Consumer electronics with RTC annoyances

Howevere, there can be a good reson for not having the machine just start where it was when the power comes back; lathes for example often are switched such that if the power stops the machine stops and will *not* start again when the power returns; as bits of the operator may be in a different place that they would be were it running. To have the machine do this is more complicated that just adding a small backup supply to the RTC.

We have some portable air con units we use in summer. We had a power cut which went on to the end of the day. So we pulled the hoses in for the night and shut the windows.

Next morning one had a damaged compressor and the place was a furnace. They had switched back on when the power was restored. Not that we were using the clock option.

Damn things have a battery back up and remember what they were doing when power is restored.

You must be joking. A single relay with a hold contact will do this perfectly. RTC, sheesh!

Jeroen Belleman

I fully agree! Modern electronics is loaded with gadgets many of which are rendered useless because of some silly oversight.

Take my portable telephone for example: It has a colour screen with loads of themes and background pictures. It also has very poor contrast. The only colour scheme that could save the day would be simple black & white, which, of course, is missing. Grrr.

Jeroen Belleman

That's essentially what is used on lathes etcetera, which in their simpler forms do not have an RTC - but that was just an example. Perhaps you missed that acronym in the subject line, and/or the original post.

On a sunny day (Mon, 11 Jan 2010 09:46:41 +0000) it happened Martin Brown wrote in :

My microwave shows a green blank LCD, indicates the clock is not set, an I have a big round clock with a battery in the kitchen for th time. and also a mechanical egg timer with a very loud bell. :-)

Main glitches are relatively rare here.

We have a gas cooker where the oven will not light unless the clock is set (to any time).

After a momentary power failure it MUST be reset. This involves a sequence of multiple button presses which is non-obvious and hard to remember.

John

Yes. I understand the need to fail safe when the power or any other essential service is removed. Many of the instruments I work on have such critical fail interlocks. Typically to protect the water cooled delicate vacuum interface cone from the 9000K argon plasma.

However, I was talking here about white/brown consumer appliances where the main purpose of the RTC is to *display* the time and switch an oven on at the appointed hour. An alarm clock that resets to midnight after a power cut whilst retaining the alarm time is neither use nor ornament.

It is perfectly sensible to disable any dangerous functions and abandon work in progress, but it is extremely annoying to have to reset the time on multiple appliances if the power glitches even for a few seconds.

Regards, Martin Brown

On a sunny day (Mon, 11 Jan 2010 17:16:09 +0000) it happened Martin Brown wrote in :

Yes, agreed, that is why I object to a summer-winter time change 2 x per year! Now whatyougonadoabouthat?

You may also need an oscillator, as the mains frequency is often used as a timebase. Although, in the case of a brief "glitch", having the clock lose a couple of seconds would still be preferable to a 00:00 reset.

Try to buy appliances where the time display is optional? I have a microwave oven that's designed this way -- it has a blank display if you haven't yet set the time, which is infinitely better than devices that flash "12:00" or whatever if you haven't done so. (I've never tried, but presumably it must display some error message if you try to program it to turn on at a certain time and the clock isn't set yet. I find it kinda intriguing that microwave ovens back in the '80s/early '90s tended to be more programmable than the ones today -- apparently few people ever programmed in delayed starts, multiple steps, etc.)

---Joel

We have a perfect solution: don't bother to adjust.

Another annoyance is that they often drift. This is nonsense in a situation where they can depend on AC line timing keeping them precise for years.

Using a supercap to keep the thing running over a power outage seems reasonable until some manager decides to start slicing cost out of the BOM. Since almost nobody would pay extra for that particular feature, it isn't really worth putting in.

On the other hand, I have a radio shack 'big LCD' face alarm clock that I got at a yard sale years ago. Nice 4" digits, easy to see without glasses. It has a 9V battery backup. The battery appears to drain after a few years, but there is a nice indicator light that tells me to replace it.

Regards, Bob Monsen

Some old movie had an accountant who never reset his watch; he just always knew that it was 23 minutes slow, and compensated in his head... (he was 'very good with numbers' :)

Duct tape works well for this particular problem. Just tape over the numbers.

Ah, maybe there is a product here. A stick-on battery powered LCD clock... just toss it when it runs out of batteries, and put another one on. :)

Regards, Bob Monsen

On a sunny day (Tue, 12 Jan 2010 09:34:57 -0800) it happened "Joel Koltner" wrote in :

Yes my microwave's display is also green (not set), I did not know there was a timed function, maybe mine does not have it, but why else the clock? It has a lot of programs, and I use those. This one is not so old, maybe 10 years.

Just as a "convenience?" So you don't need a kitchen clock?

Question for old-timers: When regular convection ovens started sporting clocks, was it so that they could be set to start/stop baking at a given time in the future? Or did some come with clocks strictly for the utility value of the clock itself (and "timed bake" as a feature came later)?

On a sunny day (Tue, 12 Jan 2010 11:22:02 -0800) it happened "Joel Koltner" wrote in :

Actually I now remember I experimented with that some years ago. I could not make this microwave start at a given hour, when using a mechanical clock like the ones you use for lighting, because when the clock would come, then the microwave would have forgotten the program. But I had an other one, with a mechanical clock, you could jam the clock, and use an external timer to switch it on and off again. That one was much cheaper too :-)

Needless problems to reset the clocks. The only thing that comes back on that I know of, is some TV sets. They will remember. Most other appliances have fail safes.

Just bought a new alarm clock. My trusty battery portable clock bit the dust. I still have a Sony Dream machine that I bought well over 10 years ago. I consider it unusable because of the display system is terrible to read, but it did have the built in 4 hour rechargable battery susyem that still works. I checked it out yesterday. The new Emerson from Target was $20. Has radio, projector, comes preprogrammed for EST, with year, month, DST, etc. I hate to change 9 volt batteries in most clocks, and they drain even though they are not needed, and can easily top the price of the clock after a few years. The Emerson has a 3 volt Lithium that should last over 5 years, but also enables a separate alarm even if the power is off. A lot for $20.

I'm still waiting for the day when refridgerators have clocks so you can set the proper defrost time of day.

greg

I don't see the problem, because the clock would control just like the microwave counterpart. I'm used to combo microwave/Turbo Ovens. They came on the market about 1980 but they did not catch on at that time, mostly because of cost. I use and own 3 turbo ovens and thet are all very different. I also have two microwaves in the kitchen one being the combo unit. I can use all at the same time, plus the regular gas oven/range. I don't recall any mechanical timer microwave having a start button. All would come on after power failure. Using those rotating mechanical timers is still superior to most anything else for speed. They still are used on some commercial turbo ovens and such.

I like to argue, all ovens are convection, until the food temperature equals the oven temperture. I use the Turbo Oven terminology because thats what the fan opperated ovens were first called.

greg