lactroi
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Battery elements for portable pi

Mon Jun 12, 2017 4:19 pm

Once a Counterculture Hallmark, the best skateboards Has Launched Into the Mainstream
We know it's not fair, but as we set out to chronicle skateboarding's
migration from the underground into the sports mainstream, the urge to work the word "dude" into the first paragraph is irresistible. As in: Dude, that's awesome.
Ok, it's out of our system. Then again, we've always been open-minded, and so we're willing to accept that the skateboarder-as-tattooed-troublemaking-outcast-teen is a tired cliche. But what about the rest of the over-30 crowd? When Mike Frazier, 26, tells people he's a professional skateboarder, the typical reaction is a condescending, "Aren't you a little old to be doing that?" Says Frazier, "They think a skateboard is just a toy for 8-year-old kids."
That toy is turning into quite an investment, as the top skaters are riding the sport's biggest-ever crest to six-figure annual salaries. Perhaps you saw skateboarding's demigod, Tony Hawk, sporting a white mustache in a "Got Milk?" ad ? "We've received a lot of media coverage over the last few years," says Hawk, 31, "and the kids who see us really understand the level of athleticism and dedication required to succeed--that it's not just a `go for it' sport that takes guts to try."
More than anyone else's, Hawk's lifestyle belies that of the counterculture skateboarder image. Soft-spoken and polite, he's a husband and father, a home owner since the age of 17, and the co-founder and partner of Birdhouse Projects, a leading skateboard and accessory manufacturer that attained an annual gross of $14 million within five years. He's been at the top of his sport since he was 14, inventing dozens of tricks and winning nearly every major event he enters. Hawk says the "varial 720"--in which his body turns two rotations in the air while he spins the board an extra half-rotation with his feet--is the most technically challenging stunt in his vast repertoire. We don't doubt it.
Hawk's ascent began at a time when the terrain and equipment for skateboarding were, by today's standards, primitive. Atop fiberglass boards, vert skaters such as Hawk blasted in and out of empty swimming pools, while street skaters held freestyle competitions on the fiats. By the end of the '80s, the boards consisted of a more efficient wood design, vert skating had evolved from pools to more maneuverable, fiat-walled ramps, and street skaters were increasingly incorporating natural terrains--benches, curbs, stairs, handrails--into their routines.
The sport has continued to evolve. as skaters feed off each other, continually pushing the envelope in their pursuit of new stunts and techniques. "Someone will invent a trick and then someone else will do that same trick higher or faster, or down a set of stairs," says Andy Macdonald, 25, one of the leading challengers to Hawk's throne. "Then, two years later, someone will do that same trick down a double set of stairs."
Image

Skateboarders didn't get their rebellious reps for nothing. They are, to be sure, fiercely individual. Macdonald points out that his sport, appropriately enough, has no regimented training program, no right or wrong way to do things. "Six different skaters might do the same trick six different ways," he says.
But rebelliousness spawned outright hostility by the mid-1980s, when the hundreds of private skate parks that had sprung up in the previous decade closed en masse, mostly for insurance reasons. "Kids were forced to skate wherever they could," says Hawk. That didn't sit well with store owners and pedestrians, who saw the sport's practitioners as public nuisances.
In recent years, the skate parks have again begun to proliferate (often built and operated by cities), fostering a rebirth for the sport. As more people witness Hawk and company performing their acrobatic feats, disdain is giving way to respect. how to turn on skateboard
IN FACT
In addition to his recent "Got Milk?" ad, Tony Hawk has appeared in commercials or campaigns for the Gap, Levi's, Mountain Dew, Coca-Cola, Pepsi, Campbell's Soup, AT&T and Gatorade, among others. He also was the mop-headed star of the seminal skateboarding documentary from 1986, The search for Animal Chin.
RAH DATA
The standard skateboard design has remained virtually unchanged for more than a decade: a platform consisting of seven plies of maple--measuring approximately 31-by-9 inches, with a tip in front and a tail in back--atop four wheels mounted by front and rear trucks.
Vert skating typically takes place on a U-shaped hardwood ramp, approximately 12 feet high, known as a half-pipe. At competitions, skaters use the walls as launching pads for a variety of aerial stunts--new ones are invented all the time--that are scored by judges.
Street-skating tricks are performed negotiating everyday ramps and obstacles: curbs, stairs, handrails, park benches, trash cans and the like. Competition courses consist mostly of cut-up vert ramps. Because of the vast differences in techniques, few professional skaters can consistently perform at a high level on both the vert and street terrains.
In downhill skating, riders squat in an aerodynamic "tuck" position, head forward, toes pointed toward the tip of the board. Courses are at least a mile long, with four natural turns. Speeds range from 45 to 65 mph. Riders race in heats of four to six skaters at a time; they wear full leathers, with carbon-fiber aerodynamic helmets.
RAH DICTIONARY
Frontside air: While performing a forward-facing jump, the skater grabs the front rail with his back hand.
Heel flip: By kicking his front foot in a forward motion, the skater uses his heel to turn the board one rotation while in midair.
Kick flip: Same as the heel flip, except the skater uses his toe, kicking his front foot in a backward motion.
McTwist: A long-performed trick in which the skater jumps and spins 540 degrees in an inverted direction.
Nose grab: While in the air, the skater grabs the tip of the board with his front hand.
Ollie: The fundamental skateboarding move in which the skater uses his back foot to pop the board into the air in order to jump over objects.
Rock `n' roll: A trick--the first one perfected by a young Tony Hawk--in which the vert skater hits the lip, taps the board and turns.
720: A midair 360-degree double somersault, one of Hawk's trademarks.
Stale fish: Another Hawk invention, in which the skater jumps frontside, grabs the heel side of the board around his back leg and puts it between his feet.
Tail grab: Same as the nose grab, except the skater grabs the back of the board.
Wilson: Slipping on a skateboard like a banana peel-named after Dennis the Menace's neighbor, Mr. Wilson. Learn how to ride a skateboard
OVERTIME
The Concrete Wave (1999: Warwick Publishing) documents the 40-year history of skateboardingwith photos, memorabilia and interviews. The book was written by Michael Brooke, a skater since 1975.
Last edited by lactroi on Thu Jun 22, 2017 5:55 am, edited 3 times in total.

W. H. Heydt
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Re: Battery elements for portable pi

Mon Jun 12, 2017 5:16 pm

1. Determine how much current *everything* requires. Convert that to Watts, using W=A*5

2. Decide how many hours you want your rig to run. Take the power requirement and get a Watt-hour figure, Wh=W*h.

3. LiPo/Li Ion battery packs are actually rated in Ampere-hours at 3.7v, so the capacity of a battery in Watt-hours will be Wh=3.7*Ah

4. Pick a battery with a Watt-hour rating high enough to power your system for the requisite time, that is Wh(battery)>Wh(system).

geoffr
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Re: Battery elements for portable pi

Thu Jun 15, 2017 12:32 am

One way to improve battery runtime is of course to reduce power draw. That raises the question of whether you could get away with a Pi Zero rather than a Pi 3? If the Pi Zero has enough grunt for your application, that could be a big power saving, and depending on the current draw of your other components, a good increase in runtime.

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Gavinmc42
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Re: Battery elements for portable pi

Thu Jun 15, 2017 3:18 am

A Zero with 7" DPI LCD would be lowest powered Pi portable.
A Pi3 with 7" HDMI would be the highest power usage version.
Search the posts for "LiFePO4"
I have put some info out there on this subject of portable battery powered Pi.
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W. H. Heydt
Posts: 10772
Joined: Fri Mar 09, 2012 7:36 pm
Location: Vallejo, CA (US)

Re: Battery elements for portable pi

Thu Jun 15, 2017 3:31 am

Gavinmc42 wrote:A Zero with 7" DPI LCD would be lowest powered Pi portable.
A Pi3 with 7" HDMI would be the highest power usage version.
Search the posts for "LiFePO4"
I have put some info out there on this subject of portable battery powered Pi.
Except, of course, that the Pi0/Pi0W don't have a DSI connector. The lowest power Pi that can work with the RPF 7" display would be the A+.

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Gavinmc42
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Re: Battery elements for portable pi

Thu Jun 15, 2017 4:29 am

DPI, parallel output
Use DPI mode on GPIO pins, er most of them.
I'm dancing on Rainbows.
Raspberries are not Apples or Oranges

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Gavinmc42
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Re: Battery elements for portable pi

Thu Jun 15, 2017 4:31 am

I'm dancing on Rainbows.
Raspberries are not Apples or Oranges

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