Please help can't figure this out, been trying for ages

For a cutting laser I don't think they should rely on the CPU at all. What if it locks up with the LASER on? A one-shot could turn it on so the CPU would have to trigger it repeatedly to keep it on. Hardware POR could ensure it starts off.

What if it locks up with the LASER on? A one-shot could turn it on so the CPU would have to trigger it repeatedly to keep it on. Hardware POR could ensure it starts off."

I think I would want an old fashioned frikken toggle switch. Automatic schmautomatic. I got a friend who will not buy a car with an automatic transmission. I like that.

The car I just put a deposit on doesn't have an automatic transmission. :)

Rick C.

Just FYI a lot depends on the _color_ of the laser. For that reason the test with a piece of paper is unreliable. For example: I have 5W 445nm blue laser (with optics). It will happily burn into a pertinax PCB, or cut a rope, all at some distance. But if you hit a piece of white printer paper with it, then nothing will happen. The reason is, in my experience, that white paper is very reflective at blue and UV wavelengths. If you have one of those (near) UV flashlights (as used for checking bank notes), normal white printer paper will light up brightly! For IR and red lasers the reflectivity will be less I think.

Ditto. I wouldn't get an automatic, I don't know why mericans seem to love them.

NT

I have driven both, prefer automatic any time. I once had a Peugot 404 station, it had a hand crack in case your battery was empty,

4 sure something to have for the real drivers ;-)

And with electric do we still need gears? But auto-pilot? No.

I've always had stick shift cars. My wife has had about half and half. The major reason they're so popular around here is city traffic and many hills.

Yes. The maximum torque from an electric motor is proportional to its volume, so unless you want to always be effectively starting off in top gear, you still need variable gear ratios (either a normal transmission or a CVT).

I'll probably want one when I'm 85 and can't drive myself anymore, but not sooner.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com

Normal white paper has fluorescent brighteners in it that make it whiter-than-white.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com

I had a Peugeot 203 in Australia four about four years - bought it when it was 17 and sold it when it was 21 when I headed off to the UK in 1971. In the UK I had a slightly less elderly 404 for about eight years, until it rusted out.

Nice cars. The 304 wasn't as good, and my wife preferred Nissans which were even more reliable.

Probably not. Torque is proportional to current through the motor, and you can use switching regulators to give you any voltage you want (though it may empty the battery rather fast if you want maximum torque at maximum revs).

Why not? It won't be perfect, but neither are humans.

--
Bill Sloman, Sydney

The tesla only have one gear, there's also some of the teams in formula E that only have one gear

I am no expert on electric motors, but see it this way: if the RPM gets higher, the same increase in pushing force is available if you apply the same amount of extra power, so there is no 'optimal' RPM where the efficiency is best. (Not very clearly stated I know). Of course there is one in more practical limits, max rpm before the thing flies apart versus max speed for the car etc. may require a fixed gear ratio.

I see the Teslas have an about 9.3 to 1 gear ratio, motor running faster than wheels, to get more force on the wheels.

a car wheel has a circumference of roughly 2 meter so that would be true for all cars

Most 'mercans are obsessed by 'convenience'[1] and so tend to regard driving a "Stick Shift" automobile (manual gearbox car) more as an undesired 'chore'. This preference has created the demand required to support the mass production of automatic transmissions in cars economical enough to compete against the simpler, if less common, production of manual transmissions.

I didn't start driving automatics on a more regular basis until nearly twenty years ago as a result of my wife's botched (left foot) Achilles tendon repair surgery which obliged her to give up driving normal cars.

Prior to that, my only experience of driving automatics was when our 2nd eldest son, who had decided to translate his teenage interest in car mechanics into a business as a self employed car mechanic, enlisted family members as temporary drivers every now and then to help him transfer cars between various dealerships located in disparate parts of the UK.

I got to drive a variety of cars ranging from brand new to ancient, including, afaicr, one old Bentley with a very iffy automatic transmission that made negotiating busy roundabouts a "very interesting" experience indeed (and by "very interesting", I mean very dangerous since trying to accelerate from a standstill involved a good two second's lag between stamping on the accelerator and the car deciding to move off the mark).

The first automatic car that we bought to solve SWMBI's mobility problem, was, afair, a rather nice 2nd hand Volvo, sourced by #2 son. I was rather impressed by its automatic transmission which, I believe, was based on a cone drive form of the variomatic principle pioneered by DAF's variomatic rubber belt drive. It was one of the smoothest and quickest automatics I'd ever driven up to that time. Sadly, it only lasted about a year or so before a surprisingly expensive transmission fault caused us to look for a replacement.

This took the form of (another 2nd hand) Y reg Vauxhall Astra 1.6 automatic, also sourced by #2 son. Amazingly, it's still going strong even today some 13 or so years on (as best as I can work it out). It's needed very little repair/maintenance work to keep it going (it passed its last MOT in May without any bother).

It's only given us one fright in the form of a potentially expensive automatic box repair that appeared to be the result of an excess transmission fluid refill by #2 son who remedied this oversight. Mind you, every time I check the fluid levels, the transmission fluid level has always been slightly above the max - the one and only time when I'd rather something on a car wasn't quite so perfectly oil tight.

The wife still likes this car despite hankering after a taller model that would ease ingress and egress. I, otoh, have always had a hate/hate relationship with its kakamaimee automatic gearbox's gear selection algorithm.

I've long since come to the conclusion that it's based on the premise that it will *only* *ever* be fully loaded up with four average weight Americans and the maximum weight trailer hitched up behind (oh, and an assumption that the engine mounts are fabricated with Chivers' finest jelly cubes rather than the more normal hard rubber compound).

It's what I refer to as "Old Man Gearbox". It never gives the engine much chance to run economically in 30mph speed limited zones as any sensible driver would in a manual transmission car where, at a steady cruise speed on the level, engine rpms of 1200 to 1500 rpm would be perfectly fine and a damn sight more economic than 2000rpm in a lower gear.

I can now see the benefit of having cruise control on an automatic (which the Astra lacks), especially these days with the proliferation of speed cameras (aka scameras) since you lose the connection between engine and road speeds that a manual provides. I hate the need for constant vigilance of the speedometer along busy urban routes just to avoid getting caught by a scamera.

I used to run my own manual cars for the first few years of the wife changing over to automatics but eventually, wasn't able to justify the extra expenses involved in two car ownership. I've been sharing the use of the Astra for the past 7 or 8 years and missing the joy of driving a proper manual car ever since.

Station wagon?

Hand *crank* (aka, "starter handle")?

I can see the value of such a feature on a vehicle that may not be so easily push started, if at all. These days, the modern solution to that is to carry one of those 8 to 12 AH LiPo battery jump starter packs in the car wherever you go[2]. :-)

Short answer is a resounding "NO!" (with the following provisos).

With a properly thought out electric transmission setup (where the BFO switching converter that supplies the electric motor(s) with appropriate voltages now stands in for all that messy mechanical business of cogs, clutches/torque converters), then quite obviously, there's no need for a gearbox at all, especially if each wheel is a hub motor with a small disk brake incorporated, neatly wrapped in a pneumatic road tyre.

In this case, we're not dealing with trying to operate an ICE close to its optimum rev/torque efficiency point, just optimising the use of a battery or fuel cell for most efficient acceleration performance and energy recovery during the majority of any decelerations (delegating the final slowdown to a stop phase to the undersized disk brakes provided for exactly that purpose) in order to maximise operating range.

You have good reason to be sceptical of the whole idea of "The Self Driving Car".

Such automation would have to become considerably more sophisticated than even the best efforts to date before the issue of safety is properly addressed, if ever. Even under the more tightly constrained conditions of railway (rail road) operation, serious accidents have still occurred despite the best of automated safety systems being utilised.

Then you have almost the opposite effect with commercial airline auto- pilot systems unexpectedly handing control back to (literally inexperienced) pilots often under the most stressful of flight conditions, where the cause of fatal crashes so often turns out to be due to 'Pilot Error'.

Here the issue is one of the lack of 'hands on control' practice by airline pilots due to the 'convenience' of hands free piloting offered by the auto-pilot. The problem is really one of automation being used to reduce the costs of flight crew provisioning by the airline operators.

That's not to say that the auto-pilot is a bad thing of itself, just that it leaves the pilots in the position of "Passengers with a privileged front seat view" for most of each flight which does nothing for keeping their actual flight skills well honed for those rare occasions when they're expected to actually earn their salaries.

If self driving cars (automobiles) were ever to become more commonplace, this lack of hands on driving experience effect will be an even bigger factor than it is in the airline industry where the pilots do at least, in the main, have a much finer appreciation of the risks than your typical automobile pilot. Unless self driving technology becomes good enough to eliminate any direct human intervention, this will always be an inherent danger.

[1] It's a culture created largely by commercial TV and Radio advertising (essentially a form of commercial propaganda that would have made Paul Joseph Goebbels happy to see his own efforts legitimised this way). The only reason why us Brits weren't subjected to such commercial propaganda until the middle of the last century was because the UK government resisted the inevitable pressure to release the airwaves into the hands of crass commercialism until 1955. After that, it was downhill all the way to the UK's present obesity/type 2 diabetes epidemic and obsession with a materialistic lifestyle that echoes the American experience. [2] Even a 12AH SLA will do the job as I discovered a few years back one winter's afternoon when the worn out battery on the Astra automatic ran out of juice whilst I waited outside the local chippy for the missus to return with our tea having stopped by on the way home from a day trip out and about.

I'd made the fatal mistake of switching the engine off with the sidelights on (I could have left them off - the street was well lit and I was parked facing the right way to show the correct reflector colours). The result, some ten minutes later, was half a revolution crank of the engine that left me with a 'dead' battery. We were only a five minutes walk away from home so we abandoned the car to enjoy our chippy tea at home before it got cold.

The NiCad based jump starter gadget that I'd been hauling around for the past few months since the last time I'd flattened the battery, I took home with me to put back on charge. It had been flat from self discharge so hadn't been of any use whatsoever in this event.

The problem with this NiCad pack is that it took at least ten hours to recharge it so I eyed up my 2nd hand, purchased from a flea market trader about 18 months earlier 12AH SLA battery (and only ever charged off a small solar panel during a fortnight's (14 days') worth of the previous summer's sunshine).

I made up a couple of one foot long 'jump leads' and walked back to the car with my son. I *did* try starting the engine again before attaching the jump starter battery, proving the car battery hadn't miraculously recovered in the meantime. Much to my amazement, the engine sprang into life first attempt with this little SLA, proving that you can use smaller capacity batteries just as long as they're capable of supplying the hundred or so amps required turn the engine over for the few seconds needed to fire it up.

--
Johnny B Good

You get more power at higher revs. More power makes the car accelerate faster:

The power applied to moving the car (after all the mechanical inefficiencies are taken into account, and neglecting friction since it's low speeds we're talking about) is the time derivative of the car's kinetic energy:

P = d/dt (m v**2/2) = m v dv/dt

so acceleration is

dv/dt = P/mv.

Thus gearing down by a factor of 2 (so that P is doubled for the same road speed) gets you twice the acceleration off the line, other things being equal.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
https://hobbs-eo.com

Very impressive posting, you are a great writer! For me, been about everywhere, got my license in Florida in an automatic long long time ago. Now that is a whole other story. I have driven in the UK but left handed traffic scares me, and a lot on the continent of course. In whatever car was available for work, or some exotic ones I had (remember Triumph Herald?). Usually I get out of the car more relaxed than when I get in, that is why I want no auto-pilot. There are some youtube videos about people using super capacitors to [help] start cars too. I have used 11.1V lipos to start a motorcycle. Yes that Peugeot was a station wagon, it had, just like that other French car 2CV, the gear change on the steering wheel. French cars are fun to drive. Car batteries often get soft at very low temperatures, maybe having some super caps in parallel all the time is a good thing for cold start. Driving is for a large part a social experience, give and take, I think that makes an auto pilot a big challenge, even if it was technically always right.

assuming you don't hit the power limit for the motor and that you can put the power to the ground, few cars can do more than 1G

aster: "

There seems to be a lack here concerning expression. First thing to remembe r is why a transmission with more than one gear ratio is necessary.

The internal combustion engine (hereafter referred to as "engine") behaves quite differently than an electric motor (DC). (hereafter referred to as "m otor")

Looking at an old Chilton's or whatever, there is a torque rating and a hor sepower rating. Engines are not all that powerful near idle. The torque wil l increase with RPMs to a certain point then levels off. the rating you see for torque is the peak torque through the RPM range. This number itself do es not take RPM into consideration thought the RPMs at which peak torque oc curs is reported.

The peak horsepower is at a higher RPM and that number increases as long as the torque does not fall off faster than the RPMs increase. That happens when the engine can no longer breathe or get enough fuel due to the air inl et size and fuel delivery. there is also a mechanical limit at which the pi eces parts come apart and then there is zero output, but that is still usua lly much higher than peak horsepower.

I remember 2 different Corvette engines, both 359 CID and both 350 HP. they also both had 350 ft lb peak torque, but in one the peak torque occurred a t a much lower RPM and the peak HP occurred at a much higher RPM. The latte r goes faster. In the former (inferior) engine, you could go just as faster but you might need an 8 speed gearbox to keep the engine within its peak p erformance range. The superior engine would require much less shifting and shifting loses power. What's more, a gearbox with a lower low gear requires a larger countergear which adds weight. More speeds also mean more weight. Same applies to an automatic but the lower low gear requires a larger plan etary set.

Now take those limitation off and you have a DC motor. This will not be a s eries wired motor because of the lower starting torque, while a shunt wound motor has good torque just about down to zero RPMs. What's more a shunt wi nding can be added to the field to effectively reduce its RPM and increase torque a bit like a gear would, but I am not aware of them doing that. They do it in the wiper motor, or at least used to, for the low speed. For obvi ous reasons they did not want lower torque, which is also why a simple resi stor was out. And a 2 speed gearbox - for the wipers ? that would probably result in fired engineers.

Also the motor has no problem with breathing. The VE is akin to the availab le voltage and current to a motor, it will produce more power until it burn s up. There is no time that comes when it can't get any more air and fuel, but there is the limitation of the battery.

I'll probably miss engines when they are all gone. But even an old fuddy du ddy borderline Luddite like me must admit that electric is better. I'll mis s tweaking them. My cars would start with 2 pumps in zero degrees and run w ell enough to get moving. they did not need to go to 2,000 RPM because I kn ew how to get the mixture right. The book be damned, it is wrong as black r ain.

They have been making progress on all of this. Batteries are better. Hell t hey had electric cars at the turn of last century, but nobody wanted them. No speed no range, complex as hell with their accelerator hitting multiple combinations of motor windings for speed control. Probably had to clean tha t all the time. not with them there big ass MOSFETS, there are very few mov ing parts. The accelerator may even be an optical pickup, I have no idea bu t I would be tempted to design it that way. Other than batteries, they have the potential to be more reliable than a car with an engine. And no more f ifty bucks worth of synthetic oil every few months. I think the problems wi ll come when they overdo the fancy electronics. If they operated on the KIS S theory it would be better.

The only uses for multiple gears on an electric car would be low for parkin g n shit to control the speed better, though that might be doable in electr onics, and a type of overdrive, if it is found that it is slightly more eff icient at a lower RPM. The torque will be there of course, but what is it p ulling from the battery ?

But then the added weight would offset most if not all of the gain I think.

HA, friend of mine is working on this scooter or something and he says it h as no gearbox. Instead it has a diesel engine which simply runs backwards f or reverse. Now there's some people who really didn't want a gearbox.

Carry an old THM400 around and see how fast you go :-)

Which is part of "other things being equal". ;)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
https://hobbs-eo.com