{"id":3962,"date":"2017-02-20T12:02:48","date_gmt":"2017-02-20T12:02:48","guid":{"rendered":"http:\/\/41j.com\/blog\/?p=3962"},"modified":"2017-02-20T15:24:30","modified_gmt":"2017-02-20T15:24:30","slug":"hp-interferometer-notes","status":"publish","type":"post","link":"https:\/\/41j.com\/blog\/2017\/02\/hp-interferometer-notes\/","title":{"rendered":"HP Interferometer Notes"},"content":{"rendered":"

I’ve been setting up an interferometer. I purchased the system from siliconsam (of Sam’s lasers) on eBay (this is the auction<\/a>). He occasionally sells old HP systems on eBay, the advantage is that the laser, optics and receiver come tested.<\/p>\n

There is however “some assembly required”. In particular, this kit is based around the \u00b5MD1<\/a>. This is essential a Chipkit DP32 (PIC32 dev board), with some firmware Sam and Jan Beck and a Windows application (written in VB).<\/p>\n

The instructions for wiring<\/a> the Chipkit DP32 are pretty straightforward. The only issue I had was that the diagrams only show the resistor color codes, this is a problem for me as I’m colorblind. However there are 6 of one type and two of the other so it was easy enough to figure out from the parts provided. At some point I’d like to design a custom PCB to avoid all the wirewrapping…<\/p>\n

You also have to wire up the optical receiver and laser head cables. Notes on these are below.<\/p>\n

10780A Optical Receiver Wiring<\/h3>\n

The optical receive uses a strange connector. I’ve seen this called a “quad BNC” (also seems to be called 4-pin BNC) and it is a bayonet style connector with 4 internal conductors. Sam’s kit provides cables wired with pins which you prod into the connector, it’s not the most robust solution in the world, but it holds together pretty well.<\/p>\n

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The 10780A documentation provides the following wiring information:<\/p>\n

\"\"<\/a>“Fused +15V RET” is essentially ground. The wiring I used is show below. It can also be found on Sam’s FAQ<\/a>.\"\"<\/a><\/h3>\n

5517B Laser head Wiring<\/h3>\n

The laser head uses an old multiconductor connector. I think this one<\/a>. You can find details of the wiring of this connector in the 5517 manual (5517 manual local copy<\/a>). I’ve also highlighted the wiring of this cable on the screenshot below.<\/p>\n

 <\/p>\n

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That’s it for now. I have a couple of videos on youtube documenting the setup:
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