[Halld-tracking-hw] CDC Ground Connections

[Fernando J. Barbosa]

Hi Curtis,

Yes, I certainly have the same concern about deflection and/or stress on 
the crimp pins (or any other part) due to the force of inserting and 
removing the cards. What if you add a thick aluminum plate, with the 
holes for the HVB connectors, after the assembly and attach it to the 
Lexan with standoffs (or directly) and to the outer and inner supports? 
This would form a box structure to take the load of insertion and 
extraction. The thickness of this plate would have to be less than the 
height of the HVB connectors.

With regards to the press-fit socket, Slava actually prefers, and found 
a similar one from Mill-Max, with slightly bigger diameter that wound 
make assembly and machining easier. The pins that are soldered to the 
ground wire are available off-the-shelf.

Best regards,
Fernando




Curtis A. Meyer wrote:
> We will take the one board that we have here and measure it on Monday. That
> should give is a pretty good idea. We would also like to try and 
> simulate the deflection
> of that force on a piece of Lexan.
>
>    Curtis
> Tim Whitlatch wrote:
>   
>> How much force do we anticipate on making these connections?10lbs? 20lbs?
>>
>> Tim
>>
>> Gerard Visser wrote:
>>     
>>> Hi Curtis,
>>> 	I endorse completely your comments regarding deflection and 
>>> reliability! There should either be more mechanical support (which could 
>>> serve as a ground connection, or not) or else there should be attention 
>>> to make an insertion/extraction tool and features in the design to 
>>> insert/extract the HVB without applying too much force that strains the 
>>> wire connections.
>>> 	For the wire pin to the ground sockets, for instance there is 
>>> http://www.mill-max.com/pdf/datasheet/pin_rec_catalog/8000-0-01-15-00-00-03-0.pdf 
>>> if you would be able to use a #19 or #20 wire. It is just slightly too 
>>> small for #18. But IMHO it should be enough - unless there is a 
>>> mechanical consideration about the wire diameter passing through the gas 
>>> seal that I don't know about.
>>> 	Sincerely,
>>>
>>> 		Gerard
>>>
>>>
>>> Curtis A. Meyer wrote:
>>>   
>>>       
>>>> Hi Everyone -
>>>>
>>>>      a couple of points on the grounding connection.
>>>>
>>>>     Sometime ago, we had proposed "continuing" one of the legs that 
>>>> supports
>>>> the connectors for the HV-boards through the gas plenum to the endplate. 
>>>> This
>>>> standoff would then serve to both support the HV connector and provide a 
>>>> solid
>>>> ground connection to the end plate. The one concern is that it might not 
>>>> be possible
>>>> to place one support for each connector such that the feed through can 
>>>> carry through
>>>> to the end plate.
>>>>
>>>>     Assuming that the above is not possible (which we still feel would 
>>>> be the best grounding
>>>> and support scheme), then we are worried that there are not enough stand 
>>>> offs in the current endplate, there are only eight as far as we can tell 
>>>> in the current design.
>>>>
>>>>     We are very concerned that there are not enough standoffs to support 
>>>> the swiss cheese
>>>> plate, particularly during insertion and removal of the high-voltage 
>>>> cards. What we see with
>>>> the models that we have at CMU is that the force needed to insert and 
>>>> pull the card is
>>>> sufficient to actually compress or pull-out the plastic plates. The way 
>>>> the connection
>>>> scheme now goes. This distortion becomes a force either directly on the 
>>>> crimp pin,
>>>> or on the glue joint that seals the chamber. These have the potential to 
>>>> break wires
>>>> in the straws or break the gas seals every time a HV board is changed.  
>>>> It is important
>>>> that additional standoffs be added, either during or after manufacture 
>>>> of the Al endplate.
>>>>
>>>>     Finally, assuming that we adopt Fernando's connector, we need to 
>>>> know if there is a
>>>> source of the .020 male part that can be soldered to the .040 wire and 
>>>> is inserted in the
>>>> press-fit hole. The connector itself is quite slick and the 60gm force 
>>>> needed to engage
>>>> it seems fine. But the male part is equally important to this working.
>>>>
>>>>
>>>>      -- Curtis
>>>>
>>>>   
>>>>
>>>>     
>>>>         
>>> _______________________________________________
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>>> Halld-tracking-hw at jlab.org
>>> https://mailman.jlab.org/mailman/listinfo/halld-tracking-hw
>>>   
>>>       
>
>
>   
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