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Molex pin header can pass down to 50uA of current?

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keith1200rs

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That version has gold plating so should be OK for low level signals. Avoid tin plated ones for low signals.

Keith.
 
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goodboy_pl

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I think gold plated connector could do that, but it would be much better to amplify such a low signal lever before transmitting it on cable.
Working on low level signals, EMI would be very important. using shielded coaxial cable like 50 ohm rg-316 and SMA or SMB connectors could reduce such interferences.

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thanks, when i say "signal", the 50uA is just the base current of a BJT, so i doubt if noise will do much harm to it?

Are there any rules concerning the minimum current that a tin plated contact can handle?

Also, what are the minimum currents that gold and silver plated connectors can pass?


Also, the above connector is very cheap...................

https://uk.farnell.com/molex/22-11-2062/header-vertical-6way/dp/1462951

...so it cant be using "full" gold, just an alloy of gold......so it is very cheap, so why dont all connectors just use this cheap gold plating?
 

chuckey

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Its not the current that is important , its the voltage. Its the low voltage that can't punch through the oxide layer, thats why old fashioned relay logic used 50V!!!
Frank
 
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The voltage between the pin header metal and the crimp terminal (inside the crimp housing is zero volts, otherwise youd get power loss in connectors....so how can the voltage have anything to do with it?
 

chuckey

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Your words - "I am told that certain connectors cannot pass very low currents, as they need a certain current level to "burn" away the oxidisation", These are rubbish.
Frank
 
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FvM

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The voltage between the pin header metal and the crimp terminal (inside the crimp housing is zero volts, otherwise youd get power loss in connectors....so how can the voltage have anything to do with it?
Presumed the contact doesn't connect initially (due to an oxide layer), the voltage won't be zero. In this situation, a minimal voltage will be required to achieve a connection. Current also matters, if the circuit has a very high impedance, the voltage won't be able to destroy the oxide layer.

Even noble metal contacts seem to need a minimal voltage for reliable connection. I have a specification of a signal relay (Omron G6K) that says minimal permissble load is 10 µA and 10 mV DC.

The Tyco version of this relay form specifies minimum switching voltage of 100 µV.
 
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one of the pins of the connector is just a logic voltage.......with no current flowing through it .....(though i suppose at the instant of connection some current must flow to charge up the microcontroller gate capacitance?)........anyway, i am hoping that the logic connection will work......i mean, in steady state, no current flows through it other than the minute bias current (<1nA) of the microcontroller input.....


....i didnt realise signal connections were so fraught with problems.

I am wondering if i need to put small capacitors on the connection nodes so that they instigate a charge current to flow at the instant of connection?....this will then "weld" the connector surfaces together?
 

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treez

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Hi again,

Some of the connections, will be logic connections, and involve no current flow whatsoever, other than the bias current of the microcontroller input that they connect to......so how do i handle these...?....will they not be properly connected?......will i need to put 1n capacitors on the connector node so that a mini "Inrush" happens when the logic value changes and "welds" the connector surfaces together?
 

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I think micro-scratches which is created on metal pins during insertion of the connector in the jack solve the problem.
gold on plated connectors will not oxidize so preserves the scratches fresh.

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Yes, but thing is, i think the situation of relays and switch contacts is different, because they may be open for some time, and the contactor surfaces may oxidise....with the header that i showed in first post, contact is made and then persists permanently, so i wonder if i can get away without using gold.....maybe i can go cheao and choose tin?
 

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for reliable contacts always use gold plated connectors. tin plated connectors suffer from oxidization and after that you will see the bad results.
complex systems (like measurement instruments made by hp) always use gold plated connectors and work for decades and only need regular calibration.
also for critical applications like automotive and avionic, leak tight lockable connectors is used which use rubber gaskets. in this way the systems continue to work properly in harsh environments for years without any maintenance.

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