When working with Phidgets sensors, the cables come in a limited number of lengths (60cm, 10cm and 350cm). There are times when you need a more specific length or something longer. Here's a fairly easy way to make your own!
Phidgets Analog Input cables use connectors compatible with Molex "C-Grid SL" connectors. Crimping cables manually is delicate work. Normally, crimping cables like this is done by a machine. As you proceed, make sure to inspect your work carefully each step of the way.
Step 1: Materials
To make a cable, you need:
- Wire (sold in 100' spools from Phidgets.com)
- Connectors (more information on these below)
- Wire crimping tools (more information on these below)
- A good quality wire stripper
Metal terminals connect to the ends of the wire. The terminals hold each wire in two places - on a short stripped section of wire, and on the insulation. The terminals slide and lock into the plastic housing. When the terminal is inserted into the housing, the housing provides strain relief. Overall, it's an incredibly reliable way of building a connector. Terminals can be removed by bending a small tab visible through a window in the plastic housings.
We recommend sourcing these parts from Digikey. Be sure to buy extra terminals and housings, it will take practice.
Terminals come in a dizzying variety - you can choose gold or tin plating. Buy gold, the thinnest gold plating will probably be fine, unless you plan on removing them repeatedly from the plastic housing (in excess of a thousand times).
Terminals come on a reel or in bulk (loose). Loose is better as the reels are built for automated crimping machines. To build a standard analog input cable, you need:
- Female terminals (series 70058): Part number 16-02-0097 for 24-30 AWG wire (Phidgets uses 26 AWG), or 16-02-0103 for 22-24 AWG.
- Female housing (also called receptacle). Receptacle part number is 50-57-9403 (for 3 pin). Terminals for 32-36 AWG are available, but are not stocked normally.
To make a cable that an analog input cable would plug into (same as the 3-pin connectors on our 1011_0 PhidgetInterfaceKit) you will need:
- Male crimp pins (70021 series): Part number 16-02-0077 for 24-30 AWG wire (Phidgets uses 26 AWG), or 16-02-0115 for 22-24 AWG.
- Male housing: Part number 701-07-0002 (for 3 pin).
You can buy knock-off connectors in Asia - but if you are making enough cables to make that worthwhile, you might as well just get the entire cable assembly made overseas.
Wire Crimping Tools:
Crimping tools crush the crimp terminals (described above) onto the stripped wire. There are a few different options,we ended up using the WM9999-ND tool, as it was found to be the best of the three choices.
WM9999-ND (Molex part number 0640160038)
- Two-step process for crimping insulation and wire.
- Only does 14-24 gauge wire crimps
This tool is easy to use and intuitive. It makes for a hassle-free, good connection every time.
WM17552-ND (Molex part number 0640160201)
- Single step
Instructions on how to use this device can be found the Molex website. While this tool is apparently designed to make the process easier, it is exceedingly difficult to position the terminal in the tool using the included magnetic terminal holder. When the terminals were positioned by hand, the device was found to be highly effective at producing a good connection every time.
If you want to make your own connector, and don't want to buy a specialized tool, you may consider needle-nose pliers an option. While it is technically possible to use pliers, it is difficult to position the wire and crimp the terminals properly with pliers. If you attempt to use pliers you will need many extra terminals, as you are more likely to destroy the terminal than to make a good connection.
Strip the wire 2-3mm from the end.
Crimp the forward clasps onto the stripped section of wire.
Then crimp the insulation section.
The final result is a securely connected wire.
Finally, insert the terminal into the housing, until it clicks into place. Tug on it to ensure it's set.
This same process can be used with the male connectors for similar results.
Step 8: Removal
To remove terminals from the housing, poke the tab with a sharp pointy object (like tweezers) and pull them out.
Step 9: Alternative Method: Cable Hacking
As a simpler, if less pretty alternative to all this, you can cut an existing cable somewhere in the middle, remove or splice in additional wire, and solder the ends together to achieve the desired length. When finished, wrap the exposed cable in electrical tape.