backchannel: grade-grubbing, business style


A couple thoughts here:

  • don’t be a grade-grubber
  • although pleasant enough, Cultura cannot compete with world-class joints of similar types:  Ginger Man in Dallas, Hoppy Monk in El Paso, etc.
  • extreme ratings (1 star and max stars) with little gradation are generally associated with minimal education.

MythTV for nomads

I don’t have a TV in a normal sense, and haven’t for a few years.  I stopped watching tv and listening to radio in real time around 2005.  Downside is no, I haven’t seen that funny new commercial.

But I do like to collect some OTA (over-the-air) shows for rainy days or when I’m tired of podcasts.  I’ve been doing this with MythTV running on a spare raspberry pi, as described here.

Setting this kind of thing up in a sticks-and-bricks house isn’t too tough, as the channels are fairly stable.  For guide data you can use: Continue reading “MythTV for nomads”

betelgeuse betelgeuse betelgeuse

My favorite constellation is Orion, and Betelegeuse is  my favorite star in it.

There’s a lot to recommend Orion;  it’s out in the winter when “seeing” is better, it’s got that neat nebula in the belt, both lovely red Betelgeuse and clean blue Rigel.  It’s also a kind of rosetta stone for locating other features.

Betelgeuse is reliably red, unlike the red of Mars that sometimes seems peachy or pink to me.

I had noticed that Betelgeuse was dimmer, but chalked it up to atmospheric interference or my aging eyeballs.  Turns out it really is dimming, and may be entering its final stages (ie, it could BTFU into a supernova).

This could happen after humanity is dead and gone, but I’d sure like to see the fireworks during my lifetime.  I hope that’s not selfish.

McDonald observatory

I’d driven past this observatory complex outside Ft. Davis a few times on my way elsewhere.  This time I decided to stop in.

Tickets for the daytime tour were $9.   They max at 30 peeps but I think there were about half that in our group.   The tours (and shuttle driving, and apparently snack bar attending) were provided by an outstanding young fellow named Stephen (black cap):

We started at the original telescope, which Continue reading “McDonald observatory”

odds and ends

These are little snippets that don’t warrant their own post.  I’ll probably start talking about trivial stuff like this in twitter, instead. (right side of the page)


I had to wait for state paperwork to stabilize before my “qualifying event” showed up;  I called the 401k/457 folks and it did show up.  So I initiated the rollover of my (smaller) 401k to the (larger) 457:

We received your withdrawal request and it is being processed.
As your transaction progresses we will keep you updated on the status.

Should be done around the end of the month.

Two more related events will occur in the next couple of months:

  1. get paid for unused vacation.
  2. get access to 457.


mechanical keyboard continues to impress.  Lovely clacks.


out with Tiny Tiny RSS, in with Feedly

out with WebUI-aria2, in with YAAW.  The former changed behavior and didn’t update documentation.  Serious error.

Still can’t decide what I think about the Brave browser.  Update:  I have moved from FF to Brave on linux.  Haven’t done it on ChromeOS yet because Chrome supports extenstions there and Brave doesn’t yet.

Brave is basically Chromium ( the FOSS project Chrome is built on)+ some microcrypto stuff.  There have been attempts to implement micropayments for tips and ad views for many years, but the Basic Attention Token seems most likely to succeed.

Gruble:  why won’t anyone gut Chromium’s horrible search keyword autoadd crapola?  FF continues to piss me off with accidental Ctrl-Q shutdowns when reaching for Ctrl-W.

The chromebook continues to be my main squeeze;  I roll out the laptop for two things:

  • minecraft
  • calibre, since the linux container has some serious file permissions limitations



I’d been using Easytether, but it required 1-5 resets/day.  Now using thirdparty firmware on the phone with a wifi hotspot V can’t detect.

winter experiments: contact heating

Last winter I used a Mr. Heater Buddy to good effect.  Since I know that works I decided to play with some other options.

electric heating

Space heating with electricity is impractical off-grid.  Contact heating, however, might have a fighting chance.

I had prior experience with these forms of contact heating:

  • electric blankets (200-300w), which worked well
  • electric mattress pads (100w-300w), which worked even better than the blankets
  • heating pads (20-45w), as one might use for back pain
  • heated motorcycle vest, gloves, and insoles, (90w) which worked amazingly well
  • weatherproof pet heating pads (20w) for doghouses and to keep water bowls from freezing

The following components were used for my testing:


the mattress pad

Starting with the heated mattress pad, it is described as having 10 power levels and is marked 180w.  Amazon reviews mentioned about 20w draw on the lowest setting.  Sounds doable to me.

In practice, however, there are complications:

  1. turning the unit on automatically starts heating at the last-remembered level.  That seems reasonable, except…
  2. it runs full blast when started (preheating?), and keeps running full blast for at least a minute before dropping down to the selected heat level
  3. full blast is way over the claimed 180w rating, usually in the low-to-mid 200s.  It spiked over 300w a few times, as measured on Kill- a -a-watt.
  4. temperature is not maintained by reducing wattage, but by running the heat full blast for short periods of time.  The lowest setting, 1 out of 20, runs the pad 200w+ for 2 seconds then sleeping at 0 watts for 40 seconds (~6w is used by the controller to run itself).  I really wish it would hold 20w over time.

It would trip up the Aims inverter sometimes, the controller would reset and it took me a while to figure out why. This doesn’t happen during start-up, only during the 2-second pulses.

It wasn’t related to battery voltage;  it might trip when Vbatt was over 14v and might not when it was closer to 50% DoD.   It wasn’t hitting the isolator’s max, since it is a continuous 300w inverter that can tolerate 600w peaks.  And if it trips you can turn it on again and it will run fine (including the lenghty, mandatory power-on preheating). If you are watching bank voltage when it trips there is no worrying sag.  Connecting to the battery terminals or to the power distribution point about a foot away makes no difference.

I suspect the resets are a function of the soft start “feature” or some other unknown interaction:

The soft start technology built into this inverter protects the unit from delivering too
much AC power at once by gradually increasing the AC voltage pushed out.  – manual (pdf)

It might be possible to disable this feature with a bit of hardware hacking, but I’d be more likely to replace it with an inverter that doesn’t do this.

The 250w inverter in the Rockpals unit can’t even even get the pad started;  the controller screen partially comes alive then goes back out.

Conclusion:  I think a “dumb” (not electronically controlled) pad would work better here.  Give me an old model with a rheostat dial.  But since this one starts fine and runs a few minutes before one of the 2-second bursts confuses the inverter, I have been using it as a pre-warmer.  If it’s a particularly cold night and the dog has wandered off I sometimes reach over and turn on the pad, knowing it will confuse the inverter after a while.


heated car seat cover

I cut the ciggy lighter plug off the heater and slapped on a 5.5mm plug so I could jack into the Rockpals.

Heats as expected.  LO power is gently warm.  HI is a little too warm, perhaps best used for preheating.  [updated to add:  even LO was a bit too warm, I ended up putting down a thin blanket over it.  Ran 9 hours overnight and there was still one bar left on the Rockpals pack.  Calling this one a success]

Conclusion:  works fine, unknown how long it will last under constant use in a way the designers could not have forseeen.  🙂

next test:  heated vest

Motorcycle heated vests work so well I’ve been meaning to try one for portable use.

The heated vest market has matured quite a bit in the last two years, moving away from proprietary (and $$$) battery packs.  Now it’s more common to buy the vest and power it with a USB generic power brick like you would charge your devices from. Since these bricks are 5v @ 2.xA, we can see they are running about 10w of power.  Doesn’t seem like much, but my motorcycle vest was 50w and I usually ran it at the very bottom of its power range.  If it was chilly on my unfaired bike I would turn it up to about 25%.

I bought a Dr. Prepare Unisex Heated Vest but it hasn’t arrived yet I’m thinking about running a USB extension to make a quick-disconnect for heating the vest when I’m sitting at the “desk”.    🙂

I’ll update with info on the vest when it arrives.

Update:  it arrived and works well for ~10w.  The heated collar section is particularly  nice.  The battery pocket is rather small on the inside and barely fits my biggest pack.  At this moment I am running it on low at the desk, connected to a usb outlet with a 3′ extension. Observations:

  • High power (red):  100% on duty cycle
  • Medium power (blue):  75% on duty cycle
  • Low power (green)  50% on duty cycle.

At the $50 price point I would like to see slightly heavier zippers, a stretch panel on the side to make it conform better for optimal heat transfer, slightly larger battery pack pocket.


possible test:  heating pad

If I find a simple heating pad at a thrift store or something I’ll try that, too.

Edit:  I tested a $15 heating pad.


backchannel: PWM makes more power at 80% state of charge than at 50%

a continuation of this reddit post:

Because I drank more coffee than usual this morning:

PWM power output fluctuates with voltage because amps * volts = watts, and panel current stays pretty stable under normal insolation. Using the Renogy 100w mono at 70F ambient again, and some crude assumptions about voltage/SoC:

  • MPPT output: 82w. Much like the honey badger, “MPPT don’t GAF about Vbatt”.
  • PWM output at a high-ish Vabs (14.8v): 5.29A x 14.8v = 78w <– very close to mppt! Hmmm….
  • PWM output at Vfloat (13.6v): 5.29A x 13.6v = 72w
  • PWM output at 100% state of charge: 5.29A x 12.8v = 68w
  • PWM output at 80% state of charge: 5.29A x 12.5v = 66w
  • PWM output at 50% state of charge: 5.29A x 12.1v = 64w <– PWM is hating life down here

Corollary 1: one could tweak PWM to get a bit more power by configuring setpoint voltages, while still staying within battery manufacturer recommendations. With PWM and similar controllers, higher battery voltages directly relates to higher overall output.

Corollary 2: This one isn’t obvious, but other things being equal PWM will typically get more power from poly panels than from mono due to the latter’s higher voltage (and necessarily lower current for the same 100w rating). In the case of the Renogy 100w examples PWM makes about 6% more power on poly than mono.

Cultura beer garden

Muffin keeps tabs on outdoor Jenga players at Laredo’s finest craft beer joint. #hyenastyle

I kept my own attention on one of Real Ale’s lime gose. Martin House salty lady is more satisfying but I didn’t see that as an option.

Lithium vs. flooded banks for beginners

Note:  for comparison purposes there’s a link in the text below to Trojan batteries on Amazon.  Buy them locally to get the best price.  There’s no shipping and you’ll be able to trade in the old cores.

From a thread on /r/vanlife:


Thank you for the thoughtful response.

I don’t disagree with your technical analysis. I am pushing back on ideas like lead is “cheapo”, that Li is “doing it right”, and that large power storage capacity is necessary for “actual living”.

I think it’s worth talking about in public a bit more to help Continue reading “Lithium vs. flooded banks for beginners”