 30cm. Implementing this should pose no challenge but has to be considered when designing enclosures.
13.5	122
13.11	123	One of the 120 ohm end resistors has to be located on the BMS in the accumulator, this is because the BMS has to be the CANbus end when the accumulator is on the handcart. The CANbus should be designed such that it total length is as short as possible, with the other 120 ohm end resistor being placed at the natural end of the bus.
13.10	124
14.2	125	Barring the used of a dedicated 120 ohm impedance bus cable, it is important to make sure the wires used when twisted together have a 120 ohm impedance. [[TP impedance calculator>>https://www.allaboutcircuits.com/tools/twisted-pair-impedance-calculator/]]
13.11	126
14.2	127	== [[image:Twisted-Pair-Impedance-Calculator.webp\|\|height="243" width="331"]] ==
	128
13.11	129	{{mathjax}}
14.2	130	$$Z=\frac{120}{\sqrt{e_r}}\cdot\ln\frac{2s}{D}$$
13.11	131	{{/mathjax}}
	132
14.3	133	(% class="wikigeneratedid" %)
14.4	134	Here e_r is the relative permittivity. For [[this>>https://no.rs-online.com/web/p/hook-up-wire/1964215]] type of wire and using e_r=3 for PVC (from [[here>>https://infinitalab.com/blog/polymer-dielectric-constant-table/]]) the impedance is approximately 113 ohm, this is close enough to 120 ohm that ensuring that any stub length is significantly shorter than 30cm and the bus is significantly shorter than 100m should ensure no problems with data transmission arise.
14.3	135
3.1	136	== SDC ==
4.1	137
	138
	139	== Analogue and digital signals ==
	140
	141
13.9	142	== System location overview ==
	143
	144
4.1	145	= Creating the harness =
	146
5.1	147	[[//Eye catching image to get you to pay //attention to //this section //specifically>>image:catInAhat.jpg\|\|height="235" width="234"]]
	148
	149	In this section the challenges, solutions to these challenges and the process I have encountered and used in the creation of the AR26/AR27 low voltage wiring harness are documented. Feel free to use this as a reference for designing future harnesses, and please update it with any useful procedures, tips or any other information you deem useful in designing a wiring harness for the benefit of future members.
	150
7.1	151	== Wire documentation ==
4.1	152
5.1	153	=== Pinouts ===
4.1	154
6.1	155	In order to create the wiring harness diagram, a overview of the pinout of all the PCBs and components is required. This has historically proved to be a big obstacle to the creation of the wiring harness because members finalize pinouts late in the design phase. In order to mitigate this a new approach is tried for AR27 by utilizing the wiki. Members should begin by designing their systems on the wiki, which features the PCB needs, how these features are implemented, which inputs and outputs are required and first draft of pinout should be present on the wiki before work in Altium starts. (Maybe veteran members also should approve the wiki design in order to ensure all required features are present) This first pinout is just a draft, unless absolute PCB trace spaghetti routing is desirable this pinout will change when the layout is finalized. This is unavoidable and has to be worked around, by getting an initial pinout draft one can begin creating the wiring documentation, pin numbers can be added later when the pinout is finalized.
5.1	156
7.1	157	=== Documentation ===
	158
	159	All the pinouts on the car should be collected in a singular place, like a google sheet. It is possible to wire the car based entirely on such a google sheet and Altium, personally I find this cumbersome and like to work from a drawn wiring diagram. For AR26 and AR27 I used PCSchematic, a free education licensed version can be downloaded [[here>>doc:.https\:www\.pcschematic\.comdaproduktergratis-automation-program-til-skoler.WebHome]].
	160
4.1	161	== Finding wire lengths ==
	162
	163
9.12	164	== Determining cable diameters ==
	165
	166	{{mathjax}}
9.13	167	$$\Delta U=I\rho\frac{L}{A}$$
9.12	168	{{/mathjax}}
	169
	170	{{mathjax}}
	171	$$\%\Delta U=100\%\cdot\frac{\Delta U}{U_{supply}}$$
	172	{{/mathjax}}
	173
	174
	175
4.1	176	== Twinning and scratch resistance ==
	177
	178
	179	== Crimping ==
	180
	181
	182	== Testing ==
	183
	184
	185	== Mounting ==

Wiki source code of Low voltage wiring

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