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| Another reason to hate "soft touch" power switches |
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| rsjsouza:
--- Quote from: IDEngineer on July 18, 2019, 03:43:17 pm ---Late in the day, I finally made it into the lab... and discovered that things with soft touch power switches had turned themselves on! Most notably for this forum, this included my Rigol DS4000 series scope. --- End quote --- This is configurable in the Utility menu. --- Quote from: SiliconWizard on July 18, 2019, 03:57:41 pm ---I'd say that a device equipped with such "soft" on/off button should NOT power on by itself in case of mains power cycling. Sounds like bad design and not something completely inherent to soft power buttons (but obviously with a simple mechanical switch, it can't happen.) --- End quote --- I agree for certain types of equipment, although for servers in remote locations the automatic power on was a lifesaver. Any power glitches were properly logged and the server gracefully recovered its services. --- Quote from: Mr. Scram on July 18, 2019, 04:01:19 pm --- --- Quote from: rsjsouza on July 18, 2019, 03:52:08 pm ---It could be worse... Keysight's E3631x series of Power supplies have no hard switch - both the fan AND the TFT backlight are turned on permanently! (...) --- End quote --- For real? I had my eye on one of those, but that's definitely a showstopper. --- End quote --- Oh, please keep your eyes on them. They are wonderful power supplies. I couldn't be more pleased. :-+ --- Quote from: Mr. Scram on July 18, 2019, 04:05:26 pm ---They solved the mains switch issue decades ago by using pushrods. Shutting down cleanly is a requirement the manufacturers created themselves but which can be solved in other ways. --- End quote --- Yes, the pushrods work really fine, although with the years of use they may develop a screeching sound due to metal-on-metal scrubbing :-DD I have a few that need some fine grease applied, but I just can't get around to do it. Power switches are critical for embedded OS equipment, as they can allow for the system to perform a proper shutdown. Clunking switches will leave temporary files behind and can cause filesystem corruption. Also, at least on our TV, keeping it on the "sleep" mode allows for a much faster power on (instead of the vaccuum-tube-era power on delay :palm:). |
| SiliconWizard:
--- Quote from: Mr. Scram on July 18, 2019, 04:05:26 pm ---They solved the mains switch issue decades ago by using pushrods. --- End quote --- Yeah. That's still a bit cumbersome from a product design POV, especially if the device is pretty crowded, so I guess the soft switches are the easy path and cost a lot less overall. I usually also don't like the "feel" of those pushrod switches much, but I admit that's a completely secondary criterion. Many lab instruments still have both a soft power switch on the front panel AND a mechanical switch on the back. Anyway as we said: switched power strips. Done. So I personally don't care much, but I can understand why some would find that irritating. |
| Mr. Scram:
Even if the graceful shutdown were an excuse not being able to turn off the screen or fan is inexcusable. |
| ejeffrey:
I can see the appeal of having a mechanical rocker switch on the back and a soft power button on the front, but realistically 99% of the time I'm only going to push the front button anyway so the mechanical switch isn't really doing anything for me. I'm sure some people religiously turn off the back power switch in those devices, but I suspect they are a tiny minority. For me a switched power strip is more convenient due to more convenient placement and the ability to power off a whole test setup at once. |
| IDEngineer:
--- Quote from: ejeffrey on July 18, 2019, 04:20:33 pm ---I think the main reason is cost. An actual mains rated mechanical switch -- especially a front mounted button with a mechanical linkage to the power supply costs a lot more than adding one more membrane switch. --- End quote --- I'd agree, except that then your soft-touch startup has to have even MORE mains-rated circuitry behind it to power up the rest of the system under soft-touch control. Something, somewhere, is switching the mains. I've designed a couple soft-touch systems and there wasn't any cost savings. It's hard to match the cost, simplicity, and elegance of a single mains-rated switch. The argument about not running AC power all over the place inside the unit has some merit, but as others have noted truly sensitive equipment solved that decades ago with mechanical devices such as pushrods. (I once had a piece of audio equipment that had a rotary knob on the front with a u-joint shaft system transferring the motion to a switch on a PCB waaaaaay in the back.) But if noise sensitivity is really an issue, just put a single mains switch on the back, such as one of those integrated with the power cord connector (and sometimes fuse too). Sure it's on the back, which won't work for rack mounted gear, but in 90% of applications that would be a very clean solution that nicely captivates the AC to a very small portion of the overall enclosure volume. In truly sensitive equipment, you optimize for performance first - and users of such equipment understand that. |
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