X10 Community Forum

🔌General Home Automation => Automating Your House => Troubleshooting Automation Problems => Topic started by: Crusty on November 28, 2011, 08:20:02 PM

Title: LM14A generating N.24 of noise
Post by: Crusty on November 28, 2011, 08:20:02 PM

Testing various lamp modules including one LM14A 2-way.  The LM14A generally seems to work with no noticeable noise on to the line except at the top two dim levels (95% & 100%?) where it spits out N.24 on my XTBM.  I've seen this on standard wall dimmers, but never noticed it on any lamp modules.  Is this at all normal?

Thanks,

Title: Re: LM14A generating N.24 of noise
Post by: Brian H on November 28, 2011, 09:53:35 PM

Regular incandescent type bulbs?
I have some dimmable LED bulbs that make noise at some dim levels and each X10 model seems to make them noisy at a different level.

Title: Re: LM14A generating N.24 of noise
Post by: Crusty on November 28, 2011, 11:02:11 PM

Simple 60w incandescent.

Title: Re: LM14A generating N.24 of noise
Post by: JeffVolp on November 29, 2011, 12:39:53 AM

The X10 transmission window occurs during the first millisecond after each zero crossing of 60Hz.  That is when a dimmer would switch on if adjusted for almost full intensity.  The switching transient can cause some ringing on the powerline.  The ringing frequency and how long it rings is determined by the line inductance and damping.

The XTBM will report as noise any ringing near the X10 bandpass that persists for at least 24 cycles, which is half that required to register as a X10 logic "1".  The intent is to track down possible problems before they become real problems.

In my testing I saw serious ringing caused by a heavy incandescent load switching on near half brightness, which is when the current transient is the highest.  Since that is outside the X10 transmission window, the XTBM does not report it as noise.

Jeff