Electronics > Projects, Designs, and Technical Stuff
Community Bench Meter
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Thermal Runaway:
@charliex

Every single time my Elektor issue comes through the post, I see the adverts for those development boards and think that it'd be pretty useful to have one around - they do seem quite comprehensive.  But I've never got myself one.  Each time I do a new project, I build a quick and dirty breadboard based dev board to suit the specific purpose.

I should get one of those though, I think.

@thread

I've no previous experience with ARM at all, although in fairness once you get into the realms of C... I guess changing processors is not much of a problem.  I've never tried it, because PIC has always suited my particular needs.

I'll watch this thread with interest.  After all the ideas have been thrashed around, someone (GeekGirl) is going to have to take control of the situation and decide on a specification for the design.  Then organise people to contribute to it.  Without the spec or the organising, nothing will get off the ground so I think it's pretty important. 

Brian
GeekGirl:

--- Quote from: Brian Hoskins on January 30, 2010, 09:46:18 am ---
I'll watch this thread with interest.  After all the ideas have been thrashed around, someone (GeekGirl) is going to have to take control of the situation and decide on a specification for the design.  Then organise people to contribute to it.  Without the spec or the organising, nothing will get off the ground so I think it's pretty important. 

Brian

--- End quote ---

Hi all,

I am watching this thread closely, I was going to do a block diagram, but I am hanging off for a little while more, as there is great discussion going on :) I am going to ask people to nominate areas they would like to help with :) If anyone wants to make up parts of the PCB layout or Schematic, as long as they provide a PDF I can incorporate it into the "master" schematic and PCB (I use ADS09 (Altium Designer Summer 09) and I do not expect other to have this package) then I will publish these back to this thread as both native ADS09 and Pdf :)

I will hope by Monday to have a list of features that have been suggested so far in one POST so we can all follow ;) (Sunday for me is going to be hectic lol)

If the group would like I can also set up a project page on Sourceforge so we can use CVS for tracking hardware, firmware and software revisions :)

Regards,

Kat.
Andrew:

--- Quote from: Brian Hoskins on January 30, 2010, 09:46:18 am ---I should get one of those though, I think.
--- End quote ---

I find them, how should I say, unbalanced. 70 or 100 buttons on a board looks great, but what on earth are they good for on a dev board? Sure, if I think hard enough I can find (artificial?) applications where I would need 70 buttons on a dev board to prototype. But if I keep it real, a prototype application needing 70 buttons warrants a separate keyboard (incl. communication protocol), and even 20 buttons on a board aren't really what one needs on a dev board.

IMHO these boards are made to impress, not to deliver the most value for the developer.


--- Quote ---I'll watch this thread with interest.  After all the ideas have been thrashed around, someone (GeekGirl) is going to have to take control of the situation and decide on a specification for the design.  Then organise people to contribute to it.  Without the spec or the organising, nothing will get off the ground so I think it's pretty important. 
--- End quote ---

I want to add another aspect  to the discussion, more basic and down to earth than just a feature list.

Since this is going to be a bench multimeter it needs an enclosure. I assume that a custom enclosure is out of the questions, so an off-the-shelf enclosure is to be used.

From my experience, when you work with an off-the-shelf enclosure it is unavoidable to settle early on in the project on a particular enclosure, because the enclosure will dictate to a certain amount how things can be build. It will to a large extend dictate the mechanical dimensions of the PCB(s), their mounting, and even partly the separation of functions into different PCBs (e.g. a separate front-panel PCB, a power-supply PCB, etc.)

I actually like the classic bench-top multimeter form factor like in

http://www.home.agilent.com/agilent/product.jspx?cc=DE&lc=ger&nid=-34037.899260&imageindex=3
http://www.bkprecision.com/products/photos/large/2831D_front_lrg.jpg
http://www.fluke.co.uk/comx/show_product.aspx?pid=37725

in particular when they come with the rubber protection (BTW, does someone know who invented that form factor for instruments?)

These enclosures are approx. 300 mm deep (including the rubber), 260 mm wide (including the handle), 110 mm high (including the rubber).

Some time ago I tried to find an affordable off-the-shelf enclosure of the above kind, but I wasn't very successful. Just finding something with the right dimensions was a problem (typically they had the wrong depth / width ratio), most didn't have a handle bar, or they had handle bars which were completely different compared to the ones in the examples (making stacking impossible). And I didn't find a single one with the rubber.

So, if someone knows a reliable source for affordable enclosures of this kind, I'd like to know it. And I would suggest that a particular enclosure is adapted very early for the bench meter.
GeekGirl:
When it comes to the enclosure I am going to suggest that we use Farnell / Newark, this is so that we can all have everything FIT, Front Panel overlays the right size etc.

I think even DigiKey maybe even mouser will have similar sizes and maybe even models.

Regards,

Kat.
EEVblog:

--- Quote from: GeekGirl on January 30, 2010, 11:29:34 am ---When it comes to the enclosure I am going to suggest that we use Farnell / Newark, this is so that we can all have everything FIT, Front Panel overlays the right size etc.

--- End quote ---

When doing a project like this I like to start with the form factor and user interface first and how that's all going to work, and then work backwards to the detailed schematic. Because a schematic does not a project make.

http://www.hammondmfg.com/
http://www.serpac.com/
http://www.polycase.com/
are some of my favorites.

Also, I'd consider a budget too, too high a price and it's going to be a show-stopper, so cost should always be factored in.

I'd probably go with PIC myself for familiarity and simplicity. 32bit ARM power is not needed for such a thing, and the development tools are harder to work with for the average punter.
It's hard to beat the $40 PICkit, MPLAB, and free (limited) C compilers for the PIC combo.
A lot of people say ARM and GNU C is cheap and free, but when it comes down to it the tools are not consistent, and harder for a beginner to use.
But of course that may not really matter if most people just want the finished pre-programmed product.
Heck, I'd even seriously consider jumping on the Arduino bandwagon here. Separating the custom front end board from the processor board entirely. Gives options and lowers the development risk. And it will excite the hacker and makers (don't underestimate that market appeal)

Dave.
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