Thu., May 3rd

Tried to see if I could remotely access my desktop using VNC, so I can help resolve any problems while I'm away.  That didn't work, so I submitted an application for VPN access to EIT.  Hopefully that helps.

Ray and I are planning to run a test of the detector with one battery.  We did that, but it didn't work - we found it has a short between the two conductors.  Emailed Samad to find out where it came from.

Wed., May 2nd

New student is visiting; Ray is talking to her about the project.

I re-mounted the FEDA board to the platform, reinstalled the cooling unit onto it, and reconnected the +5V power to the FEDAM, and the +12V power to the fan, and reconnected the 3 detector cables and the timing-sync cable to the newly-soldered SMA jacks in our preferred arrangement.  Getting ready to show Ray the startup sequence...

The FEDAM's Wi-Fi (Node #1) seems to be having trouble getting enough power through the FEDAM board; possibly this is because the hand-made connector through the gender bender keeps coming loose.  I made a new power connection for it directly from Samad's board.  That works, but some day we need to make a more robust connector.

Went through the startup sequence and data format with Ray.  Need to write up a little document on the startup sequence and data format.  OK, did that; created "COSMICi User Manual" document on docs.neutralino.org and shared it with Ray.

Tue., May 1st

Samad dropped off the batteries; I just need to figure out how these barrel-plug connectors on them are supposed to be used; [x] look that up. - Couldn't find one, and Samad said he couldn't either.  My main question is whether the first battery's output can be plugged into the second battery's charging input as a way of effectively connecting both batteries together in parallel.  If the first battery's level fell below the second's, the second would spill charge over into the first and fill it up to the point where they're equal again; amirite?

Also need to revise the PCB design for the new OCXO board.  OK, did that, and uploaded the new CAM files.  Order is ready to submit to Sunstone now.  Here's a layout image:

Layout of the new breakout board for the OCXO module.  Decreased line width on
output trace from 50 mils to 20 mils to minimize parasitic capacitance on this signal node.
Also added dimensions, a board descriptor, & added my initials to the vanity tag.

Other things to possibly do today:

• [/] Solder down SMA connectors on FEDM board.
• [/] Drill holes in platform for fastening down power cables.
• [ ] Use circular saw to make a larger hole to run cables through - maybe do some more planning first though.
• [ ] Make sure Ray understands the startup sequence. - He left for the day before we had time for this - we can do it tomorrow though.

OK, I soldered the connectors:

Right-angle SMA connectors soldered onto the appropriate pads of the FEDA module.
Slight discoloration around the pads is leftover cleaning fluid which I used to wash off the
excess solder flux.  If I knew where our can of air was, I would try drying it more quickly...

The FEDA (Front-End Data Acquisition) board needs to be re-tested, although perhaps I should wait for the cleaning fluid to dry completely first.  Idea:  Lay it on my household cooling fan (pointed straight up).

My little personal cooling fan doubles as an electronics dryer.

If I can get it looking dry before it's time for me to go today, I will reinstall it on the main platform and try running a system test.

Meanwhile, I drilled holes in the main platform to allow me to fasten down the ATX cable with cable ties (as opposed to the earlier electrical tape, which looked messy and was pulling away):

New ATX power cable arrangement.  Appropriately-sized holes were drilled in the main
platform at appropriate locations to allow me to pass large cable ties through the platform
which allows the ATX cable to be held down securely in a compact configuration.

The FEDA board is still not quite dry, so I don't think I'm going to be able to reassemble and retest the whole system today.  Guess I'll leave it drying overnight...

Meanwhile, did one more little thing:  Found some new top washers to hold down the cooling system bracket, to replace the larger ones that the guys had to cut down earlier (presumably to help them install/remove the cooling system around the board more easily).

New smaller washer to go under bolt head;
compare to the larger one which stuck out too
far and had to be cut back.  We'll still use the
large ones on the back side of the board, though.

Foo

Fri., Apr. 27th

Did two things today:

1. Installed thermometer/hygrometer on the silver quarter-circle next to the kiosk, where the electronics platform will go, using double-sided tape; I will leave it there for several weeks (until I get back from China probably), to measure the maximum temperature & maximum relative humidity over this period.  I asked Reed to remove it and check the values if he notices the display going dim, since this would probably indicate the battery is dying.  I don't know if it will really last the 7 weeks until I get back.  

2.  Went up on roof, and took a photo of the air vent we will use to feed the GPS antenna cable into the building:

Air vent on the roof of CLC that we will use to feed the GPS antenna cable into the building.
We will ground the lightning surge protector to the grounding cables seen here.  

3.  Also, while on roof, measured the slope of the roof near the center point using the iCarpenter app on my iPhone.  Actually, the CLC staffer who let me up onto the roof was nice enough to do the measurement for me, following my instructions (climbing up on the planetarium roof would be tricky for one who warps space and time as strongly as I do).  He measured the slope at two points near the lightning rod at the center of the roof; one measurement was slightly below 9 degrees and the other was slightly above, so we'll say 9 degrees is the slope of the roof.  I'd guess that's probably accurate to within +/- 1 degree.  Close enough for government work.  Below is a close-up of the area near the lightning rod where he did the measurements.  You can't see much from this angle, but you get the idea...

Lightning rod at center of planetarium roof.
I'm currently thinking of placing the GPS antenna
somewhere nearby.

Note to self:   Before we actually place the order for the new OCXO board, it would probably be a good idea to change the width of the CLK_OUT trace from 50 mils to something like 10-20, to reduce parasitic capacitances, which otherwise might smear out our rise time a bit.

Thu., Apr. 26th

Coordinating w. Reed via email re: plans for mounting GPS antenna on rooftop.  We need to know roof slope and roofing material to design an appropriate attachment for a pole on which to attach an antenna like that Spectracom one I've been looking at (the ANT-35).  We can probably fabricate the pole/roof-mount assembly at the College machine shop.

The ME students installed the detector shelves and emailed photos of them, below.  They probably still need to be painted to match the walls or another thematic color of the exhibit hall interior, but that is relatively easy - I'll coordinate with Reed on that.

Southwest detector shelf.  Above exit sign near rest rooms in main exhibit hall at CLC.

Southeast detector shelf.  Above double doors leading into large classroom off main exhibit hall, next to LEM module model at Duval St. entrance.

Northern detector shelf.  Under awning next to display kiosk.  Just across from entrance to planetarium.

David and I created the CAM files for the new OCXO board design, and generated the quote through SunStone.  Ray said he'll pay for the boards to be ordered.

New OCXO board layout - about to be taped out to SunStone. 

Before I lose the piece of paper, here are the notes on which detector/cable currently connect to which SMA ports on the FEDA board.  This configuration leads to event rates on the three channels that are relatively more equitable with each other than in other configurations.

• Case #2 - Cable #2     - PMT #1 - Input channel #0
• Case #3 - Cable #3     - PMT #2 - Input channel #1
• Case #1 - Cable #1     - PMT #4 - Input channel #2
•                           NC    - PMT #3 - (Input disabled)
• DE3/CTU CLK_OUT - TimingSig - Timing sync datapath

Wed., Apr. 25th

Today I brought the new hygrometer and the tape measure and went over to the Challenger Center.

Spoke with Reed about the detector arrangement.  Michelle Personette expressed a preference that the detectors be placed out in the exhibit area for easier public viewing.  Some good spots seem to be:  

1. Hanging from I-beam above double doors leading into big classroom.
2. Hanging from I-beam above exit sign near the rest rooms.
3. Inside awning above blank circle quadrant beside kiosk (near entrance to planetarium).  A notch may have to be cut out of the edge of the shelf to prevent overlap with awning support.

Using my tape measure, Reed and I confirmed that #1 and #2 are very close to 30' apart, and #1 and #3 are very close to 30' apart.  (We didn't measure #2 to #3, but eyeballing, it looks pretty close.)

The ME students (George & Brian) went to get more mounting hardware, hopefully they will come back later this afternoon and do the install of the detector shelves at least, at the locations we discussed with Reed.  Reed says he is staying pretty late tonight (8:30 or so).

We discussed mounting the main electronics platform sideways on the blank circle quadrant next to the kiosk.  This will allow for much easier public viewing.  However, this will require new planning as to exactly how it will be mounted.  Also, I doubt that the copper cooling rod would be stable in that configuration - the thermal paste probably isn't strong enough by itself to keep it from falling.  This location for the electronics platform will probably also necessitate buying new, longer coaxial cables to feed to the three detectors, due to the paths along which some of the cables will have to be routed.  (This will cut our sensitivity slightly due to cable attenuation.)

Regarding the GPS antenna cable:  After considering a couple of possible paths, a consensus emerged that the easiest, shortest, and least-likely-to-run-afoul-of-building-codes solution was the following:  

• GPS antenna on roof of planetarium (perhaps at center for easy cross-referencing to building blueprints), with a lightning protection device connected to the grounding cables strung along the roof.  (See Spectracom's technical note on lightning surge protection.)
• Antenna cable enters building through unused exhaust vent on roof of planetarium.  Protection device is installed where cable enters vent; ground runs from there to building's grounding cable which goes nearby.  See picture below.  (Damn, I should have taken iPhone photos while we were up there!  Go back tomorrow...)

• Antenna cable goes into crawl space/attic space above planetarium, and then down through area between walls, coming out ceiling tiles just inside the planetarium interest, then going over to the main electronics platform mounted there on that quarter-circle.

The length of the antenna cable in this configuration would be fairly short; perhaps even short enough that we wouldn't need a repeater, or at most just one repeater.

Let's do a calculation.  Suppose our total antenna cable length is 100'.  If we use RG213 (KX4) cable, that attenuates at 0.35 dB/m, so total cable attenuation would be 35.5 dB, including a 0.5 dB connector, plus another 1 dB for the Lightning Protection device gives 36.5 dB total attenuation.  This could be mostly compensated for by a high-gain antenna, e.g., SpectraCom's ANT-35 is +35 dB.

Interesting; Spectracom provides an OEM module that integrates a GPS receiver and an OCXO.  This might have simplified our CTU design a bit.  However, they only claim 25 ns accuracy, which isn't an enormous improvement over the 68 ns of the DeLorme board.  We might do better with averaging.

Regarding the dewpoint measurement:  I took a measurement near the kiosk, and got temp = 22.4 C, rel. humidity 48%, which imply dewpoint = 11 C - same as I got at home last night.  However, Reed warned that there could be significant seasonal fluctuations in temperature, and humidity might vary when people are coming in & out.

The hygrometer actually has a "MIN/MAX" feature to take minimum/maximum readings over an extended period; I could place the hygrometer at the approximate location of the electronics board and leave it there for a while; the maximum temperature/humidity values could then be used to calculate an upper bound on the dewpoint over that period.  I just need a little double-sided sticky-tape thingy to affix the hygrometer to the quarter-circle about where the electronics board will be.

Tue., Apr. 24th

I want to spend some time today trying to prioritize a list of things to accomplish before I leave for China.  I'm leaving May 4th, so that gives me 8 work days between now and then (including today) to get stuff done.  Here are some work items I can think of:

1. Ray requests an operating manual.  That should not take very long.  However, I want to do it last, so it can reflect the most up-to-date state of things.
2. I would like to do at least one example of a module that actually provides interactive real-time graphs of some meaningful data - e.g. the discrepancies between the intervals between subsequent PPS pulses and the nominal second defined by the OCXO reference (10M OCXO cycles, or 750M PLL cycles).  That way, if someone wants to pick up from there, and do some more graphs, they will have a model to use as a starting point.
3. Figure out the configuration of the GPS antenna cable and order the components we need for that, and work with Reed Lambdin to plan out the route that the cable will take.  First step:  Try to figure out how much attenuation the GPS module can tolerate while still receiving satellites.
4. Someone (not necessarily me) needs to solder the SMA connectors to the FEDM at some point before it is physically installed at CLC.  The FEDM should be re-tested afterwards.
5. Someone (not necessarily me) needs to go through the Quartus design that Juan and Michael Dean were working on, and identify whether it really implements the same logic as the previous version of the high-speed components - it seems to me that it can't, or else the Fmax would be the same.  One thing:  The XORs can be moved out; although that shouldn't really affect it.  We should also go through the compilation settings side-by-side and compare them with the baseline project (the one on Q:\).  Darryl expressed some interest in helping with them.
6. At some point, someone (not necessarily me) should figure out what is a reasonable voltage level to operate the thermoelectric plate at, and we should rig up a power supply for it.  Goal:  Keep FPGA package surface close to (but not below) the maximum indoor dew point in the classroom.  According to Wikipedia, a dewpoint of 13-16 C is "comfortable."  So 16 C might be a good guess.  But to be safe, we should probably measure the actual dewpoint in the classroom.  The dewpoint can be calculated from the temperature and relative humidity.  Cheap hand-held digital meters capable of measuring this information can be purchased at outdoor/sporting goods stores.  Maybe I'll pick one up on my way home.
7. At some point before we install, someone (not necessarily me) should fasten down more of the loose cables/connectors on the electronics platform.  Some of this has to wait until the SMA connectors are soldered.  The power cable needs holes drilled thru the board to run a heavy-duty cable tie through.
8. At some point, someone (not necessarily me) should cut the ventilation hole(s) and wiring hole(s) in the plastic enclosure.  Alternatively, someone also suggested that holes could be drilled in the platform for routing some (or all) of the cables - this might provide a neater look.  I think a circular saw hole (about 1" diameter) near the center of the platform would provide relatively easy access for all of the cables we'll need.  Here's a list of all these:
   • Main AC power cord for the ATX supply.  (This is the only power input, assuming here that we can also power the thermoelectric cooler through Samad's board.)
   • GPS antenna cable, snaking in from some long pathway coming down from the rooftop.
   • Bundle of 3 coax cables and 3 power cables (speaker wire), these to split out in pairs (one coax cable +  one speaker cable) to enter 3 conduits fanning out to the 3 detectors.
9. At some point soon, someone (not necessarily me) should construct the power cables for running the 12V power to the detectors.  Ray got the barrel connectors, so they just need to be soldered to one end of the speaker wire (cut to ~40' lengths), and for the other end, we still need to rig up some kind of connection for plugging into Samad's board.  Maybe yellow (+12V) and green (GND) jumper wires?  -  OK, I went ahead and pulled out three yellow/green pairs from the power supply board, each to a 2-pin male header - one end of the speaker wire can be soldered to this.  On the speaker cables, let's use white = +12V, copper (clear) = ground.
10. The new OCXO board (designed by David & Samad last week) needs to be "taped out" to CAM files (show David/Samad how to do this), and submitted to Sunstone for fabrication.  We have solder paste and a hot-air gun which should be suitable for the soldering the SMT OCXO parts, which are on order.  We have the other parts needed (male 2-pin header, and right-angle SMA connector) so we should be able to complete assembly as soon as the fabbed boards and the OCXO get in.
11. Empirically (using waveform generator and scope) measure signal propagation delays down the 3 main coaxial cables we're using.  This is important for reducing systematic error in our measurements of the relative arrival times of pulses at the 3 detectors, and also for reducing systematic error in our measurements of the absolute arrival times of pulses (i.e., arrival times relative to the GPS reference).  This should be easy, I have everything I need for it - signal generator, scope, and coax splitter.  Oops, no, correction:  I really first need an SMA-to-BNC adapter of the right type.  (SMA female to BNC male.)  The one we have is the other type.  [ ] Look for this at Radio Shack.

The "La Crosse Technology
Indoor Comfort Level Station"

I went out shopping for a hygrometer.  After striking out at Kevin's and Trail and Ski, at Lowe's I found a nice little digital combination thermometer/hygrometer for $20.  Tried it at home just now; got a temperature of 24.3 C (75.74 F) and a relative humidity of 44%.  Found a little iPhone app called DewPoint that calculates the dew point temperature from this data - it says the dew point is 11 C.

Let's try checking this figure against the approximate dew point formula on Wikipedia:  http://en.wikipedia.org/wiki/Dew_point#Calculating_the_dew_point.  Made a spreadsheet Dewpoint.ods (in my FAMU/COSMICi Dropbox) to perform that calculation.  Using the same inputs, it gives 11.256 degrees Celsius, suggesting that the little iPhone app and the Wikipedia formula are both reasonably accurate, or at least about equally inaccurate.  :)  Probably the app is rounding.

OK, now I  just need to bring this little measurement box into CLC, hold it up near the ceiling where the electronics platform will be, run the calculation in the app, and then we will have a baseline estimate for what the "typical" dewpoint at that location may be.  To get a clear idea of the maximum dewpoint, we'd probably need to take a lot more measurements at all different times of day/night, different seasons, different outdoor weather conditions (humidity, etc.).  This is a prohibitive amount of work (unless we set up some kind of automated data collection, which also is a lot of work), so instead, we should probably just take a few measurements and add a slop factor (safety margin).  Anyway, one would hope that the building's climate control system normally succeeds at keeping the humidity at a reasonably low level.  Not necessarily a very good assumption, but perhaps a reasonable starting point.