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>> OK, now I'm confused. A graph of current against voltage? But current
>> is completely *determined by* voltage! o_O
>
> Of course it is determined, but it's only a linear relationship (V=IR)
> for resistors. LEDs are diodes and are certainly not linear, so you
> need a graph. You could draw a graph for a resistor if you wanted like
> I said, but it would be a bit pointless because we know V=IR for a
> resistor.
Wait a sec - so you're saying there are devices which actually violate
Ohm's law?
>> OK... so... why not an open circuit then? That would have infinite
>> resistence?
>
> Then the input would be equally connected to 0V and V+ with near
> infinite resistances, that's called a "floating" input, because it can
> be persuaded very easily to either go to 0V or V+, depending on the
> exact details inside the IC (and maybe some state of the other inputs,
> who knows?!). Best to ensure you have at most around 100K of resistance
> to one of the rails to fix the input reliably.
Uh... so have it always connected to one rail, but through such a high
resistance that the rail can't affect it?
Well, you're the one with the engineering degree, but it *still* doesn't
make any sense to me...
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> Wait a sec - so you're saying there are devices which actually violate
> Ohm's law?
Yes, more exactly, there are devices which do not have constant
resistance/impedance.
> Uh... so have it always connected to one rail, but through such a high
> resistance that the rail can't affect it?
>
> Well, you're the one with the engineering degree, but it *still* doesn't
> make any sense to me...
Maybe it would help if you imagined that inside the IC there is a big
resistor (eg 1Mohm) connecting the input to one of the supply rails (but you
don't know which one). In order to ensure this resistor cannot affect the
input voltage, you need to make sure the input is always connected to the
voltage you want through a smaller resistor (electricity likes the lowest
resistance path!).
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scott wrote:
>> Wait a sec - so you're saying there are devices which actually violate
>> Ohm's law?
>
> Yes, more exactly, there are devices which do not have constant
> resistance/impedance.
Are you saying the resistence doesn't determine the current? Or are you
just saying that the current can cause the resistence to change?
>> Well, you're the one with the engineering degree, but it *still*
>> doesn't make any sense to me...
>
> Maybe it would help if you imagined that inside the IC there is a big
> resistor (eg 1Mohm) connecting the input to one of the supply rails (but
> you don't know which one). In order to ensure this resistor cannot
> affect the input voltage, you need to make sure the input is always
> connected to the voltage you want through a smaller resistor
Hmm, OK.
> (electricity likes the lowest resistance path!).
Now, see, I always thought electricity just takes *every* path, with the
current being determined by Ohm's law.
So, if you have a high-resistence path from A to B, and then you add a
second, lower-resistence path from A to B, does the current flowing
through the first path change? Or does it remain the same?
(Clearly the *potential* at A and B will be changed - there's more
current flowing now...)
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>> Yes, more exactly, there are devices which do not have constant
>> resistance/impedance.
>
> Are you saying the resistence doesn't determine the current? Or are you
> just saying that the current can cause the resistence to change?
If you want to look at it like that, yes, the resistance will depend on what
the applied voltage is, rather than always being constant. Nobody really
talks of "resistance" with such devices though, it's just accepted that V is
not linearly proportional to I, and that for any given V you can look up the
I from the chart.
> Now, see, I always thought electricity just takes *every* path, with the
> current being determined by Ohm's law.
It does, and if use Ohm's law to work out the voltage at a point that is
connected to 0V with a 1kOhm resistor and to 5V with a 1Mohm resistor, you
will see the voltage is essentially 0V. OK so it will actually be very
slightly above 0V, but that's why there is a tolerance range on the input of
such devices.
> So, if you have a high-resistence path from A to B, and then you add a
> second, lower-resistence path from A to B, does the current flowing
> through the first path change? Or does it remain the same?
It remains the same because neither the voltage across the high value
resistor, nor the resistance of the resistor itself have changed, and then
I=V/R. Of course you get some additional current flowing through the lower
resistance path now, but still the same amount through the high resistance.
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>> Are you saying the resistence doesn't determine the current? Or are
>> you just saying that the current can cause the resistence to change?
>
> If you want to look at it like that, yes, the resistance will depend on
> what the applied voltage is, rather than always being constant.
You you mean stuff like if you put power through a wire, it heats up,
and resistance varies by temperature?
> Nobody
> really talks of "resistance" with such devices though, it's just
> accepted that V is not linearly proportional to I, and that for any
> given V you can look up the I from the chart.
Hmm, how odd...
>> Now, see, I always thought electricity just takes *every* path, with
>> the current being determined by Ohm's law.
>
> It does, and if use Ohm's law to work out the voltage at a point that is
> connected to 0V with a 1kOhm resistor and to 5V with a 1Mohm resistor,
> you will see the voltage is essentially 0V. OK so it will actually be
> very slightly above 0V, but that's why there is a tolerance range on the
> input of such devices.
Hmm... my head hurts now! Heh.
>> So, if you have a high-resistence path from A to B, and then you add a
>> second, lower-resistence path from A to B, does the current flowing
>> through the first path change? Or does it remain the same?
>
> It remains the same.
Oh thank God for that! At least something about my understanding of
electricity is correct...
The whole "electricity chooses the easiest path" makes it sound like
when an easier path becomes available, all the current goes down that
and ignores the other paths! o_O
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> You you mean stuff like if you put power through a wire, it heats up, and
> resistance varies by temperature?
Yes pretty much, now imagine that in your design the resistance of the wire
changes enough to have a big impact on how your circuit works. If you
connect an LED to a voltage source and gradually turn up the voltage from 0
volts, you will see that almost no current flows, it's like nothing was
connected inside. But suddenly, you will get to around 2V or something the
current will shoot upwards, and from then on you only need make tiny
increments to the voltage and the current will keep getting larger and
larger very quickly until the LED blows haha
> Oh thank God for that! At least something about my understanding of
> electricity is correct...
Recipe for solving circuits with resistors:
1) Label each unknown voltage node as V1, V2, etc
2) Write out Ohm's law for each resistor in terms of V1, V2 etc
3) Solve the set of equations you wrote out in 2) for the unknown voltages
> The whole "electricity chooses the easiest path" makes it sound like when
> an easier path becomes available, all the current goes down that and
> ignores the other paths! o_O
If the "easiest" path is of *much* lower resistance than the others, then
yeh you can usually ignore the others.
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scott wrote:
>> You you mean stuff like if you put power through a wire, it heats up,
>> and resistance varies by temperature?
>
> Yes pretty much, now imagine that in your design the resistance of the
> wire changes enough to have a big impact on how your circuit works. If
> you connect an LED to a voltage source and gradually turn up the voltage
> from 0 volts, you will see that almost no current flows, it's like
> nothing was connected inside. But suddenly, you will get to around 2V
> or something the current will shoot upwards, and from then on you only
> need make tiny increments to the voltage and the current will keep
> getting larger and larger very quickly until the LED blows haha
Is that why LEDs display a non-linear brightness response too?
>> The whole "electricity chooses the easiest path" makes it sound like
>> when an easier path becomes available, all the current goes down that
>> and ignores the other paths! o_O
>
> If the "easiest" path is of *much* lower resistance than the others,
> then yeh you can usually ignore the others.
I presume you mean you can "ignore" them for the purposes of figuring
out the total current flowing through the system. Clearly the current
flowing through each path only depends on the resistence of that path
and the potential difference...
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> Is that why LEDs display a non-linear brightness response too?
Non-linear with respect to what? The brightness response is pretty linear
with respect to current, double the current you get double the brightness to
within a few %.
> I presume you mean you can "ignore" them for the purposes of figuring out
> the total current flowing through the system. Clearly the current flowing
> through each path only depends on the resistence of that path and the
> potential difference...
I meant if you have a point of unknown voltage connected to two (or more)
other known voltages via resistors. If one of the resistors is drastically
lower than all the others, then you can just assume the unknown point is
directly connected through the lowest resistance and treat all the other
resistors as essentially not connected.
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scott wrote:
>> Is that why LEDs display a non-linear brightness response too?
>
> Non-linear with respect to what? The brightness response is pretty
> linear with respect to current, double the current you get double the
> brightness to within a few %.
Well, I had a diagram for a circuit where you connect a lamp to the
battery through a linear potentiometer. The brightness of the lamp
varies roughly linearly. But the brightness of an LED... does not.
(I'm showing my age now! Can you imagine trying to buy a 3V lamp today??)
>> I presume you mean you can "ignore" them for the purposes of figuring
>> out the total current flowing through the system. Clearly the current
>> flowing through each path only depends on the resistence of that path
>> and the potential difference...
>
> I meant if you have a point of unknown voltage connected to two (or
> more) other known voltages via resistors. If one of the resistors is
> drastically lower than all the others, then you can just assume the
> unknown point is directly connected through the lowest resistance and
> treat all the other resistors as essentially not connected.
Right. Gotchya.
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"Invisible" <voi### [at] dev null> wrote in message
news:49196e5f$1@news.povray.org...
>
> Yeah - maybe I should get said to write open source software?
>
> Oh, wait...
You may not always get paid to write open source, but it's good practice at
writing real applications and working with (lots) of other people, and it
looks very good on a CV
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Gail wrote:
> You may not always get paid to write open source, but it's good practice
> at writing real applications and working with (lots) of other people,
> and it looks very good on a CV
You're not the first person to point this out.
Unfortunately, it requires real talent. (And, usually, C/C++ skills.)
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> Well, I had a diagram for a circuit where you connect a lamp to the
> battery through a linear potentiometer. The brightness of the lamp
> varies roughly linearly. But the brightness of an LED... does not.
LED brightness is proportional to current not voltage!
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Invisible <voi### [at] devnull> wrote:
> losers they were! I still remember the weekly paper fights. Oh, and the
> C'paddy races. (The objective being to say the word "c'paddy" the most
> times in 60 seconds.) Like, WTF?
Was there running and wrestling at the same time? If so, could be this:
http://www.kabaddi.org/History.htm
http://en.wikipedia.org/wiki/Kabaddi
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Bill Pragnell wrote:
> Invisible <voi### [at] devnull> wrote:
>> losers they were! I still remember the weekly paper fights. Oh, and the
>> C'paddy races. (The objective being to say the word "c'paddy" the most
>> times in 60 seconds.) Like, WTF?
>
> Was there running and wrestling at the same time? If so, could be this:
>
> http://www.kabaddi.org/History.htm
> http://en.wikipedia.org/wiki/Kabaddi
...OK, I think that's possibly even more insane than c'paddy races! o_O
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Invisible wrote:
> MOST companies need salesmen. Not all of them, but most of them.
Every company needs at least one salesman. Sometimes that person is also
(say) the inventor, president, and CEO, tho. :-)
>> Most jobs requiring competence don't advertise. It's mostly
>> word-of-mouth.
>
> ....and since I don't know anybody, it's not going to be me.
That is definitely a stumbling block. Another kind of thing you learn
at school...
> SOME people want somebody who can definitely do the job RIGHT NOW.
Yes. And not infrequently, those are exactly the companies you don't
want to work for, because everything is a broken mess and they don't
have any money to pay you even if they knew what they wanted. At least
in the software world.
> (E.g., I suspect if you applied to work for Google,
Not if their interview process is anything to go on.
--
Darren New / San Diego, CA, USA (PST)
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Invisible wrote:
> How many resistors can you see? Because I count NONE!
I look at an Intel chip stuck to my motherboard, and I don't see any
transitors, either. The gate-level logic is working with bits, not
voltages. You're not going to see the analog stuff that makes the bits
work there.
--
Darren New / San Diego, CA, USA (PST)
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Invisible wrote:
> Wait a sec - so you're saying there are devices which actually violate
> Ohm's law?
There are devices whose resistance changes over time, depending on what
the current is doing.
Inca descent light bulbs. Florescent light bulbs, for a different
reason. Capacitors. Inductors. Basically pretty much everything except a
plain old resistor.
They're not violating Ohm's law. They're just changing resistance.
--
Darren New / San Diego, CA, USA (PST)
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Darren New wrote:
> Invisible wrote:
>> How many resistors can you see? Because I count NONE!
>
> I look at an Intel chip stuck to my motherboard, and I don't see any
> transitors, either. The gate-level logic is working with bits, not
> voltages. You're not going to see the analog stuff that makes the bits
> work there.
...which is why I'd rather work at the gate-level. ;-)
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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Invisible wrote:
> Now, see, I've never been able to comprehend stuff like this. To me,
> this diagram just looks like when you close the switch, all the current
> will flow straight from one rail to the other, shorting out the battery
> and not providing any current at all to the input of the gate.
Nope, some will be dumped, but not much, besides its a 10K ohm
resisitor. Most current will go to the NOT gate.
Play with this applet for a bit...
http://www.falstad.com/circuit/e-resistors.html
--
~Mike
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On Wed, 12 Nov 2008 09:19:36 +0000, Invisible wrote:
>>> Yeah - maybe I should get said to write open source software?
>>>
>>> Oh, wait...
>>
>> http://www.novell.com/careers
>>
>> Getting paid for developing open source does happen.
>
> Yeah, it does - just not particularly often. ;-)
Tell that to all of those employees here or at RedHat who get paid.
But there is an added advantage to working on OSS projects - helps build
a resume and people can see your work.
Jim
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On Wed, 12 Nov 2008 09:18:41 +0000, Invisible wrote:
> Jim Henderson wrote:
>> On Tue, 11 Nov 2008 20:39:06 +0000, Orchid XP v8 wrote:
>>
>>>> You could try submitting your resumé to Novell, RedHat and the likes.
>>> ...are either of those companies still going? I thought Novell went
>>> under years ago, and RedHat vanished off the face of the earth once
>>> they realised that trying to sell Linux services isn't profitable.
>>
>> Who do I work for again? ;-)
>
> Uh... you tell me?
Have a look at the IP address and do a reverse lookup on this message.
I've mentioned it before in this very forum - and in discussions you
participated in.
>> And RedHat is currently selling more Linux than Novell. Turns out
>> customers *want* service contracts for things their business depends
>> on.
>
> OK. So why have I not heard anything about RedHat for several years?
Very likely a product of your choice of reading material. Have you
looked at a copy of Linux Format lately? There recently was a huge
article there on training, specifically about RedHat training. With a
big ad in the middle of the article, at that.
> Have they gone into some kind of specialised market or something? Once
> upon a time you used to hear of them quite a bit, and now they seem
> awful quiet...
Nope, they haven't gone into a specialized market. They're losing market
share to Novell (which owns SUSE Linux) and to Canonical, but absolutely
still around.
If you spend all your time around Windows advertising and gaming
magazines, you probably won't hear much about Linux. Though with the MS/
Novell deal, Microsoft is selling SUSE Linux Enterprise Server to their
customers as well - surely you've heard of *that* deal? It's been
ongoing for about 2 years now....
Jim
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>>> And RedHat is currently selling more Linux than Novell. Turns out
>>> customers *want* service contracts for things their business depends
>>> on.
>> OK. So why have I not heard anything about RedHat for several years?
>
> Very likely a product of your choice of reading material. Have you
> looked at a copy of Linux Format lately? There recently was a huge
> article there on training, specifically about RedHat training. With a
> big ad in the middle of the article, at that.
Woah - there's a "Linux Format" now? o_O
Mind you, there's enough people using Linux, I guess it makes sense...
>> Have they gone into some kind of specialised market or something? Once
>> upon a time you used to hear of them quite a bit, and now they seem
>> awful quiet...
>
> Nope, they haven't gone into a specialized market. They're losing market
> share to Novell (which owns SUSE Linux) and to Canonical, but absolutely
> still around.
>
> If you spend all your time around Windows advertising and gaming
> magazines, you probably won't hear much about Linux. Though with the MS/
> Novell deal, Microsoft is selling SUSE Linux Enterprise Server to their
> customers as well - surely you've heard of *that* deal? It's been
> ongoing for about 2 years now....
Actually, come to think of it, I *do* vaguely remember that announcement...
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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Mike Raiford wrote:
> Play with this applet for a bit...
>
> http://www.falstad.com/circuit/e-resistors.html
Oh goodie. Everything I thought I knew about electronics turns out to be
incorrect. Yay, me. :-S
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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On 11-Nov-08 21:39, Orchid XP v8 wrote:
> I did look into a few companies such as IBM, HP, Nokia, etc. But they're
> all based either in London or in other remote areas of the country.
I like that 'London or other remote areas'. BTW I hope you do realise
that the main reason for asking was that I probably am going to ask you
to apply for a PhD position in Amsterdam somewhere next year. (and if I
don't that will probably mean that I had to find a new job elsewhere too).
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andrel wrote:
> On 11-Nov-08 21:39, Orchid XP v8 wrote:
> > I did look into a few companies such as IBM, HP, Nokia, etc. But they're
> > all based either in London or in other remote areas of the country.
>
> I like that 'London or other remote areas'.
Well, London isn't "remote", but no sane person would want to go there.
The people who aren't in London are in places like Southampton, York, etc.
> BTW I hope you do realise
> that the main reason for asking was that I probably am going to ask you
> to apply for a PhD position in Amsterdam somewhere next year. (and if I
> don't that will probably mean that I had to find a new job elsewhere too).
Um... the obvious problem here is that I'm obviously not intelligent
enough to do a PhD. :-P
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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Orchid XP v8 wrote:
> Um... the obvious problem here is that I'm obviously not intelligent
> enough to do a PhD. :-P
I think intelligence is one of the less-needed skills. Writing, some
level of research, persistence, dealing with other people, dealing with
bureaucratic BS, and yes some amount of learning graduate-level computer
stuff, since you need the MS first. (Assuming you're getting a PhD in
computers.)
The PhD (at least in computers) doesn't teach you anything about
computers. It teaches you about "philosophy." Hence the name.
You probably need to be a lot smarter to get a PhD in (say) physics or
engineering than in computers.
--
Darren New / San Diego, CA, USA (PST)
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Darren New wrote:
> Orchid XP v8 wrote:
>> Um... the obvious problem here is that I'm obviously not intelligent
>> enough to do a PhD. :-P
>
> I think intelligence is one of the less-needed skills. Writing, some
> level of research, persistence, dealing with other people, dealing with
> bureaucratic BS, and yes some amount of learning graduate-level computer
> stuff, since you need the MS first. (Assuming you're getting a PhD in
> computers.)
>
> The PhD (at least in computers) doesn't teach you anything about
> computers. It teaches you about "philosophy." Hence the name.
>
> You probably need to be a lot smarter to get a PhD in (say) physics or
> engineering than in computers.
Fact: I absolutely *suck* at research. At uni, every assignment
involving any element of research was consistently graded very poorly
indeed. Several such modules I failed outright.
Fact: I also suck at report writing. I'm good at writing technical
stuff, but reports are supposed to have a specific structure and I don't
really grok that. Also I'm not very good at structuring large documents;
the flow tends to end up rather muddled.
Fact: I don't actually need a PhD for anything. Certainly I don't have
the money to pay for one. Time would also seem to be an issue.
I could almost be tempted to do math classes - but again time and money
would seem an issue. (As well as the minor detail of finding a suitable
class somehow.)
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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On 12-Nov-08 22:48, Orchid XP v8 wrote:
> andrel wrote:
>> On 11-Nov-08 21:39, Orchid XP v8 wrote:
>> > I did look into a few companies such as IBM, HP, Nokia, etc. But
>> they're
>> > all based either in London or in other remote areas of the country.
>>
>> I like that 'London or other remote areas'.
>
> Well, London isn't "remote", but no sane person would want to go there.
?
> The people who aren't in London are in places like Southampton, York, etc.
>
I happen to be in Amsterdam actually. Or don't I count as people? (or is
that '... do I not...')
>> BTW I hope you do realise
>> that the main reason for asking was that I probably am going to ask you
>> to apply for a PhD position in Amsterdam somewhere next year. (and if I
>> don't that will probably mean that I had to find a new job elsewhere
>> too).
>
> Um... the obvious problem here is that I'm obviously not intelligent
> enough to do a PhD. :-P
Intelligence is not a prerequisite for a PhD position. As long as you
have a MSc or equivalent you could be hired. Please, leave the job of
finding reasons why you are not qualified to the selection committee.
BTW if it ever comes to this I will probably not take part is the job
interview. I might know too much about you to be objective.
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On 12-Nov-08 23:03, Orchid XP v8 wrote:
> Darren New wrote:
>> Orchid XP v8 wrote:
>>> Um... the obvious problem here is that I'm obviously not intelligent
>>> enough to do a PhD. :-P
>>
>> I think intelligence is one of the less-needed skills. Writing, some
>> level of research, persistence, dealing with other people, dealing
>> with bureaucratic BS, and yes some amount of learning graduate-level
>> computer stuff, since you need the MS first. (Assuming you're getting
>> a PhD in computers.)
>>
>> The PhD (at least in computers) doesn't teach you anything about
>> computers. It teaches you about "philosophy." Hence the name.
>>
>> You probably need to be a lot smarter to get a PhD in (say) physics or
>> engineering than in computers.
Strange as it sound but this would be in medicine. Because the research
will be carried out in the faculty of medicine. It would still be for
programming/math/gui/graphics/database work (unless you like animal
experiments or genotyping or some mechanical construction, then we can
throw them in as well).
> Fact: I absolutely *suck* at research. At uni, every assignment
> involving any element of research was consistently graded very poorly
> indeed. Several such modules I failed outright.
I'd like to meet someone with an inquisitive mind that sucks at research.
> Fact: I also suck at report writing. I'm good at writing technical
> stuff, but reports are supposed to have a specific structure and I don't
> really grok that. Also I'm not very good at structuring large documents;
> the flow tends to end up rather muddled.
Good, we'll teach you!
> Fact: I don't actually need a PhD for anything. Certainly I don't have
> the money to pay for one. Time would also seem to be an issue.
Sorry? We pay you to get a PhD, that is the way it works here.
> I could almost be tempted to do math classes - but again time and money
> would seem an issue. (As well as the minor detail of finding a suitable
> class somehow.)
Every PhD student has to take some relevant classes, if that would be
math that's fine.
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scott wrote:
>> Well, I had a diagram for a circuit where you connect a lamp to the
>> battery through a linear potentiometer. The brightness of the lamp
>> varies roughly linearly. But the brightness of an LED... does not.
>
> LED brightness is proportional to current not voltage!
Also, are *human eyes* linear? Would you notice when brightness is changing
perfectly linearly? :)
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When you go on these rants about your childhood... With some things I feel
sorry for you, with other things I feel like you're talking about my life
and not yours.
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Invisible wrote:
> Have you heard my voice? I certainly *sound* retarded! (I talk waaaaay
> tooo sloooowllllyyyy...)
You're not retarded. You just have all the common hallmarks of true
geeks. People will think you're retard, gay, weirdo, coward etc. Face
it: if you want more of life than just a job, a marriage and a house,
you're not part of them.
We sound awkward because our brains are typically multithreading through
a range of intelectual subjects rather than just the weather, sports
happenings, showbiz celebrities or someone else's life.
> Well anyway, the first school I went to was a rough school. Kids could
> beat up other kids just for entertainment. Whoever the weakest kid was,
> he or she got beat the most. Wanna guess who the weakest kid in my class
> was?
Calvin and Moe. Typical infant problem. I used to bleed a lot, but was
proud of myself of once handling two bullies at once. :) They were so
astonished that left me alone for a while...
> I can vividly remember being chased across the playground screaming blue
> murder begging for somebody to save me. But the staff just stood there
> smoking, not really paying attention. Afterwards I asked one of them
> "why didn't you save me?!" The disinterested individual casually
> responded "uw, I thought they woz just playin widja". Yeah, thanks for
> that.
Come on, now when you think of it don't you see the whole silliness of
the scene? They probably see that everyday. It's not like some kids
are truly massacring other kids, so it's really fun to watch. :P
It's a part of becoming apt for life, I guess. Including all the
traumas and neurosis.
> So then I got moved to this school for weird kids. And my god, were they
> weird! Some of them couldn't even speak properly, or at all. Almost all
> of them were very obviously strange.
Genius children? Mutants? Perhaps they just communicated by
telepathy... ;)
> Originally I assumed that I went to this school because I couldn't read
> or write. But now, looking back, it has gradually become clear to me
> that *I* am not normal either. I do things that normal people don't do.
> There clearly *is* something wrong with me. And I know it's incurable. I
> find this extremely upsetting.
Unless you're talking superpowers, I feel very much alike, except I
don't feel weird nor wrong, it's just me being me among many other
pathetic life forms^^^ people. ;)
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>> Well, London isn't "remote", but no sane person would want to go there.
>
> ?
Heh. You'll get me into trouble. :-P
>> The people who aren't in London are in places like Southampton, York,
>> etc.
>>
>
> I happen to be in Amsterdam actually. Or don't I count as people? (or is
> that '... do I not...')
I meant the other companies I researched. A lot of them were in London,
and the rest were in far-flung parts of the UK.
Korg UK is in Milton Keynes. But there office is about 10 square feet,
so I'm guessing it's just an admin office...
>> Um... the obvious problem here is that I'm obviously not intelligent
>> enough to do a PhD. :-P
>
> Intelligence is not a prerequisite for a PhD position. As long as you
> have a MSc or equivalent you could be hired.
Well, I don't have an MSc. I only have a BSc.
(You know the random Asian guys asking me to fix their Java? *They* were
the MSc students!)
> Please, leave the job of
> finding reasons why you are not qualified to the selection committee.
> BTW if it ever comes to this I will probably not take part is the job
> interview. I might know too much about you to be objective.
Why would you want me anyway? Surely somebody who already lives in
Amsterdam would be a more sensible choice? :-P
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>> MOST companies need salesmen. Not all of them, but most of them.
>
> Every company needs at least one salesman. Sometimes that person is also
> (say) the inventor, president, and CEO, tho. :-)
OK, I rephrase: Some companies need far fewer salesmen that others. It
depends what they do.
>>> Most jobs requiring competence don't advertise. It's mostly
>>> word-of-mouth.
>>
>> ....and since I don't know anybody, it's not going to be me.
>
> That is definitely a stumbling block. Another kind of thing you learn
> at school...
The only thing *I* learned at _school_ is that people are terrifying
things to be avoided at any cost.
Fortunately I have now unlearned that one. Unfortunately, I now have no
starting point.
>> SOME people want somebody who can definitely do the job RIGHT NOW.
>
> Yes. And not infrequently, those are exactly the companies you don't
> want to work for.
Yeah, I gathered. ;-)
>> (E.g., I suspect if you applied to work for Google,
>
> Not if their interview process is anything to go on.
O RLY?
You know something about this then?
(All I know is that all the "interesting" companies like Google, NI,
etc. seem to be in other countries. Not this one.)
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>> Yeah, it does - just not particularly often. ;-)
>
> Tell that to all of those employees here or at RedHat who get paid.
>
> But there is an added advantage to working on OSS projects - helps build
> a resume and people can see your work.
I'm not disputing that getting paid for OSS is a good idea - I'm just
saying it's highly nontrivial to achieve this.
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Nicolas Alvarez wrote:
> scott wrote:
>>> Well, I had a diagram for a circuit where you connect a lamp to the
>>> battery through a linear potentiometer. The brightness of the lamp
>>> varies roughly linearly. But the brightness of an LED... does not.
>> LED brightness is proportional to current not voltage!
>
> Also, are *human eyes* linear? Would you notice when brightness is changing
> perfectly linearly? :)
Probably not. But when the light stays off, and then suddenly turns full
on, with nothing in between, I'm fairly sure that's non-linear. ;-)
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"Invisible" <voi### [at] devnull> wrote in message
news:491bf342$1@news.povray.org...
>>
>> Not if their interview process is anything to go on.
>
> O RLY?
>
> You know something about this then?
Google for google interviews. Quite a bit has been written about their
interview process.
> (All I know is that all the "interesting" companies like Google, NI, etc.
> seem to be in other countries. Not this one.)
Google's EU headquarters are in Ireland (though that is another country)
http://www.google.co.uk/intl/en/jobs/index.html
They seem to have a lot of openings. Won't suit you though, they're in that
horrible, terrible place that no one want to go (London)
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Gail wrote:
> Google for google interviews. Quite a bit has been written about their
> interview process.
...the irony...
> Google's EU headquarters are in Ireland (though that is another country)
>
> http://www.google.co.uk/intl/en/jobs/index.html
> They seem to have a lot of openings. Won't suit you though, they're in
> that horrible, terrible place that no one want to go (London)
Sadly it seems that 80% of all UK jobs are in London. Regardless of
which industry.
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"Invisible" <voi### [at] devnull> wrote in message
news:491bf7ae@news.povray.org...
> Gail wrote:
>>
>> http://www.google.co.uk/intl/en/jobs/index.html
>> They seem to have a lot of openings. Won't suit you though, they're in
>> that horrible, terrible place that no one want to go (London)
>
> Sadly it seems that 80% of all UK jobs are in London. Regardless of which
> industry.
Well, yes. It's the capital city and (iirc) the largest city in the UK.
Hence most things will be there
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>> Sadly it seems that 80% of all UK jobs are in London. Regardless of
>> which industry.
>
> Well, yes. It's the capital city and (iirc) the largest city in the UK.
> Hence most things will be there
This is not surprising.
What *is* surprising (to me at least) is that lots of things happen in
cities near to MK, but very little happens in MK itself. I'm not sure
why that would be...
(I'm thinking more of social events - I'm not really sure what the jobs
markets are like.)
Also... the UK has plenty of other large cities besides London. Yet not
many of these seem to have huge quantities of work available. I'm not
really sure why.
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Invisible wrote:
>> "normal" ones work at all sorts of voltages, it even varies from piece
>> to piece quite significantly. But you never drive an LED directly by
>> applying a fixed voltage, you always drive it by regulating the
>> current to a fixed amount (like 20 mA or whatever). Adding a series
>> resistor to a raw LED is a quick and crude method of fixing the
>> operating current.
>
> This doesn't make sense to me.
>
> Presumably the resistence of the LED is finite and fixed. How does
> adding another resistor help? There are several schematics in my
> electronics kit that involve LEDs and no resistors at all.
>
Sorry I've been away and missed the fun.
I hook up a LED this way:
A LED will always drop or *consume* a fixed voltage - again, that's
voltage not current.
A LED is NOT a resistor - in the most basic sense it generally will not
prevent current from flowing through it once it starts flowing - it
starts flowing at it's rated voltage drop.
The typical voltage drop for a basic red LED is 1.7 volts.
For most LEDs you can use this number for calculations.
Be aware, that different colors may have a higher voltage drop.
A LED will generally not light up unless your voltage across its leads
goes above it's drop.
A LED likes to have between 10mA and 20mA - to be safe you can use 10mA
in calculations. The current will affect brightness, but too much
current will cause it to burn out. You are better off to select a
*bright* LED with a high light output rating than try to get more light
by putting more current through it.
So some easy calculations:
lets say 5v power source
1.7v LED
10mA current
the LED drops 1.7v so the rest of the circuit will drop 3.3v
(5v)-(1.7v)=(3.3v)
If don't put a resistor in then the current through the circuit will be:
I=V/R from V=IR
I=(5v)/(0 ohm)
not good too much current - things get hot
(note: LEDs should not get hot)
we want the current (I) to be about 10mA
so R=V/I again from V=IR
R=(3.3v)/(10mA)
R=330 ohm
330 ohm happens to be a common resistor value
so put one in
if your source is 12v then you need a 1,030 ohm resistor - not a common
value. But 1,000 ohm is - so use it instead.
Typical resistor values are only +-10% anyway - so a 330 ohm resistor
could be as low as 300 or as high as 360 and you don't know it.
So picking something slightly off from the *calculated* value is OK.
After all, you are just trying to make a LED light up - not try to
maximize it's brightness.
Tom
Different LEDs drop different voltages, but you can usually safely bet
on 1.5V and still be safe.
Then there is the current rating of the LED - usually 10mA to 20mA - you
can pick 15mA and be pretty safe.
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Orchid XP v8 wrote:
> Darren New wrote:
>> Invisible wrote:
>>> How many resistors can you see? Because I count NONE!
>>
>> I look at an Intel chip stuck to my motherboard, and I don't see any
>> transitors, either. The gate-level logic is working with bits, not
>> voltages. You're not going to see the analog stuff that makes the bits
>> work there.
>
> ....which is why I'd rather work at the gate-level. ;-)
>
The problem is that digital electronics are based on analog circuits. A
lot of digital circuits can be wired up with out knowing anything about
analog, but when something doesn't work as you expect, you might quickly
get lost.
And as you have found out with LEDs, even when you think you are only
dealing with digital, you are dealing with analog as well.
You don't have to understand breakdown voltages and the like to
successfully work with LEDs, you just have to understand some of their
base characteristics.
Even something as simple as a button or switch can cause problems.
When you close the contact there are literally thousands of connections
made and broken in the very short time before the contact is completely
closed. If you have a counter, it might count 4 or 5 on each button
press, not just one. That's what debounce circuits are for, but they
can be analog - go figure.
Electronics can be deceptively simple, but insanely complex.
I think you have the capacity to really work well in electronics - but
you just don't have the background in how it all comes together. That
comes mostly with experience.
Books will tell you how to calculate you need a 524 ohm resistor -
that's insane.
Experience will tell you that 470 ohm (a typical value) is OK.
Don't get discouraged when things don't work as you think they should.
Pretend that you don't know anything about what is not working and go
research it. You will learn loads and loads.
If a LED doesn't light, go learn how it works.
The same goes for most anything else.
Don't try to build a rocket ship - build something simple.
Get a book that doesn't just say hook this wire here and there, but that
actually goes through how it all works.
The CMOS Cookbook I pointed out earlier is a good book in that reguard.
Tom
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>> ....which is why I'd rather work at the gate-level. ;-)
>>
>
> The problem is that digital electronics are based on analog circuits. A
> lot of digital circuits can be wired up with out knowing anything about
> analog, but when something doesn't work as you expect, you might quickly
> get lost.
Yeah, this is the thing. I had assumed that the digital devices you buy
in the shop are carefully designed to behave in a simple, predictable
mannar, even though their internal construction is a tangle on analogue
devices. I thought you could just treat a 7400 as a black box.
Apparently not...
> And as you have found out with LEDs, even when you think you are only
> dealing with digital, you are dealing with analog as well.
The LEDs actually worked just fine. It's the gate driving them that
didn't do what it was ment to.
> Even something as simple as a button or switch can cause problems.
> When you close the contact there are literally thousands of connections
> made and broken in the very short time before the contact is completely
> closed. If you have a counter, it might count 4 or 5 on each button
> press, not just one.
I wouldn't find this surprising. Rather, to be expected.
> That's what debounce circuits are for, but they
> can be analog - go figure.
Presumably a debounce circuit is merely a low-pass filter?
> Don't try to build a rocket ship - build something simple.
Heh. I got stuck just trying to get a truth table out of a logic gate. :-S
> Get a book that doesn't just say hook this wire here and there, but that
> actually goes through how it all works.
> The CMOS Cookbook I pointed out earlier is a good book in that reguard.
...does it matter that I'm using TTL?
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Orchid XP v8 wrote:
> Um... the obvious problem here is that I'm obviously not intelligent
> enough to do a PhD. :-P
Yes you are (compared to the folks I knew in grad school). And yes,
Darren is correct: Perseverance and desire is a bigger factor than
intelligence.
--
I think animal testing is a terrible idea. They get all nervous and give
the wrong answers.
/\ /\ /\ /
/ \/ \ u e e n / \/ a w a z
>>>>>>mue### [at] nawazorg<<<<<<
anl
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Darren New wrote:
> bureaucratic BS, and yes some amount of learning graduate-level computer
> stuff, since you need the MS first. (Assuming you're getting a PhD in
> computers.)
Depends on the university. In a number of well known grad schools in
the US, they actively discourage you from getting a MS, and strongly
encourage you just go straight to the PhD - in fact, they often don't
offer funding if you don't go directly into PhD, because they assume you
just want an MS and will leave.
(Talking of computer science departments here...)
> You probably need to be a lot smarter to get a PhD in (say) physics or
> engineering than in computers.
Engineering?
Not really. I think it's on par with CS. Both have areas that will
require a lot of smartness, and both have areas that don't.
--
I think animal testing is a terrible idea. They get all nervous and give
the wrong answers.
/\ /\ /\ /
/ \/ \ u e e n / \/ a w a z
>>>>>>mue### [at] nawazorg<<<<<<
anl
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Orchid XP v8 wrote:
> Fact: I absolutely *suck* at research. At uni, every assignment
> involving any element of research was consistently graded very poorly
> indeed. Several such modules I failed outright.
Oh please! First, what people call research at the undergrad level
often isn't.
Second, you've been doing research all these years. Being curious and
learning stuff - especially technical stuff - is virtually research. All
that's left is to do some new interesting stuff in it. And generally
your adviser will guide you through that.
> Fact: I also suck at report writing. I'm good at writing technical
> stuff, but reports are supposed to have a specific structure and I don't
> really grok that. Also I'm not very good at structuring large documents;
> the flow tends to end up rather muddled.
Writing papers for journals is a pain the first or second time. Beyond
that, you have the template figured out and you just write. It's
actually less painful than the lab reports I had to do in undergrad.
And not all papers are large.
And when you've spent time working on something, then trust me, you'll
probably have more difficulty trimming it down than trying to fill
space. Just look at your own Haskell evangelism!
> Fact: I don't actually need a PhD for anything. Certainly I don't have
> the money to pay for one. Time would also seem to be an issue.
*Nobody* needs a PhD.
And don't pay for one. Few people do. In the US, it's usually paid for
either by being a teaching assistant or being a research assistant (you
get a good enough stipend). I'm sure you can figure out how to get it
paid for in the UK (government scholarship, etc). If not, come this side
of the Atlantic or cross the Channel and do it in Europe.
Seriously. I think it's the best advice you've been given. You get paid
to do all the fun geeky stuff your adviser wants you to do. And it's not
that rare that you'll also want to do it too! You'll be around smart
people (which *may* make you feel stupid for a while, but that'll go
away). And not sure about the UK and Europe, but (many) campuses in the
US have a good social environment. Lots of great speakers visit campus
and give talks - spanning the whole spectrum from science to politics.
And no, you don't *have* to be social if you don't want to ;-)
Others can give advice regarding the PhD in the UK and parts of Europe.
If you want to consider the US as an option, I can likely help you on
some of the details (GRE, etc).
> I could almost be tempted to do math classes - but again time and money
> would seem an issue. (As well as the minor detail of finding a suitable
> class somehow.)
I went to grad school in electrical engineering. I told myself that
while there, I'd try to get a MS in either physics or mathematics. My
mathematics background when I joined was likely no better than yours. I
did the work for a MS in physics more or less as part of my EE PhD (not
yet completed) - so I won't get the MS in that. I was half way through
the mathematics requirements before I got sick of homework.
Not to start a flame war or anything, but the MS in mathematics in the
US is generally not that advanced. Probably half of the courses are done
at the undergrad level in many places in Europe.
Bottom line: At least in the US, they're very flexible about things.
Even if you're doing a PhD in engineering or CS, there's nothing
preventing you from taking courses in mathematics. And because of the
(*cough*) lower standards (*cough*) in mathematics, you won't have
trouble filling any missing maths prerequisites and going further
towards an MS in it.
--
I think animal testing is a terrible idea. They get all nervous and give
the wrong answers.
/\ /\ /\ /
/ \/ \ u e e n / \/ a w a z
>>>>>>mue### [at] nawazorg<<<<<<
anl
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Mueen Nawaz wrote:
> [ lots of stuff ]
I'll second everything she said, including helping you find and get
involved in the right place if you want.
Places in the USA pay you to get the graduate degree, because "famous
alumni" are how they sell the school to the paying undergraduate
schools. If you were doing an undergrad in physics, wouldn't you prefer
to go to the school where Hawkings got his PhD? Our schools aren't
nearly old enough to have reputations on their own without famous people
associated with them. :-)
It's also an excellent way to meet (a) friends and (b) business
contacts. You'll be in a mile-square place with thousands of people your
own age, most pretty smart, most rather more tolerant of differences
than places with less explicit mixing of cultures going on, etc. You'll
also be around people whose job it is to travel around the world meeting
with and talking to people with interesting problems, and whose other
job it is to talk people into giving them money to solve interesting
problems they didn't know they had.
It's not about the computers. It's about the people.
--
Darren New / San Diego, CA, USA (PST)
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Mueen Nawaz wrote:
> Depends on the university. In a number of well known grad schools in
> the US, they actively discourage you from getting a MS, and strongly
> encourage you just go straight to the PhD - in fact, they often don't
> offer funding if you don't go directly into PhD, because they assume you
> just want an MS and will leave.
Odd. Never heard of that. I can see your point, but I would think the
number of people who go thru the MS saying they'll get a PhD and knowing
they're going to bail before then must be fairly low. Maybe where that
has happened too often they instituted this policy.
>> You probably need to be a lot smarter to get a PhD in (say) physics or
>> engineering than in computers.
>
> Engineering?
>
> Not really. I think it's on par with CS. Both have areas that will
> require a lot of smartness, and both have areas that don't.
Maybe. The few engineering courses I sat in on seemed a lot harder.
Maybe I'm just better at computers.
--
Darren New / San Diego, CA, USA (PST)
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Invisible wrote:
>
> Yeah, this is the thing. I had assumed that the digital devices you buy
> in the shop are carefully designed to behave in a simple, predictable
> mannar, even though their internal construction is a tangle on analogue
> devices. I thought you could just treat a 7400 as a black box.
> Apparently not...
>
To a point you can - knowing that point is the trick - and likely some
of what you are facing.
>> And as you have found out with LEDs, even when you think you are only
>> dealing with digital, you are dealing with analog as well.
>
> The LEDs actually worked just fine. It's the gate driving them that
> didn't do what it was ment to.
>
One think to keep in mind, you are best off not trying to drive the LED
directly from the chip. Some chips can do it, but most cannot. Lots of
times you need to put a *switch* that the gate switches.
see:
http://www.rason.org/Projects/transwit/transwit.htm
http://www.eecs.tufts.edu/~dsculley/tutorial/transistors/transistors1.html
remember, you need a resistor in the path from + to ground with the LED.
>> Even something as simple as a button or switch can cause problems.
>> When you close the contact there are literally thousands of
>> connections made and broken in the very short time before the contact
>> is completely closed. If you have a counter, it might count 4 or 5 on
>> each button press, not just one.
>
> I wouldn't find this surprising. Rather, to be expected.
>
Good, something won't catch you by surprise. But it's all those little
things that can add up and frustrate you.
>> That's what debounce circuits are for, but they can be analog - go
>> figure.
>
> Presumably a debounce circuit is merely a low-pass filter?
>
can be - it can be implemented purely analog, or it can be filtered in
programming.
You can also use some logic gate tricks to debounce.
>> Don't try to build a rocket ship - build something simple.
>
> Heh. I got stuck just trying to get a truth table out of a logic gate. :-S
>
So, keep trying to do it. That's how you start. Overcome the things
that keep it from working. How else do you learn.
You can certainly ask questions here - you've already gotten an ear full.
>> Get a book that doesn't just say hook this wire here and there, but
>> that actually goes through how it all works.
>> The CMOS Cookbook I pointed out earlier is a good book in that reguard.
>
> ....does it matter that I'm using TTL?
TTL & CMOS are very similar in their logic, but completely different in
how they work internally.
You can't just hook the two together. At you level you are better off
sticking with one or the other.
CMOS is much lower power and is what is typically found in newer
electronics - tho TTL has its place as well.
There is a TTL cookbook by the same author - it is basically the exact
same book.
You can use either book, they are both good starts.
The TTL Cookbook is what opened my eyes that I could actually do
electronics and it was relatively easy. I had to return it as it was a
loaned book, but then I bought the CMOS cookbook and took off from there.
I highly recommend either of the books if you are really interested in
learning some about electronics. Unless you have $100 in TTL chips, I
recommend that you go the CMOS route as it is more likely what you would
encounter when dealing with more specialized chips (think CPU).
If you get one, start reading it from the beginning and learn the
fundamentals.
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Tom Austin wrote:
> I highly recommend either of the books if you are really interested in
> learning some about electronics. Unless you have $100 in TTL chips, I
> recommend that you go the CMOS route as it is more likely what you would
> encounter when dealing with more specialized chips (think CPU).
Just keep in mind CMOS is very easy to cook.
--
~Mike
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