Although I’ve set my MythTV box to shutdown when not in use, we still have a constant power drain of 34 watts even when the system is turned off due to various peripherals and parasitic power drains.
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My mythtv box uses a SiliconDust HDHomeRun external network based tuner. Every so often (1 out of 5 boots) the network subsystem does not get started up before the mythtv-backend daemon. This causes an error where the mythtv-backend does not find the tuner, so it can not record any shows. Continue reading
On my 0.21-release-fixes codebase, MythWelcome would pause for a long time (2-3 seconds) after I pressed the “MENU” key before making the menu pop up. This was because a call to “mythshutdown –status” was taking several seconds to return, and MythWelcome waited for the return value of that message before drawing the menu (It wanted to know if it should draw a “unlock” or a “lock” button.)
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Our MythTV entertainment system uses a decent amount of electricity. While watching TV, the television, DVD/Amplifier and computer (plus misc other items) use 335 watts of power. However, as we only average an hour or two of TV a day, this isn’t as large as the continuous power draw from the system when it is not in use. Even though we turn the TV and DVD/Amplifier off when not in use, the computer, HD Tuner, external HD, antenna preamplifier, printer, etc take up 141 watts when idle, and around 160 when recording, trans-coding, or detecting commercials in a television show. As the MythTV computer runs 24/7, this adds up to just over $10 a month of electricity (101 kW/h).
In an effort to save power, I have configured the MythTV system to shut itself off when idle, and wake up automatically five minutes before the next television show it is scheduled to record. This saves power, but has the major downside that the computer is not running and instantly ready whenever we want to watch TV. If the MythTV box isn’t already awake recording a show, you have to manually push the power button and then wait for two minutes while it boots up and gets itself ready. We are no longer able to press the TV-Power button and start watching TV five seconds later. However, this saves about 105 watts whenever the system is off (about 20-22 hours a day), or about $75-$84 a year.
We still have a constant drain of 36 watts, even when the system is turned off due to various peripherals and parasitic power drains.
With the exception of the 10 watts from the UPS/Computer, the other power draws could be eliminated by using a “master-controlled” power-strip (such as the APC P7GT), which automatically turns off the controlled outlets when the computer (plugged into the master outlet) is turned off. This would save 26 watts whenever the computer was turned off, and would save about $20 worth of electricity in a year, paying for the fancy power saving power-strip in less than two years. Also, if I replaced the UPS with a “green” version, it would take less than 10 watts to keep the battery topped-up, but that cost savings would take longer to pay for itself.
We recently replaced most of our incandescent bulbs with instant-on CF light-bulbs. I cheated by upgrading our light output (using 100 watt equivalent bulbs to replace 60 watt incandescent bulbs) but each bulb should still save 34 watts.
I loosely estimated our daily light usage (over weekdays and weekends) on the newly CF fixtures as the following:
Bedroom (1 bulb): 1 hour
Bathroom (3 bulbs): 2 hours
Hallway (2 bulbs): 6 hours
Sewing Room (2 bulbs): 1.5 hour
Living Room (5 bulbs): 7 hours
We are saving (57 bulb hours * 34 watts) 1938 watts a day, approximately 2 KWh a day, or 60 KWh a month, or $6 a month (at $0.10 a KWh). We should pay for the CF light bulbs in seven months.
In an attempt to free up more of the spare bedroom for quilting supplies (“the stash”), we built some storage space into our attic. As you can see from the pictures below, our attic consisted mostly of blown fiberglass insulation (about 8-10″ deep, which is almost adequate).
Blown Fiberglass insulation plus random construciton debris
Drilling the holes for the adjustment screw
Angle Iron's with skate bearings mounted using bolts
I decided that a full set of 3 bearings at 120 degree intervals would take too much alignment and precision so I fell back to the tried and true home-brew DIY pipe and bearing system that uses 90 degree angle iron with skate bearings bolted to it. I used steel angle iron that is 1/8 inch thick and 3/4 inches wide. It cost me $11.23 for a four foot length at my local (over-priced) hardware store. I also purchased eight 1/4 inch bolts, nuts, and nylon lock nuts to hold my bearings for $8.48. (If you purchased bulk boxes the hardware cost would be much cheaper!) Continue reading
Bracket & Bearing Assembly on Pipe
I manufactured a second copy of my bracket and used my hand drill to put a few holes in them to hold bearings. The idea is to mount 3 inline skate bearings at 120 degree increments around a pipe to limit motion to 1D (two of these on one side, plus two 2D mounts on the other side, make a Z-axis platform). I estimated the space taken up by the washers, and got it wrong, so if I wanted to use this design I will have to tweak my design and make a few “off-size” brackets to pair with the current ones I have. (Making all new brackets does not sound like fun, as each of them take almost 2 hours of routing time). The alignment and motion is a bit rough (I did eye-ball the holes) but I think I could improve upon that enough to make them passable with enough practice. However, due to the two-hour build time, I’m seriously considering using the “standard” angle-iron solution for my Z-axis.
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I have designed a bracket that I used as my first attempt to manufacture something with my CNC mill. Because I’m still using python code I wrote myself and have not yet calibrated my stepper coordinates into real-world measurements, I had to design the bracket in Inkscape, print it out, and manually move my router bit to each point to determine the stepper coordinates along the path I wanted to cut out. This really sucked, and I plan on switching over to the parallel port controller board and EMC2 very soon so that I do not have to keep writing code. (I had to add code to cut out the bracket that interpolates between two endpoints so that I could route semi-accurate 60 degree lines.)
The piece of wood was secured Continue reading