My contribution to the increasing entropy, and eventual heat death of the universe
Archive for March 2018
The 5517B is a dual frequency zeeman laser produced by HP/Agilent/Keysight for interferometry applications. When you buy it as a kit it often comes with a tripod, but most of the systems that turn up on eBay don’t have this tripod. When I’ve seen the tripods for sale, they’re about 1000USD.
So I 3D printed a really simple jig, you can find the STL files here: lasermount
It’s designed to fit a specific “bowl mount” tripod. This is the one I picked up on eBay: tripod.
Some time ago I picked up a Veeco/Bruker AFM on eBay. The lot only contained the probe microscope itself (similar to that shown to the left). So, the control unit (a 2U box to electronics which contains among other things the high voltage drivers for the Piezo tube etc) was missing. One of the connectors was also damaged (unusable). They use fancy expensive connectors so replacing this one connector would cost about 100USD (the whole used unit was 400USD). For reference a complete new system is somewhere in the region of 200,000USD…
Anyway… I was pulling it apart recently and wanted to post some internal pics of the unit. These instruments are actually pretty simple (though I’ve not pulled apart the optical part just which I think is mostly just a quadrant photodiode…).
Mostly I was interested in how they do the coarse approach, here’s a picture of the complete coarse approach system extracted from the AFM:
The coarse approach uses a Portescap 30:1 geared stepper motor. This appears to be nothing particularly special, though it’s pretty low profile. That’s connected to a coupler. The coupler itself is kind of interesting. It connects the motor (using grub screws) to a adjuster on the Piezo head/stage. The connection to the stage does not use grub screws. This uses a hex/allen type head which just sits loosely in the coupler. I think this means that when the stepper is not engaged there’s less mechanical coupling between these parts. This possibly helps with vibration isolation. I found it interesting anyway, and I’d be curious to know where you can buy these kinds of couples (and the adjuster which the hex end). The adjuster looks to be something like 100TPI, though I didn’t measure it exactly.
The head itself, looks very hand made. You can see the piezotube and the solder connections to this without disassembling the unit. For the coarse approach, there are 3 adjusters. The one that is driver by the stepper (shown above) and two others hand driven (with knobs on) when setting up the instrument you’re supposed to do some manual adjustment before starting the approach to get the head kind of close (and the orientation right).
I’ve not looked closely at the rest of the electronics in the unit. I’d guess there’s nothing super interesting going on. It didn’t look like any of the high voltage drive electronics was present (the Piezo tube needs ~100V drive voltage).
Anyway… a bunch more pictures follow for reference:
My name is Nava Whiteford. I’ve worked for a few sequencing companies. I have equity in a few sequencing companies based on my previous employment (I try to be unbiased in my posts). You can contact me at: new@sgenomics.org
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