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Comment Whatever was wrong with local solar time? (Score 3, Interesting) 598

Changing everyone to use UTC all the time in order to obviate the problems with Daylight Saving Time is offering a cure rather worse than the disease. Nothing is all that wrong with the system of timezones, defined so 12 Noon is more or less in the middle of the day for everyone. By itself and for certain technical purposes UTC is a good choice, in the same way that base-16 number encoding is, but for everyday civil use it doesn't do the job well. Local time and base-10 works much better there.

If the Daylight Saving is the problem then the solution is to get rid of that then? Stay on local solar time as the existing timezone stipulates, and do not turn the clocks one hour back and forth every few months. The easiest solution is the negative one, in that it means not doing the stupid thing anymore.

Comment Re:What if he was using metric units? (Score 1) 512

Well since he is Italian, and was on his way to Canada, and if he were doing applied engineering math he might have been using metric units.

However, as his field of learning is economy, the most likely specific units that he might have been using would have been dollars ... which if not exactly metric, at least have the familiar base-10 divisions. But as he was working on some differential equations at the time, the use of specific units or even much in the ways of numbers would not be likely.

Comment Re:legalism is a crap philosophy. (Score 2) 582

25 MPH (or 40 km/h) on a road of the quality seen in the video will usually feel like it is too slow, and it is not surprising that there are many that exceed this limit.

I notice that most arterial roads around here have the equivalent of 30 MPH (50 km/h) though reduced to 40 km/h or 25 MPH past schools. Where there also is at least one speed bump or raised pedestrian crossing (basically a speed bump with the crosswalk on top). Non-arterial roads have 30 km/h (which would correspond to 20 MPH), and there are always speed bumps.

Comment Re:Needless limiting of options (Score 1) 170

Where not only the so-called TIPs, (by which is meant a certain series of reasonably popular power transistors in TO220 packages, designed by Texas Instruments) but also other devices such as 2N2222, LM386, and "bipolar transistors" and so on, are no longer to be used. Just because they might not be the best choice for switching loads controlled by an Arduino or similar.

So, I am not an EE, but it seems like what he's actually saying is that the MOSFET takes an order of magnitude less turn-on current and that it wasts an order of magnitude less power as heat. Is that true? And if so, why would you not want to save power? Are your driver transistors doubling as a heater?

A lot of the energy budget depends on the circumstances. When running on batteries, power draw is much more of a concern than when running on mains power. Similar with heating -- it may or may not be anything that needs to be attended to. Now having said that, there are several good reasons to use the MOSFET instead of the bipolar transistor, but they are not so overwhelmingly good that it makes sense to discard all kinds of bipolar transistors just because ot that.

The turn-on current for the MOSFET comes from charging the capacitor formed by the gate -- the instantaneous current is C dV/dt, in other words, the faster the transistor is asked to turn on, the larger, though briefer, will the current pulse required be. Once the transistor is turned on it doesn't require any current to stay on. There will however be another similar current spike, in the opposite direction, when the transistor is to be turned off and the gate capacitor is discharged. When the load is something like a motor, these time requirements won't be all that strict, so a controller is quite likely to be capable of driving the transistor. Now, without the necessary additional protective passive components (diode across the motor, maybe also a resistor and capacitor "snubber" circuit there as well; further diodes and resistors and capacitors around the MOSFET that serve to "eat" the energy coming from the motor being turned off) -- there is a nonzero risk that the load will turn on and stay on, having fried the MOSFET and maybe also the output circuitry of the microcontroller or Arduino...

In contrast, the bipolar transistor will require a steady base current for as long as the load is to stay powered, and they are more robust, less sensitive to surges and other influence of the load, and this does make it easier to make the circuit reliable, easier to make it work and easier to make it keep on working properly, The TIP120 and many of its relatives, being Darlington pairs, do have a fairly large current gain, so the required drive current is likely to be small enough for the microcontroller IO line to drive. But they have a voltage drop, and corresponding power loss, and are thus less optimal for driving motors. Which may or may not be a problem-- it will all depend on the actual application.

Thus, using a MOSFET for a switch has its advantages and its pitfalls like everything else -- and I don't have any objections to Tom Jennings recommending MOSFETs over bipolars for turning things on or off. What I do object to is the wholesale discarding of all bipolar transistors as if turning things on and off with the MOSFETs were the be-all and end-all of all electronics -- as we well know that is not so.

Comment Needless limiting of options (Score 5, Insightful) 170

Where to begin?

Should one even bother to do anything about advice from someone who goes on about enhancement MOSFETs while everything else is rubbish, and then present the circuit symbols for Junction FETs as examples? Makes one wonder what else is inaccurate there.

The actual advice of throwing out anything designed in the past century is at

Where not only the so-called TIPs, (by which is meant a certain series of reasonably popular power transistors in TO220 packages, designed by Texas Instruments) but also other devices such as 2N2222, LM386, and "bipolar transistors" and so on, are no longer to be used. Just because they might not be the best choice for switching loads controlled by an Arduino or similar.

This makes for a needless limiting of options -- If all one ever does is to turn things on or off from some microcontroller maybe, but with whatever designs I make I find that to be a small fraction of what is happening. The rest are things like multi-frequency linear or RF where all kinds of semiconductor devices might be applicable. Even vacuum tubes in some cases.

And then looking around the site and discovering the author is in his own words, "reasonably obsessed with the early history of electronic (not necessarily digital) computing" --- and then he advocates discarding what amounts to the elements of the analog electronic computers? This does not ring true.

Comment Re:Sticking with a 1982 design (Score 1) 698

From what I remember, the numerical keypads with 789 on the top row were inherited from ancient calculating machines, not entirely unlike the QWERTY ordering of the keyboard -- it was the way it was laid out and as it wasn't broke no-one ever bothered to fix it. There were some mechanical reasons for this originally, then it carried over to electronic calculator keyboards and then their descendants, the computers.

The phones keypad pedigree is different: from various circular dials that opened and closed a switch a number of times corresponding to the number the user wanted to dial, the keypads that replaced the dials got the numbers in a natural top-to-bottom ascending order, usually with keys organized in a 3 wide 4 tall matrix.

Comment Re:yes please: (Score 1) 698

I use the keypad while paying bills. There are account numbers, the amounts themselves, then these other long identifier strings of numbers that makes it certain that the mony ends up where it is supposed to go. Much easier than using the top row.

As for caps lock -- since I use vi a lot, the accidental turning on of this makes a lot of confusion since the various letter commands are different between upper and lower case: j moves down, J joins the line and the following then u is undo but U is undo to original text of the line. Then :e! starts over for another try...

Changing it to ctrl isn't great either, I'd type away at some website like this, then hit ^A and a couple letters later it is all: Where TF is all my text gone! Damn...

Thus, most of the keyboards here have the key removed so as to avoid the above kinds of hassles.

Comment Re:it could... (Score 1) 148

The closest I can think of when it comes to real-world devices that have a large reduction ratio, would be something like the mechanical tachometer/hour counter combinations seen on old tractors and similar -- where the dial indicates something like "hours at 1500 RPM". That makes for a reduction rate of 900000 from the engine shaft to the rightmost wheel of the counting device if that were to rotate once per 10 hours.

But in these, the reduction would be done via several stages of worm-drives, and the reduced speed is important, not the increased torque. And they are thoroughly obsolete -- anything made since the 1980s would use electronic devices to do this.

For torque multiplication, this would require some seriously strong materials in the later stages. Even then, the total power would be limited by the maximum speed of the first stages as well as the maximum torque of the latter stages. Yes, with sufficiently strong materials it could move a house though it would have to do this over a period of several months. Hard to see how this could be practical outside of mechanical instrumentation applications.

Comment Re:Reversing what now? (Score 2) 421

Why would that be a probable outcome ? Why couldn't we just add a little bit of the aerosols, measure the effect, and slowly add some more ?

There is pretty good historical evidence of what did happen when a big volcano blew out lots of ash and particles. Mount Tambora for example, that had an eruption in 1815, and the following year, 1816, became known as "the year without a summer", because of this. There is no good reason to expect a significantly different outcome from filling the atmosphere with other similar particles. It will become colder.

On the other hand, this does argue for the possibility that the system can behave somewhat predictable, with negative feedback as it were, within a smaller range of excitations, like varying the speed of an aircraft as long as it runs faster than stall speed. But once driven past some inflection-point that we can expect to be there, given that the system is chaotic, all bets will be off.

Still, this suggested solution seems to be worse than the problem. The possible increased temperatures and CO2 will just make for better growth conditions for all kinds of plants, of which many are food for animals which in turn are eaten by humans. Less sunlight, less heat, less CO2 and there will be less foliage, then eventually less food available. How can that good for anything?

And finally, back in the 1970s and 1980s, there was a lot of argumentation about acid rain, caused by partculate pollution from coal-fired plants, where the sulfur was precipitated as acid. Countries have managed to put a stop to this kind of pollution, though there are still localized problems with particulate pollution in cities. And now there are someone arguing that this sort of thing actually could be worthwhile in an attempt to halt a perceived warming process?

Comment Reversing what now? (Score 2) 421

This is supposed to "reverse" the climate change? As in making it essentially perpetually cloudy? This sounds nothing so much like a nuclear winter, though without the nukes...

How something like that is going to reverse anything, now climate being that chaotic as it is doesn't easily move forwards or backwards along some line, like a car or animal does. It will change it, sure. Probably to the nuclear winter-like conditions, as if that were anything better than today's situation. Or maybe this would also keep heat in, so we would get what is essentially a runaway greenhouse... now wasn't that what was supposedely the problem initially?

This is just wrong on so many levels...

Comment One day per hour, more or less (Score 1) 163

Going West (from Europe to the US for example) I wake up really early the next morning, then one hour later each subsequent morning. Takes about a week for a 7-hour time difference.

Going east is different. First morning after I am up around 7 or 8, second day I can sleep until 1 PM if allowed to. Then it alternates the following days like that, for about a week for 7 hours as well.

Seems there is some kind of 25-hour cycle active on stretching the day, and a 48-hour cycle in action on compressing the day.

Shorter differences, 1 hour or 3 hour are similar, but the transition time is correspondingly shorter.

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