| Electronics > Projects, Designs, and Technical Stuff |
| Another reason to hate "soft touch" power switches |
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| IDEngineer:
--- Quote from: tautech on July 18, 2019, 10:06:47 pm ---They ADD the ability to have a powerful OS that permits incorporation of complex features into an instrument and that OS needs be shut down gracefully to retain settings. --- End quote --- Sure, but as has already been noted in this thread, embedded systems commonly handle loss of power. A soft touch power switch does not protect from AC interruption, and most equipment doesn't say "Must be used with suitable UPS". Most folks here would consider T&M equipment that bricked due to AC loss to be a terrible design. Thus they must design for that, in which case the soft touch switch adds nothing. |
| Alex Eisenhut:
My Tektronix 547 wouldn't even turn on with a direct lightning strike! |
| magic:
--- Quote from: IDEngineer on July 18, 2019, 09:38:37 pm --- --- Quote from: magic on July 18, 2019, 09:22:55 pm ---They probably wanted to make it power up instantly when it is turned on with the mechanical switch. --- End quote --- ...in which case, what is the value of a soft touch power switch? --- End quote --- The value of a soft button is that it can be cheaply and conveniently placed on the front panel among other low voltage stuff. The value of a true switch at the rear of the unit might be that it is mandatory for devices which aren't insulation class II rated or something like that, I'm not familiar with the rules myself but I think I've heard it's a requirement in the EU these days. --- Quote from: SiliconWizard on July 18, 2019, 09:57:05 pm ---Well, if any engineer or technician was dumb enough not to even think of trying to press the power button on the front panel before declaring the device dead, I'd be tempted to think that they would deserve getting nothing but DOA equipment anyway... :-DD --- End quote --- These are scopes for kids :P Besides, I can imagine some oldschool tech turning the switch on, cursing Rigol for having placed in at the rear and not realizing that there is another button to be pressed. |
| tautech:
--- Quote from: IDEngineer on July 18, 2019, 10:14:25 pm --- --- Quote from: tautech on July 18, 2019, 10:06:47 pm ---They ADD the ability to have a powerful OS that permits incorporation of complex features into an instrument and that OS needs be shut down gracefully to retain settings. --- End quote --- Sure, but as has already been noted in this thread, embedded systems commonly handle loss of power. A soft touch power switch does not protect from AC interruption, and most equipment doesn't say "Must be used with suitable UPS". Most folks here would consider T&M equipment that bricked due to AC loss to be a terrible design. Thus they must design for that, in which case the soft touch switch adds nothing. --- End quote --- Nope, you're missing something. Loss of power without the proper shutdown only loses the users last settings like if you were using some specific settings for triggering and channel settings. Instruments default to particular settings for you then to need to reset to what you were using before. Nuthing at all like turning it into a brick..........but, for loss of power while doing a firmware update, that's an entirely different matter and a risk that's warned about in firmware upgrade instructions. Still that's recoverable if the manufacturer permits it with the correct external SW input. Typically instruments with dumber OS'es have hard switches and ones with complex OS'es use soft switching.....yes, it's that simple ! |
| IDEngineer:
--- Quote from: tautech on July 18, 2019, 10:32:34 pm ---Loss of power without the proper shutdown only loses the users last settings like if you were using some specific settings for triggering and channel settings. --- End quote --- I'm not talking about firmware upgrades, which is a special case. As noted earlier herein: --- Quote ---However, proper design is an option, where you have a high priority interrupt triggered by loss of AC and you know the rails will survive for XXX milliseconds - during which your firmware's sole job is to stabilize its volatile data. Heck, even spinning disk drives have a version of this where they sense freefall and lock their heads into a safe position that doesn't risk damaging the platter surfaces. And that's in the mechanical realm. --- End quote --- It is entirely possible to design a system with a hard switch that saves its configuration during powerdown, because powerdown would be no different than loss of AC. This is actually a better design, because the same procedure is used whether the shutdown is intentional or accidental. The results when the device powers back up are the same in either case, and (again) no soft touch power switch is required. Reliable, predictable behavior regardless of why the unit shut down. |
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