cram@sunpix.east.sun.com (Marc W. Howard) (11/06/90)
I'm having an interesting problem with X-10 appliance modules. I have a fair amount of computer equipment at home. To keep from reaching for several (always hidden) power switches or power strips I instead leave all the equipment 'ON' and controlled by X-10 appliance modules. This works fine except for a HP LaserJet IIP printer. It feels 'left out' if other equipment is turned on and it isn't. It rectifies this by turning itself on several (about 3 - 5) seconds after the other equipment turns on. If it is then commanded to turn off it will but then turn back on again shortly thereafter. If I wanted to design a circuit like this it probably wouldn't work as reliably ;-). Unfortunatley LaserJet's seem to use a fair amount of power just sitting there, hence the desire to keep it off. Now before anyone wants to suggest the obvious: 1 - Yes I've tried more than one module. In fact three; two of the newer beige ones and one of the old ugly Plug n' Power ones. 2 - Yes the unit code is not shared by anything else. 3 - I've even tried this with the RS-232 cable to the printer pulled, no difference. Yes I know that appliance modules will turn on if they sense a LOAD change. This may be swell for lamps & TV sets, but not in this application. I'm assuming that what turns on the module is either RFI or power surges caused by the other equipment powering up. What I'd like to know is if there is a way to modify the modules to get rid of that annoying auto-on feature. I assume that it just looks for a (small) voltage change across an internal series resistance. If someone out there knows what to clip to defeat this I'd appreciate hearing about it. Marc W. Howard Sun Visualization Products Research Triangle Park, NC cram@sunpix