I hereby certify that I am not simply asking someone else to design a footprint for me.
Newbie here - Is there a library layout for track ‘fingers’ for a 3.96mm / 0.156" PCB edge connector?
I’m hoping to make an extender board for a Tektronix 500 series frame, which has a double-sided 28-way edge connector for the plugin modules (SG 501 etc). The track layout couldn’t be simpler - straight lines from one end to the other! (But I’d like to incorporate a couple of inline fuses and test points.)
Where will I find such a standard layout, and at what point do I place it on the board, please?
Sorry for such basic questions but I have no idea (or experience).
There will also need to be a keying slot.
I’d be very gratefull for any help with this.
John
and I was a bit surprised there is no wizard for creating edge connectors. But it is also understandable. Edge connectors are generally very simple, and KiCad’s footprint editor has a very nice and elaborate array function, and functions to batch change pad properties. Once you are familiar with these it is very quick and easy to draw all the pads manually. You can study some the edge connector footprints KiCad’s default libraries. The BUS_AT and BUS_PCI connectors do not have lines on Edge.Cuts, as older KiCad versions did not have support for this. the BUS_PCI_Express_* connectors do have their outline defined on Edge.Cuts.
You will find a 28 pin (or 56 pin) connector in the Connector_Generic library and fuses in the Device library. I use renamed, (to TPx) single pin connectors for test points.
You have two choices, either four 28 pin connectors or two 56 pin connectors. see below.
Note; the use of Rotate and Mirror to locate the symbols.
When you have completed your schematic, we’ll work on the footprints.
I am not sure whether JohnBB wants to attempt to make the PCB without a schematic, but I agee with jmk that this is not a good idea.
For the wiring in the schematic, it can be as simple as placing two connectors on top of each other and then pull them apart (although this can also go horribly wrong sometimes, but it’s easy to redo). With many fuses and test points direct wiring becomes messy quickly.
Another option is with labels. Just place a label ending in a number on the schematic, and then hold down the [Ins] key until you have enough of them. Then add wires in the same way, and then duplicate the whole block with [Ctrl + d] for the other connector.
Just the pads and tracks are OK, BUT the op wants some fuses and test points. These TPs and fuses will probably be mounted as THT, ,so now there is the problem of running the tracks to avoid pads both on top and bottom and the extra nets. In this case it will be easier with the schematic.
JMHO
Maybe.
Don’t forget the fuses and TPs. Will the top and bottom be symmetrical with those added?
Fuses and test points were the reason to suggest the label approach.
First draw a big column of labels with the [Ins] key repetition funcion.
Move or drag some of the labels horizontally to make some room for fuses and other stuff.
Draw / fix the wiring issues.
I don’t understand. It’s the schematic, not the PCB.
On the PCB you can draw a few tracks (also use the f key to finish the tracks to speed it up. and then you can use Copy & Paste if the PCB layout has a lot of symmetry. I experimented with this in 2019 and it worked quite nicely and quick back then.
Thank you both!
There’s a lot for me to digest and see if I can understand.
I can drop the onboard fusing, and test points, and KISS!
There will be [flexible] wiring going from the far end from the PCB edge connector to the [flying] female connector. I can add the fuses there.
Thanks, John.
So you wish to produce a plug made from PCB with 28 pins either side and a locating keyway between two of those pins. The other end is 56 through hole pads into which wires are soldered.
Something like the below?
The yellow pads have holes to solder wires into.
The blue tracks go to pads on the back side of the board.
The white outline is the board with a keying slot.
Absolutely spot-on!
The only caveat is that some tracks may need to be thicker as they are carrying power.
I’ll check the specs.
Later…
It’s complicated, but here goes:
The main frame power supply is shared between 5 edge connectors, so I guess absolute max drain from one would be about 1/3 of total (assuming some modules draw more than others.)
There’s + & - 33.5VDC fused at source at 2.5A each. And each rail is delivered via two connector contacts.
There’s +11.5V DC fused at source at 7.5A. And that is also delivered via two connector contacts.
There’s 17.5V AC not fused at source at all. (Delivered via a single connector contact.)
There’s 24.5V AC not fused at source at all and stated to be 500mA. (Delivered via a single connector contact.)
The Oscilloscope plugin has two fuses, one at 0.3A, and one at 0.75 A
The 550MHz Counter plugin (with LED numeric display) has a fuse at 2A.
I don’t think any contact is intended to carry more than 2A. That’s my guesstimation!
Putting fuses and test points on your PCB makes testing more reliable (fuses) and easier (test points). The PCB is a rigid structure and that feels like a good place to add these things. Hacking those parts in elsewhere is easier for the PCB design, but makes it less universal.
If your fixture looks anything like jmk is guessing, then adding a single or dual row male header is a good option. Then you have test points on all wires and you can easily make temporary connections with “dupont” wires.
A second connector footprint will allow pins for test points on up to all tracks, or just place the odd pad where needed.
Extend the board and fit a plastic or metal bar (pink bar) to clamp all the wires to the board, otherwise, after a few uses, wires will break off the board where soldered.
A few more comments:
The through hole connectors are 100 mil (1/10 inch) spacing between pads and between rows. How good is your soldering, especially with the pads connected to the back layer? Would you prefer larger pads more widely spaced?
Tracks shown are 30 mil wide.
The “finger pads” are “edge connector” type pads but I have no idea of the size and distance between pad centres you require. Same goes for where and width of key way.
Both the edge connector footprint and through hole connector footprint are created by making a single pad and then using the Array tool. The back layer “finger pads” are formed using the Duplicate tool, changing the layer in Properties then placing that row under the front row.
I haven’t yet read Paul’s FAQ, however it is my bed time.
Will check in tomorrow.
I agree about placing the fuses and TPs. Let’s see how I get on with the basics!
Yes, I think JMK has read my mind!
Are Dupont wires like sockets on the end of a wire - like ferrules?
Thanks
“Dupont wire” is just a historical name that stuck for some reason. I guess everybody know these things, but not all recognize the name. the black plastic is a 2.54 by 2.54mm square, and you can use them to make arbitrary connections between pins on 2.54mm headers or breadboards.
Note: the cheap ones do not even have copper wire (I guess it’s aluminimum), and they have a higher resistance then you would expect from a wire, so you can not use them for higher currents. But they are low cost and easy to replace while fiddling or when worn out and this makes them convenient to use anyway. They are available in all 3 combinations of Male / Female and you can buy them in different lengths.
I once had a PC that refused to boot without the (non existing) fan. So I used a dupont wire to tap of the tacho signal from another fan and plugged it into that otherwise empty fan connector. (I just forced in a male pin of the dupont connector in between the plastic and the metal of the other female fan connector. It was a 2 minute fix and it lasted for years until I bought a new PC and scrapped the old one.
Use “dog bone” corners or draw rounded corners after making certain that the mating connector will accept those.
Otherwise a lot of unnecessary communication with the manufacturer occurs.
