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Leveraging the PCB Proto Industry

Update 4/5/2011: More thoughts on automation PCBs here and more resources here.

In the past, Printed Circuit Boards were not a good choice for small volume machines because you had to pay significant Non-Recurring Expenses (say $500), and then buy 100 boards or so. If your design changed, well, all the boards in stock are now useless. If you make a mistake (somehow very easy to do with connectors), well, you either have to fix it (if possible) on all those 100 boards or throw them out. I’ve seen both problems first hand.

I still use break out boards and DIN-rail mounted terminal blocks for prototypes. Now with all the PCB prototype houses available, you can buy PCB’s in very small volumes with no NRE, so it makes sense to look at making PCBs even for very low volume designs. For example, with a credit card, for $96 plus shipping I can get, in four days, from Sierra Proto Express three double layer boards of the same design up to 60 sq in each (update 9/27/07 – well, Sierra’s changed their No Touch a bit; they claim the new pricing is even less expensive).

The idea is to design custom circuit boards to interface between my components (sensors, pneumatics, etc) and my I/O to reduce assembly time, improve reliability, and reduce troubleshooting. The PCB’s are mounted in DIN Rail holders.

Designing a simple 2 layer interface PCB is not that hard. For the first time through, you will need some help learning how to set everything up for the board house.

PCB software appropriate for creating interface PCBs ranges in price from free (e.g. PCB 1-2-3, gEDA) to $1200 $1494(unlimited version of Eagle PCB).

DIN-rail mount PCB holders are available from a number of sources. Two companies with a good selection of products are Phoenix Contact (especially UMK and UM series) and Weidmuller. I’ve used Phoenix Contact’s UMK series.

Phoenix, Weidmuller, Wago, and others make a wide variety of PCB mount terminal blocks including screw, clamp, and IDC. IDC terminals are very nice if the wire size is in the right range. Good sources for small volume electronics parts include Digikey, Mouser, and Jameco.  Mouser typically has Phoenix products available in smaller quantities than Digikey.

Tony

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