Electronics > Projects, Designs, and Technical Stuff

Another reason to hate "soft touch" power switches

<< < (11/13) > >>

soldar:
I still have an old CRT TV that after a power outage turns on with audio volume at whatever level it was set. I once came back from a long trip and the neighbors were surprised to hear I had been gone because the TV had been blasting away for days. Now I remember to turn the volume down if I am leaving for more than a few days.

I have mentioned in another thread that I have a big multimeter that has the only switch in the back, like computers, where it is unreachable with the instrument mounted in rack or shelves. I put an inline switch in the power cord. Which is still a pain.

exe:
Huh, my micsig oscilloscope turns on when I... turn off the bench (the scope has internal battery). It does so with a delay and it cannot be powered off before it finishes booting. It also does it inconsistently, like in 50% of the time. Just unplugging the oscilloscope from the power brick doesn't do anything, but unpluging the brick from mains triggers power on. So, every time I do something with a scope I have to think what power state it will be in the end. I ended up using it from battery only. Horrible design...

rsjsouza:

--- Quote from: IDEngineer on July 19, 2019, 02:52:22 am ---
--- Quote from: rsjsouza on July 19, 2019, 02:20:59 am ---the main reason I can see is to be quick enough to have application data be written to the non-volatile media before the power is off. The reason the data is in RAM is most probably due to running performance - in the world of ultra fast SSDs, RAM is still the absolute performance king.
--- End quote ---
No question there. But the discussion has been about storing user preferences, front panel setups, etc. to nonvolatile memory.
--- End quote ---
The discussion has been about what the soft button ADDs to your system. My point is they add more predictability to a system that can benefit from still having available power to guarantee extra reliability during critical operations by means of a controlled shutdown. It could also improve bootstrap performance by keeping the system in some sort of suspended or sleep mode state. Just picture a high end oscilloscope with a HLOS and it becomes much more difficult to move away from the soft switch. It is not impossible if you are rolling your own OS or use one of the expensive real-time HLOS around (VxWorks, QNX, etc), but much more difficult if you have a commercial HLOS running on the machine. Again, the soft switch can bring an added value if one desires a commercial HLOS on such equipment. 

Specific to the user preferences, etc., small amounts of data like these can be written to flash directly in an unbuffered operation. Even still, the internal RTOS or HLOS may need to queue this operation before it has time to properly finish this operation. Being carefully planned, the most critical operations before a powerdown (the ones that can potentially corrupt the system) must be tied to a NMI to avoid interrupt priority queuing, but perhaps other less critical operations (such as user settings or preferences) may or may not be fully completed before the power is completely lost - manifesting themselves as operations not saved at the next power up (a nuisance). Now, queue a power loss in the shape of a user-operated clunking switch, which happens orders of magnitude more often than an actual power loss: the probability of the nuisance errors happening is magnified.

Is it impossible to make a system completely bullet proof? No, and I mentioned my experience in my previous post, but the limitations there are a tradeoff that I am willing to have. 


--- Quote from: IDEngineer on July 19, 2019, 02:52:22 am ---(...) there's simply no reason that an AC power loss detection circuit that drives a hardware interrupt can't do double duty and protect against both unplugged line cords and turned-off hard switches.
--- End quote ---
Depending on the complexity of the system, that may not be the case. Just picture a high end oscilloscope with a HLOS and it becomes much more difficult to move away from the soft switch. It is not impossible if you are rolling your own OS or use one of the expensive real-time HLOS around (VxWorks, QNX, etc), but much more difficult if you have a commercial HLOS running on the machine. Again, it is a tradeoff between added functionality and implementation details.


--- Quote from: Mr. Scram on July 19, 2019, 06:13:30 am ---
--- Quote from: rsjsouza on July 18, 2019, 09:15:15 pm ---I agree this is shameful. However, it doesn't detract from where it matters the most: when the power supply is actually turned on.

--- End quote ---
Unless you're running a factory where equipment is up 24/7, I'd argue the off state is as relevant as the on state. Even if you're not looking at it while the device is in it. I can't confirm or deny this is intended behaviour, as I don't own one of these power supplies.

--- End quote ---
??!?? Really ??!!??  :-DD

Each to its own... To me a power supply in the OFF state is almost completely irrelevant as it does not fulfill its main function, which is to power stuff around. At power off, the only function it does is to look good in my bench and impress my technically inclined friends. For that, I don't think I can fault it either - it looks really good!  :-+


--- Quote from: Mr. Scram on July 19, 2019, 06:39:03 am ---Implementing complex OSs with a hard switch is a doable engineering problem. Implementing soft switches with the associated downsides like power consumption and apparently costs seem to be lazy engineering. It's strange people are content to give up core features when they're offset with some shiny gimmicks. It can do everything except for things equipment did 50 years ago.  :palm:

--- End quote ---
I didn't say it isn't. See above. But to me a clunking switch is not a "core feature" but a small detail in the overall system. Again, each to its own.

Mr. Scram:

--- Quote from: rsjsouza on July 19, 2019, 10:43:31 am ---The discussion has been about what the soft button ADDs to your system. My point is they add more predictability to a system that can benefit from still having available power to guarantee extra reliability during critical operations by means of a controlled shutdown. It could also improve bootstrap performance by keeping the system in some sort of suspended or sleep mode state. Just picture a high end oscilloscope with a HLOS and it becomes much more difficult to move away from the soft switch. It is not impossible if you are rolling your own OS or use one of the expensive real-time HLOS around (VxWorks, QNX, etc), but much more difficult if you have a commercial HLOS running on the machine. Again, the soft switch can bring an added value if one desires a commercial HLOS on such equipment. 

Specific to the user preferences, etc., small amounts of data like these can be written to flash directly in an unbuffered operation. Even still, the internal RTOS or HLOS may need to queue this operation before it has time to properly finish this operation. Being carefully planned, the most critical operations before a powerdown (the ones that can potentially corrupt the system) must be tied to a NMI to avoid interrupt priority queuing, but perhaps other less critical operations (such as user settings or preferences) may or may not be fully completed before the power is completely lost - manifesting themselves as operations not saved at the next power up (a nuisance). Now, queue a power loss in the shape of a user-operated clunking switch, which happens orders of magnitude more often than an actual power loss: the probability of the nuisance errors happening is magnified.

Is it impossible to make a system completely bullet proof? No, and I mentioned my experience in my previous post, but the limitations there are a tradeoff that I am willing to have. 

Depending on the complexity of the system, that may not be the case. Just picture a high end oscilloscope with a HLOS and it becomes much more difficult to move away from the soft switch. It is not impossible if you are rolling your own OS or use one of the expensive real-time HLOS around (VxWorks, QNX, etc), but much more difficult if you have a commercial HLOS running on the machine. Again, it is a tradeoff between added functionality and implementation details.

??!?? Really ??!!??  :-DD

Each to its own... To me a power supply in the OFF state is almost completely irrelevant as it does not fulfill its main function, which is to power stuff around. At power off, the only function it does is to look good in my bench and impress my technically inclined friends. For that, I don't think I can fault it either - it looks really good!  :-+

I didn't say it isn't. See above. But to me a clunking switch is not a "core feature" but a small detail in the overall system. Again, each to its own.

--- End quote ---
The ability to turn off equipment so that it's not consuming power, heating up the room, wearing out the equipment itself and not a potential fire hazard is definitely a core feature. It's the baseline of what can be reasonably expected. Can you imagine not being able to turn off your car?

exe:
Same here on off-"feature". Most my T&M equipment used less than 1% of the time, except lab power supplies and my laptop.

I cut mains off when I don't use my lab, I don't want my house to be burned by a malfunctioning device (I have about twenty devices plugged in the lab, some of them second-hand and old).

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod