Connectors in Alignment Electronics for New Small Wheel

© 2015 Richard Studley, Brandeis Univiersity HEP Electronics Shop


Acceptable Orientations
Light Sources


The problem of confusing the various types of ribbon cable connectors (Flexible Flat Cable, or "FFC") has cost us countless hours of productivity over the years. We have come to the conclusion that there is no convention that will cover all use cases and that each implementation must be thought out thoroughly to avoid confusion. We try to establish consistent use in new Small Wheel electronics to avoid hours of troubleshooting later.

There are many factors to consider with cable orientation:

The problem is not as trivial as it would first appear.


Rule: All ICX-424 minimal heads must be interchangeable. All ICX-424 devices must maintain the same pinout on flexible connectors.

Recommendation: No reversible (top and bottom contacts) flexible connectors should be used.

Rule: The Bar Head (A208201B) sets the standard for the orientation of new Small Wheel connectors.

We look down at a camera board with a connector on top. We orient the camera connector facing left. Both connectors are right angle with the pin connections on top. In this orientation, pin 1 is away from us. (In the image, pin 1 is on top, and pin 12 is on the bottom.) We will make all image sensors and minimal heads compatible with this orientation.

Figure: Flex connector pinout. The bar head is a surface mount connector with pins up.

Convention: The connector on the A208201B board above is referred to as a "right-handed" surface-mount-pinout. We abbreviate this "FLEX-12-RSR" for flex, 12-pin, right-angle (R), surface-mount (S), right-handed (R). The connector on the minimal head is a "left-handed" orientation of a through-hole connector.

Figure: A right handed flex connector. When the opening is away from you and the pin connectors are up, pin one is on the right.

Look at a flex connector with the connector opening facing away from you and the pin connections on the near (top) side of the cable. If pin 1 is on the left you have a "left handed" connector. If pin one is on the right you have a "right handed" connector.

A left-handed footprint with pin connections on top is the same as a right-handed footprint with pin connections on the bottom.

Acceptable Orientations (Camera)

Board Connector Type Pin Connections Footprint
Camera Head CCD connection Surface Mount Top Right-Handed
Camera Head CCD connection Surface Mount Bottom Left-Handed
ICX-424 Minimal Head Camera Connection Surface Mount Top Left-Handed
ICX-424 Minimal Head Camera Connection Surface Mount Bottom Right-Handed
Table: Examples of functional orientations for ICX-424 devices.

Recommendation: When a board has different versions requiring different footprints, a table should be placed on the schematic dictating the different footpritns and parts required.

Light Sources

Conventions for light source pinouts are yet to be determined.