Electrical conducting pivot

[MountainLogic]

I need to add a small lever to a Printed Circuit Board (PCB) to push a small plastic part with a max force of about 200g. This is part of a high impedance, low power circuit running at 0.5 A at 4.5V for 1 second with an infrequent duty cycle (in simple terms, I'm dumping 3 AAA into 1/2 ohm resistance load with in line current limiting resistance added to keep it at 0.400 mA). The power runs through this pivot/bearing. I need to keep the resistance down to below 5 ohms and the resistance needs to be constant over time. The pivot (a round PCB PEM nut that press fits into the PCB) is described as "300 Stainless Steel Passivated and/or tested per ASTM A380" The pivot has an OD of 0.219". A tubular sleeve with lever arms fits over the pivot. A wire is connected to the pivot arm that carries the current.

My questions are:
1) Is a similar SS material the best choice for the sleeve/arm or can I use easier to machine steel and plate it (and plate it in what way)?
2) Should I use conductive grease?
3) How much slop should I allow for between the pivot and the sleeve?


FYI, more details of the KPS6 pivot:

http://select.pemnet.com/interactiv...ARCH_PRODUCT2&FPRODUCTID=2424&PAGEID=

Thanks

 

[MikeHalloran]

If the range of rotation is less than a couple of turns, you could just attach a wire across the pivot and let it bend, like in steering wheel clocksprings.

If it has to rotate continuously, the traditional solution is a carbon button and a stainless leaf spring, like in a distributor cap and rotor.



Mike Halloran
Pembroke Pines, FL, USA

 

[itsmoked]

With only 4.5V you will likely have reliability issues. No way you can use a switch huh?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[MacGyverS2000]

We use pogo pins riding on bare traces... gives plenty of up/down slop, and we haven't worn out a track yet.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[zappedagain]

To continue Keith's comment, with only 4.5V you won't have enough voltage to 'arc' across molecules of dust and dirt and grunge that will build up. Eventually you will have a poor contact because it doesn't have enough voltage to be self cleaning. Check some of the switch manufacturer's sites for more info about this.

Z

 

[itsmoked]

Below about 10V you want gold contacts unless you are running a substantial current.

macgyvers2000's comment is good as pogo pins are generally gold.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[roydm]

Some sort of mercury wetted contact/pivot might work for you