[TriEmbed] Favourite electrical connectors?

[Pete Soper]

The cable requirement for CANBUS is explicitly dictated by the bus 
standard (covered in this TI blurb 
<http://www.ti.com/lit/an/slla270/slla270.pdf>): you'll be using 120 ohm 
twisted pair. Accommodating the 120 ohm termination resistors needed at 
the two ends of the bus is a side issue that might interact with 
connector choice. The easy choice for cable is UTP (aka CAT3/5/6) with 
as few twisted pairs as you can get by with (since canbus only uses one 
pair). Somebody recently gave away hundreds of feet of this stuff at a 
TriEmbed meeting, so I think this is a good choice.

The bus is only two wires, plus one more for an optional shield. So a 
very simple connector will do it. IMO the lowly RJ11 will get the job 
done. I have three crimping tools you can borrow. :-) The male 
connectors are cheap as dirt. Here's a Digikey jack 
<http://www.digikey.com/product-detail/en/A-2014-0-4-R/AE10390-ND/2183641> 
(35 cents at Q50). Some of the "big boys" use RJ45, but I can't see the 
need for that and it's just extra cost wrt PCB area.

The lowly RJ11 combined with UTP cable might be a practical solution. 
The connector is "keyed", trivial to get in and out, but stays in place. 
You could also arrange a convention where a termination resistor could 
either be crimped into two additional connector sites (so the 
termination is part of the cable) or handled on the PCB. A weather boot 
would be used for cases where crud might get inside the connector, as it 
is highly exposed. Using dielectric grease to exclude oxygen would be a 
good idea too for cases where the connection is going to be exposed.

-Pete

On 09/25/2015 10:18 AM, Charles West via TriEmbed wrote:
> Hello,
>
> I'm working on a board for the CanInstall autoregistration project and 
> I'm not really sure what connectors to use for it.  I'm currently 
> leaning toward either DF13-4 connectors or simple 4 pin headers.  If I 
> may ask, are there any other connectors that you would recommend or 
> have used in your projects?
>
> Pros/cons:
> DF13:
> The upside is that they are very small, connect very securely and SMD 
> female connectors are $.41 per.  The downside is that they are 
> extremely hard to get out (don't pull on cable, very gently pry with 
> finger nail on one side, then the other) and cables for them are 
> extremely hard to find/expensive ($1.5 per in lots of 20 is the 
> cheapest I've found).
>
> Vertical Headers:
> The plus is I can get break apart SMD headers at roughly $.05 each 
> including shipping at lots of $5 
> (http://www.ebay.com/itm/10pcs-2-54MM-1-40Pin-SMD-SMT-1-40Pin-Male-Single-Row-Pin-Header-/261879748701?hash=item3cf93fd85d), 
> cables at $.22 per in lots of $5 
> (http://www.ebay.com/itm/20pcs-2-54mm-to-2-54mm-Dupont-Wire-Cable-Connectors-4P-to-4P-Pin-Header-20cm-YG-/111487505711?hash=item19f52c552f) 
> and they are pretty standard for hobbyist projects (and extremely 
> similar to servo connections).  The downsides are that they have no 
> polarity control, are much more likely to slide out and take up a lot 
> more board real estate (translating to either bigger boards or less 
> connectors).
>
> Thanks,
> Charlie
>
>
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