Today's Message Index:
----------------------
1. 07:08 AM - Re: PCB Mfg board house (Eric M. Jones)
2. 07:25 AM - Re: Re: PCB Mfg board house (Robert L. Nuckolls, III)
3. 08:02 AM - Re: Re: PCB Mfg board house (Bill Watson)
4. 08:18 AM - Re: Audio Amp input (Robert L. Nuckolls, III)
5. 09:11 AM - Re: Audio Amp input (user9253)
Message 1
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| Subject: | Re: PCB Mfg board house |
My two cents:
Eagle is a great program compared to many PCB design programs. It comes in several versions. It would be my first choice for boards that need autorouting. It's probably worth reviewing: http://en.wikipedia.org/wiki/EAGLE_(program)
I use www.ExpressPCB.com exclusively now, since my PCBs are the size of postage stamps. Their great advantages are:
1) Lightning fast delivery. I can finish a design Tuesday am and get the PCBs Friday
am.
2) Stunning easy to learn. The learning curve is a "One Cup of Coffee to Expert"
experience.
3) Schematic Capture and Layout modules are FREE.
And yes, they will send you the Gerbers for a reasonable charge after your first
order (I think).
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=418995#418995
Message 2
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| Subject: | Re: PCB Mfg board house |
At 09:07 AM 2/19/2014, you wrote:
>
>My two cents:
I use www.ExpressPCB.com exclusively now, since my PCBs are the size
of postage stamps. Their great advantages are:
1) Lightning fast delivery. I can finish a design Tuesday am and get
the PCBs Friday am.
2) Stunning easy to learn. The learning curve is a "One Cup of Coffee
to Expert" experience.
3) Schematic Capture and Layout modules are FREE.
I will echo Eric's sentiments. For the kinds of things
I do, time is often of the essence. I submitted an order
for proof of concept boards to Exp-PCB yesterday morning,
will have boards tomorrow morning and assembled samples
in my customer's hands Friday morning (or even late
tomorrow night if they so wish) . . . even tho I live
in cow-town KS . . .
The software is stunningly easy to learn, custom
components easily crafted, turn-around times difficult
to better. Their software also spits out .dxf files
of the board with holes and parts locations so that
creating an assembly drawing in any dxf friendly
cad program is greatly assisted.
Had one customer voice some amazement that holes
in the board I provided "lined up exactly" with
CAD/CNC holes in his target assembly. Don't know
where his previous disappointments came from but
the transitions from Exp-PCB -> cad -> g-code ->
aluminum are in solid lock-step with each other.
When you're charging my exorbitant fees for $time$,
the external costs for materials and services are
relatively insignificant. Most customers are interested
in shortest path to workable solutions. I think there
may be some services on a par with Exp-PCB but I've
used Exp-PCB for many years with no note-worthy
incentives to change.
Bob . . .
Message 3
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| Subject: | Re: PCB Mfg board house |
On 2/19/2014 10:24 AM, Robert L. Nuckolls, III wrote:
> <nuckolls.bob@aeroelectric.com>
>
> At 09:07 AM 2/19/2014, you wrote:
>> <emjones@charter.net>
>>
>> My two cents:
> I use www.ExpressPCB.com exclusively now, since my PCBs are the size
> of postage stamps. Their great advantages are:
>
> 2) Stunning easy to learn. The learning curve is a "One Cup of Coffee
> to Expert" experience.
>
> The software is stunningly easy to learn, custom
> components easily crafted, turn-around times difficult
> to better.
On a somewhat unrelated note, the ExpressSCH software (free) is an
excellent tool for documenting aircraft electrical diagrams if one does
not already have skills with an appropriate drawing tool. Though
intended for use in designing custom circuit boards, it adapts well to
the task of drawing electrical diagrams for your project. Since it
'knows' circuits, it works in a way that is compatible with generalized
electrical diagram documentation. Not as good as Autocad/Turbocad but
much easier to learn for this simple task. I can pick it up after 6
months to make a change and am able to use it without relearning
anything. As Bob said above, "Stunning easy to learn". Great for 'one
time use'.
Thanks to whoever originally suggested this.
Here's my Z-14 drawn using ExpressSCH
Z-14 for RV10
<https://www.dropbox.com/s/3006csh1jkh84fa/PDF%20of%20Z-14.pdf>
(ExpressSCH is one of the two components of the ExpressPCB package. You
only need the ExpressSCH to draw diagrams for your aircraft.
Message 4
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| Subject: | Re: Audio Amp input |
At 07:28 PM 2/18/2014, you wrote:
Bob's audio amplifier
http://www.aeroelectric.com/DIY/Audio_Iso_Amp_9009-700L.pdf has 10
microfarad capacitors connected to the LM386 input. Does the
polarity matter in this circuit? If so, I assume that the curved
part of the capacitor symbol is negative.
Are the values of the input capacitors and resistors critical? I
have seen similar circuits whose capacitors are 1 microfarad and
whose resistors are 10K or even 100K.
Thanks, Joe
Those resistors were selected with two criteria in
mind
(1) the input impedance of the amplifier was crafted
to be in the same ballpark as the aviation headsets
150-600 ohms. Hence the suggested first-choice values
for resistors on the gain-selection sockets of 150 ohms.
(2) the 'amplifier' didn't really need to have any
gain . . . we're wanting to simply mix a combination
of headset audio values together into an output on
the same order. The LM386 chip as a minimum gain
of 20
http://tinyurl.com/ps3zj69
so the downstream resistor wanted to offer some
attenuation of the incoming signal. In this
case, 10 ohm resistors offered a 15:1 attenuation
ratio.
The figures on Page 8 of the assembly manual show
dipped tantalum capacitors in most of the slots, exceptions
being 120, 121 and 127 which are monolythic ceramics.
However, these three capacitors COULD also be tantalums
which is why the parts locator drawing has polarity dots
on the capacitor locations to denote the more positive
terminal.
Input coupling capacitor polarity is not critical . . .
if any DC differences are expected between the amplifier
and a signal source, it is supposed to be zero to very
small . . . there is little potential for undesired
performance should these capacitors be installed the
other way.
Most schematics will use the flat-plate/curved-plate
symbol for all capacitors. About the only time you'll
find flat/flat symbols is in the legacy literature.
If the bill of materials calls out electrolytic
for a particular capacitor, then the schematic will
often included a + adjacent to the positive terminal
but lacking specific instructions, the flat plate is
supposed to always be +.
http://tinyurl.com/ps3zj69
Flat/flat capacitor symbols didn't garner favor for
very long. Some of the oldest Heathkit and ARRL publications
went flat/curved for all variants of the capacitor
Emacs!
Bob . . .
Message 5
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| Subject: | Re: Audio Amp input |
Bob and all, thanks for the explanations. Using a capacitor symbol with a curved
line avoids confusion with the symbol for relay contacts which has two straight
lines.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=419005#419005
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