INSTEON over CAT5; was Re: What can I replace this latching relay system with?

In response to a recent comp.home.automation question on how to retrofit wiring to provide dimmed lighting and (preferably) provide automation to a house that uses 1950's vintage relay-controlled lighting (Subject: "What can I replace this latching relay system with?"), I bread-boarded a concept using INSTEON power line control (PLC) devices that I had previously tested with X-10 but didn't end up using.

The original poster's challenge is that the existing wiring to the wall switches is suitable only for low voltage and installing new wiring is not acceptable. The low voltage switches on the wall control latching relays in the ceiling that switch the AC power to the ceiling-mounted lights. The AC wiring to the ceiling lights is not individually "home-runned" to the entrance panel, so centralized dimmers would require re-wiring the AC wiring which is also not acceptable.

The circuit below solves these issues and provides for both dimming and home automation control of the lighting using the existing wire infrastructure. It transmits powerline control signals and sufficient AC power to power an INSTEON device for input and signaling purposes only over the existing low voltage wiring from the AC power and ceiling lamp to the wall switch.

The wall-mounted INSTEON dimmer(SW1) sends dimming and other signals to INSTEON dimmer SW2 which in turn controls the light. INSTEON SW2 also repeats the signal received ensuring that it is available in the AC wiring throughout the house for conventional home automation control.

I tested this arrangement 'on the bench' using both ~200 feet of CAT5 wire and ~200 feet of 24-gauge non-twisted telephone wire as the interconnect. The gauge of the wire needs to be sufficient for the load. Current through the nominal 24AC control line was about 200mA with an INSTEON ICON switch (relay) connected for SW1.

One could also control a small load on the isolated INSTEON device by using sufficiently large transformers and interconnecting wires of appropriate gauge and installation.

120VAC C1 C3 Hot ------+----------+-||-+ +-||-+ (black ) | | | | | (black) INSTEON(red) + +-->>-----------
Reply to
Marc_F_Hult
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It is useful and perhaps necessary to explain the purpose of the two transformers, T1 and T2 in part because many folks may think that their sole function is voltage conversion.

They also serve as current-limiting devices which is the function that protects the wiring from short circuits or other high current conditions. They also provide galvanic isolation and eliminate the ground connection.

The UL-listed, Class-2 transformers in my bench test setup are rated at

20VA (volt-amp = watts) which is greater than the power limit of the present form of Power Over Ethernet (POE) of 15 watts. The present version uses two conductors per leg; a proposed version of POE will up the power rating to 30 watts or more. The regulatory considerations are more complex than the physics, and I will not deal with the former here. Suffice it to say for now that the 20VA rating of the transformers used is appropriate for the 18 gauge (AWG) wiring commonly used for doorbells and other common-low-voltage residential applications. And that a smaller transformer with a lower VA rating (also readily available at Big-Box home improvement centers) would be more protective for Cat-5 .

HTH ... Marc Marc_F_Hult

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Marc_F_Hult

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