In the previous post, I described two of the three significant X10 problems we had when setting up our home automation system. This post will cover the third problem, latency.
Although all our lights have conventional switches (well, momentary switches in conventional locations), we use a lot of X10 RF Remotes and X10 Motion Sensors to trigger lights and other devices. Initially, we used a TM13U RF Transceiver Module that receives the X10 RF signals and converts them in to X10 powerline signals. If we stopped here and let the powerline signals trigger the X10 devices directly this solution would probably be okay. However, we wanted computer control so we have another level of indirection. The powerline signals are then received by the X10 CM12U Transceiver and sent to the house computer. The computer then figures out how to react to this signal and, if the action involves an X10 device, sends another signal back to the CM12U where it is sent on the powerline.
The problem with this setup is that the X10 powerline is slow, so converting the (fast) RF signal to a slow X10 signal to get it to the computer is not very smart.
Additionally, RF devices repeat their signals which in turn get repeated on the powerline. While the repeats are going on, the computer, responding to the first received signal, is instructing the X10 Transceiver to transmit a command on the powerline. This results in frequent collisions leading to noticeable delays (and X10 powerline signalling isn't fast to begin with).
So, we purchased a W800 X10 RF Receiver and gave up on the TM13U. Using the W800 serial port receiver, the X10 RF could be read directly by the house computer. This avoids the delay and the collisions of the X10 powerline signals for the trigger and any triggered X10 commands.
The W800 was a solid piece of kit and worked very reliably. However, in the end, I replaced it with an RFXCOM RF Receiver as that was able to receive additional protocols. I expect I'll rave about RFXCOM products in future posts.