[Halld-tracking-hw] CDC Ground Connections

[Fernando J. Barbosa]

Hello everyone,

Zero insertion/removal force would be great. I think we already have 
that feature with the mounting screws and brackets on the board - the 
screw is captured on the bracket so it can be used for insertion and 
removal as it is tightened and un-tightened to the spacer standoff. 
This, of course, still needs to be done with care.

Best regards,
Fernando



Curtis A. Meyer wrote:
> Hi Everyone -
>
>    we are trying to get a setup to measure the force, however our 
> experience with
> the hardware indicates that 1lb is probably too small. We still feel 
> that additional
> standoffs are needed, but it would probably be good to start thinking 
> about a
> "force-free" scheme to install and remove the cards. 
>
>    One possibility would be small tabs that extended beyond the current 
> ends of the
> connectors with a matching tab on the HV board. We could imagine a 
> modified pair
> of pliers for insertions and a modified pair of reverse-pliers for 
> extraction.
>
>     Curtis
> Tim Whitlatch wrote:
>   
>> Hi All,
>>
>> In the current configuration, a 1/2 inch thick lexan (polycarbonate) 
>> plate will deflect approximately 2mm with a 20 lb force applied 
>> between the standoff positions. This can be reduced below 1mm if we 
>> double the number of central standoffs to 16. Data for the EDAC 
>> 307/357 series connector indicate that the force is more like 1 lb. If 
>> we increase the thickness of the lexan to 5/8 inch, we can reduce the 
>> deflection in half again.
>>
>> Slava has posted layouts of some of the latest grounding schemes and 
>> support rods at;
>>
>> http://www.jlab.org/~vgr/CDC%209-18-2009/
>>
>> Please have a look.
>>
>> Cheers,
>>
>>       Tim
>>
>> 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
>>>>>>
>>>>>>  
>>>>>>     
>>>>>>             
>>>>> _______________________________________________
>>>>> Halld-tracking-hw mailing list
>>>>> Halld-tracking-hw at jlab.org
>>>>> https://mailman.jlab.org/mailman/listinfo/halld-tracking-hw
>>>>>   
>>>>>           
>>>       
>
>
>   
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