Boxes are overpriced

Hah, Welcome to my world. That's seems like a reasonable price to me... you've now got to get it machined and silk screened.

We make these

~1.5" x 1.5" x 2.5", for about $10 each with the powder coating, but not counting the back panel with text. But we buy several hundred at a time. Before that we were using pomona boxes, (blech)

George H.

Sure, looks nice but not too much detail yet.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net

Don't they all carry plastic cased cell phones? I don't know if it is a stock thing, but plastic is often metal coated on the inside for EMI. Something this small shouldn't have structural problems really. Does it have connectors? A connector is usually fastened to the PCB and not the case on lower end units. Even $100 routers use this method. Students manage to not destroy them.

How do they encase Raspberry Pis in plastic cases? Is everyone just ignoring the EMI issue?

--

Rick C

If you're going to use 0.080" end panels, all you really need is the extrusion and have the end plates custom punched. 0.080" is well within what can be done with sheet metal technology and does not require milling, so you're ok there. However, if you go to 0.125", you might need to mill the end plates, which is expensive.

It's not just the top that has a sliding ground contact. The PCB slides into a slot that also lacks a decent ground. There's not enough clearance for copper finger stock, even if you use a 0.032" thick PCB. The copper/tin PCB to aluminum connection was good for corrosion and RF noise due to electrolytic action. If you anodize or paint the extrusion, you get an unreliable grounding connection.

That's why I suggested the diecast case. You mount the board on the over using PEM nuts, standoffs, or tubular spacers, all of which provide a better ground than a sliding connection. The only gotcha is that the sides have a slight angle. Most people don't notice, but the mating connectors on an ATE (Automatic Test Equipment) fixture will complain. Try to avoid putting connectors on the sides, or mill the connector area perpendicular.

Everyone complains about the ugly looking diecast case. I like to polish them on a buffer, but that doesn't last. So, it's anodize, alodyne, or paint.

You might also consider a two piece extruded cover. That allows easy mounting with standoffs instead of sliding into a slot: It's the wrong size, but I suspect I can find something that can be convinced to fit. The reason you can get two pieces for less than the price of one piece is that extruding a "box" shape is far more difficult than an open "C" shaped extrusion.

Same here. If I can arrange to have all the (right angle) connectors go through one side of the box, I don't have to waste space on the cover for connectors. However, dealing with the slight (mold or casting release) angle of the sides might require milling.

Ok. How much ground clearance to you have on the 120mm edges? Are there any holes near the corners and middle of the PCB that can be used for mounting with standoffs?

Those are PEM nuts. The one in the above link is for 0.090 minimum thickness and will need to be tweaked to match the case thickness. These nuts are designed for sheet metal but can be used on some castings and extrusions, especially for the larger (1/4-20) sizes.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

Aliexpress.com

how about using boxes with "wings"

as an alternative we also have end plates made with an bend to do double duty as both end and "wing"

-Lasse

Interesting company. This item is not too bad with shipping fees of 50% of the purchase price, but that is for slow boat shipping. I was looking at a wall mount version where e-packet shipping is not an option and shipping costs are twice the price of the unit. The shipping costs per unit are still more than half the total price. The cheaper one is a split case so maybe the shipping is driven by the size rather than the weight?

--

Rick C

apparently it depends

-Lasse

The noise floor is a few femtoamps per root hertz, so EMI is an issue for sure. It may or may not be enough to have screws in the four corners of each end plate--we'll see.

They usually aren't bolted to a three-ton optical table with BNC cables all over the floor though. Trust me, it's a real issue--the RG-58 pullout test. ;) I'm using a through-hole, metal cased BNC with bulkhead threads. Those threads are what will hold the board in position, so if the back panel flexes a bit during the torture test, hopefully it won't crack the connector loose.

Probably so.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net

It's the wrong size, but I suspect I can find something that can be

Probably a millimetre on the front edge (where the photodiode goes) and zero on the back, because of the BNC attaching there.

There will be mounting holes near the corners.

These

nuts are designed for sheet metal but can be used on some

My current plan is to mount it on the inside of the box, so that it sits flush and can't easily be pulled out by overtightening. I'll have to see how that looks.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net

Good box, but I see a possible problem. Those are the EXTERNAL case dimensions: External Size: 24*102*120mm 0.93*3.98*4.72inch PCB size (H x W): 120*97.6mm (the web page says 20mm but methinks that's a typo). The 99 x 120 x 25 mm PCB is not going to fit unless you shrink the width from 99mm to 97.6mm or less.

The web page also shows 14.2mm clearance above the component side of the PCB. That's more than enough to clear a right angle BNC which is typically about 7.5mm high.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

On Wed, 11 May 2016 12:31:26 -0400, Phil Hobbs Gave us:

Don't know what you mean.

It has IP67 SMA and SMC connections and hermetically sealed EMI pass thru pins and an O-ring design that would be good down to about 30 meters. The screws were outboard of the protected area and there is a Nomex barrier at the bottom which delivers about 1500V/mil are resistance. It would work in either Aluminum or Delrin or Teflon.

I did not include the cap in the photo, bur it uses socket head cap screws in counterbored holes.

It is about as detailed as it gets. Unless you were talking about your stuff not needing that level.

Not enough room for big mil connectors and Lemo is too expensive and especially so if sealing is needed. It can be attached to a plate for conduction cooling if there are dissipation requisites.

Den onsdag den 11. maj 2016 kl. 19.17.20 UTC+2 skrev Jeff Liebermann:

if you can find an edge launch maybe, a regular right angle is at least double that

-Lasse

The 1/4"-20 PEM nut you specified will need to fit under the PCB where the above drawing shows only 4.7mm clearance. The PEM nut is 0.17" or 4.32mm high, so you're not going to have much clearance. What every you use for the optical bench mount, the PCB will probably need clearance holes for the 1/4" bolts.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

Den onsdag den 11. maj 2016 kl. 19.30.53 UTC+2 skrev Jeff Liebermann:

you'd probably want that anyway, or it'll only be matter of time before someone uses too long screws and plow them through the pbc

-Lasse

Thanks, I thought about those. They'd be okay for an OEM box, but for lab use you really want to be able to bolt the thing to your existing optical setup, which over here is nearly always 1/4-20 bolts on 1-inch centres. I could probably add 6-mm on 25mm centres for metric optical tables, but ISTR hearing that there aren't that many of those even in Europe.

The other approach would be to use an OEM mounting plate and attach it to the box with screws, but that would be on the pricey side.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net

Edge-launch BNCs are all going away, at least from the good quality makers.

The one I'm using is .

I'll have to see if it passes the RG-58 pullout test.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net

I picked one that looks reasonable from Google images: Oops. I just noticed that it's 75 ohms, but that shouldn't matter.

For example, this connector at 18mm height would NOT work: It's not double but still a problem.

Also, finding a right angle BNC that works into the upper GHz areas will take a bit more effort.

More right angle BNC's.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

It's 15.6mm high. It won't fit in the above box, which has only

14.2mm clearance on the component side of the PCB.

Only $349.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558