The TS272CN is an acceptable substitute for the TS272ACN in the
PICTIC II but as noted has a higher input offset voltage. This
can be compensated for in the second stage by adjustment of
the offset trimmer. I selected premium parts for temperature
stability in the application. Sorry the manufacturers are
making "human compatible" devices obsolete and only carrying
over surface mount devices as they go Pb free for the EU
market. Makes it difficult to keep up with what's available
and harder for amateurs with fat fingers and poor eyesight
like myself to build simple projects!

Richard

Hi Richard,

Yes, used to feel that way - until acquiring a surplus dissecting
(stereo) microscope, now I actually prefer surface mount.  Much
easier to move parts around, it's easy to apply paste & solder entire
boards in a $50 toaster oven, and access to all the latest parts.
Hard to believe, but really is easier once you can clearly see.  For
some nice tuturials, see the sparkfun website, also the schmartboard
website.  Also, when I lay out surface mount boards, they tend to be
smaller overall, and so a bit lower cost.

Please do try with a low cost stereo microscope - it changes
everything :)

-Bob

p.s. Finger size is no issue - tweezers work nicely.  Oh and surface
mount resistors & caps are unbelievably low cost in cut tape, and
super easy to handle that way.  Much better than loose parts IMO.

On Jul 19, 2010, at 4:59 PM, Richard H McCorkle wrote:

Not to mention not having to drill holes anymore. I built a 15Ghz
prescaler over the weekend. Total time from concept to completed (and
operational!) prototype was < 2 hours. No muss, no fuss, just design
the circuit, print out the toner transfer, paste it onto the board,
etch, apply paste & parts, drop into the toaster, er, reflow oven,
pull it out, inspect and turn it on.

You don't even need to go as far as the microscope (though they really
do make the job easier). A simple $10 set of magnifying eye pieces or
a 5x magnifying glass lamp ($30 @ Harbor Freight) does a great job.

Am alternative is a webcam that will focus up close. I hooked up an
old TV camera with a macro lens (ebay, $5) to a video capture USB
dongle (ebay again, $15) and put it on an old retort stand. I can look
at it on the screen on the workbench and even do video capture of the
board. Pretty much the ultimate in cheap magnification.

I covered some of this in a presentation at the NEWS conference last winter.
http://www.fastbobs.com/bob/radio/power_meter.ppt

Bob

On Mon, Jul 19, 2010 at 9:22 PM, Robert J Marinelli bobm@stanford.edu wrote:

A few short videos shot with the camera/usb video capture setup I
mentioned earlier:

http://www.fastbobs.com/bob/radio/video1.mpg Video 1 - Black & White
inspection of a prototype power sensor. Low magnification
http://www.fastbobs.com/bob/radio/video2.mpg Video 2 - Colour
inspection of same sensor. Same magnification. About 2-3x
http://www.fastbobs.com/bob/radio/video3.mpg Video 3 - Longer version
of #2. Note lighting changes in 2nd half.
http://www.fastbobs.com/bob/radio/video4.mpg Video 4 - Short, color,
higher magnification
http://www.fastbobs.com/bob/radio/video5.mpg Video 5 - Longest,
highest magnification. Same probe as earlier shots. Note lighting
changes as the light source is moved around showing shadows.

On Mon, Jul 19, 2010 at 9:22 PM, Robert J Marinelli bobm@stanford.edu wrote:

Bob,

Thank you for the video
Now all we need is a robot and software to filter the jitter from my hands.
Maybe a little less expensive than the da Vinci robot.
http://www.davincisurgery.com/

Stanley

 
----- Original Message ----
From: Bob Bownes bownes@gmail.com
To: Discussion of precise time and frequency measurement time-nuts@febo.com
Sent: Mon, July 19, 2010 11:09:50 PM
Subject: Re: [time-nuts] surface mount (was PICTIC II Parts from Mouser)

A few short videos shot with the camera/usb video capture setup I
mentioned earlier:

http://www.fastbobs.com/bob/radio/video1.mpg Video 1 - Black & White
inspection of a prototype power sensor. Low magnification
http://www.fastbobs.com/bob/radio/video2.mpg Video 2 - Colour
inspection of same sensor. Same magnification. About 2-3x
http://www.fastbobs.com/bob/radio/video3.mpg Video 3 - Longer version
of #2. Note lighting changes in 2nd half.
http://www.fastbobs.com/bob/radio/video4.mpg Video 4 - Short, color,
higher magnification
http://www.fastbobs.com/bob/radio/video5.mpg Video 5 - Longest,
highest magnification. Same probe as earlier shots. Note lighting
changes as the light source is moved around showing shadows.

On Mon, Jul 19, 2010 at 9:22 PM, Robert J Marinelli bobm@stanford.edu wrote:

time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Stanley,

Your brain will do an excellent job of translating your finger
motion to the micro motions necessary to move surface mount parts
around with tweezers.  Barring disease, the usual solution to finger
jitter is to keep tweezers pressure light, and lay off the coffee.

Even if you do jitter a bit, there are many tricks you can use to
keep it to a minimum.  I use the little finger on my tweezers hand
as a balance point for my hand.  Just the act of having it touch the
stage, or board removes all of the jitter.

-Chuck Harris

Stanley Reynolds wrote:

On 20 July 2010 18:51, Chuck Harris cfharris@erols.com wrote:

If only our 1PPS signals had a little finger that could rest somewhere :-)

Peter

You'll probably also find that your fine motor control improves a bunch when
you can actually see what you are doing in 3D.  I got a stereo microscope
a year or two ago, and I'm amazed at how finely I can control the tip of a
pair of tweezers or a knife point or soldering iron under the microscope.
It works much better than trying to do the same thing with a one-eyed
magnifier like a loupe, partly because a microscope gives you more working
distance, but mostly because of the full 3D view of what you're doing.

My first stereo microscope was a surplus AO 40 that cost $100, so being able
to see what you're doing doesn't have to be expensive.

 Dave

On Tue, Jul 20, 2010 at 10:51 AM, Chuck Harris cfharris@erols.com wrote:

It's amazing what one can do by hand.

In the 1970s I worked in an electrophysiology lab where we put glass
microelectrodes into rat neurons.  The microelectrodes were made in the
lab by heating 1 mm diameter glass tubing to an orange heat and pulling
abruptly.  (This was done in a simple machine.)  The tube necked down to a
very sharp point.  Too sharp - needed more tip area to allow for the 3
molar potassium chloride solution within to make adequate electrical
contact with whatever was being probed.  The tip was far smaller than a
wavelength of light.  The tip image degenerates into an interference
pattern when looked at with an optical microscope.

Solution?  Put the tube on the stage of a 2000x microscope with the tip in
view.  Take an ordinary glass rod in one hand and manually bring the tip
into view through the microscope.  Gently tap the tip with the rod,
breaking the tip back until an adequate opening is achieved.  How is the
"gently tap" achieved?  One merely thinks of moving the rod.  There is
enough leakage from intent to action that the rod will move enough to do
the job, this being a few wavelengths of light.  All this is done
freehand, although the wrist must be on a rest of some kind.

It turns out that almost everybody can do this, and I was able to do it on
the first try.  To my considerable surprise.

Joe

From:
David Martindale dave.martindale@gmail.com
To:
Discussion of precise time and frequency measurement time-nuts@febo.com
Date:
07/20/2010 02:16 PM
Subject:
Re: [time-nuts] surface mount (was PICTIC II Parts from Mouser)
Sent by:
time-nuts-bounces@febo.com

You'll probably also find that your fine motor control improves a bunch
when
you can actually see what you are doing in 3D.  I got a stereo
microscope
a year or two ago, and I'm amazed at how finely I can control the tip of a
pair of tweezers or a knife point or soldering iron under the microscope.
It works much better than trying to do the same thing with a one-eyed
magnifier like a loupe, partly because a microscope gives you more working
distance, but mostly because of the full 3D view of what you're doing.

My first stereo microscope was a surplus AO 40 that cost $100, so being
able
to see what you're doing doesn't have to be expensive.

 Dave

On Tue, Jul 20, 2010 at 10:51 AM, Chuck Harris cfharris@erols.com wrote:

time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.