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Entry  Sat Jan 22 19:54:20 2011, Zach, Electronics, GYRO, RFPD box PD_box.pdf
    Reply  Sat Jan 22 21:59:46 2011, Alastair, Electronics, GYRO, RFPD box 
       Reply  Sun Jan 23 12:17:45 2011, Zach, Electronics, GYRO, RFPD box 
          Reply  Mon Jan 24 00:47:54 2011, Koji, Electronics, GYRO, RFPD box 
             Reply  Mon Jan 24 12:06:14 2011, Zach, Electronics, GYRO, RFPD box 
                Reply  Mon Jan 24 12:57:15 2011, rana, Electronics, GYRO, RFPD box 
                   Reply  Mon Jan 24 13:16:01 2011, Zach, Electronics, GYRO, RFPD box 
                      Reply  Wed Jan 26 01:42:44 2011, Zach, Electronics, GYRO, RFPD box 
                         Reply  Fri Jan 28 17:40:28 2011, Zach, Electronics, GYRO, RFPD box PD_box.pdf
Message ID: 1257     Entry time: Mon Jan 24 12:06:14 2011     In reply to: 1256     Reply to this: 1258
Author: Zach 
Type: Electronics 
Category: GYRO 
Subject: RFPD box 

You are right about the side panels in the figure from the manual will actually be the top and bottom panels; I did it this way so that the un-tappable side profiles will not be on the top or bottom (where we will mount the PD to the base). The dimensions will be in a different ratio to what is seen there. If you are facing the PD so that the diode is looking at you, it will be 120 mm wide x 70 mm tall x 42 mm deep, something like an old digital camera.

About the PD not being centered, I did it this was to minimize the size of the box (since the PD is not centered on the PCB). I could move one of the mounting holes to be directly below it, but I guess I imagined that we will---at least eventually---use a solid base instead of a post, so we will be rotating the entire block and then clamping it down with dogclamps or something.

I am of course open to suggestions about this, but I think Rana didn't like the idea of using posts.


I could not get how the PD is mounted to a pedestal.

The PD should not move back and forth by the rotation so that the beam can not be defocussed.
Horizontal translation of the PD by the rotation is barely tolerable if the tilting of the PD by ~20deg makes the translation of the center by several mm.
Otherwise, the PD may escape from the range of the steering mirror everytime when we tilt the diode against the beam.
This naturally limit the distance of the diode surface from the rotation axis to ~10mm.

But the rotation axis should not be too much distant from the center of mass so that the PD can stably stand without a fork.

Considering the density of the optics on the table, a slim, thin, and tall (but not too much tall) PD which is left-right symmetric is the natural choice.

Then, we may need some amount of compromise in the above conditions.

Ed: I opened the PDF and got that the PD is actually skinny and tall. I was a bit confused by the page 5 as the side panels at P.5 is actually the top and bottom plates
as far as I understand. The only improvement I can thing about is that the PD is not at the symmetric location with regard to the mounting hole at the bottom.


Yeah, I was imagining that this would be a box for any such PD. I thought we would order some and have them sitting on the shelf next to the boards. In any case, we could have 4-5 of them made special for the gyro; that sounds like fun.



Maybe we can have a different name than "Generic PD" on the box though.  I only called the files that because the board is designed to be generic until it is stuffed.


 I've used Front Panel Express's design program to build a box for the RFPD. The attached PDF has 4 panels (front, back, top, bottom). The other two sides are fixed-width (42mm) side panels that are made by FPE. I have attached one page of their enclosure design manual so that you can get a rough idea of how it is put together.

The overall dimensions are 120 mm x 70 mm x 42 mm. All panels except for the bottom are 4 mm thick anodized blue, while the bottom is 1 cm thick (for rigidity) with natural finish.

The PCB that Alastair designed and has ordered will mount onto the front face of the box (where the PD will emerge from the bottom of the board), with the voltage regulator contacts mounting to the top of the box.

I am fairly sure that I've done it correctly, but the one thing I am not sure about is the SMA flange mount, which was not built in as a macro so I had to do it myself. In building it I realized that it is not really clear how we will connect the SMP ports on the board (for DC & RF Out) with the BNC and SMA outs on the back of the box. I assume that there are adapters for just this purpose, but we should double-check this before we put out the order.

As it stands now, the total quote (including the panels and hardware but not including the connector flanges which they don't sell) is $172. That seems a bit pricey, but we might be able to trim a little off by changing the design slightly. For example, they charge $10 for each of the panels on which they have to mill the bottom side. They have to do this for the front and back panels so that the edges fit into the side profiles. Presumably, the entire panel is anodized, so we can just have the edges milled out on the front side when we don't have to have anything written on it (like the front panel where the PD sticks through). All I would have to do is reposition the hole for the PD accordingly. Of course, the price goes down slightly if we order 5+.


Click on the picture to open the multi-page PDF.






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