[time-nuts] Form factor

Chris Albertson albertson.chris at gmail.com
Wed Dec 22 00:26:48 UTC 2010


I wrote some more ideas, I'm trying here to write what might later,
after some edits become a "consensous document". that captures what
most people want.   Edit away, maybe some of this will make it to the
web site...


++++++++++++++++++++++++++++++++++++++++++++++
Here is an idea for the top of the web page:

How is the Open Counter project "open".
1) The basic design of the counter is open to the addition of new
modules and new technology.  New modules can be pllugged in or replac
older modules.  The interface between modules is published, anyone is
open to design or build a module

2) The design of each module is open for all to see.  Anyone can
provide kits or parts or make PCBs.  (There may be some restrictions
on commercial sales.)

3) The designs are publishing using open file formats that are industry standads

4) the design tools, compilers, schematic captures, word processors,
used to read and modify the design files are available to all wit at
the most a very modest fee or preferable are Open Source tools

5) the hardware is designed such that it can be physiclly built by
anyone with "amateur level" skills. the parts can be build by an open
group

+++++++++++++++++++++++++++++++++++++++++++++++++++++++
Form Factor: One more idea.  I think there is a way to have "all of the above"

Let's say we agree to make all PCBs the same size as a 160-3U Eurocard
but with four holes in the corners too.  A real Eurocard system is
expensive but I'm just saying to use the same size rectangle but no
back plane.   If you do this they will (mechanically, not
electrically) fit in a Euro card cage they will also fit in those
Hammond boxes and with four holes people can stack them on threaded
rods with spacers or mount them in  1U  chassis on standoffs.  They
could also by mounted with standoffs to a "disk sled" and then go into
a computer or file server chassis.

The spec is easy to write and understand too:
"Cards shall be 100mm x 160mm, less than 2mm thick and have 5mm holes
in each corner spaced 5mm from each edge."

These cards would fit perfectly into a Hammond 1455P2201 box or as I
said above mounted just about any way that has so far been suggested.


+++++++++++++++++++++++++++++++++++++++++++++++++++++++++
The next thing to work on is the rear facing edge of the card.  We
really need to minimize the number of different connectors and signal
levels.  The smaller the set the better.  I'll take a stabe at it
below and

This is for the REAR edge:
1) power:  four pins on 0.1 inch centers for +12, -12, +5 and ground

2) frequency reference can be 1Hz, 10MHz or ?? as required but will
use SMA connector

3) Data, for command and setup and digital output wiil use a shared
100Kbps i2c bus (also called "two wire") Each card is to have two
connectors so the multiple cards can be diasy chained.  cards shall
NOT allow there internal components to be visible on this external i2c
bus.

4) Many cards such as a trigger or pre-scaeler will produce output
signals that need to to sent point to point to the rear edge of other
cards I'll suggest SMA for this

(I hope this covers everything.  unless we might need digitized
signals and these can be very high bandwidth)

The FRONT edage of each card is reserved entirely for signals that the
user would directly interact with, such as input jacks or status/power
LED or a data connectors for a computer or network


The next level of interface design is the format of the data to go
over the I2C bus.  Some ideas.

1) Each card type (trigger, counter,  Interface,...) will have it's
own unique number.  Each physial card will have it's own "instance
number"  So if two cards of the same type are in the system each is
numbered 0, 1, 2,..  Cards in an Open Counter are identified by
combining the two numbers.  There are many options but all allow for
over 100 cards in one system.

2) As a minimum each card must implement one command, that would be
"Identify yourself".  The card must respond with at least a one bit
status saying  "present".   By this mmeans any card can find out what
other cards are present.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
At some point we need to say what is and what is not an "Open Counter"....
Open Counter System requirements.

1) An Open Counter system will always require a minimum of two cards
with one being an "Interface card" and the other some kind of signal
handing card.  An Interface card connects the data in the 12c system
bus to a computer, network or to a human operator via a display or
status LEDs.

2) Notwithstanding the above, single cards must be usable devices when
used by themselves.  cards may poll the (disconnected) i2c bus to find
that they are isolated and then must default to standalone mode.

3) Cards must allow that multiple instance of their own type may be
connected on the same system i2c bus, that is, all output data shall
include the card's instance number. (This allows for a multi channel
Open Counter)  This requirement applies to Interface Cards too.    A
large Open Counter system might have multiple input channels and also
a set of interface cards connecting it to a network and a computer via
USB and a front panel with a large LCD screen.

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

The above, if accepted has a design implication.  Cards can not track
the state of the system by simply remembering the set of commands they
have transmitted.  That is because other cards may have transmitted
commands.   To make an analogy you should never assume Joe is at home
because to told Joe to go home.  You must ask Joe his location
whenever you need to know it.

There are likely 1,000 other implications from the above proposals and
these need to be worked out.  But in most projects you only find them
during the first cycle of detail design
I
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++




On Tue, Dec 21, 2010 at 11:05 AM, Don Latham <djl at montana.com> wrote:
> I agree about the ebay finds. Bad to design the boards form factor around
> old chassis.
> Maybe the thing is to find out from the electronic design how big the
> board(s) will have to be or what the electronic footprint is, then go from
> there? If the boards are designed so that idiosyncratic mounting is
> possible, we can all mount them according to our own taste?
>
> Don
>
> Chris Albertson
>> You can't plan a project like this around eBay junk.  How would you
>> assemble
>> 100 kits if each kit requires that you find a specific HP instrument on
>> eBay?
>>
>> If cost is a big issue then I'll go back to my first idea.  Make your PCB
>> about
>> the size os a disk drive.  Then yu get a llength od 1 x 1/4 inch aluminum
>> L
>> and bend it into a three sided "U" and attach it to three sides of the
>> PCB.
>>
>> The finished assembly should fit into any enclusre designed to hold SATA
>> disk drives.  A PC case could work but there are nicer looking boxes, rack
>> mount and diesktop
>>
>> This trades a bit of metal working for the cost of a Hammond box.  But
>> the metal work requires only a hack say and drill.
>>
>>
>>
>> On Tue, Dec 21, 2010 at 8:35 AM, Bob Bownes <bownes at gmail.com> wrote:
>>> I do the same with Tek 500/500series instrumentation plugins. You can
>>> get
>>> the TM504 mainframe for < $50 on ebay and scrap grade modules for < $10.
>>> Plus you get a linear power supply, backplane and already RF rated
>>> enclosure.
>>>
>>> On Tue, Dec 21, 2010 at 11:12 AM, <EWKehren at aol.com> wrote:
>>>
>>>> Hi
>>>> One source of boxes to consider is old HP equipment, some is very
>>>> reasonably priced, like 37203 for small boxes and a 59401A makes an
>>>> ideal
>>>>  housing
>>>> for a Rb with clock GPS and backup power. Some times you can even use
>>>>  part
>>>> of the guts. I even went as far as repackaging my 5062C into a HP case
>>>> of
>>>> that generation, heresy in the eyes of some of you
>>>> Bert Kehren   Miami
>>>>
>>>>
>>>> _______________________________________________
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>>
>>
>>
>> --
>> =====
>> Chris Albertson
>> Redondo Beach, California
>>
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>
>
> --
> "Neither the voice of authority nor the weight of reason and argument are
> as significant as experiment, for thence comes quiet to the mind."
> R. Bacon
> "If you don't know what it is, don't poke it."
> Ghost in the Shell
>
>
> Dr. Don Latham AJ7LL
> Six Mile Systems LLP
> 17850 Six Mile Road
> POB 134
> Huson, MT, 59846
> VOX 406-626-4304
> www.lightningforensics.com
> www.sixmilesystems.com
>
>
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-- 
=====
Chris Albertson
Redondo Beach, California



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