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I've built a system using a pressure sensor on my chair, which in-turn controls a switching-relay such that when I get up from this chair, power to all my LCD screens is switched-off by the relays, automatically. That is, I do not have to manually press the power switch on each of the LCD monitors.

So, the question is - is it safe to remove power from working LCD screens in this way ? Can it cause problems for the LCD monitors in some way ? Is pressing the power switch on the LCD, result in a different method of switching the LCD monitors that is better ?

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    \$\begingroup\$ Depends, are the lcd power switches hard or soft power switches? \$\endgroup\$ – Passerby Jul 11 '13 at 14:46
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    \$\begingroup\$ Alternative idea: Connect your pressure sensor to a USB device with a driver that puts your monitors to sleep when you get up from the chair. That way, you are 'powering down' the monitors in the way the manufacturer intended instead of just cutting the power line. \$\endgroup\$ – us2012 Jul 11 '13 at 15:07
  • \$\begingroup\$ @Passerby hard power switches. My relay just cut off power from AC power splitter. \$\endgroup\$ – Igor S. Jul 11 '13 at 15:08
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    \$\begingroup\$ If the original lcd power switches are hard switches, they physically cut off the power. That means your relay and the switch are no different. Like my playstation 2. It has a soft power switch on the front, and a hard power switch on the back. \$\endgroup\$ – Passerby Jul 11 '13 at 15:29
  • \$\begingroup\$ Anyone cares to explain, why this might not be a good idea, if it's a soft power switch ? Does the playstation manual forbid direct poweroff by pressing the rear hard switch ? \$\endgroup\$ – icarus74 Jul 11 '13 at 17:08
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On my monitor the soft-press button puts the device in a Sleep mode. The screen is off but the power button remains on, just orange rather than green(Powered on)! I noticed that when I press the soft power button again the monitor turns on more quickly then if I pull the power and then restore it. All things considering if your LCD has a back-light being turned off and on would makes me wonder about the stress on it. I'm not sure there's any evidence that turning it off and on in this manor would worsen it. I believe the back-lights are fluorescent bulbs and simply removing the power to theses should present no problem! My thought is go for it!

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