At 02:15 AM 7/13/2010, Jake Anderson wrote: >I'm designing a tool length measurement device for a mill. >I've settled on the mechanical design which is a tripod arrangement, but >what I'm after is some contacts to actually make and break the connections. >I know such beasts exist but I'm having difficulty finding sources for them. > >At the moment its looking like I'll have to settle with gold plated PCB >as the contact material. > >I'm looking for gold at the moment because I want to run the contacts at >a very low current/voltage to minimise arcing. Some more info would be useful. Does the device move about or is it stationary when contact is being made? How much height do you have available for the connection? If it is stationary, I'd consider using magnets to hold it in place. I've done projects where the magnets themselves were the current-carrying contacts (worked very well) but if that doesn't work for you, you might also consider using pogo pins - either contacting a PCB or contacting another pogo pin. The magnets I used for my projects were rare-earth magnets and matching steel cup-holders from Lee Valley Tools. Although Lee Valley was one of the first people from whom I could purchase these magnets, I see that there are lots of suppliers now. But: the plated steel cup holders still appear to be best obtained from Lee Valley - I've seen some knock-offs from other suppliers and wasn't much impressed. The nickel plating that completely covers the exterior of the magnet carries current quite well. I was passing perhaps 2A and measured a few mV drop across the connection. The magnet and cup-washer combination was inserted into a flat-bottomed hole drilled into plastic (forstner bit) such that the surface of the magnet was just proud of the plastic. The connection was made by soldering wires to the bottom of the plated steel cup-washers. dwayne -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist