Electronics > Projects, Designs, and Technical Stuff

DIY Modular Test Equipment Project

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prasimix:
I'll let you know what Varisom from Portugal could offer. Their initial price for customized solution was really appealing but lately our communication became slow (maybe we should take into account EURO 2016 factor :)

pmc:

--- Quote from: void_error on July 14, 2016, 06:54:01 am ---Initially I wanted to use ribbon cables to connect the modules to the UI, ... but I figured out shortly after ...

--- End quote ---

Ok, stacked packaging was never a driver for the project. Got it.


--- Quote ---... but there will still be the possibility to add more functions which comes with a few small drawbacks like having to use some extra wiring if the board is located  further down the stack requires connections to the front panel ...

--- End quote ---

That's what puzzled me on first reading -- stacking functions behind a flexible UI sounds interesting, but then extra wiring and loss of generality for front panel arrangement sound less interesting.

So, the idea thrown out for your consideration was basically: keep the UI in the front panel of some box and stick the T&M connections out one side of the box, directly off the edge of each module PCB. More modules -> deeper box/longer side behind the same front panel.  (thinking one side to avoid locking in other dimensions/board area)

That said...

Requiring a lot of clearance for that side -- to see, reach and push/twist/pull whatever connector on the 4th card back -- seems like a strike against. Aiming each card's connectors ~45deg toward the front might make side connections more usable. So that side would be, um, louvered. And you could see connectors/jacks/sockets/whatever without clearance for your skull + near point distance alongside the unit. Plausibility requires some design idea for simple construction -- IFF you think the result would be desirable. (have half an idea. or just short wires.)

And...

Out-the-front is still attractive for a single-function assembly like the freq gen arrangement you've modeled. PCB pads arranged for attaching either "vertical" or right-angle connectors (or angle adaptificator) would give the option to build a first/only module either way.

Makes sense?

Just some thoughts. Your ball.

void_error:

--- Quote from: pmc on July 21, 2016, 05:28:16 am ---So, the idea thrown out for your consideration was basically: keep the UI in the front panel of some box and stick the T&M connections out one side of the box, directly off the edge of each module PCB. More modules -> deeper box/longer side behind the same front panel.  (thinking one side to avoid locking in other dimensions/board area)

That said...

Requiring a lot of clearance for that side -- to see, reach and push/twist/pull whatever connector on the 4th card back -- seems like a strike against. Aiming each card's connectors ~45deg toward the front might make side connections more usable. So that side would be, um, louvered. And you could see connectors/jacks/sockets/whatever without clearance for your skull + near point distance alongside the unit. Plausibility requires some design idea for simple construction -- IFF you think the result would be desirable. (have half an idea. or just short wires.)

--- End quote ---
I think I get what you mean.

Say you're looking at the front panel on the Z axis, perpendicular to the plane formed by the X (horizontal) and Y (vertical) axis.
Say you want the connectors on the right side, so you take the connector which would normally be on the X axis (sticking out to the side) and twist it clockwise on the Z axis by 45 degrees.

That would be quite neat but on mechanical side of things there's going to be more work... and wires.

Let me know if I really get it.


--- Quote from: pmc on July 21, 2016, 05:28:16 am ---And...

Out-the-front is still attractive for a single-function assembly like the freq gen arrangement you've modeled. PCB pads arranged for attaching either "vertical" or right-angle connectors (or angle adaptificator) would give the option to build a first/only module either way.

Makes sense?

Just some thoughts. Your ball.

--- End quote ---
The UI can also work as an (expensive) alarm clock or a development board. Some other modules I have in mind are a mains Watt Meter and a Frequency Counter.

If you use right-angle connectors you could use stripboards for board interconnects as all the signal/power connectors are aligned to a 0.1 inch grid - breadboard/protoboard compatibility.

Trying to keep it quite simple, mostly for time reasons. I want to have something done by the end of this year.


--- Quote from: void_error on July 15, 2016, 08:42:34 pm ---80mm tall

--- End quote ---
Different enclosures for different functions. As long as it has an easy to drill front panel.

rollingstone:
Hi, Nice project. Sorry, I didn't followed Your post from the begginning. Just remembered I did once something like this. It was 8 HF generator modules and 8 HF amplifier modules using standardised EUROCARD subracks. What case you going to use for modular design? I used this one : http://lt.farnell.com/schroff/24563-191/subrack-3u-175mm-84hp/dp/1455794
http://www.farnell.com/datasheets/95177.pdf?_ga=1.224072792.2973774.1448267837
Only 40 eur and does it's job. Then you can use plug in units to slide in:
http://www.farnell.com/datasheets/95306.pdf?_ga=1.216596437.2973774.1448267837
or shielded module:
http://lt.farnell.com/schroff/20809-537/card-frame-3u-227mm-10hp/dp/1370403
You just need to drill or to cnc front plate to make holes for indicator LEDS, switches and BNC connectors and stuff like that.
You can make one universal power with many regulated voltages (3.3, 5, +12, -12, 24 volts etc.) as plug in unit for entire rack, and then many other modules that you can plug in and plug out into rack and make it configurable and very universal.
I don't have any photos but it looks something like this:
http://dinrackis.com/euro-card-racks.html
http://mulogic.com/UCF-3HE-rack.html
 (immages from internet).
 

void_error:
You got it a bit wrong, it's not the case that's going to be modular, it's the stuff inside the case.
Those rack-mount frames do look nice but the plug-in units are bloody expensive. I've already decided what kind of enclosures I'm going to use and I won't have anything standardized across all the different bits of test equipment I'm making, the decision to have everything share a common front panel was made mostly because of time available for this project.

As far as progress goes it seems that I've reached that part where I tweak stuff - quite happy with that.

Another change to be made to the UI is replacing the 74HC4094 shift register used for driving the backlight LEDs of the pushbuttons with a 74HC595 as it's also used for multiplexing the Chip Selects and other things on the Waveform Generator speaking of which... the PCB is quite a pain in the a$$ to route, taking longer than expected, and I want the whole assembly to mount into a 100mm tall enclosure - that makes the Waveform Generator board size have a limit of 90mm. There's the option to make the board physically larger at the cost of... well... cost. It'll take some time until I figure out the best compromise although I've got quite a few ideas... stay tuned.

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