[Halld-tracking-hw] CDC Ground Connections

[Curtis A. Meyer]

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
>>>>   
>>
>>
>


-- 
Prof. Curtis A. Meyer		Department of Physics
Phone:	(412) 268-2745		Carnegie Mellon University
Fax:	(412) 681-0648		Pittsburgh PA 15213-3890 
cmeyer at ernest.phys.cmu.edu	http://www.curtismeyer.com/