SMD Blade Female Contact

Thread Starter

jpanhalt

Joined Jan 18, 2008
10,522
I need to make or modify something to connect a mini-thermocouple male plug to my board. I have the Omega/Newport connectors ad they are just a little (0.050 or so) too high. One option is to mill out the PCB, mount a strap across the bottom, and be done with it. Bottom clearance is also very tight.

After an afternoon of searching, I found edge blade connectors like this:
1583359730799.png

Unfortunately, all are crimp, but could be modified and soldered to the board. I would prefer something designed for SMD or even with tabs for TH. Ordinary automotive blade connectors ("quick connects" ) might also work, are available in TH PCB versions, but the insertion and removal forces are high.

Here is what the male looks like:
1583360783375.png

The blades are 3.2 mm and 2.4 mm wide ( about 0.126" and 0.094") wide. The closest automotive blade sockets are for 0.187" and 0.110" wide blades.
Here is what the Keystone version looks like:
1583360615180.png
Not bad, but I would like something a little easier to disconnect.


Any suggestions?

John
 

Thread Starter

jpanhalt

Joined Jan 18, 2008
10,522
That's exactly what I have.

They are too high to mount on the top of the board. My clearance is 4.6 mm (0.181"). The thought occurred to me grind off the nylon(?) part and solder. However, they are "too" good. Every part of the socket, except the welded tabs, is either chromel or alumel (that's probably why they are so expensive). So my solder joint would just be the tab. They are the lowest profile of any "TC" socket I found, and as I mentioned, I could have the board milled to accommodate the housing and then support it with a piece of 1/32 PCB soldered to the bottom. That is my current design, but before sending it off, I wanted to see whether there was a better solution. Current design:

1583362266904.png

The strap is shown on top. Ignore the routing -- that's how I do it until ready for the final version. Everything at that connection should be isothermal with room temp, so additional metal interfaces shouldn't matter.
 

Reloadron

Joined Jan 15, 2015
5,667
I figured it was your CJC point so Cu would be fine but what I didn't figure was height. :( You may be able to just grind down the Cu version? You got me?

Ron
 

Thread Starter

jpanhalt

Joined Jan 18, 2008
10,522
I am probably the only one interested in thermocouple (TC) connectors but decided to close the loop anyway. Spent a Jackson on an assortment of potential connectors based on availability at DigiKey and pictures in datasheets (mfg. part numbers):

1) TE Connectivity (AMP) 1-179316-2: Pretty good (picture)
2) Molex 0433740001: Too wide for narrow blade, very tight
3) Molex 0433750001: Very tight, but opens a little w/use, solder on bottom may affect
4) TE Connectivity 1971785-2: No good, opening for thicker blade than TC has (0.83 mm)
5) Molex 0357460110: Too narrow for wider (-) TC blade
6) Weidmuller 14800000000: Nice feel, but blade wobbles and needs support (picture)
7) Keystone Elec 3571: Very high insertion force, not good for repetitive insertions
8) Keystone Elec 3545: Very high insertion force, not good for repetitive insertions
9) Omega TC guts: Works, but critical keeper can't be soldered (picture)

Pictures (numbers 1, 6, and 9):
#1:
TE Con 1-179316-2 (a).png
This is the best of the non-Omega types tried. There are two contact fingers on top and one for added pressure on the bottom. Sliding force felt good. One must be careful not to solder past where I have gone or it might interfere with the spring action of the bottom contact. Plug did not wobble in the socket and could be inserted fully. It is only partially inserted for the picture to show the bottom contact. Both female contacts are the same width. One would need a cover or something to ensure correct polarity.

#6:
Weidmuller 1480000000 top.pngWeidmuller 1480000000 side.png

The Weidmuller contacts had a very nice feel to them. They were also the most expensive. The bottom has a retention tongue that helped with aligning on the board. There is no support for the blade after the contact area, so one could wobble the connector (side view). If the instrument case added support,this wold be a nice connector. A wobbly connection, however, would probably not work well for a TC.

#9
Omega guts top.pngOmega guts side.pngOmega guts front.png

The Omega/Newport is the commercial connector mentioned above. I ground off the nylon case to get the guts. It is the only connector of those tested designed specifically for TC's. Metal contacts are chromel/alumel as appropriate. They are a two-part connector. The contacts are a pair of leaves that is welded to a copper lug for soldering. There is an addition metal piece that applies additional pressure to the leaves. It is slightly misaligned in the top view and shown in the side view. That piece of metal is magnetic and my plan was to solder the front portion to the PCB for added security and alignment. Unfortunately, it could not be tinned, even after careful grinding (last picture).

I will probably stick with the commercial connector for the first prototype as it is polarized and sure to work, if it fits. The Keeper/Strap mentioned above can be designed to accommodate #1 as an alternative. Since I will be getting more boards than I need, that will allow me to do experimentation.

Regards, John
 
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