gmane.comp.hardware.microcontrollers.pic

Re: [EE] underground pipe/wire finder

Dwayne Reid — 2013-05-21T17:44:49

Hi there, Bob.

I'm wondering if I gave you bad information.

I regularly use two different types of wire tracer - the 'fox and 
hound' type tracer that follows an electric field and the 
magnetic-type that use a pickup coil.  I sort of use them 
interchangeably, so I might have gotten it wrong when I suggested 
that following the electric field should work for following an 
underground cable.

The reason I'm now thinking that is because I've always used my 
Jumper Tracer (with ferrite pickup coil) or one of our units 
(open-air wound coil) whenever I've had to follow a buried cable.

The solution is simple - add a pickup coil to your high-gain 
amplifier.  That can be an air-wound coil a couple of inches in 
diameter or even an old AM radio loopstick antenna.

Now you have to drive some current into that underground wire - 
either ground the far end of the wire or, if you have two conductors, 
just short them together at the far end.  You won't get anywhere near 
as much detection range if the two conductor

Re: [EE]: Would you add zeners to automotive PIC analog inputs?

Mark Rages — 2013-05-21T17:36:53



If you design the circuit to have two caps in series, you can use your
existing caps and tolerate failure (of one of the caps, anyway).
 "automotive" MLCCs
are constructed like this internally.  But they cost well more than twice
as much as the non-automotive part, so you might as well put them in series
in your circuit.  Remember that capacitors in series are
inverse-of-sum-of-inverses, like resistors in parallel.  But if exact
capacitance values are important to your circuit  you've already gone
astray with high-dielectric MLCCs.

Automotive and soft-termination caps are expensive and hard to source.   At
the end of the day, the humble through-hole capacitor starts looking pretty
attractive.

If you're just hacking stuff together, you can try tenting two capacitors
together to put them in series on pads made for one capacitor.  Not a very
robust construction technique.

RE: [EE]: Would you add zeners to automotive PIC analog inputs?

2013-05-21T17:16:28

You may like to pre-heat the caps first. I know a company that assembles PCBs for us has had significant problems with MLCC caps cracking as a result of thermal shock. Preheating the cap reduces this as you don't end up with the same temperature differential along the cap.

Re: [EE]: Would you add zeners to automotive PIC analog inputs?

Bob Blick — 2013-05-21T17:02:28

Please fix your address book. Your "TO:" line has the Piclist repeated
and we get duplicate messages. Then if someone does a reply-all we get
two replies!

Thanks,

Bob

On Mon, May 20, 2013, at 07:54 AM, Electron wrote:

Re: [EE] Uses for stepper motors

John Gardner — 2013-05-21T16:56:56

If you have'nt seen it, may give you some ideas...

http://www.parallax.com/portals/0/Downloads/docs/prod/sic/Web-122-28100-SicMiniProjects-v1.0.pdf

Oriented towards their products, of course.

Re: [EE]: Would you add zeners to automotive PIC analog inputs?

Electron — 2013-05-20T14:54:24

At 18.39 2013.05.19, David VanHorn wrote:


Thanks, this is very interesting.

I digged some info and these are Samsung caps, so they shouldn't be too crap.
I can't be the ESD I first guessed, also because they are 10uF and no special
ESD was there (it wasn't even installed on the engine the 2 times it happened!).

So now I discovered the world of MLCC cracking, thank you.

The board definitely suffered physical stress (bending etc..) during work.

It must have to do also with my hand soldering technique: I first solder one
pad (using a small spoon-like tip), this way the 0603 cap is now tacked and
it'll let me solder the other pad (tons of liquid flux and again the spoon
like small tip), I finally add flux to the first pad and resolder it again to
get a better joint than the first I managed to make (which never gets perfect
and is useful mostly to get the component tacked in place).

Now I am concerned that this soldering technique will damage these delicate
MLCC SMD caps.

As I already bought a (costly) r

Re: [EE]: Would you add zeners to automotive PIC analog inputs?

Electron — 2013-05-20T14:54:24

At 18.39 2013.05.19, David VanHorn wrote:


Thanks, this is very interesting.

I digged some info and these are Samsung caps, so they shouldn't be too crap.
I can't be the ESD I first guessed, also because they are 10uF and no special
ESD was there (it wasn't even installed on the engine the 2 times it happened!).

So now I discovered the world of MLCC cracking, thank you.

The board definitely suffered physical stress (bending etc..) during work.

It must have to do also with my hand soldering technique: I first solder one
pad (using a small spoon-like tip), this way the 0603 cap is now tacked and
it'll let me solder the other pad (tons of liquid flux and again the spoon
like small tip), I finally add flux to the first pad and resolder it again to
get a better joint than the first I managed to make (which never gets perfect
and is useful mostly to get the component tacked in place).

Now I am concerned that this soldering technique will damage these delicate
MLCC SMD caps.

As I already bought a (costly) r

Re: [EE] Uses for stepper motors

Kerry Wentworth — 2013-05-21T16:01:03

I think if it was me, I'd start simple, like attaching a couple of 
steppers to the knobs on an Etch-a-sketch.
Get it to draw lines.
Get it to draw arcs / circles.
 From there, either go to G-code interpretation or rig up an XY(Z) table.

How far you could get would depend on time, talent, motivation and parts 
available, but you would start with more or less instant gratification

Re: [EE] Uses for stepper motors

John Ferrell — 2013-05-21T16:00:29

I have a cheap Quad Copter ($100), much fun, considering larger one.
No sheep. The farmer next door sold the goat herd the day after 8 were 
killed by unknown preditors, probably coyotes introduced by the Feds.

On 5/20/2013 8:01 PM, IVP wrote:

Re: [EE] Uses for stepper motors

John Ferrell — 2013-05-21T15:22:21

I vaguely recall seeing a project somewhere that drew on a wall with an 
ink jet cartridge suspended by two cables.
Once upon a time I considered a plotter that was a small car that ran 
around the paper raising and lowering a pen to produce the drawing. 
Think Turtle Graphics.
I have not ruled out an XY mechanism for my PCB drill project that 
implements two, crossed 1/4-20 lead screws (0.05 inches per rev) from 
the hardware store.

On 5/21/2013 4:03 AM, alan.b.pearce< at >stfc.ac.uk wrote:

RE: [EE] Uses for stepper motors

2013-05-21T11:47:49

I am reminded of an opinion my first boss had, about Asian students that went through the Engineering School at the university he went to in NZ. He said that the Asian students were absolutely useless at anything mechanical, and he put it down to them not having played with Meccano as children, to get a feel for how mechanical things worked.

Equally one of my nephews, who is a pretty bright lad anyway, who has always had an engineering bent (he gets it from both grandfathers) sailed through the same engineering school as by boss, mentioned above, and when he went out looking for a job had a full time position inside a week.

RE: [EE] Uses for stepper motors

2013-05-21T11:41:52

I was lucky that my father also had an interest in radio, and when I got a book out of the library describing how to build a crystal set, he was in boots and all to help.


LOL ...


Maybe he thought it was fed with a signal generator at a rather higher frequency ...

One of the courses I did when I was an apprentice, the lecturer described how he used to confuse guys from the NZED (New Zealand Electricity Department, the outfit than ran the national grid power distribution) by having a pair of open feeder wires stretched across the ceiling of the laboratory. He had a light bulb one end, a signal generator the other, which must have had a reasonable output capability, even to light a small torch bulb, and then part way along the overhead wires he had a pair of wires dropped down to a knife switch, Close the switch and the light came on, open the switch and the light went off.

IIRC he had the signal generator running somewhere in the 150MHz range, which would give about the right wavelength for the length o

Re: [EE] Uses for stepper motors

KPL — 2013-05-21T11:34:56

In some countries that was happening until the crisis came. A lot of
men had to learn to do stuff themselves or live without.

--
KPL

Re: [EE] Uses for stepper motors

IVP — 2013-05-21T11:09:06

Same here. Loved my Meccano and built it up to a pretty hefty
suitcase full. IMVHO a constructional toy is at least as important
as eg sport to develop brain and motor skills at a young age

"A new study shows that less (aaargh - fewer !!!) men are doing
their own home repairs. Could DIYers be an endangered species?"

http://www.diylife.com/2011/04/25/diy-decline/

I've heard this often and considering the number of odd jobs I'm
asked to do for otherwise seemingly fit intelligent but cack-handed
(as my dad would have said) husbands it could be true

Joe

Re: [EE] Uses for stepper motors

KPL — 2013-05-21T10:29:30

In my childhood I got the most learning from the meccano-like kit. I
got a huge set at an (too) early age, but it lasted for many many
years, with some additions at some points.
In USSR we actually had to carry smaller kits to school, they were
part of obligatory learning in some grades.

I was using those parts for prototyping even after my childhood was over.
Larger kits included some motors, gearboxes, bulbs, switches etc.

I'm wondering what could be the best learning tool for my son. Lego's
are good, but you need those extremely expensive advanced sets to get
any real mechanics. Meccano-style sets that I have seen locally are
also very small, primitive and expensive.




--
KPL

RE: [EE] Uses for stepper motors

Bob Ammerman — 2013-05-21T10:00:07

My parents encouraged my mechanical/electrical/electronic interests at a
young age. I remember on several occasions when they bought a second copy of
something (eg: a cassette tape recorder) after I taken apart the first to
see how it worked. It seems that in those days I sometimes couldn't get
things back together. This was especially amazing because our family had
little $ for extras.

I remember "improving" small transistor radios by connecting them to higher
voltage batteries (18V?) and larger speakers. The sound output was
impressive, for a while.

Another story: when I was about 10 my dad was doing some remodeling and had
to install a wall switch for a light. He thought the simplest way to do it
was to wire it in parallel, _across_, the line. He reasoned that when the
switch was on the current would go through it rather than the light bulb. I
set him straight, and from that point my mom wouldn't let him do any more
electrical projects.

Re: [EE] Uses for stepper motors

IVP — 2013-05-21T09:58:47

 

Yes, you're right. I was having a think about this today

What I need to do is make up a small Meccano-type box of fittings.
A couple of lead screws, a few nuts and bolts, bit of drilled panel,
that sort of thing. Enough to make a crane or something with wheels

I've had someone down in Christchurch wants a couple for a line-
following bot for a uni project. I'm happy enough to oblige

Joe

RE: [EE] Uses for stepper motors

2013-05-21T08:03:47

The problem is that anything to do with motors requires a reasonable amount of mechanics to do something useful, which is probably beyond time and available effort in a classroom.

If you could provide the basics of an X-Y mechanism that could hold a pen (I am thinking ordinary ballpoint or pencil here), along with some means of raising/lowering the pen, then the classroom project becomes a programming one instead of a mechanical one, which is probably a lot more do-able. You would need to provide some failsafe drive electronics for the motors, so that incorrect programming doesn't pop the drive transistors.

Then I suspect you would get some interest in using motors.

Re: [EE] Uses for stepper motors

Justin Richards — 2013-05-21T05:37:00

I also had an interest in electronics at a young age, but it never occurred
to me to go to my parents, I simply begged, borrowed or stole what I needed.

I did ask my father from time to time if he could borrow the iron from his
work place as this was the quickest way to connect leads to batteries.

So my parents rather than supporting my interest they endured it.  My
brother on the other hand was more in tuned and bought me a 50in1 which I
loved to bits.

Justin

Re: [EE] Uses for stepper motors

John Gardner — 2013-05-21T03:58:42

... Got sheep ?

I wish. Lamb is rich people's fare these days, in the land

of grocer cartels...  :(

Re: [EE] Toner transfer weirdness

John Ferrell — 2013-05-21T01:28:46

HP has a good reputation for toner transfer. I use an 1102W. It will 
feed 3x5 paper. I bought a package of HP presentation paper and it is my 
favorite. I have only made a few boards. I use an iron that is intended 
for covering model airplanes.
On 5/20/2013 8:04 PM, Bob Blick wrote: