Spark Logic

Connections?

turboscrew Sat Jul 07, 2018 6:58 pm

How do you connect devices to boards?
I’m loosing my mind with an Si4432-module.
I soldered JST-GHs at the module end and crimped DuPonts to the other end of the wire (with Engineer-09 pliers).
The JST-end was ready-made with 10 cm wires, and I folded the other end (peeled) before crimping. I think the wire is AWG 28,
so the DuPont crimp would probably be loose if I didn’t fold it.
I still keep getting quite a lot of SPI-errors.

I was thinking about soldering the wires onto the boards, but I don’t have a good wire for that.
The holes in the Si4432 module are for 1.25 mm raster connector and I have problems of finding thin enough wire.
And it seems that many of the ribbon cables (thin enough) are made of material that repels solder.

How do you guys make reliable connections?

Replies

Pito Sat Jul 07, 2018 7:10 pm

The most reliable connections are the wire-wrap ones :)
WireWrap.JPG
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turboscrew Sat Jul 07, 2018 7:32 pm

Hm. I do have a wire-wrapping pen and some wire-wrap wire left, but I don’t think it’s good stuff between boards – it’s single core.
And I think the raster (1.25 mm = 0.049 in) makes it hard to find suitable pins. Also I think the pins would be too close to each other for the wire-wrapping pen.

I tried to cut a piece of ribbon cable with duponts into half and solder the JST and DuPont wires together, but the solder didn’t stick to the ribbon cable.

With the magnet wire you mean the wire used in coils?

Pito Sat Jul 07, 2018 7:38 pm

https://www.ebay.com/itm/polyurethane-E … iSTyV7bgAw

Not for movable connections the magnet wire, however.

Best do find an cat5e ethernet patch cable with stranded copper core inside the twisted wires. The insulation is great and good for movable connection between the boards. The stranded core is perfect. When left originally twisted its impedance is around 110ohm, good for our cmos logic matching..
It could be the dupont crimp crimps fine on that stranded patch wire..

With 0.1in pitch there are flat ribbon cables with male/female connectors you simply press onto the cable.

turboscrew Sat Jul 07, 2018 9:32 pm

That ethernet patch cable sounds good.
And yes. There are plenty of options for 0.1 inch pitch, but the manufacturer of the Si4432 modules uses this 0.049 inch pitch (12 pins).
There is also a pin header included, but I haven’t figured out what can be connected to 0.049 inch pitch pin header.
Despite of quite some googling, I haven’t found a single female connector for those pin headers.

turboscrew Sun Jul 08, 2018 7:38 am

I wonder why I didn’t find the 1.27mm pitch connectors… I was googling like crazy last year to find something usable.
Maybe I was only looking for 1.25 mm pitch connectors in ebay. I recall looking for 1.27 mm too, but maybe only in AliExpress.

I already have 10 pairs of 12-pin JST-GHs. with 10 cm wires in the female contacts. (Only one radio board in use yet.)
I just think that’s where the connection problem lies, because my CC1101-module works fine with DuPonts at the processor board end.
(The radio end has 2 mm pitch pin header and 2 mm pitch DuPonts.)

hobbya Sun Jul 08, 2018 8:29 am

This is how I connect my breakout module.
20180708_162155.jpg
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hobbya Sun Jul 08, 2018 8:50 am

Another example.
20180708_164740.jpg
20180708_164740.jpg (37.6 KiB) Viewed 303 times

turboscrew Sun Jul 08, 2018 12:58 pm

Not a bad way! Not at all.
How do you make the module stay put on the “dot board”?

hobbya Sun Jul 08, 2018 1:05 pm

A piece of double sided foam, no magic.

turboscrew Sun Jul 08, 2018 3:02 pm

Kind of suspected that… :)

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