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Inheco Control 96 + CPAC Ultraflat Notes (TEC/Peltier)

June 19, 2018, 5:08 am

I picked up this Peltier system on eBay a while back. I guess it’s for heating eppendorfs as part of some larger system.  The device is an example of the sub-contractors/assemblies all the way down mentality  you see in so much industrial equipment. The control unit uses a Watlow 96 PID controller, and a Watlow LSTW driver, which they’ve put in an INHECO branded chassis.

When I received it the controller seemed to be misconfigured. The TEC wouldn’t heat, and could not be set beyond 50C. Datasheets for the CPAC Ultraflat state that it should be able to go to 70C. So I needed to do some fiddling to figure out what exactly was going on.

The LSTW driver doesn’t seem to be documented anywhere on the web, I couldn’t find anything similar on the Watlow website either, so it’s possibly some kind of custom OEM module they have… However, as far as I can tell it’s just an H-bridge taking a 12v input.

It’s controlled by two pairs of inputs from the PID controller, one sets the output positive, the other negative. So from what I can tell it’s using purely digital control.

Looking at the PID controller itself, output 1 and 2 are wired up. As is the RTD temperature sensor:

The Watlow control interface is a bit of a pain, but it’s functional enough once you know what’s going on, and I configured inputs/outputs as follow:

Sensor: Wired for 2 wire RTD 100Ohm Platinium.

Outputs 1 and 2 on, switched DC open collector output.

Output 1 set to control heating.

Output 2 set to control cooling.

I also set the control limits to +/- 100C. I’ve pushed it to 90C and it seems to work, though it takes a while to get up to temperature. Not sure what effect running it out of spec will have. Quick thermal image with a FLIR one below. When I can find my temperature probes I’ll probably try and do some more tests… That’s it for the moment, more pics below.

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5517B Laser Tripod Mount

March 20, 2018, 5:54 am


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.

 

 

 

 

 

 

 

 

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Veeco/Bruker AFM (nanosope) head teardown pics

March 19, 2018, 2:51 am

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:

 

 

 

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uMD1 – ChipKIT 32 – HP Interferometer Interface

April 4, 2017, 7:20 pm

I’ve put together a simple interface for use with Sam’s and Jan’s HP Interferometer code for the ChipKIT 32. It’s really just a layout of the design listed on their site, however avoids some wire-wrapping. You can find the Kicad files and gerbers on github.

I decided to use all through-hole components to make it easy to assemble. In a future revision I might move to SMD, the mounting points need re-positioning. I’d also like to try laying out the PIC32 on the same board. The board however works well for me, and it depends if I get any interest in developing it further. If you’d like one let me know and I’ll put it in my shop.

The board I’ve designed routes power traces to terminal blocks to which the receiver and laser head are attached. This helps simplify wiring.

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