|nsA: Knurled nut
|FP presses against top of
collar. The 2mm thickness of the knurled nut enables FP
thicknesses to 2.6mm. However, how do we ensure that the nut
doesn't scratch the front of the FP? Perhaps there is no visible
scratching with these round knurled nuts. However, without a
flat-washer or better still a lock-washer, the nut may be prone to
Maybe the FP is covered in most places by a screen-printed-from-behind polycarbonate faceplate/decal, as in the Devil Fish. If so, it is best not to have nut pressure on the polycarbonate. So the polycarbonate label would be punched with a hole to clear the knurled nut diameter, which is 8.0mm.
I wonder where very fine internal tooth lock-washers could be found for the 5.9mm (actual) diameter threaded bush.
|nsB: Knurled nut and flat washer
(2.0 + 1.0 or less mm)
|FP presses against top of collar.
The flat washer is 10mm diameter. It might be best to get some which are less than 1.0mm thick. If we could get one about 0.6mm thick, then we could use a 2.0mm FP. This avoids any visible scratching of the FP.
|nsC: Hex nut and flat washer
(1.5 + 1.0 or less mm)
|FP presses against top of collar.
This is more promising, since the hex nut is thinner, even with a 1.0mm thick flat washer, we can accommodate a 2.0mm thick FP without any trouble.
|nsD: Knurled nut and flat washer
(2.0 + 1.0 or less mm)
|Collar goes through FP hole, so FP presses against the top of the main plastic body.
This reduces the Panel Gap by 1.0mm.
Now we have 5.6mm to play with, the 2.6mm taken up by the the nut and washer is no problem. We can use a FP thicker than 2.0mm and/or have a lock-washer or split-spring washer behind the FP to help stabilize the nut.
(We can't have a circular 7.8mm hole without the flat washer, or perhaps an internal-tooth lockwasher, on top of the FP, because both the knurled and hex nuts would fall into the hole. Even if the truncated-circular collar-shaped hole was punched or laser-cut, there would be too little FP material for the nut to press against.)
|nsE: Hex nut and flat washer
(1.5 + 1.0 or less mm)
|As for nsD, but we have an extra 0.5mm for the FP thickness and/or a lock/spring washer.
|nsF: Just a knurled nut somewhat recessed in a judiciously countersunk hole in the FP.
|This allows still greater FP
thicknesses, or with packing washers between the socket's collar or
body and the bottom of the FP, a greater Panel Gap thanis possible with the above approaches.
|Panel Strategy and Nut Strategy
|psA with nsA, nsB, or nsC (all 6.0mm holes)
|The socket mounts conventionally on the PCB and the FP presses against the collar.
|psB with nsF (6.0mm holes)
|Somewhat greater than 11.4mm, say 12.0mm.
|The socket mounts conventionally on the PCB and the FP is some small distance from the collar, with one or more flat washers, split-spring washers or internal/external lock-washers between the bottom of the FP and the top of the collar.
|psC with nsD or nsE (7.8mm holes)
|The socket mounts conventionally on the PCB and the FP presses against the body of the socket, with the collar going through the FP hole.
|psD with nsD or nsE (7.8mm holes)
|10.4mm to as little as 9.0mm
|Bend the four feet out to
some degree (see photo 10), or as far as bending them at right-angles
so they do not lift the socket's body off the PCB at all. For the
lowest Panel Gap, it may be possible to cut these feet off rather then
bend them out, but I think bending them out would be easier.
With this strategy, it may suffice to cut the Primary and NC Contact terminals short rather than squeeze the lug part to be 2.0mm wide, since the whole socket is now closer to the PCB and we may not need the lug part of these terminals. However, see below about stresses on the Primary Contact terminal.
When the plastic body is flush against the PCB, with the four feet bent out of the way at right-angles, the tip of the plug may touch the PCB. Normally there is 16.0mm between the entrance of the bushing and the top of the PCB, but with the four feet bend out of the way, this is reduced to about 14.6mm. As far as I know, there's no technical standard for the length 3.5mm plugs. (From the PDF for the Lih Sheng LJE0352 mentioned below, here is a drawing of a stereo plug, with the length specifed as 14.0mm: 3.5mm-stereo-plug-dimensions-from-Lih-Sheng-Precision-Industrial.png .) Are any longer than 14.6mm? . . . quick measurements of plugs around the workshop found lengths between 14.1 and 14.8mm. It probably doesn't matter if the plug is stopped by the front panel from going the last 0.2mm or similar fully into the socket, but we need to ensure that there are no copper tracks in that vicinity. A hole or countersunk area might be better than the plug hittingthe PCB.
|12.0 to 14.0mm?
|If there was some way of
mounting the socket with its four feet 0.1 to 2.0mm above the PCB, this
would increase the above Panel Gaps by this amount.
|Manufacturer, model, photo and link
|EST - Marushin / Shogyo MJ-1235N
Likewise the QingPu WQP-PJ3010B: http://www.qingpu-electronics.com/en/products/WQP-PJ3010B-37.html
|This is a similar to the WQP-PJ3010BM but with a non-threaded bush.
The Shogyo "earphone jack" PDF is from 1994 and specifies gold plating for the contacts and a phosphor-bronze (I assume this is the meaning of "PBs") main contact spring.
|Lumberg / Schurter / Pro Signal MJ-355
These are "Pro Signal" (house brand) sockets from element14, catalogue number 126-7382:
These appear to be identical to the Lumberg 1502 03:
http://www.lumberg.com/...produktname=1502_03 , the Schurter 4832.2211: http://www.schurter.com/en/.../4832.2211 and the Kobiconn (Mouser house brand, I think) 161-MJ355W-EX: http://au.mouser.com/.../161-MJ355W-EX/?qs=... .
|This uses a coil spring to bolster the spring nature of the primary contact. The NC contact is a single point.
The terminals are not for PCB mounting, and it would be difficult to squash them smaller. However they are long enough that the solder-lug ring can be cut off.
The plug may protrude a fraction of a mm into the PCB if the socket is mounted flush.
The body depth is 9.1mm. The collar depth is 1.0mm. The bush depth beyond the collar is 4.1mm. So with the collar inside the FP hole, the Panel Gap would be 9.1mm - or 10.1mm if only the bush was in the hole.
Similar sockets are also made by other manufacturers.
|This would suit a Panel Gap of 12.5mm to something like 14.0mm.
They have a single point of contact NC arrangement. I think they
are similar to these sockets, which I use in the Devil Fish:
Instead of the ground terminal being at the bottom of the socket in the drawing, it emerges from the top and goes backwards.
|QingPu PJ3410 , Lih Sheng LJE0352
See this Muffwiggler forum thread: http://www.muffwiggler.com/forum/viewtopic.php?t=71955
with photos of a similar socket - the Lih Sheng LJE0352-4R, which is a stereo socket with a single switched contact: http://ec.lihsheng.com.tw/catalog/product_info.php?cPath=38&products_id=88 .
Here is an image I adapted from one of the photos at the abovementioned thread:
I think all the connector manufacturer sites I have seen could be greatly improved with better photos of their products.
Update 2014-05-29: These are available in batches of 50 from Thonk in the UK: http://www.thonk.co.uk/product-category/diy-accessories/jacks/ .
|There are three versions of this - two of them stereo and one of the mono with NC contact style we are interested in.
I know nothing about the internal construction or robustness.
The drawing shows the terminals get wider near the body, so perhaps the PCB seating plane would not be flush with the body.
This may be suitable for Panel Gaps of 13.0 to 14.0mm.
This has a plastic bush with an 8mm thread, and so has a much larger diameter knurled nut.
|Lumberg KLB 13 . . . but this is a Stereo socket, without an NC contact
http://www.lumberg.com/main/common/serie.asp?ser=015&cat=4&lang=eng Schurter have the same socket as 4831.2300: http://www.schurter.com/en/Components/Connectors/Audio-Plug-Sockets/4831.2300
My guess is that the manufacturer of all these is Kobiconn: Here is the PDF datasheet from Mouser in August 2013. The Kobiconn parts supplied by Mouser appear to be identical to those sold as Lumberg by element14. Kobiconn 161-7400-EX 3.5mm stereo jack.
|These might be useful, for a Panel Gap of to 11.6mm12.0mm. The body depth is 11.6mm and the bush depth is 4.5mm.
However, the terminals are not really suited to PCB mounting. They are wide and close together, so care would be needed to get the holes and pads arranged properly.
|There are quite a few
other sockets, both stereo and mono, in the 3.5mm section of the QingPu
site - more than I saw at any other site.
Whittle 2013 - 2014 –
First Principles and Real World Interfaces
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