Inside a Nexa PER-1500

I was looking for double pole relays suitable for mains voltage and noticed that one such relay is almost as expensive as a Nexa receiver, which got me wondering how remote switches does it.

I had an unused Nexa PER-1500 that I chose to disassemble and found that it uses a single pole relay, which to me was a bit unexpected since then you won’t know if it will switch the live or neutral.

Closeups of crud on ks10008 board

I believe that some liquid have entered this board, most likely through the hole in the dvi connector, more specifically the hole from analog ground which has no metal pin.

Some close-ups using the usb microscope camera.

photo_2016-04-14_12-17-55

Part of board closes to the DVI connector:
crud-png

Another image close to the connector:
mix

A bit further from the connector:
nc1

Reprogramming SFP modules

I needed a fiber connection to my HP 2824 switch, but it would not allow me to use non HP SFPs.

So what did I do? I reflashed a D-Link DEM-311GT using the EEPROM data from an HP SFP using a Raspberry Pi (and an old broken switch as a breakout board for the SFP).

Switch as SFP breakout board

The EEPROM in the SFP is just an ordinary I2C EEPROM (basically the same as is used for the EDID in monitors).

There was one problem though: the DEM-311GT SFP was write protected, so I had to solder a wire to the write-protect pin to make it writeable.

DEM-311GT with patched write-protect