[feature] Shield/Screen individual cores #330
Comments
scottbouch
changed the title
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@scottbouch, thank you for sharing your use case. I don't know how to better accomplish your request with the current versions, but maybe a future version can support this. See also #56 for other discussions about complicated cable structures. Before starting a PR adding such a feature, it might be a good idea to discuss here:
As suggestions to points 2 and 3 above, see 2 examples below that still allow the original syntax for the simple cases: cables:
w:
colors: [RD, BU, YE, GN]
shield: [YE, GN]
cables:
w:
colors: [RD, BU, YE, GN]
shield:
ShieldP1: [RD, BU]
ShieldP2: [YE, GN]
ShieldAll: [ShieldP1, ShieldP2]
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Hi @kvid, thank you so much for responding to this request!
Its a bit hard to see in the images, but under the restoration section, the original cable shown has lost its outer jacket, exposing the construction. It has an un-screened red conductor, and individually screened yellow and green. The screen braid is pulled back from the last inch of wire and formed into a 'tail' and given a black insulating sleeve: https://scottbouch.com/mcfs/lightningt5t55/27l-1290-connector-personal-equipment-aircraft-portion.htm Many thanks again for the interest in this request, hopefully I can support further development from my own practical wiring experiences. |
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In this example, red and blue are not screened, but green and yellow are. The screens are wrapped in a plastic films, so are kept isolated from each other across the length of the cable. Some versions of this cable type allow the screens to touch. The option for individual screening of specific cores would be of benefit. Thanks, Scott
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@scottbouch, thank you for all the real-world examples that show my suggested examples might be useful and not not too complex. A consequence of implementing my suggestions above, is that the order of wires within the cable node might need to be reordered from the specified order (and numbering) to be able to draw a loop around consecutive wires. About point 3, where you wrote "It would be good if the loop touched the screen 'wire' to show an electrical connection.": I agree with you, but I've not yet found a way to obtain that. I used a table with rounded border inside a multi-row cell in the table of wires, and if I reduced the space around the rounded border to make it touch the shield wire below, it would also touch the wire above and the cells on each side. Maybe someone with Graphviz experience might suggest a trick for such a thing? |
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Hi @kvid , thanks for the work on this. The order that they appear in the cable node doesn't really matter in this instance as its the colours that matter, but actually this is a DEF-STAN cable, so the green and yellow would end up together anyway. However, I suppose there may be occasions though where a user builds up their own harness including screened and non-screened wires, they may wish to lay them out in a mixed combination to suit their own needs. Example here of a junction box connector with a mix of screened and un-screened wires, see PL1, SKT1 and SKT2. This is the fixed wiring inside a junction box, but you can also imagine the harnesses plugged in would require the same combination of screened and non-screened wires:
Regarding the loop around the wires, what you displayed before was good, maybe go with that then in the future see if the gap could be closed up? I.e.: its still a significant improvement! Worth noting the alternative approach from this above document of dashed parallel lines instead of a loop (dated 1964). But probably best see how it's done in ISO standards, which may well be a loop as discussed. Thanks again, Scott |
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@scottbouch wrote:
I agree - we can probably live with the small gap until someone finds a way to improve it.
The dashed parallel lines could be an alternative visualization for individual screened wires, but I'm not sure how it can be used to show that multiple wires have a common shield. I've not found "how it's done in ISO standards", but I found examples using dashed loops around a single wire or group of wires and one with references to IEC 60617-2019 and IEEE Std 315-1993. I also have seen a copy of the latter and can confirm it uses dashed loops around the wires. It seems IEC uses a dashed circle around a single wire, and a dashed circle outside a group of wires with arrows into each of the shielded wires. The latter alternative allows unshielded wires in-between shielded wires in the same group (see note A5 at the last linked page), but it might be a bit hard to read. IEEE allows separate dashed loops to be connected with a dashed line when not all wires in the common shield are adjacent in the diagram, but the IEC alternatives are also allowed. I've tried using dashed loops in one of my examples, and I made one of the loops with a thicker line (using 2 pt which is equal to the shield connection spline thickness) to see if that is better: Click to expand Graphviz
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Hi @kvid, that is a very good website, thanks. Overall, it would be good to implement whats presently easy or possble, with a 'TODO' list for future improvements. Another take on it, in this example, the screens are shown as single circles connected by a line, even if they are drawn next to each other. These mic/tel wires are the exact wiring type I shred an image of, for aircraft communication circuits. Maybe it would be good if possible to ideally give the user the option to connect circles with lines, or to draw ovals enveloping several wires, this gives freedom. Also worth noting that the multiple arrows are used in this drawing, but not for screens, instead are used to provide wiring harness identification. Cheers, Scott |
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I have just been reading IEEE 315-1975; it turns out the multiple headed arrows can be used for a variety of reasons, such as the application of screening or identification nomenclature as shown in these posts, plus the arrows can also be used to assign wires to twisted pairs. It also defines long dashes for screening/shielding:
Here the arrows are used to show which conductors are shielded (3 out of 7), plus we are into the use of circles and ovals:
Note how the solid loop (last examples below) is used to identify multicore cables, not screening:
The next section of the standard is onto RF coaxial cables, but that can wait for a future date! (I don't have a copy of IEC 60617 for comparison.) Cheers, Scott. |
Hi, I need to draw a cable where only two cores of a 4 core cable are screened. Presently I have just added a note to the cable properties, but it would be nice to be able to show it with oval shaped rings around the screened cores as you would see in diagrams.
Is there a way to graphically show screens on individual cores?
My example: https://scottbouch.com/tmp/UHF2.html
(Many thanks for this wonderful solution to drawing cables, I love it!)
Cheers, Scott
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