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Flyable Brassboards

 
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nuckollsr(at)cox.net
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PostPosted: Mon Feb 06, 2006 6:46 pm    Post subject: Flyable Brassboards Reply with quote

Many times over the years, I've had to fabricate little circuits
for some task wherein I needed the flexibility of a brass-board
but with a reasonable degree of hardness suited for flight.

I had occasion to dig out an old tool today for another task
and thought I'd share it with the List. See:

http://www.aeroelectric.com/Pictures/Tools/flyable_brassboard_1.jpg

http://www.aeroelectric.com/Pictures/Tools/flyable_brassboard_2.jpg

I cut down a strip of experimental brass-board stock and with
a tad bit of sculpting on the belt sander, I was able to fit it to
the inside of the lid on this die-cast box. Add a d-sub or other
handy connector and you've got an enclosure with features that
permit quick fabrication but with reasonable robustness for handling
when closed up. If I expect unusual vibration, I'll use hot-glue
to stick the components and wires down to the board. The hot glue
doesn't run into the holes and strips off after the experiment is
done.

The circuit in the pictures is a gain of 100 amplifier I needed
to amplify a strain gage signal up to the range of my poor-man's
data acquisition system. The all-metal enclosure lends itself to
the shielding of relatively sensitive circuits. I keep several such
prepared boxes laying around and they've saved a lot of time when
I needed to get something up and running . . . today.

In this case, I'm setting up the data acquisition system to get
some numbers on the performance of a Schumacher Wonder Charger . . .
lots of push-buttons and indicators. Really cool battery charger.
The goal is to deduce return on investment and real utility of
this tool in the ownership and operation of and airplane (or any
other vehicle fitted with a battery). I need a gain of 60 amplifier
for the battery ammeter shunt.

If any of you are inclined to craft specialty circuits that
are best flight tested before committing to etched circuit
board . . . or you just need a one-time circuit for a test,
I can recommend the technique illustrated here.

Bob . . .
< What is so wonderful about scientific truth...is that >
< the authority which determines whether there can be >
< debate or not does not reside in some fraternity of >
< scientists; nor is it divine. The authority rests >
< with experiment. >
< --Lawrence M. Krauss >


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retasker(at)optonline.net
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PostPosted: Mon Feb 06, 2006 8:37 pm    Post subject: Flyable Brassboards Reply with quote

I understand what you are doing and know that you understand the
limitations of this type of breadboard and will not use it for long or
in any flight critical application.

However, I am not sure that everyone reading this list does.

This type of breadboard is good for bench testing of relatively low
frequency (<1MHz or so) circuits. It has a relatively large capacitance
between pins/insertion points which limits the high frequency utility
and can provide unwanted feedback in sensitive circuits. It is also not
very secure unless it is new and from a good quality manufacturer. The
insertion points tend to get loose with time, especially if one inserts
a larger lead one time and a smaller lead the next.

I would recommend that one use these boards as they were intended - try
out the circuit on the bench in a nice benign environment. When you are
satisfied that it will do what you want, then purchase one of the PCBs
available that exactly mimic the insertion points and buses and solder
your circuit on that (for instance, Radio Shack Catalog #: 276-170 -
http://www.radioshack.com/search/index.jsp?kwCatId=&kw=breadboard -
fifth one down on the page). They are also available from Digikey.
This will give a circuit that is stable and robust and could be used as
a permanent installation if so desired.

The rest of your suggestion (using the aluminum box) is a great idea!

Dick Tasker

Robert L. Nuckolls, III wrote:

Quote:


Many times over the years, I've had to fabricate little circuits
for some task wherein I needed the flexibility of a brass-board
but with a reasonable degree of hardness suited for flight.

I had occasion to dig out an old tool today for another task
and thought I'd share it with the List. See:

http://www.aeroelectric.com/Pictures/Tools/flyable_brassboard_1.jpg

http://www.aeroelectric.com/Pictures/Tools/flyable_brassboard_2.jpg

I cut down a strip of experimental brass-board stock and with
a tad bit of sculpting on the belt sander, I was able to fit it to
the inside of the lid on this die-cast box. Add a d-sub or other
handy connector and you've got an enclosure with features that
permit quick fabrication but with reasonable robustness for handling
when closed up. If I expect unusual vibration, I'll use hot-glue
to stick the components and wires down to the board. The hot glue
doesn't run into the holes and strips off after the experiment is
done.

The circuit in the pictures is a gain of 100 amplifier I needed
to amplify a strain gage signal up to the range of my poor-man's
data acquisition system. The all-metal enclosure lends itself to
the shielding of relatively sensitive circuits. I keep several such
prepared boxes laying around and they've saved a lot of time when
I needed to get something up and running . . . today.

In this case, I'm setting up the data acquisition system to get
some numbers on the performance of a Schumacher Wonder Charger . . .
lots of push-buttons and indicators. Really cool battery charger.
The goal is to deduce return on investment and real utility of
this tool in the ownership and operation of and airplane (or any
other vehicle fitted with a battery). I need a gain of 60 amplifier
for the battery ammeter shunt.

If any of you are inclined to craft specialty circuits that
are best flight tested before committing to etched circuit
board . . . or you just need a one-time circuit for a test,
I can recommend the technique illustrated here.

Bob . . .

--


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that a significant number of electrons may have been temporarily inconvenienced.
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nuckollsr(at)cox.net
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PostPosted: Tue Feb 07, 2006 5:50 am    Post subject: Flyable Brassboards Reply with quote

At 11:35 PM 2/6/2006 -0500, you wrote:

Quote:

<retasker(at)optonline.net>

I understand what you are doing and know that you understand the
limitations of this type of breadboard and will not use it for long or
in any flight critical application.

Name one "flight critical" application . . . Smile
Quote:
However, I am not sure that everyone reading this list does.

The operative term is "brassboard" . . . a modern incarnation
of the yesteryear's techniques for "breadboarding". This technology
is useful for one-of, low bandwidth tasks. This technology is a
low-time-to-operation but short-lived activity such as the
examples I described for engineering flight and/or bench
testing.

Any permanently installed device . . . or a device not intended
to be shepherded by flight test persons should not be assembled
in this manner.

Quote:
This type of breadboard is good for bench testing of relatively low
frequency (<1MHz or so) circuits. It has a relatively large capacitance
between pins/insertion points which limits the high frequency utility
and can provide unwanted feedback in sensitive circuits. It is also not
very secure unless it is new and from a good quality manufacturer. The
insertion points tend to get loose with time, especially if one inserts
a larger lead one time and a smaller lead the next.

Absolutely. This is the ONLY reason I keep PVC, 22AWG solid wire in
the shop. I specifically limit the size of conductors pushed into
the holes to 22AWG or smaller.

Quote:
I would recommend that one use these boards as they were intended - try
out the circuit on the bench in a nice benign environment. When you are
satisfied that it will do what you want, then purchase one of the PCBs
available that exactly mimic the insertion points and buses and solder
your circuit on that (for instance, Radio Shack Catalog #: 276-170 -
http://www.radioshack.com/search/index.jsp?kwCatId=&kw=breadboard -
fifth one down on the page). They are also available from Digikey.
This will give a circuit that is stable and robust and could be used as
a permanent installation if so desired.

VERY labor intensive by comparison and you still have to box it
and furnish a connector. I find the spring-boards particularly
useful in situations where you have a lot of people standing around
charging to your work-order and things don't move ahead until YOUR
contribution to the task is running.

They ARE life-limited. I've refurbished several of these tools
when one or more contacts got funky. I keep several new
spring-boards on the shelf. It takes 10 minutes to pry the
used one off and replace it. They're easy to build
and have great return on investment but as you've noted, NOT
a substitute for more robust packaging for long term
applications and especially when the device will be used
by non flight test personnel. It is, after all, a brassboard.

Bob . . .


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