M12-A connectors, CAN bus and off the shelf cables - Page 1
Forum section: electronics / projects

author: Simon
author_rank: Unknown
timestamp: December 31, 2023, 06:41:03 pm
content: I'm looking at using 8 way M12-A connectors to distribute low level power and CAN bus signals. My hope is to use off the shelf cables as the do it yourself plugs are 45-50mm long before I worry about the bend radius. In the past I have run CAN bus over twisted pairs. While I would expect the standard cables to have consistently made wire where the wires would be twisted to a degree will this be sufficient?I need fairly short cables such as 200mm but the shortest seems to be 500mm. Anyone know of a source, or will I have to resort to custom made cables?

author: Tomorokoshi
author_rank: Super Contributor
timestamp: December 31, 2023, 08:08:50 pm
content: Look at:https://www.turck.us/en/https://www.murrelektronik.com/Others will have them too. I've encountered CAN over M12-5 where one pair is power, the other is CAN, with an additional ground. They come in variations of each pair separately foil shielded, with an overall outer foil or braid. Watch out for color and keying options. Sometimes the various colors have special meanings.8-conductor M-12 may not have the shielding you might want. I've always found the twist to be around 2 to 3 cm per cycle.

author: Simon
author_rank: Unknown
timestamp: December 31, 2023, 09:50:46 pm
content: Yes I have found various M12A-5 cables for CAN bus and they may not be consistent.https://www.provertha-admin.de/out/tinymce/DS_I60_01_Canbus_M12_Verb_Ltg.pdfhas 2 different wire sizes, not sure which is which, I assume the bigger is the power.https://www.oem.ee/pdfs?q=/ui/product-resources/oem/-_-131974.pdf?att=False&hash=0E571D60665CE3B48EFEC88C7B1D3897&title=BG20208-Mxxx_1200659615.pdfthe yellow and green which are traditionally CAN H/L are in the pins that on the other cable are marked as power. No clue about the cable twisting.So I take it there is no standardization.

author: coppercone2
author_rank: Super Contributor
timestamp: December 31, 2023, 09:51:54 pm
content: why not just use m12 connectors with twisted pair cables? it sounds like you need a different type of cable to be put with the same connectoryou just need to be careful stripping them and assembling to not get twisted pairs mixed up because some cable are confusinghave you checked to see if there is crimp or solder connectors that are stubbier?I noticed the solder/screw ones are long. But if you can find a crimp pin insert one it should be shorter.

author: Simon
author_rank: Unknown
timestamp: December 31, 2023, 09:55:03 pm
content: Well i was hoping to find off the shelf cables, if there is a standard for CAN bus great, apparently maybe not?

author: mm1
author_rank: Newbie
timestamp: December 31, 2023, 10:18:45 pm
content: Have you looked at marine cables for NEMA2000 ? Ancor marine and Garmin sell cables , tees that are easy to use.These are not 8 pin, but at least some sort of standard

author: Simon
author_rank: Unknown
timestamp: January 01, 2024, 08:03:13 am
content: well I don't mind what I use. I was looking to have 5V and 24V power with the CAN bus. But if a consistent M12A-5 cables exist for CAN bus then I'd take just 24V around the system in exchange for the standard.So NEMA2000 looks like M12-A-5P connectors, perfect if there are readily available cables and adapters.

author: voltsandjolts
author_rank: Unknown
timestamp: January 01, 2024, 09:53:03 am
content: Never used NMEA2000 myself but interestedhttps://www.maretron.com/products/nmea-2000-cables-and-connectors/https://www.ancorproducts.com/en/products/Wire-and-Cable/NMEA-2000

author: Simon
author_rank: Unknown
timestamp: January 01, 2024, 10:31:40 am
content: Quote from: voltsandjolts on January 01, 2024, 09:53:03 amMy main gripe is the minimum 500mm cables, I found one source of 300mm. I'm a little confused about the power tap tee in one of your links, it has two female screws on it, but all cables are male to female so put that mid run and you have a problem although I expect someone does cables to suit.As a system it looks handy. I'm not sure if I want to put one socket on my devices and use the tee pieces or put two sockets on each device and only use the cables, again this is a problem as now I have to use a plug and socket to work with the cables or see if I can find the cables that are plugs both ends.

author: voltsandjolts
author_rank: Unknown
timestamp: January 01, 2024, 10:40:31 am
content: There also seems to be a boatload (pun intended) of stuff on amazon for "nmea 2000 cable", you might find something suitable there.

author: Simon
author_rank: Unknown
timestamp: January 01, 2024, 10:47:00 am
content: Yea, the thing to remember with connectors is that there are connectors and connectors. A female pin made from a tube with a slit in it is never going to work as well as a proper contact with miniscule sprung wires inside that envelope the male contact and form a secure vibration proof connection.I am connecting together items on a machine with a motor bolted to it and it the future the motor will also have M12 connectors on it.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: January 01, 2024, 05:02:45 pm
content: Need more definition. The connections on the two devices need to be completely defined before ordering anything. Basically, consider all M12 and similar cables to be custom.Work through this configurator to narrow in on options:https://www.turck.us/en/productgroup/Connectivity/Cordsets##downloadsProductpageFor example:https://www.turck.us/en/product/777046422https://www.turck.us/attachment/B2301_M12_Eurofast_Cordsets_and_Receptacles.pdf

author: Simon
author_rank: Unknown
timestamp: January 01, 2024, 09:00:03 pm
content: In an ideal world I would have a 6 pin connector (that does not exist) carrying three twisted pairs for 5V, 24V and CAN bus using the 5V GND as it's reference. Now 8 pins do exist and this is fortunate as the 8 pins are only 2A rated and I hoped for a little more, but the spare pair can be 24V as well so 4A of capacity versus the 5A of the 5 pin connector, I'd be happy.But then I would have to either accept that I will be buying standard off the shelf cables that do not have specific twisted pairs in them in order to get any length I want or I will have to have them made.Now something like NEMA 2000 means that I can get cables specifically for the job but I have to sacrifice one of my supply voltages. Given that NEMA 2000 means following a specific way in which these cables work to the point that I can only have leads that have a plug and socket and still I can only get them in lengths down to 300mm I do think that maybe I'm just taking on more problems to fix others with a solution that is still not ideal and that maybe I should just stick with my original plan to use M12-A5P connectors, either I take the risk with the much looser cable twisting or I get them made specifically.The reason I really want to keep my two supply voltages is that I will have to send 24V around the machine and while I could derive 5V from it this will mean a DC/DC converter at every node or a hot linear regulator working at just 20% efficiency which quickly turns a tiny module into a much larger nightmare.