Overwatch - Hardware - Daughter board installation
Many EQSS Overwatch kits contain daughter boards. Correct installation is critical to reliable performance.
The correct fitment of these daughter boards is crucial to the reliable operation of an Overwatch system. This Tech Doc is an addition to the instructions within the EQSS Overwatch Installation Manuals and is intended to highlight the importance of good preparation and correct PCB pad dressing. If the preparation was done poorly, the Overwatch simply will not function reliably.
Example of an EQSS Harness and Daughter Board
Steps:
First clean mechanically all solder joints where the EQSS Overwatch Daughter board spring pins will connect to the scissor control board. All glue/silicon/conformal coating must be removed to properly expose the solder joints. Then the control board contact points must be cut back with electronics side cutters until they are flush.
Use a fine, sharp pair of angled side
cutters to trim down the PCB pin contact points.
Ensure the pins are cut flush with the PCB to allow the Overwatch daughter
board spring pins to make suitable and
secure contact.
Example below: sharp, flush - side cutter (Tsunoda TM-10)
The photos below should be used as a guideline to ensure reliability in the final assembly.
When all preparations have been completed for the attachment of the daughter board, the bolting down of the daughter board onto the scissor control board can be finalized.
To assemble - use whatever method is easiest for you, but DO NOT USE SUPER GLUE to hold down the spacers during assembly, as most likely it will also end up on the spring loaded pins - rendering them non usable. When all spacers and screws are mounted loosely in place, gently wriggle the daughter board until satisfactory seating of the daughter board spring pins is achieved. Then carefully and evenly complete the tightening of the screws. When all screws have been tightened (do not over tighten), carefully check that the spring pins are making good contact with the control box PCB. You may need to look at the spring loaded pins at a number of angles to visually validate good contact. A more definitive continuity test can be used if an ohm meter is available. You will be looking for a very low DC resistance (typically less than 1 Ohm).
An example of a properly mounted daughter board
Example of what not-to-do (Super Glue over the spring pins and over tightening)
Testing spring pin integrity and continuity
When the screws of daughter board have been tightened on the control board, the spring pins can be tested for continuity with a resistance meter function on a multimeter. The easiest method of completing this task is to trace to a convenient PCB track/solder joint on the control board where the spring pin will connect and then finding a convenient PCB track on the daughter board to which the spring pin is soldered. Then probe with the two multimeter lead tips to those chosen points. The multimeter should read less than one Ohm of DC resistance.
If no resistance is measured (open circuit) then the daughter board pin is most likely not making contact with the machine control board. Partially unscrew all of the daughter board mounting screws and re-position the board slightly to re-align the spring pins.
If a high higher than one Ohm resistance is found, then also partially unscrew all of the daughter board mounting screws and re-position the board slightly to re-align the spring pins.
Screw down the mounting screws again and re-test for continuity. If all of the spring loaded pins measure less than one Ohm then the daughter board install is complete.
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