Author Topic: Boolean algebra, A AND 1 = 0 WTF ?  (Read 8909 times)

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Simon

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Boolean algebra, A AND 1 = 0 WTF ?
« on: May 17, 2014, 06:15:12 pm »
so my BTEC L3 course states that one of the 12 laws of boolean algebra is that:

A and 1 = 0

How can they claim this if A is not defined because as i read it:

1 x 1 = 1
0 x 1= 0

if A was the first digit in those two the so called rule does not work.....

T3sl4co1l

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Re: Boolean algebra, A AND 1 = 0 WTF ?
« Reply #1 on: May 17, 2014, 06:15:45 pm »
Could be a typo.
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Simon

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Re: Boolean algebra, A AND 1 = 0 WTF ?
« Reply #2 on: May 17, 2014, 06:18:44 pm »
So i'm not going mad.....

When will education go back to where it used to be, this course is a pile of crap, it's a good job i already know what I've learnt so far or I'd be real confused.......

Bored@Work

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Re: Boolean algebra, A AND 1 = 0 WTF ?
« Reply #3 on: May 17, 2014, 06:21:03 pm »
A and 1 = A
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Simon

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Re: Boolean algebra, A AND 1 = 0 WTF ?
« Reply #4 on: May 17, 2014, 06:27:25 pm »
A and 1 = A

Could be what they meant, I'm starting to wonder who is the teacher and who is the learner here. I'm going to keep a log of all inaccuracies, what worries me is what happens when i do get to stuff that I don't know and need to learn and they are making errors.

The guy who wrote the course was supposedly part of the HNC/D qualifications specifications team but then he just did the examples and questions so probably learnt as he went along.

Zero999

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Re: Boolean algebra, A AND 1 = 0 WTF ?
« Reply #5 on: May 17, 2014, 06:33:31 pm »
He could've meant A AND 0 = 0

Simon

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Re: Boolean algebra, A AND 1 = 0 WTF ?
« Reply #6 on: May 17, 2014, 06:39:09 pm »
He could have meant anything, if there are going to be typos where fundamentals like this are explained it throws the whole thing out of the window, they should paying extra care to write these theorems correctly because they underpin any further discussion on logic networks and calculations and simplification of boolean expressions. Fortunately the text book that comes with the course also covers the 12 basic theorems infact they give 18.

IanB

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Re: Boolean algebra, A AND 1 = 0 WTF ?
« Reply #7 on: May 17, 2014, 08:24:13 pm »
Typos often happen in worksheets and handout materials.

Although you find it slightly annoying, having such mistakes to find is actually good for you. You should test everything you are taught in your own mind to see if it makes sense. If you find something that doesn't seem to make sense it will make you think harder about it and will reinforce your learning.

As and when you cover more advanced material you can also think to yourself, "What are the assumptions made here?" "What are the limitations?" "When might it not apply?"

So be cool about it, and smile to yourself when you spot something that seems to be wrong, and later find out you were correct.
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Simon

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Re: Boolean algebra, A AND 1 = 0 WTF ?
« Reply #8 on: May 17, 2014, 08:32:35 pm »
no I'm sorry but this course is just crap all over. The explanation of using a current limit resistor on an LED was incredibly stupid, apparently you need the resistor to make up for the differences in voltage between LED's even though made in the same batch (manufacturing tolerances), they totally omitted the fact that a diode will not control current but allow as much through as you try and push until it blows and that is why you need the resistor.

On a more advanced level yes you could regulate the voltage in the LED and leave out the current limiting resistor for efficiency sake but that is an advanced topic beyond this level of course. If it wasn't for the fact that this is the only course available in the UK I'd have sent it right back! The explanation of the zener was also ridiculous, they didn't even mention that a minimum amount of current is required to guarantee the voltage across it.......

Simon

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Re: Boolean algebra, A AND 1 = 0 WTF ?
« Reply #9 on: May 17, 2014, 08:35:59 pm »
and as soon as they want to make a more detailed explanation they refer you to a web page that could be taken down any day....... there is distance learning and there is learning attached to the internet, they could at least refer me to the text book they included with the course.

IanB

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Re: Boolean algebra, A AND 1 = 0 WTF ?
« Reply #10 on: May 17, 2014, 08:39:05 pm »
no I'm sorry but this course is just crap all over. The explanation of using a current limit resistor on an LED was incredibly stupid, apparently you need the resistor to make up for the differences in voltage between LED's even though made in the same batch (manufacturing tolerances), they totally omitted the fact that a diode will not control current but allow as much through as you try and push until it blows and that is why you need the resistor.

There you are, you have understood the range and limitations of what you were taught and put it into context with other things you already know.

But I have to say, the current limiting resistor does not seem as stupid as you think. It is very common in electronics to use series resistors to provide for even current sharing between parallel devices. Without such resistors small variations in manufacturing tolerances can produce large imbalances in current flow.
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Simon

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Re: Boolean algebra, A AND 1 = 0 WTF ?
« Reply #11 on: May 17, 2014, 08:49:49 pm »
no I'm sorry but this course is just crap all over. The explanation of using a current limit resistor on an LED was incredibly stupid, apparently you need the resistor to make up for the differences in voltage between LED's even though made in the same batch (manufacturing tolerances), they totally omitted the fact that a diode will not control current but allow as much through as you try and push until it blows and that is why you need the resistor.

There you are, you have understood the range and limitations of what you were taught and put it into context with other things you already know.

But I have to say, the current limiting resistor does not seem as stupid as you think. It is very common in electronics to use series resistors to provide for even current sharing between parallel devices. Without such resistors small variations in manufacturing tolerances can produce large imbalances in current flow.

Yes but the explanation implied that you would be expected to run an LED straight off a voltage source but for manufacturing tolerances, they failed in the explanations of diodes, zeners and LED's to explain that a diode based device cannot be connected to a non current regulated voltage source or it would short out and blow, the explanations were of no practical use and need more information before I would be able to use the components but for the fact that I know this stuff already.

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Re: Boolean algebra, A AND 1 = 0 WTF ?
« Reply #12 on: May 17, 2014, 08:54:59 pm »
Simon has a point though - if you know enough about the basics to spot fundamental errors in the easy stuff it undermines your confidence in the tutors and makes it harder to trust their explanations of the more advanced topics.

IanB

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Re: Boolean algebra, A AND 1 = 0 WTF ?
« Reply #13 on: May 17, 2014, 09:00:08 pm »
Yes but the explanation implied that you would be expected to run an LED straight off a voltage source but for manufacturing tolerances, they failed in the explanations of diodes, zeners and LED's to explain that a diode based device cannot be connected to a non current regulated voltage source or it would short out and blow, the explanations were of no practical use and need more information before I would be able to use the components but for the fact that I know this stuff already.

Their explanation is essentially correct on the whole. I don't think you should be so ready to dismiss it. You are being presented with information from a slightly different perspective than you have thought about before. Rather than dismissing it, you should consider whether your current understanding is incomplete.

You can, of course, connect an LED to a non-current regulated voltage source. An LED has a voltage/current curve just like any other device. If you apply the right voltage to it the expected current will flow and it will light up. It will not short out and blow...it will simply pass as much current as the applied voltage induces.

In reality an LED does have variations in manufacturing tolerances and other causes of variation in its voltage/current curve and that makes it difficult to reliably apply the right voltage. That is exactly why you need to stabilize the current with a series resistor in a practical circuit.
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IanB

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Re: Boolean algebra, A AND 1 = 0 WTF ?
« Reply #14 on: May 17, 2014, 09:07:47 pm »
Simon has a point though - if you know enough about the basics to spot fundamental errors in the easy stuff it undermines your confidence in the tutors and makes it harder to trust their explanations of the more advanced topics.

One should also be careful about rejecting taught material without due consideration. In my first year of university study I was occasionally indignant about being presented with "wrong" information when it challenged what I thought I already knew. Later on I understood the lecturer was correct, but I was not calm and patient enough to see it at the time.
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grumpydoc

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Re: Boolean algebra, A AND 1 = 0 WTF ?
« Reply #15 on: May 17, 2014, 09:24:30 pm »
Quote
One should also be careful about rejecting taught material without due consideration. In my first year of university study I was occasionally indignant about being presented with "wrong" information when it challenged what I thought I already knew. Later on I understood the lecturer was correct, but I was not calm and patient enough to see it at the time.
Fair point but in that case a good tutor should be able to explain things to you, or at least show you enough for you to realise that you need to wait to get the full picture.

ejeffrey

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Re: Boolean algebra, A AND 1 = 0 WTF ?
« Reply #16 on: May 17, 2014, 09:35:06 pm »
When will education go back to where it used to be

Don't worry, there was never a time when textbooks were without errors and instructors were never wrong.  There have always been good and bad classes, good and bad instructors.  Textbooks have mostly been uniformly mediocre, although bad ones certainly exist.  Maybe you've got a bad class, maybe they just had a bad day, but going back to the "good old days" isn't going to fix anything.  I am sure any of the guys even older than me around here can attest to that as well.  The good thing about technical stuff like logic is that if you are paying attention you will figure out when they are wrong, even when they get to new material.  If a history text tells you that the battle of hastings was in 1104, you just have to take their word for it until you look like a total idiot at a dinner party.  If a text book tells you that "1 and X = 0" is an identity, you can figure out that it is inconsistent and go figure out or find the correct answer.

Simon

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Re: Boolean algebra, A AND 1 = 0 WTF ?
« Reply #17 on: May 17, 2014, 09:37:24 pm »
I am afraid Ian that in this case the material is deficient, the explanations given so far have been so vague it beggars belief. BJT transistors were explained with a scarce mention of hfe, it was made to sound like a secondary consideration, there are virtually no equations presented to explain component choices, like i say, if i really knew nothing this material would have taught me nothing and if anything just left me more confused. why am i being asked to take more explanations off the internet than from the course material ? I was given a 2 page wishy washy explanation of JFETS's and MOSFET's and then given addresses to online tutorials that are several pages long for more information but was warned that there was more information there than i needed (the basic maths maybe ??). The idea of having a book is that you read it, not keep ping ponging from book to internet because the book is incomplete.

2 of the "activities" tell me to watch "a video" - what video ? none was supplied, none is on the materials check list and no internet resource was cited, i was being asked to take measurements of waveforms in the video off the screen. There is clearly very little will in this course to explain and illustrate stuff, as soon as it means a bit of work there is either a gaping hole or I'm told to use a website that could be taken down tomorrow just so they didn't have to draw a graph or explain something. As it stands i could write the first 50 pages of this course myself and do a damn better job.

I'm just going to start the op-amp section, god only knows what I'll not be finding in there!

Simon

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Re: Boolean algebra, A AND 1 = 0 WTF ?
« Reply #18 on: May 17, 2014, 09:43:11 pm »
When will education go back to where it used to be

Don't worry, there was never a time when textbooks were without errors and instructors were never wrong.  There have always been good and bad classes, good and bad instructors.  Textbooks have mostly been uniformly mediocre, although bad ones certainly exist.  Maybe you've got a bad class, maybe they just had a bad day, but going back to the "good old days" isn't going to fix anything.  I am sure any of the guys even older than me around here can attest to that as well.  The good thing about technical stuff like logic is that if you are paying attention you will figure out when they are wrong, even when they get to new material.  If a history text tells you that the battle of hastings was in 1104, you just have to take their word for it until you look like a total idiot at a dinner party.  If a text book tells you that "1 and X = 0" is an identity, you can figure out that it is inconsistent and go figure out or find the correct answer.

I see more of a tendency now to write books just to make a buck with little intention of helping the reader (Don't touch McGraw Hills books with an effing barge pole unless it's highly recommended by someone, been burnt too often with their unchecked and non proof read garbage). We used to have standards and writers were more honest, there is making an honest mistake and there is being negligent and lazy, these days we just want people to make a token gesture to get a grade, I don't want the damn grade, i want the knowledge. the guy that wrote this garbage was supposedly on the team that did the HNC/D course but then he only produced the exercises for it so probably learnt from his colleagues and then went and wrote this crap.

ejeffrey

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Re: Boolean algebra, A AND 1 = 0 WTF ?
« Reply #19 on: May 18, 2014, 12:25:44 am »
I am afraid Ian that in this case the material is deficient, the explanations given so far have been so vague it beggars belief. BJT transistors were explained with a scarce mention of hfe, it was made to sound like a secondary consideration,

hfe is a secondary consideration.  It is usually introduced first due to historical reasons and because a current gain model is simpler than the Ebers-Moll model, but it is not accurate enough for most calculations other than as an estimate of the current required for a saturated switch.

Marco

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Re: Boolean algebra, A AND 1 = 0 WTF ?
« Reply #20 on: May 18, 2014, 01:01:14 am »
Could be in Hex

Simon

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Re: Boolean algebra, A AND 1 = 0 WTF ?
« Reply #21 on: May 18, 2014, 07:09:40 am »
Could be in Hex

At the moment that would not make it any worse. started on the op-amp section, they sorry he has not bothered to explain the virtual earth between inputs just said that the output is gain x (+in + -in) the input resistance is infinite and the output resistance 0 in an ideal opamp, then give the inverting and non inverting configurations and formulas wasting time explaining that he has called one resistor R1 and the other R2 and that is you reverse the resistor notation in the diagram you reverse it in the formula, i mean duh ? this is a level 3 course not a kindergarten lecture.......

And apparently the opamp symbol is supposed to look like the not gate symbol for some reason........

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Re: Boolean algebra, A AND 1 = 0 WTF ?
« Reply #22 on: May 18, 2014, 07:13:28 am »
A teacher with tenure, risen to the top level of his incompetence.

Simon

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Re: Boolean algebra, A AND 1 = 0 WTF ?
« Reply #23 on: May 18, 2014, 07:18:11 am »
Well I hope that the rest of the HNC/D team are not like him, I am doing this BTEC L3 so that I know i have all of the basis covered before going for a HNC or a HND which is as near to a degree as you can get without getting a degree, a HND will certainly be equivalent to an undergraduate degree so I'm hoping this clown did not do too much damage to that course as again there is only one HNC or HND course by distance learning in the UK and they estimate it takes 5 years to do and i have been told that I'll need solid grounds in maths, they want £487 for a "bridging module" in maths so it sounds like it may be a more serious course.

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Re: Boolean algebra, A AND 1 = 0 WTF ?
« Reply #24 on: May 18, 2014, 07:22:43 am »
Go to your local community college and see what they have as maths in night courses. Even if you only can do a little you will learn more face to face than by correspondence. It will help you a lot, the maths is steep at times but they will bring you up to a better level quite fast. Scary thing is once you start learning it it makes many things a lot easier all of a sudden, and teaches you better on things like logical deduction and why things work.

Smf