Showing posts with label Cable. Show all posts
Showing posts with label Cable. Show all posts
Saturday, October 29, 2016
Cable TV Outer Limits
There is nothing wrong with your television set. Do not attempt to adjust the picture. We are not controlling transmission. We can't make it louder by bringing up the volume. We can't make it softer, we can't tune it to a whisper. We can't reduce the focus to a soft blur, or sharpen it to crystal clarity. We will not control the horizontal. We will not control the vertical. For the next thousand words, sit quietly while we don't control all that you see and hear. You are about to experience the awe and mystery which reaches from the inner mind to... The digital cable less Outer Limits. Because you can't easily hook up an interface box on most boats!
It's a problem for boaters now, and it is only going to get worse quickly. Back in the good old days, just a few years ago, getting cable TV in a marina was easy.
Get out your yellow Marinco coax cable, screw one end into the pedestal, and the other into the boat, and you had cable. Analog cable that is. Today, not so much depending on where you live. The days of analog cable are nearing the end, and digital cable now rules.
Not that digital cable is bad, it's that most boats are poorly equipped to use it, if at all.
The yacht club trip ends up in a marina that looks like every other marina, but.... The cable company has switched to digital.
You plug into the pedestal, ready to watch your favorite TV shows, and nothing appears. Huh what's going on? Down to the dock masters office you go, and ask, "What's up with the cable?" The dock master says, "You now need a converter box for cable here. I will loan you one." The dock master reaches into a cabinet and pulls out a small box, a 110VAC power adapter, some cables, and a remote control. "Here you go, just plug this into your TV and you will have 300 zillion channels.
The dazed boater takes the gear back to the boat and stares at his TV, and the converter stuff. Okay let's see, I have to get to the back of the TV, how do I do that? Where do I plug this adapter thing in? In just a moment or two, he gives up.
Marinas and yacht clubs are caught in a conundrum. Where in years past, it was easy to provide their users with standard analog cable, in the digital world, this is no longer easy, for the boater at any rate.
In a quick survey of local marina basins, two still have analog cable service available providing about 50+ channels. One has very limited analog service (7 local channels). Anything else requires a cable box. Another no longer has analog service available, and doesn't provide any cable service. The last has digital cable only, with loaner boxes available.
This is just a tiny slice of of the 8,000 to 9,000 marinas in the US. So what can be done about this, and what options do marinas have? The answer is not many. As time quickly goes by there will be less analog, and more digital cable availability. Digital cable requires a converter box, which takes us right back to where we started in the beginning.
There is only one option I can think of, and that is to have marinas provide on air digital TV, and feed it out to the docks. You could place several on air antennas on the roof pointing in several directions. You feed this to an antenna signal combiner, and then use amplifiers to feed the docks.
This equipment is surprisingly inexpensive. For just a few thousand dollars, you can say goodbye to digital cable TV your boater's effectively can't use, and give them something they can use. In the case of the Sarasota area you could receive 40-50 crystalline on air digital channels. Granted there are some duplicates in there such as ABC Sarasota, Ft. Myers, and Tampa, but you also get multiple feeds from many channels to make up for it. Boaters with newer TV's would have no problems, and those with older TV's could just add a digital tuner to their boat.
The boater has other options. Almost all can get good on air digital TV in most urban areas. Another approach is to do a one shot rewiring of the boats TV wiring system that would make it easier to plug a cable box in. A set of outlets could be installed that could accommodate external installation of a variety of cable system boxes.
The only current option a boater now has to consistently watch TV while you cruise is a satellite TV system. You will have to bite the bullet, and shell out the capital cost to buy and install it, but when done, you will have TV almost anywhere in north america.
Don't despair boaters, I predict that in very short amount of time, when you pull into a marina your TV's and chartplotters will automatically sync and connect to the marinas WiFi system, and will start to stream the TV shows of your choice on demand along with original content. Oops, you can do this now!
You could as an alternative always load up your Kindle and read some good books, or borrow the real paper versions from your grandparents. Shoot, did I say that out loud? Sorry.
The photo of the antenna is a Winegard HD7084 antenna. I spec'ed this and a small amp for a local sports bar chain. They use it to pick up Ft Myers channels about sixty miles away. Ft Myers is out of the Buc's blackout zone, and since they don't sell out often, it's often blacked out. It works a treat.
Marinas and yacht clubs are caught in a conundrum. Where in years past, it was easy to provide their users with standard analog cable, in the digital world, this is no longer easy, for the boater at any rate.
In a quick survey of local marina basins, two still have analog cable service available providing about 50+ channels. One has very limited analog service (7 local channels). Anything else requires a cable box. Another no longer has analog service available, and doesn't provide any cable service. The last has digital cable only, with loaner boxes available.
This is just a tiny slice of of the 8,000 to 9,000 marinas in the US. So what can be done about this, and what options do marinas have? The answer is not many. As time quickly goes by there will be less analog, and more digital cable availability. Digital cable requires a converter box, which takes us right back to where we started in the beginning.
There is only one option I can think of, and that is to have marinas provide on air digital TV, and feed it out to the docks. You could place several on air antennas on the roof pointing in several directions. You feed this to an antenna signal combiner, and then use amplifiers to feed the docks.
The only current option a boater now has to consistently watch TV while you cruise is a satellite TV system. You will have to bite the bullet, and shell out the capital cost to buy and install it, but when done, you will have TV almost anywhere in north america.
Don't despair boaters, I predict that in very short amount of time, when you pull into a marina your TV's and chartplotters will automatically sync and connect to the marinas WiFi system, and will start to stream the TV shows of your choice on demand along with original content. Oops, you can do this now!
You could as an alternative always load up your Kindle and read some good books, or borrow the real paper versions from your grandparents. Shoot, did I say that out loud? Sorry.
The photo of the antenna is a Winegard HD7084 antenna. I spec'ed this and a small amp for a local sports bar chain. They use it to pick up Ft Myers channels about sixty miles away. Ft Myers is out of the Buc's blackout zone, and since they don't sell out often, it's often blacked out. It works a treat.
Tuesday, August 23, 2016
Four Cable Drawing Machine
Each of the four stepper motors is connected to a pulley and string. By winding in or letting out string on each corner the computer can position the draw head anywhere in three dimensional space, or at least within its work envelope of roughly 590x590x220mm.
The machine is controlled with LinuxCNC using a custom kinematics module and python script written by Kevin Loney. Its input files are standard g-code, the same format used for controlling a CNC mill, all the weird coordinate transformation math is handled by the kinematics wrapper.
More construction info and photos after the video,
By far the hardest thing on this build was getting the machine to to home fully automatically. For those new to motion control, I am using stepper motors, these are open loop which means that I can move them incrementally, but I have no idea where they actually are. To determine their current state, I have to move them to a known position, and call that home. This is fairly easy on a traditional CNC machine where each axis is independent and on guides, but quite painful when all four are tied together and made of string.Many ideas were floated to solve this, from IR range finders, to vision based systems with openCV and a webcam. Finally for reliability I settled on simple switches.
From here though, there are two main problems, first, how do you trip a switch with a length of string, and second how do you keep everything taught and tangle free when you haven't got a clue where the drawhead is starting from.
Now, to get the drawhead to trip the switch I have to have slack from the opposite side. The first thing I tried was to just spool out cable on one motor as I spooled in on the other. For a two cable machine this technique works great, once you get two more cords in the mix, and a lack of space to use gravity to keep things taught, a lot of tangles result. The solution was a bit of a hack, but one I am rather proud of. Stepper motors have no direct mechanical connection between the shaft and the body of the motor (well, other than the bearings), its the magnetic field in the coils that causes the shaft to turn. This means that stepper motors can slip without damage if the force on the shaft exceeds the holding torque of the coils. Further, the stepper motor driver I am using allows the current going into the motor to be adjusted with a resistor which then adjusts the holding torque. Yup, that's right, the motors have a tug of war. One is stronger than the others so it just reels it in with some enthusiasm, everything stays taught and you are off to the races.
This video shows the switches getting hit, I need to upload another video showing the unholy chunking and shaking that happens during the tug of war phase.
The construction of this machine was a mixture of hand machining, carpentry and a bit of laser cutting for the towers and overwrap guides. The head is replaceable, for the early tests I had a larger head that could mount a pen and do some fairly accurate drawings, only issue was that in a more resistive material like sand it tended to flop around a lot.
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