I am drawing a schematic symbol for a Wurth WE-Flex transformer. Originally this was 1 simple symbol with 6 windings/12 pins. This led to confusion because I had to add lots of labels, then ‘map’ the labels in my head all over the schematic. Finally I made a mistake on the PCB because of this
So now I have converted each winding (N1…N6) to a ‘unit’ (A.F).
Each winding has an associated ‘N’ value (N1, N2, N3, N4, N5, N6). The data-sheet tells you (for example) “N1:N2 = 1:3.6” etc
So it would be nice if I could add a text label ‘N1’ etc to each winding.
But this is not possible because only 1 global text label is created. After I create labels N1…N6 I find that ALL units have label “N6”.
A similar problem exists with winding orientation ‘visually’. So primary should have pins ‘facing left’ and secondary wants pins ‘facing right’.
It is possible to compensate using schematic feature like ''Place text" or ‘Mirror Y’ of course.
Now if you were trying to use a single winding and putting it elsewhere in the circuit. I would not recommend that. I would use a consolidated symbol and have labels at the different places in the circuit.
I have used the WE Flex and similar from Coilcraft, TDK, & Coiltronics (?? unsure because the company name has changed several times.). I am not sure I understand your problem.
I would draw one transformer symbol with 6 windings along with 12 pin numbers and 6 phasing dots. If drawing all of the 12 wires in your schematic diagram is clumsy, I would use local net labels.
I just looked to see…I have not created that symbol but I do have one with two windings. This symbol is for a transformer with two windings on a (maybe a 14?) pin bobbin. Each winding end is connected to two pins. I think the 6 winding symbol could be constructed similarly… FWIW this symbol was created in KiCad 5 but I am now viewing it with 5.99.
The transfomer has 6 windings. There is no problem with phase dots (already done). ‘Revision 1’ of the symbol looks exactly like the WE-Flex data sheet, so far so good.
My problem is that with 12 pins and some arbitrary circuit making use of those pins, direct wires would be hard to keep track of, leading to the type of mistake I made.
Therefore, on the schematic I labled the symbol with names such as “SEC4_dot”. But I would find it more intuitive/easy to read if I could place the winding symbol close to where it is used, and it would save me adding 12 labels.
Also, as a general comment it is possible I’d like to break out/make into units (for example) a transistor array. some of these has NPN and PNP, some have internal connectuions but only between specific pairs.
So one unit might have 2 transistors, one might be NPN, one could be PNP. Again it could be it looks neater to use those units locally on the schamtic rather than have a bunch of labels or many crossing wires.
You cannot break an existing symbol but you can make a symbol as parts.
eg. draw one winding, label pins 1 & 4 then save that as “part A”.
Change the pin numbers to 2 & 5 and then call that “part B” etc.
The same principle applies for arrays. Check out some of the gate arrays in the 4000 or 7400 for examples.
Or maybe even a LM747 for twins to your 741.
The simplest extra would be to allow per-unit text labels. In my case it could be a winding identifier like “N3”.
More generally when the schematic is better drawn with a device exploded into units, it could be potentially useful to allow units to be non-identical.
As mentioned above, I can imagine wanting to break up a transistor array having for instance different device polarities. Even something like a PLL might be a part that would look better broken into “logical units”.
I understand. I disagree but I understand. Having many times worked on products (especially in my younger days) I’ve picked up many a schematic and had to figure out how it worked before I could fix the problem. From that standpoint having transformer windings on a common core separated like a dual 741 is not intuitive.
Having all the windings of an apparently complex transformer grouped together in a single symbol can also make the schematic less readable.
It’s always some kind of compromise.
What is far more important is whether some thought is going in how the schematic is being drawn. Thoughtlessly cobbled together schematics are a pain to read, and 741 is clearly putting effort into it to make something he thinks that will work.
I have a strong tendency to keep signals flowing from left to right, and voltages from top to bottom.
Another important part in the readability of a schematic is some notes about what each IC does. For example if you have a microcontroller with an I2C bus that connects 20 IC’s that all go into the same analog maze, then having to study the datasheets of all those 20 IC’s just to get an overview is time consuming. Things like this are usually not obvious to the person who makes the schematic, because he very likely knows all those IC’s by hart.
Another thing that makes schematics harder to read is to cram together everything on a single A4 page. Draw parts in logical blocks and leave some room around them, so it’s easy to recognize as a logical block. Drawing lines in between those logical blocks to further separate them is counterproductive. A bit of empty space works well, an those extra lines are a pain to maintain as those blocks have a tendency to get re-arranged in order during schematics design.
I do find that adding some much bigger text then all the other texts to identify what a certain block does helps in getting a quick overview of a schematic.
I agree wholeheartedly. Some folks don’t understand, you can write anything you want on a drawing (well nothing obscene). Explanations, dotted lines around sections etc. You should add any special requirement of a part. i.e. NPO cap with note “important of delay… to be within spec” or whatever.
Another important note is the identification of high current traces, special EMC related devices or intellectual property limitations (likely not common).
I personally prefer to keep transformers together in a symbol, especially if the schematic has multiple transformers. I can always come up with a global label the allows the reader to quickly understand the function(s). But again just my opinion.
The two things I detest are:
crossed wires with a connection (dot or not I think it is a bad practice)
