Reply by Przemek Klosowski●February 6, 20122012-02-06
On Sat, 28 Jan 2012 23:00:34 +0000, Simon Clubley wrote:
> On 2012-01-28, Mark Borgerson <mborgerson@comcast.net> wrote:
>> If you can print legibly, your hands are probably steady enough. A
>> good binocular microscope is handy for more than soldering and
>> shouldn't cost more than $300.
>
> While such a microscope would be affordable, for me, that would count as
> a investment I would not want to make until I was sure of myself.
While a nice binocular microscope with large field of view and focal
distance, and perhaps with long and movable arm is expensive, I am using
a ghetto microscope that I got on Ebay for $30. I use it for electronics
and for ton of other household tasks (splinter removal and other domestic
surgeries), probably at least once a week over last several years. One of
the better tool investments I made.
I don't see it now for the price I got it from, but it is almost exactly
like this one:
http://www.ebay.com/itm/Inspection-Binocular-Microscope-Coin-Rock-Stamp-
Circuit-/200279748681?pt=LH_DefaultDomain_0&hash=item2ea19a7049
Reply by Przemek Klosowski●February 6, 20122012-02-06
On Sat, 28 Jan 2012 23:00:34 +0000, Simon Clubley wrote:
> On 2012-01-28, Mark Borgerson <mborgerson@comcast.net> wrote:
>> If you can print legibly, your hands are probably steady enough. A
>> good binocular microscope is handy for more than soldering and
>> shouldn't cost more than $300.
>
> While such a microscope would be affordable, for me, that would count as
> a investment I would not want to make until I was sure of myself.
While a nice binocular microscope with large field of view and focal
distance, and perhaps with long and movable arm is expensive, I am using
a ghetto microscope that I got on Ebay for $30. I use it for electronics
and for ton of other household tasks (splinter removal and other domestic
surgeries), probably at least once a week over last several years. One of
the better tool investments I made.
I don't see it now for the price I got it from, but it is almost exactly
like this one:
http://www.ebay.com/itm/Inspection-Binocular-Microscope-Coin-Rock-Stamp-
Circuit-/200279748681?pt=LH_DefaultDomain_0&hash=item2ea19a7049
Reply by Tim Wescott●February 3, 20122012-02-03
On Sun, 29 Jan 2012 11:58:32 -0600, Frnak McKenney wrote:
> This is a branch from the "ARM (or other 32 bit) MCUs in PDIP ?" thread.
>
> On Sat, 28 Jan 2012 17:23:01 -0500, Rich Webb
> <bbew.ar@mapson.nozirev.ten> wrote:
>> On Sat, 28 Jan 2012 15:14:45 -0600, Joe Chisolm
>><jchisolm6@earthlink.net> wrote:
>
> [...]
>
>>>SchmartBoard has a line of adapters. Easy to work with. Never had any
>>>issues ordering from them.
>>>
>>>http://www.schmartboard.com/index.asp?page=products_smttodip
>>
>> One feature of the Schmartboard is their "ez technology" which puts the
>> SMT leads onto recessed pads, so they sort of "fall into place." Can't
>> get much easier...
>
> I took a look at their three-minute video:
>
> http://www.schmartboard.com/index.asp?page=movie
>
> and it looks like a neat technique. I wonder if it could be
> approximated by creating "Y"-shaped pads like these:
>
>
> Top View
>
> /---------------------------------\
> / |
> / Pad |
> ---- /----------------------------/ +----------------
> | |
> | | Lead
> ---- \----------------------------\ |
> \ | +----------------
> \ |
> \---------------------------------/
>
> +----------------
> |
> Side View | Lead
> |
> +----------------
> -----------------------------------------+
> Pad |
> -----------------------------------------+
>
> where the copper shape and thickness itself provided the "trough"? The
> "trough" might not be as deep as the ones manufactured by SchmartBoard,
> but all it has to be is "good enough".
>
> Assuming that pads could be etched / deposited with a narrow enough
> width and not present other problems (current capacity, etc.), this
> might be accomplished by a simple (and possibly automated) edit of the
> appropriate component libraries.
>
> ( Heck, a suitable ALIDHTBI 3D CNC machine could "rout"-out
> troughs, lay down a thin layer of conductive paint, and even drill
> holes for a few through-hole components! )
>
> Jes' curious...
It sounds like an excellent solution to a nearly-nonexistent problem.
I have no trouble soldering 0.5mm pitch parts onto bare (no solder mask)
boards; while I have the advantage of an assembly microscope, even before
I got it I could still get the job done with a watchmaker's loupe and
some care taken.
You just tack down the corners of the chip, goober solder on all over
everything without worrying about solder bridges, then use desoldering
braid to remove all the bridges you just created.
That seems "schmarter" than using someone else's prototyping board, to me.
--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?
Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com
Reply by Frnak McKenney●February 3, 20122012-02-03
Hi, Mel.
Thanks for jumping in.
On Tue, 31 Jan 2012 11:08:17 -0500, Mel Wilson <mwilson@the-wire.com> wrote:
> Frnak McKenney wrote:
>
>> This should leave a "trough" that the TSOP-8 (or whatever) lead
>> can lie in, and this will help keep the IC from moving about as
>> much as it would on an unaltered pad.
>
> On the board I'm looking at, the SMT pads are the same width as
> the leads. A routed trough that leaves any copper on the board
> at all will be too narrow for the lead. ...
Oh.
> ... There isn't a lot of
> room to widen that pads either. (Really covet one of those
> AdaFruit USB microscopes right now.) Risk solder bridges or
> frying the infinitesimal copper strips off the board during
> rework. From what I've read, the current scheme of things
> counts on the surface tension of the melted solder to pull the
> part into alignment.
... "Nevermind!" (*)
This is probably what linnix was trying to tell me. (Sorry about
that!)
For what it's worth, I have one of those USB 'scopes, and it takes
really nice pictures, but it does have a few drawbacks for someone
who wants to use it in place of an assembly/inspection microscope.
First, it's hard to focus: the "knurled" focus adjustment is stiff
and tends to shift the microscope while you adjust it. It's often
easier to set the focus, then move the microscope around to get
the view you want. Second, it's light, and unless you're
extremely careful it gets bumped so the object being disappears
out of frame. Hand-held pictures are not impossible, but tricky
without an arm rest.
I've been meaning to build something out of an old gooseneck lamp,
but haven't gotten "a round tuit" yet.
If you're curious, you can find a number of USB microscopes here:
http://www.bhphotovideo.com/
Just do a search on... well, "usb microscope". <grin!>
Frank
(*) http://en.wikipedia.org/wiki/Emily_Litella
--
The study of history is a painful antidote to contemporary
arrogance. It is humbling to discover how many of our glib
assumptions, which seem to us novel and plausible, have been
tested before, not once but many times and in innumerable guises;
and discovered to be, at great human cost, wholly false.
-- Paul Johnson
--
Frank McKenney, McKenney Associates
Richmond, Virginia / (804) 320-4887
Munged E-mail: frank uscore mckenney aatt mindspring ddoott com
Reply by Simon Clubley●January 31, 20122012-01-31
On 2012-01-31, Paul <paul@pcserviceselectronics.co.uk> wrote:
> In article <jg7d1i$fmq$1@dont-email.me>,
> clubley@remove_me.eisner.decus.org-Earth.UFP says...
>>
>> BTW, where do you buy your boards from in the UK ?
>>
>> Two distributors are listed for the UK; Active Robots and Proto-Pic,
>> neither of which appears to sell this type of board:
>
> I have used Active Robots as my source a few times over the years.
> Generally spoke to them on the phone, helpful bunch of folks.
>
>> http://www.schmartboard.com/index.asp?page=products_smttodip&id=451
>
> Give them a ring and ask them, they also distribute Sparkfun so you
> avoid customs and import paperwork, if that is an issue for you.
>
Thanks. I've been in touch with them and am waiting to hear back from
them on pricing.
(And yes, customs is a major importing issue as far as I am concerned. :-))
>> A question about this product is the placement of decoupling capacitors
>> and crystal (thanks to whoever pointed this out) next to the MCU
>> instead of on the baseboard which the adapter would plug into.
>>
>> For the people here who have actually used this product, how did you
>> solve this problem ?
>
> I have used the square boards and put decouplers usually 0805 or 0603
> caps on the corner SMT mounting pads, sometimes a few pullups there as
> well.
>
> Generally my projects involve many clocks and often I have external
> oscillator solution (a few gates and quartz as not too high frequency)
> this works best as often same clock or subclock is needed eleswhere
> so instead of multiple crystals I run the buffered clocks around the
> board. In one case I needed one 12 MHz and two 6MHz so I created a
> master 12MHz oscillator at 3V3 uning picogates, fed into PLD and did
> divide by 2 in there and then ran 6MHz from 2 picogate buffers. The
> two buffers were for a 5V and 3V3 clock. A few picogates uses less
> space than multiple cystals.
>
>>
>> Did you use the spare pads provided on the board and was this sufficiently
>> close to the MCU manufacturer's specifications to work ok ?
>
> For caps it was, not normally enough room for a crystal, so buffered
> clock drive was easier.
>
Thanks for the detailed design notes (and thanks for the example
photograph in your other posting). It helps me to understand how
you are using the boards.
Thanks,
Simon.
--
Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP
Microsoft: Bringing you 1980s technology to a 21st century world
Reply by David Brown●January 31, 20122012-01-31
On 31/01/12 18:42, George Neuner wrote:
> On Mon, 30 Jan 2012 23:53:29 +1100, Zoltan Kocsi
> <zoltan@bendor.com.au> wrote:
>
>> First, the standard specifies that each volatile access has to be a separate
>> actual access. That generates a lot of unnecessary code:
>>
>> typedef struct { int fld1:20, fld2:5, fld3:5, fld4:2; } myreg;
>>
>> volatile myreg * const ptr = SOME_ADDRESS;
>>
>> then you want to initialise the register (say it's some config reg):
>>
>> ptr->fld1 = val1;
>> ptr->fld2 = val2;
>> ptr->fld3 = val3;
>> ptr->fld4 = val4;
>>
>> will read and write the register 4 times and of course it will mask and set
>> the fields individually. Except when some buggy versions of gcc decide to
>> optimise it out and do a single write. Or possibly 2 reads and 2 writes, with
>> half sized accesses. If you go through gcc versions from say, 4.0.x to 4.5.x
>> and see what it generates from volatile bitfield code (at least for ARM), it's
>> sheer horror.
>
> One thing I haven't seen mentioned in this thread is the possibility
> of the CPU combining multiple narrow writes into a single wide write,
> or swallowing (only writing the last of) back to back writes to the
> same location. The compiler has no control over any of this.
>
> Much of the discussion has been about too many (code visible)
> accesses. Regardless of the disassembly, the hardware actually may be
> doing something different. If you really need multiple writes to
> occur, some CPUs require a pipeline flush or write barrier occur after
> each write. I am not aware of any compiler that correctly handles
> this.
>
> George
Many processors allow you some control over this through an MMU or
similar mechanism - you can define areas that will not be cached, and
for which all reads and writes are executed as originally ordered. For
some cpus you may also need some sort of synchronisation or barrier
instruction to enforce the order (like the PPC's "EIEIO" instruction).
Compilers won't generate these automatically - you need to add them
yourself where you need them, and be aware that they often cost a fair
number of cycles due to pipeline flushes/stalls.
Reply by George Neuner●January 31, 20122012-01-31
On Mon, 30 Jan 2012 23:53:29 +1100, Zoltan Kocsi
<zoltan@bendor.com.au> wrote:
>First, the standard specifies that each volatile access has to be a separate
>actual access. That generates a lot of unnecessary code:
>
>typedef struct { int fld1:20, fld2:5, fld3:5, fld4:2; } myreg;
>
>volatile myreg * const ptr = SOME_ADDRESS;
>
>then you want to initialise the register (say it's some config reg):
>
>ptr->fld1 = val1;
>ptr->fld2 = val2;
>ptr->fld3 = val3;
>ptr->fld4 = val4;
>
>will read and write the register 4 times and of course it will mask and set
>the fields individually. Except when some buggy versions of gcc decide to
>optimise it out and do a single write. Or possibly 2 reads and 2 writes, with
>half sized accesses. If you go through gcc versions from say, 4.0.x to 4.5.x
>and see what it generates from volatile bitfield code (at least for ARM), it's
>sheer horror.
One thing I haven't seen mentioned in this thread is the possibility
of the CPU combining multiple narrow writes into a single wide write,
or swallowing (only writing the last of) back to back writes to the
same location. The compiler has no control over any of this.
Much of the discussion has been about too many (code visible)
accesses. Regardless of the disassembly, the hardware actually may be
doing something different. If you really need multiple writes to
occur, some CPUs require a pipeline flush or write barrier occur after
each write. I am not aware of any compiler that correctly handles
this.
George
Reply by Mel Wilson●January 31, 20122012-01-31
Frnak McKenney wrote:
> This should leave a "trough" that the TSOP-8 (or whatever) lead
> can lie in, and this will help keep the IC from moving about as
> much as it would on an unaltered pad.
On the board I'm looking at, the SMT pads are the same width as the leads.
A routed trough that leaves any copper on the board at all will be too
narrow for the lead. There isn't a lot of room to widen that pads either.
(Really covet one of those AdaFruit USB microscopes right now.) Risk solder
bridges or frying the infinitesimal copper strips off the board during
rework. From what I've read, the current scheme of things counts on the
surface tension of the melted solder to pull the part into alignment.
Mel.
Reply by Frnak McKenney●January 31, 20122012-01-31
On Sun, 29 Jan 2012 10:14:32 -0800 (PST), linnix <me@linnix.info-for.us> wrote:
> On Jan 29, 9:58 am, Frnak McKenney
><fr...@far.from.the.madding.crowd.com> wrote:
>> This is a branch from the "ARM (or other 32 bit) MCUs in PDIP ?"
>> thread.
>>
>> On Sat, 28 Jan 2012 17:23:01 -0500, Rich Webb <bbew...@mapson.nozirev.ten> wrote:
>> > On Sat, 28 Jan 2012 15:14:45 -0600, Joe Chisolm
>> ><jchiso...@earthlink.net> wrote:
>>
>> [...]
>>
>> >>SchmartBoard has a line of adapters. Easy to work with. Never
>> >>had any issues ordering from them.
>>
>> >>http://www.schmartboard.com/index.asp?page=products_smttodip
>>
>> > One feature of the Schmartboard is their "ez technology" which
>> > puts the SMT leads onto recessed pads, so they sort of "fall
>> > into place." Can't get much easier...
>>
>> I took a look at their three-minute video:
>>
>> http://www.schmartboard.com/index.asp?page=movie
>>
>> and it looks like a neat technique. I wonder if it could be
>> approximated by creating "Y"-shaped pads like these:
>>
>> Top View
>>
>> /---------------------------------\
>> / |
>> / Pad |
>> ---- /----------------------------/ +----------------
>> | |
>> | | Lead
>> ---- \----------------------------\ |
>> \ | +----------------
>> \ |
>> \---------------------------------/
>>
>> +----------------
>> |
>> Side View | Lead
>> |
>> +----------------
>> -----------------------------------------+
>> Pad |
>> -----------------------------------------+
>>
>> where the copper shape and thickness itself provided the "trough"?
>> The "trough" might not be as deep as the ones manufactured by
>> SchmartBoard, but all it has to be is "good enough".
>>
>
> With this, you would have to cut out every other pins of the chip to
> prevent shorting. A better way may be to pre-groove the fiber board
> prior to copper deposit. Easy enough for prototypes, but might not be
> cheap enough for productions.
Hi, Linnix. Thanks for responding.
However, I'm a bit confused, and I suspect that (to quote an old
film) "Whut we hayev heah is fail-yuh tuh c'mun'cate"... I'm just
not sure how. <grin!>
I'll try to add a bit more description to the two drawing above
(Top and Side views). Imagine a PC board is etched leaving a set
of "standard" copper pads for a (say) TSOP-8 package. Then
imagine that a router (the drill kind, not the packet-shovelling
kind) is then used to remove a strip down the center of that pad.
The result is (vary roughly) "Y"-shaped, where the base of the "Y"
is the trace leading off to other components or traces.
This should leave a "trough" that the TSOP-8 (or whatever) lead
can lie in, and this will help keep the IC from moving about as
much as it would on an unaltered pad.
Does that make more sense? Or have I misunderstood what you were
saying? If the latter, could you explain in a bit more detail?
I agree that adding a groove in the board itself (as in the
SchmartBoard "ez" process) would add even more "stability"
(non-moving-ness) to the IC, but it requires an additional step in
creating the board. It seems as if a slightly differently-shaped
pad could accomplish much of the same purpose without that extra
step, and easing the soldering effort for boards from any source
with minimal redesign effort.
Frank
Frank McKenney
--
This evening they began to push the cars around to make way for
the wrecker train. The English soldiers turned out and so did the
nurses and Friends. Maran Lu got off a statement that will go
down in history. "I hope we never have to travel by airplane like
the Sixth Army girls," she said. "We travelled by jeep and had to
get out and push the jeep. We travelled by truck and pushed the
truck, by raft and had to push the raft, by train and had to push
the train. I shouldn't like to have to get out and push an
airplane!" -- Gordon S. Seagrave / Burma Surgeon
--
Frank McKenney, McKenney Associates
Richmond, Virginia / (804) 320-4887
Munged E-mail: frank uscore mckenney aatt mindspring ddoott com
Reply by Paul●January 31, 20122012-01-31
In article <jg7d1i$fmq$1@dont-email.me>,
clubley@remove_me.eisner.decus.org-Earth.UFP says...
>
> On 2012-01-29, Paul <paul@pcserviceselectronics.co.uk> wrote:
> > In article <jg1uu7$k7o$2@dont-email.me>,
> > clubley@remove_me.eisner.decus.org-Earth.UFP says...
> >>
> >> On 2012-01-28, Rich Webb <bbew.ar@mapson.nozirev.ten> wrote:
> >> > On Sat, 28 Jan 2012 15:14:45 -0600, Joe Chisolm
> >> ><jchisolm6@earthlink.net> wrote:
> >> >
> >> >>SchmartBoard has a line of adapters. Easy to work with. Never had any
> >> >>issues ordering from them.
> >> >>
> >> >>http://www.schmartboard.com/index.asp?page=products_smttodip
> >> >
> >> > One feature of the Schmartboard is their "ez technology" which puts the
> >> > SMT leads onto recessed pads, so they sort of "fall into place." Can't
> >> > get much easier...
> >> >
> >>
> >> Several people have now pointed me in the direction of these people.
> >>
> >> I'll have a look through their website and get up to speed on what they
> >> offer.
> >>
> >> Thanks for the pointer everyone.
> >>
> >> Simon.
> >
> > They are available UK, I have used them and keep a few.
> >
>
> I am now mostly up to speed on them; this is a very nice product.
>
> I was worried about the comments here about using jumper wires to connect
> to the board, but I see they also offer boards (for the QFN parts) in
> which you can insert the traditional 0.1 inch pitch connector strips which
> makes for a robust connection to the stripboard/veroboard.
>
> BTW, where do you buy your boards from in the UK ?
>
> Two distributors are listed for the UK; Active Robots and Proto-Pic,
> neither of which appears to sell this type of board:
>
> http://www.schmartboard.com/index.asp?page=products_smttodip&id=451
>
> A question about this product is the placement of decoupling capacitors
> and crystal (thanks to whoever pointed this out) next to the MCU
> instead of on the baseboard which the adapter would plug into.
>
> For the people here who have actually used this product, how did you
> solve this problem ?
>
> Did you use the spare pads provided on the board and was this sufficiently
> close to the MCU manufacturer's specifications to work ok ?