Scale Wiring.                    Last Updated: 12/17/2005

This modification is based on Bill Havens excelant article 'Reliability and the Chinese scales "Experience"' that can be found in the files section of the Yahoo ShumaTech group.

I first connected my scales using phone wire directly soldered to the scale and connected to the socket that fits the optional header on the DRO board.  The display was always jumping so I made new shielded cables as discussed below and changed the filter threshold to 50.  I think the default is 12.  I grabbed the 50 number out of the air and it worked.

Parts (www.digikey.com part numbers)

This is enough parts to wire three scales

Qty   Part                        Description

 3      WM2036CT-ND  Header Vertical
 3      WM2088-ND       Housing
25     WM1112-ND       Crimp pins  (4 per scale needed, the rest are for mistakes)

http://dkc3.digikey.com/PDF/T053/0087.pdf

2    9 Foot S-video cables, Philips brand that I found at WalMart.

I bought the vertical header but then decided that I wanted to mount it horizontally so I cut off the pins that would go through the board to allow the header to fit.  There are no holes on the board anyway so the pins have to come off no matter which header you use.  I tinned the contacts on the board and the header.  The spacing of the pins does not exactly match the spacing of the contacts on the board but it close enough that it will work.  Position the board so that the face is aligned with the edge of the board and so that the pins line up with the contact as much as possible.  Take a small conical pointed soldering iron touch where the pin meets the trace.

(click to enlarge)

(click to enlarge)

Next test fit the board back into the housing.  Trim housing as needed.  One of mine needed no trimming and the other needed a small amount because the I was using a Harbor Freight 6" caliper on my Z lathe axis which has a smaller head.

(click to enlarge)

Cable

Bill mentions in his article that some S-Video cables have the sheilds bonded together which will not work in our application.  A cable I had laying around that came with a TV or DVD was like this so test all of the pins with a meter to make sure they are connected together before cutting the cable.  I found that a Phillips brand cable that I got from WalMart worked just fine.  Buy a 9' foot cable so that when you cut in in half you can get two cables out of it.

The crimp pins are really small but I was able to get them on without solder or the correct crimper.  I could have done them completely by hand but I have a crimper from Radio Shack that cost about $10 which worked for crimping the tangs that grab the insulation.  The tangs that grip the conductor were closed by holding the wire and the pin done to the table with my fingernail and bending each tang over with a scribe.

The pictures below show the cable as its striped and twisted.

This is the vertical header

Radio Shack Crimper
276-1595

Also See: Scale Mounting