more curved icicles

Where do you live to get such nice snow and ice? We're dying up here in Ottawa, Ontario. Dry and warm (25=B0 C).

I have a $5 bet with my nephew that we'll get at least 1 cm of snow before June.

-- Joe

Did you get the rain that hit the US northeast?

We're in Truckee, California. It snowed all night and the sun came out this morning, 0° C right now. I have a season pass at Alpine Meadows, and they got six feet of new snow in March. The Sierra snowpack, the Bay Area's main year-long water supply, is about 105% of normal, which means we can have long, hot showers.

Truckee often sets the record-low temp for any town in California, sometimes the entire country. The record snowfall was the winter of

1937-38, 813 inches.

I'm simulating a digital control loop, essentially a constant-voltage current-limited power supply using an ARM cpu with adc/dac, until the half-day tickets go on sale at Tahoe Donner. $8.

John

LOL, how did you get them to do that ??

;-)

You must get some wind up there.

It comes down to the tolerances of the discrete components used to test for the voltage set-point in the feedback loop that the adc gets fed from, and any components downstream from that, if any prior to the output, if you were dumb enough to take the test from other than the output taps.

It has to be a function of the prevailing wind current at that location on the house.

At that side of the house, and blowing the same way for hours on end.

That is a function of the structure position and shape, and the wind direction that day. Wind alone is never that continuously laminar, so it is definitely a function of the house itself creating the needed wind current with the non-laminar normal surface flow as the feeder. It is a 'natural' wind tunnel.

We only caught the edge of it. It's been like that most of the winter, and now a very early "spring".

-- Joe

It looks as if the edge of the snow curves down as it slowly slides off the roof, and since it never quite melts, it curves right around.

--
John

Wow! I've never seen anything like that. Thanks for sharing!

-- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico@nctdevpuntnl (punt=.)

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The setpoint is a number in the uP, not a voltage. There are two ADC inputs, output voltage and output current. Current is sensed with a 15 ohm resistor and scaled up by an opamp and applied to one channel the uP ADC. The output voltage is picked up by a diffamp and fed to another ADC channel. The ADC's dac drives the series pass element. All the control stuff is software. I'm futzing with simulations to get good dynamics over a range of loads, and to get clean switchover between constant-current and constant-voltage modes. It's looking like I can do the whole loop iteration, including calibrations, in under 1 microsecond. Allow another microsecond for protection logic, and I'm good to go. If I run at 100K hits/second, the ARM can sleep 80% of the time, which is good since I don't have enough power to run it full blast.

John

No.

John

Yes.

John

It's not wind doing this. The snow on the pitched roof does a slow glacier sort of creep, and curls as it crawls over the edge, taking the icicles with it.

John

That is not the mechanism that made them freeze on a curved path though.

Are the two pictures of the two sides of the house or one side from two directions. Now I see what you're talking about; a totally different process than I was assuming (and had seen before). Cool.

Both shots were from the same south-facing window, looking east and west. Maybe the sun on the sloping roof makes the snow creep and curl. I've looked at a lot of other houses in the neighborhood (all the construction is very similar... draconian HOA rules) and I haven't seen this anywhere else.

The icicles are clearly growing as their bases curl, resulting in the curved shapes and branches. Tricky timing.

Neat planet we live on.

John

NOT on the 'a' side of the adc, you dingus.