Coil Heater

30 09 2010

All photos.

The persistent switch on the superconducting magnet needs a computer controlled heater. The heater itself is just a coil of nichrome wire around the YBCO:

With some experimentation I determined that it takes about 300 mA to make the heater warm to the touch.

Now I want to computer control the heater using a digital output on the NI USB 6008. The 6008 will control a higher current transistor (or darlington) and the transistor will control the current to the heater.

Seeing that the NI USB 6008‘s output is either +5V or 0V, my first instinct was to try this:

This failed. FAIL.

I looked at the docs for the NI USB 6008 and I found this:

The default configuration of the NI USB-6008/6009 DIO ports is open collector, allowing 5 V operation, with an onboard 4.7 kΩ pull-up resistor.

So basically the digital output  is either an open circuit or a path to ground. The 4.7 kΩ pull-up resistor brings the output to +5V when it’s ON, but when you ammeter from DO1 to ground you don’t see any current.

However in this configuration you will see a current turn on and off with DO1:

How do we go from a current to a voltage? A resistor!

This schematic represents the working solution:

Here is a video of computer controlled current:

From 2010-09-30


30 09 2010

Just got a quote from a vendor down the street to clean and passivate my vacuum chamber and all conflat fittings: ~$225.00

Currently I would describe my chamber as filthy. Passivating it would restore all vacuum parts to a factory new condition.

Would my ceramic feedthroughs and glass viewports be damaged by the strong acids used in the passivation process? I’m guessing so.

Liquid Nitrogen

28 09 2010

All photos.

Gearing up for another test of the superconducting magnet. So liquid nitrogen.

What is this… Halloween?

Sorensen Manual

28 09 2010

Here is the manual for the Sorensen XT S20 bench power supply:

Unfortunately it does not seem to have information on programming with the J-305 analog interface:


Here is the j-305 pinout:

So far I’ve tried to get the TTL shutdown to work, unsuccessfully.

RGA Progress

27 09 2010

All photos.

I tried the RGA today and finally made some progress. Check this out:

Looks like the RGA works, but it still needs calibration.

Seems we have hydrocarbons and water in the chamber. Where did O2 come from (or is that air)

Wonder what mass 26 and mass 30 and 29 are?

Here is partial pressure over time:

I doubt I’m even using it right. There is a lot to learn.


27 09 2010

All photos.

I’m back from a refreshing vacation. Started by cleaning up my desk:

Stuart gave me this cool old small parts drawer:

I’m going to start by taking another crack at the persistent switch for the superconducting magnet.

Also, if you have been trying to get a hold of me… now is a good time.


19 09 2010

Friday the 10th was my last day at Gucci for the time being.

I’ve been on vacation for the last week. I’m currently visiting family in PA.

My last apartment lease also ended, so I’m looking for a new sublet in NYC before I can return.

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