Gas station without pumps

2017 September 6

Wilder Ranch

Filed under: Uncategorized — gasstationwithoutpumps @ 11:27
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Yesterday, my son and I took a bike ride through Wilder Ranch State Park and UCSC.  We had a fun, though somewhat warm ride.  The weather was unseasonably hot over Labor Day weekend, hitting an all-time high for Santa Cruz of 108°F.  We were promised cooler weather on Tuesday, but the temperature was well over 80°F at noon.  We waited until 1:30, when the temperature finally dropped below 80°F before leaving the house.

We headed out on the paved bike path to Wilder Ranch, up Engelman’s Loop  and Long Meadow Trail to the Chinquapin Trailhead, then across Empire Grade to UCSC property, down past the Painted Barrels (there are actually two sets of barrels—Google doesn’t map the more northerly set, which were just after we entered the woods again from Marshall Field).  On the way down from campus, we stopped at the overlook above Pogonip Park and at the UCSC farm stand, where I bought some apples, cauliflower, and flowers.  The farm stand seems to have less produce this year than in previous years—I don’t know whether this is because the farm is producing fewer varieties or that they have better marketing outlets elsewhere.

Because we were doing the ride mid-week, we saw only a few other bike riders—maybe 5 or 6 on the paved path out to Wilder Ranch, one couple on the trails in the park, a pack of middle schoolers with adult guides on the UCSC trails, and a few bike commuters on the UCSC roads.  I suspect that the Wilder Ranch trails are more populated on weekends.

A map of our route. It was 13 miles (21 km) with 1178 feet (360m) of climbing.

I used Google Maps to make a route map of the route we took, which was harder than I expected.  At first I just dragged around intermediate points using Google directions, but Google kept throwing out the route.  Then my son pointed out that I could use the “+” button in directions to grow the route incrementally, though that required  couple of tries to work also, as there is a small limit on the number of points you can add, so I had to be very choosy about which points I added.

The weather was really a bit too warm for strenuous exercise, but we had cloud cover for much of the ride, so it wasn’t as bad as it could have been (certainly not as bad as last weekend would have been).  Today might have been a better choice, as the hot weather seems to have ended and we’re back to more normal temperature swings.

Neither of us have mountain bikes—my son rides a commuter bike with narrow road tires, and I have my Vanguard long-wheelbase recumbent.  The loose gravel, deep dust, and ruts of the trails in Wilder Ranch were a little difficult for us to handle, though mountain-bike enthusiasts would have found them tame.  I had to get off and walk my bike on a few steep hills, because I fell below my minimum balance speed and couldn’t start again on the loose gravel.  I only fell once—trying to get out of a rut on a steep uphill and falling below minimum balance speed.

It would have been good to do more bike riding this summer with my son—he’s headed back to UCSB in just over 2 weeks, and we’re making a trip to Boulder to see my Dad next week, so I doubt that we’ll have time to schedule another bike ride.

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2017 August 26

Review of cheap buck regulators

Filed under: Robotics,Uncategorized — gasstationwithoutpumps @ 14:15
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I recently bought some very cheap buck regulators from Ali Express:

https://www.aliexpress.com/item/MP1584EN-ultra-small-DC-DC-3A-power-step-down-adjustable-module-Buck-Converter-24V-turn-12v/32382698190.html

At only 44¢ each with claimed specs

Input voltage: 4.5V-28V
Output voltage: 0.8V-20V
Output Current: 3A (maximum)
Conversion efficiency: 96% (maximum)
Output ripple: <30mV
Switching Frequency: 1.4MHz (highest), typical 1MHz
Operating temperature: -45 to +85 degrees Celsius
Dimensions: 22mm * 17mm * 4mm

they seemed too good to pass up.  The data sheet for the MP 1584EN chip seemed to justify the claims, so I bought three of them to try out.

I’ve done a little testing with a 12V input and the output set to 6.08V, and they seem not to work as specified:
DC RMS voltage [V] DC RMS current [mA] Peak-to-peak ripple [mV] ripple freq [kHz]
6.091  0 15.09 6.29
6.098  1.9  69.1  34.0
6.084  16  70.1 65
6.077  194  75.8  930.4
6.072  376  104 929.1
6.072  568  122.8  929.7
6.163 1309 2266 168.1
6.084  2131  1576  230.3

The regulation to an average voltage is fine, but the ripple is enormous! Adding a capacitor (470µF aluminum polymer) helps at higher currents, but not much, and hurts at the 0.3–0.6A level:

DC RMS voltage [V] DC RMS current [mA] Peak-to-peak ripple [mV] ripple freq [kHz]
6.090  0  7 0.0396
6.090  1.9  28.2  35.5
6.090  15.8  18.4  3.6
6.077  194  75.5  930.3
6.078  375  310.3  465.2
6.083  568  630.6  465.8
6.091  1246  910  464.9
6.088  2112  1028  461.4
A 1µF ceramic (instead of a 470µF electrolytic) actually helps more at the higher currents, possibly because the electrolytic capacitor is too slow to respond (large equivalent series resistance and lead inductance).
DC RMS voltage [V] DC RMS current [mA] Peak-to-peak ripple [mV] ripple freq [kHz]
6.090  0  11.4 7.8
6.090 2.2  59  30.7
6.090  16.7  62  62
6.077  194  82  930.3
6.077  376  123  929.3
6.071  577  137  929.6
6.075  1297  189  928.0
6.088  2155  636  305.4

Still the regulator is way out of spec for ripple pretty much across the board.

The only explanation I’ve come up with for this way-out-of-spec behavior is that the manufacturers may have used a very cheap inductor which saturates at a much lower current than the 3A this regulator is supposed to provide.  A 150mA 10µH inductor costs about 3¢, while a 3.2A one costs about 17¢ (in 1000s)—on a 44¢ device, that’s a big difference in cost!  (In single-unit quantities, the price is more like 50¢ each for a beefy enough inductor.)

The inductor is not labeled, so determining what it is would require removing it from the board and soldering on some test leads.  That might be worth doing, especially if I could find a decent inductor of the same size (both physically and in terms of inductance) to replace it with.  If a 50¢ part fixes the boards, they might still be worthwhile, as adequately beefy DC-DC converters from reputable companies cost $10 or more, and designing and building my own board would cost a lot more than just replacing the inductor.

2017 August 25

Door locks replaced

Filed under: Uncategorized — gasstationwithoutpumps @ 22:19
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Today was my day for repairing things.  Not only did I fix the oven (see Oven repair headache), but I replaced the deadbolts on the front and back doors, plus the lever set for the back door.

A week or two ago, the deadbolt on the back door started feeling funny—it still functioned, but the key and the thumbturn seemed loose.  I opened it up and noticed that a metal spring had broken—this spring normally sits against flat spots in the shaft, giving the lock its bistable characteristic.  Without the spring the lock easily slid from one end to the other, without clicking into the “open” and “locked” positions.

The brand of deadbolt that we had no longer seems to exist (at least, the only example I found on the web was a used one on eBay), so I decided to upgrade to new Schlage locks.  Because the front and back deadbolts are keyed the same, I needed to replace the front deadbolt at the same time.  My wife also requested that the door knob on the back door be replaced to be the same finish as the new deadbolt on the door.  She wanted satin nickel for the back door and antique brass for the front door.

I ordered the locks from handlesets.com, who had decent pricing.  When the order arrived, I realized that I had made a mistake in the entry of the order, and ordered a satin chrome deadbolt instead of a satin nickel one.  The lever set for the door was satin nickel, and did look better.

So I had to call their customer support to find out how to rectify the mistake.  They needed to know the number stamped on the key, so that they could send me a properly keyed replacement lock, and they sent me email to print a UPS return label, promising to credit my credit card when they got the lock back.  A few days later the replacement lock arrived, properly keyed and in the right finish.

Putting the deadbolts into the doors was fairly straightforward, as the backset and drill sizes he been fairly standardized for a while (the doors on the house are at least 30 years old, and probably more like 50 years old).  The holes in the edge of the door were just a tiny bit tight, so I used a round file to open them up just enough to squeeze in the new deadbolts.

The lever set was a bit more of a problem—putting it into the door was no problem, easier even than the deadbolts, but the strike plate was smaller than the old strike plate on the door jamb.  The bottom screw needed to be in the same place as for the old strike plate, but the top screw would have gone into empty space where the larger old strike plate had had an opening.

To fix the problem I used a razor saw to cut a tiny piece of pine (1″×½”×⅝”) and glued it into the hole with Gorilla wood glue.  I’ll have to wait a day for the glue to dry, then shave a little off the block to make the strike plate fit perfectly.  I’ll probably also prime and paint the bit of wood so that it doesn’t stand out, though the whole door and jamb really need painting.

Oven repair headache

Filed under: Uncategorized — gasstationwithoutpumps @ 21:46
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Our gas oven (LG brand model LRG3093SW) stopped working a week or two ago—it wouldn’t light any more.  It had been flakey for a while, but it had finally failed completely.  I suspected that the problem was that the oven igniter had failed, for two reasons:

  • It is the most failure-prone part on gas ovens.
  • We had had the igniter replaced once before in a similar situation (on the same stove).

I first went through the trouble-shooting instructions in the manual, which are a very short list of things to check (like whether the stove is plugged in and the gas turned on), ending with calling a professional.  Under “Oven Control beeps and displays any F code error”  subpart “You have ‘F11′” (the code it displayed), it suggests checking the oven gas shutoff valve (and cross-references “Surface burners light but oven burner does not”).

I decided to check the oven gas shutoff valve first, before checking the igniter.  The manual shows where the valve is located, but the drawing is so poor that it is not possible to make out what it is supposed to look like.  “PULL TO OPEN” is not very informative.  I ended up looking at oven gas shutoff valves on the web, and realized that the “lever” was a sheet-metal cam that pulled the valve open.  I toggled the lever and made sure I left it with the gas valve open, but this did not restore function.

I then looked at videos online for testing and replacing the igniter.  The videos by RepairClinic are pretty good, even if their parts price is among the highest on the web.

I disassembled the oven (taking off the door, removing the bottom plate of the oven, removing the heat diffuser over the burner) and checked whether the igniter glowed when the oven was set to turn on—it didn’t.  So my next step was to turn off the power to the stove to take out the igniter.

Unfortunately, the outlet for the stove is inaccessible (behind the stove, under the counter), so I needed to turn it off at the breaker box.  The stove outlet is not on the indoor breaker box, so I had to use the breaker in the outdoor box.  That turned out to be more effort than I expected, because the contractor who installed my solar panels 2 years ago had painted the box to match the house.  Unfortunately, he had painted the box shut, and I couldn’t slide the front down to swing it open.  I had to chip out the paint in several places with a knife, then tap the panel with a hammer and a solid screwdriver, before the paint seal was broken.

Having opened the box and figured out which of the unlabeled breakers was the stove, I turned off the stove to test the igniter. (I labeled that breaker when I was done.)  I didn’t bother removing the igniter, just made the wires to it accessible and tested for continuity with an ohmmeter.  The igniter was definitely broken, showing an open circuit.

I cleaned the pieces and put the oven back together (having a little trouble getting the door back on, until I watched the video again and realized that I was missing the step of opening the door completely after re-inserting it).

So I spent a little time on-line looking for a decent price for the igniter.  I found prices from $20 (on eBay for a generic igniter that looked like the one that had just failed) to $125 for ones that claimed to be OEM (original equipment manufacturer). I finally chose to go with a mid-priced option: $68 from Sears Parts Direct which claimed to be manufacturer-approved (though not necessarily OEM).  I believe we had bought the stove originally at Sears, so it was not too surprising that they stocked parts for it.

The new igniter arrived today, so after supper I decided to replace the broken one.  Because I had recent disassembled the oven, I figured that there would be no trouble—it would be a quick job. Ha!

It did go smoothly at first.  Oven door off, racks out, bottom panel removed, heat diffuser removed, igniter cable detached (and screwdriver inserted to keep connector from falling back into the oven out of reach), first screw holding the igniter removed, and then frustration. No matter how much I turned the second screw (the back one that was harder to reach), it would not come out.  It turned, but did not back out of the hole.  I enlisted my son’s aid—he had no more luck than me. (He did help me find the one screw that I had gotten out—it had wandered half a room away.)

Eventually, I decided to take out the whole burner assembly (it is only held by two easily removed screws), so I could get better access to the screw.  This didn’t help much. Eventually I tried pushing on the tip of the screw, while turning the screw head with a phillips screwdriver bit in a socket-wrench handle.  I got the screw about halfway out when the head broke off.  So I grabbed what was left of the screw with visegrips and managed to unscrew it the rest of the way.

I now had the broken generic igniter off the burner assembly, but I was short one screw for reassembling everything.  The screw needed appears to be a coarsely threaded self-tapping sheet metal screw, probably #8.  I looked through all my boxes, jars, bags, and piles of screws and finally found one that looked like it might work (I’ve no idea what it was left over from).  It wasn’t self tapping, but the threads seemed to be the same size as the remaining screw.

I cleaned out the hole where the stuck screw had been by screwing and unscrewing the self-tapping screw that remained a few times.  After that, my newly found screw worked in the hole with no problems.  I then attached the igniter to the burner assembly, replaced the burner assembly, turned on the power, and checked to see with the new igniter glowed.  It did! and the stove lit!

I turned off the stove, replaced the heat diffuser, the bottom plate, the oven racks, and the door.  There were no problems with the reassembly this time.  I checked the stove once more, and it ignited fine.  I ran the oven at 350°F for about half an hour to drive out any residual fumes from packing materials or whatever—there was some smell, so there probably was something that needed to be burned off.

The repair took me about three times longer than I had expected, and the unremovable screw was pretty frustrating, but I’m pleased now that I got it fixed. And that my outdoor breaker box is now accessible in an emergency.

 

 

2017 August 21

UC salary numbers

Filed under: Uncategorized — gasstationwithoutpumps @ 13:12
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UC posts their entire payroll (redacting names for student jobs) each year.  The 2016 numbers can now be found at https://ucannualwage.ucop.edu/wage/

I was curious about several things: who were the most highly paid at UCSC, how much coaches were paid (the top four payments systemwide were UCB and UCLA coaches), and how my pay corresponds to my colleagues.

Most highly paid

UCSC had 87 people paid $200,000 or more in 2016.  The most highly paid was Chancellor Blumenthal at $396,866 (though I don’t think tat includes the value of his housing and other perks). There were about 24 administrators in this group, though many of them are technically also faculty, even if they aren’t currently teaching.  All five of those who make over $300,000 are faculty, though only one of the five (Lederman) is listed as a professor, rather than by an administrative title.

A surprising number of those paid over $200,000 were astronomers—they get paid more than I expected.  The highest-paid faculty who are not also listed as administrators are Lederman, Madau, and Lin (all physics, astrophysics, or astronomy).

Although I think that a few of those making over $200,000 are overpaid, the numbers are not ridiculous (unlike the millions spent for some of the employees at UCB and UCLA).

Coaches

There are 671 employees across all campuses with “coach” in their title, with payments ranging from $125 to $3,577,299.  UCSC has 45 of them, but the pay range is only $1,708 to $74,902.  This does not count the 4 “ath trainer” positions at UCSC ($9,736–$43,447).

Coaches are not being paid generously at UCSC, so though I still think it unwise for students to be paying fees for supporting intercollegiate athletes (rather than physical education and recreation, which all can participate in), the coaches are not getting rich off the students (unlike UCB and UCLA, where 53 of the top-paid 60 UC coaches work).  If we add in the “ath mgr” positions, UCB comes out even worse.  A big chunk of UCB’s deficit comes from the stadium boondoggle, but UCB continues to pour money down the athletics rathole.

I’m glad that UCSC is not wasting money at the rate that UCB and UCLA are, but I do wish that UCSC would return to the days when student athletes paid for their own entertainment, rather than taxing other students.

Me

My pay is relatively modest—I came out 430th on the list for UCSC.  UCSC is listed as having paid 12,288 people in 2016, though many of those got only tiny amounts.  Of those getting $1000 or more, there were 10,480, of those making $21,000 or more (CA minimum wage at full time) there were 4,248, of those making $30,000 or more (UC’s theoretical $15/hour minimum at full time) there were 3,580.  So I’m estimating that I’m at around the 89th percentile for full-time workers at UCSC: a comfortable pay, but nothing extraordinary.  Among the professors at UCSC who are listed as professors (not administrators), I’m at 263 out of about 566: a little above the median (the total count includes faculty who were only there for part of the year or who had “visiting faculty” positions, but not “recall faculty” who have retired but are rehired to teach a course or two).

In the UC system as a whole, I’m at position 26,585 out of 141,138 making $30k or more (only about the 81%ile—the med-center campuses pay a lot more than UCSC does).

Postdocs

I was curious was postdocs get paid across the UC system and at UCSC.  The range is huge across the system from $14 to $255,950.  (The tiny amounts are probably not really pay—there are tiny reimbursements and honoraria that get counted as pay in the UC system.)  The huge amount is from UCSF, and probably comes from clinical work by an MD.

At UCSC the range is $557 to $70,833, similar to the range for coaches.  The median pay for postdocs at UCSC is $39,150.  This is just above what the City of Santa Cruz requires as a living wage (currently $16.21/hour plus benefits) and is reasonable for a single person, but not for someone supporting a child as well.

There are not many postdocs listed as such on the UCSC payroll (only 173), and many of them were probably there for only part of the year, so the number of postdocs on the payroll at one time is probably only 100–120.

Teaching Assistants

Graduate teaching assistants (“teachg asst” in the compensation database) are more numerous—there are 1003 listed (without names) for UCSC with payments from $91 to $41,927.  The median pay is $15,219.  Given that the median workload is 20 hours a week for 33 weeks, that is a respectable $23/hour, but it is not enough to live on in Santa Cruz.  MIT’s living wage calculator estimates that a single adult in Santa Cruz County needs about $27,779 before taxes (though the calculation probably needs to be fixed for grad students, as they do get some medical and transportation benefits that can reduce costs, but housing within reasonable distance of campus is more expensive than county-wide).

I was a little surprised to see the variation in how much TAs were paid at UCSC, as I thought that the pay scales were fixed.  Quite a few students got $14,995 (so that was probably the scale amount), but above that almost everyone had a different amount.  I wonder what made the differences?

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