Wired remote control for a BenQ SP831 Projector

October 31st, 2014 Leave a comment Go to comments

Recently we needed to control a digital projector outside of the IR range of its remote.  The projector and remote were both capable of connecting via a cable, but no documentation was provided on how to do so.  This is what we discovered in testing:

- The plug required is 2.5mm TRS (stereo).  TS did not work.
- Though TRS is required, only two conductors (RS) are used.
- The jack on the remote is recessed far enough that the housing of most 2.5mm plugs we tried prevented them from being plugged in.  We eventually found a mobile phone headset cable that fit.  Its hairlike wires required soldering with painstaking precision.

Due to using pre-installed and unused cable, our finished product was as follows:

Custom-built 2.5mm TRS to RCA adapter -> 50' of RCA cable -> RCA to XLR adapter -> 200' of XLR cable -> custom-built XLR to 2.5mm TRS adapter.

This project would have been significantly simpler if the remote (a) did not have a recessed jack and (b) accepted a TS cable (which would be compatible with TRS).  Since only two conductors are used, it's pointless to design a jack that demands a three-conductor plug.

Update: We discovered that the remote inexplicably stops working if it is plugged in for an indeterminate amount of time.  So, we unplug the remote when it is not in use.

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