On Mon, 16 Jul 2012 10:19:40 -0000, you wrote:
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>> >Then the first finger would actually come in contact with the mating
>> >surface for the last finger at first then be slid past all the other
>> >contacts before coming in contact with its mating contacts at the end of
>> >the cards travel.
>> Connectors are not designed for that kind of sideways force. The
>> actual wiping would be done across the socket, not perpendicular to.
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>The wiping action would have to rotated, the contacts would be pushed far apart (and need to be stacked for any kind of appreciable contact density)
That's what TEK did. The connectors were all spring loaded (the
entire body), and were designed to connect from one plugin to another,
sitting in an adjacent slot in the scope. The fingers were oriented
horizontally, there were three rows high, by perhaps 10 deep.
There are a few important things to note:
1) Tektronix NEVER recommended inserting plugins with the power on,
which included these.
2) most of these are ground, and presumably, if you ∗did∗ do a hot
insert, the signals could be grounded momentarily without (much)
damage.
3) I've never seen this on another series of plugins.
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>> Tektronix did this with one or two plugins in their 7000 series scopes
>> (7T series and 7S series) which were designed as units. Those
>> connector mechanisms were complicated, and are seen frequently
>> damaged.
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>Had a quick search but could not find a picture of the Tek contacts though it may a similar concept that would work. There are some contacts that are soft landing, such as those for ISO SIM card sockets where there are two columns of pads, you would just have to extend this to more. The ideas is that there is no power on the contacts until the card is pushed all the way home. For those sockets that are intended for repeated/continuous duty they make use of soft landing contacts to give them some kind of life, the card is 1mm from the final position before the contacts are lowered to make contact, you could use the same idea with a few rows of contacts that only squeeze together as the card bottoms out.
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That'll work to make a somewhat decent connector, but the circuits on
this connector are specifically designed so they can tolerate voltage
on the input leads without a power supply. (or it might be vice
versa, please check the NXP literature on hot insertion of I2C cards,
where the power leads are of different length than the signal leads)
The problem you're dealing with is that if this is made for a hot
insert, then your design HAS to tolerate miswiring with EVERY pin
connected wrongly until the card is fully seated.
If made for cold insert only, then you are still wiping across the
existing contacts (unless rotated) and you will destroy the contacts
for the board edges in short order.
>(http://www.smartcore.com.br/datasheet/ddm_www.smartcore.com.br_catalog_s.pdf) This (big) catalogue shows some embodiments. Some of the smaller SMD contact arrays (Contact Array 844-07) that are indended for repeated wiping of the SIM cards could be stacked with 4x2 contacts at a time. Downrate the life by how much extra wiping is expected.
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>Not to be recommended.
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>As mentioned by others using DE9, DA15 or DB25 (http://en.wikipedia.org/wiki/D-subminiature NOT DB9) as cheap and reliable connectors is a good idea. I have done designs with DE9 and DA15 in the past with small plastic VERO guides in the case, they are not officially rated for hundreds of insertions but hold out much better than edge connectors or 0.1" pins.
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>The OP has some specific reason for his query that should have gone past the engineering department (:-) before prototyping or else he is hoping that the finance department will accept unusual custom connector styles.
I missed the engineering design requirement for the connector style. I
wonder if you couldn't insert the card fully ∗above∗ the connector,
then mechanically push it down into the socket, giving him the best of
both worlds. Mechanically more complex by far, but at the risk of an
extra 1/4 to 1/2 inch, may solve the problems.
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>If the idea is to use the card to 'bridge' the top and bottom circuitry it is still better done with two connectors at the end of the card. The perceived cost or mechanical issues in having to route connectors to the end of the slot may be reasons here that we don't know about.
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Agreed. I'm going through posts in the order that the email program
gets them, so I'll see what others think.
Harvey
>Kalle