On Wed, 9 Oct 2019 08:47:31 +1100, "AlexK" wrote:



"Tim+" wrote in message
...
Dave Plowman (News) wrote:
In article ,
Tim+ wrote:
This is the resistor from my macbook power supply.

It *look* to me to be black, orange, white (or grey), silver, brown.

https://photos.app.goo.gl/ZDY1qe8L3xKc4JBG8

I thought it would be easy to calculate the value but I think it falls
into a special category (5 bands, fourth band silver) so I'm not
confident about deciding it.

What is it?

Tim

Since it looks to be in good condition, measure it? That can give clue to
what system they are using.

Um, the other side is burnt. It’s fecked.

That’s unusual, one side of a power resistor burnt and the other perfect.

You sure it wasn’t burnt by what it was next to ?

I would think it's perfectly possible. Film type resistors are often
in the form of a spiral track on the body, and one part of a spiral
can blow, making a small burnt hole in the paint.
--
Dave W

"Dave W" wrote in message
...
On Wed, 9 Oct 2019 08:47:31 +1100, "AlexK" wrote:



"Tim+" wrote in message
...
Dave Plowman (News) wrote:
In article ,
Tim+ wrote:
This is the resistor from my macbook power supply.

It *look* to me to be black, orange, white (or grey), silver, brown.

https://photos.app.goo.gl/ZDY1qe8L3xKc4JBG8

I thought it would be easy to calculate the value but I think it falls
into a special category (5 bands, fourth band silver) so I'm not
confident about deciding it.

What is it?

Tim

Since it looks to be in good condition, measure it? That can give clue
to
what system they are using.

Um, the other side is burnt. It's fecked.

That's unusual, one side of a power resistor burnt and the other perfect.

You sure it wasn't burnt by what it was next to ?

I would think it's perfectly possible. Film type resistors are often
in the form of a spiral track on the body, and one part of a spiral
can blow, making a small burnt hole in the paint.

He didn't say a small burnt hole tho and they don't usually
fail like that when their power rating is exceeded.

Yes, in theory those spiral power resistors can be made bad
and fail like that, but that is very rare indeed, particularly
with the higher quality stuff like Apple gear.

On Thu, 10 Oct 2019 07:53:01 +1100, AlexK, better known as cantankerous
trolling senile geezer Rodent Speed, wrote:


I would think it's perfectly possible. Film type resistors are often
in the form of a spiral track on the body, and one part of a spiral
can blow, making a small burnt hole in the paint.

He didn't say

Oh, shut your stupid senile gob and jump back into your roo's pouch you
escaped from, you obnoxious senile trolling cretin from Australia!

--
Website (from 2007) dedicated to the 85-year-old trolling senile
cretin from Oz:
https://www.pcreview.co.uk/threads/r...d-faq.2973853/

In article dd6cec1d-1a3b-4331-bbf9-d7f6c268fcf3
@googlegroups.com, says...


Today we are running a lab titled Embeded Systems.
Which uses a freescale development board the first part shows them how to connect a push switch to the GPIO and then an LED off that.
The LED is shown in the diagram as connected to a 300 Ohm resistor the lecturer has even bothered to draw the resistor in place showing how to connect it up to a protoboard and the resistor with the colour code LtoR ! of Red Black Orange.

So I have 40 odd (very odd) students coming to me asking why I don't have any 300 ohm resistors.

Back in the late 60s I ran the service department of a Radio &
TV dealer and we alaso sold lots of components.

I stocked E12 series 5% carbon film resistors.

Lots of kids at the local school liked to build projects from
magazines such as Practical Electronics.

Lots of these articles were obvious written by engineers
working for likes of Marconi, STC, etc. and a lot of it was
obviouly 'back of a fag packet' design, so lots of values fell
into the 1, 2, 5, 10 sequence.

So the value 5.1k kept popping up which we didn't stock and I
would offer 4.7k as a substitute which seemed to cause some
confusion until I pointed to the note at the bottom of the
component list that said "All values ±20% tolerance unless
otherwise stated" and I could demonstrate that my 4.7k 5%
resistor was much more accurate that a 5.1k 20% possibly could
be (if anybody actually manufactured such a nonsensical 20%
value, anyway!)


One student was very proud of the fact of working out he could use 2 150R to make a 300R resistor, I did say he could use a 270R or a 330R and all that would do is change the brightness of the LED, I also said if he used the 330 then that would reduce the amount of current and help the world cut down on global warming and perhaps save trees too.
I've stopped a couple of them walking off with 330K resistors, as they weren't sure of the relivance of the R & K after the digits
But don't forget I'm not allowed to teach students, but I am allowed to and expected to impart my knowledge, which strangley enough doesn't warrent a salery scale increase.

When the subject of yolerance came up elsewhere a while ago I
devised this table to illustrate the tolerances of different
eanges of resistor. Feel free to show it your students.

https://www.dropbox.com/s/qdeyfp7lzzdsrdr/Resistor%
20Tolerances.png?dl=0

or https://tinyurl.com/y2jdjh7o

--

Terry

--
This email has been checked for viruses by AVG.
https://www.avg.com

On Fri, 11 Oct 2019 19:03:34 +0100, Terry Casey
wrote:

In article dd6cec1d-1a3b-4331-bbf9-d7f6c268fcf3
, says...


Today we are running a lab titled Embeded Systems.
Which uses a freescale development board the first part shows them how to connect a push switch to the GPIO and then an LED off that.
The LED is shown in the diagram as connected to a 300 Ohm resistor the lecturer has even bothered to draw the resistor in place showing how to connect it up to a protoboard and the resistor with the colour code LtoR ! of Red Black Orange.

So I have 40 odd (very odd) students coming to me asking why I don't have any 300 ohm resistors.

Back in the late 60s I ran the service department of a Radio &
TV dealer and we alaso sold lots of components.

I stocked E12 series 5% carbon film resistors.

Lots of kids at the local school liked to build projects from
magazines such as Practical Electronics.

Lots of these articles were obvious written by engineers
working for likes of Marconi, STC, etc. and a lot of it was
obviouly 'back of a fag packet' design, so lots of values fell
into the 1, 2, 5, 10 sequence.

So the value 5.1k kept popping up which we didn't stock and I
would offer 4.7k as a substitute which seemed to cause some
confusion until I pointed to the note at the bottom of the
component list that said "All values ±20% tolerance unless
otherwise stated" and I could demonstrate that my 4.7k 5%
resistor was much more accurate that a 5.1k 20% possibly could
be (if anybody actually manufactured such a nonsensical 20%
value, anyway!)


One student was very proud of the fact of working out he could use 2 150R to make a 300R resistor, I did say he could use a 270R or a 330R and all that would do is change the brightness of the LED, I also said if he used the 330 then that would reduce the amount of current and help the world cut down on global warming and perhaps save trees too.
I've stopped a couple of them walking off with 330K resistors, as they weren't sure of the relivance of the R & K after the digits
But don't forget I'm not allowed to teach students, but I am allowed to and expected to impart my knowledge, which strangley enough doesn't warrent a salery scale increase.

When the subject of yolerance came up elsewhere a while ago I
devised this table to illustrate the tolerances of different
eanges of resistor. Feel free to show it your students.

https://www.dropbox.com/s/qdeyfp7lzzdsrdr/Resistor%
20Tolerances.png?dl=0

or https://tinyurl.com/y2jdjh7o

--

Terry

That's rather good!
--
Dave W

In message , Dave W
writes
On Fri, 11 Oct 2019 19:03:34 +0100, Terry Casey
wrote:
Snip
When the subject of yolerance came up elsewhere a while ago I
devised this table to illustrate the tolerances of different
eanges of resistor. Feel free to show it your students.

https://www.dropbox.com/s/qdeyfp7lzzdsrdr/Resistor%
20Tolerances.png?dl=0

or https://tinyurl.com/y2jdjh7o

--

Terry

That's rather good!

20% resistors were a bit before my time but the chart demonstrates what
I always thought about the apparently strange value choices.

Make a batch of carbon resistors...... test for value and designate a
fit in one of the available bands. No wastage:-)

--
Tim Lamb

In article ,
Tim Lamb wrote:
Make a batch of carbon resistors...... test for value and designate a
fit in one of the available bands. No wastage:-)

Transistors in the early days. ;-)

--
*How about "never"? Is "never" good for you?

Dave Plowman London SW
To e-mail, change noise into sound.