A Multi-Scale Problem, In Your Living Room

The previous post, on the topic of how to wrap your head around a multi-scale problem, provides a general framework for conceiving of a problem on multiple scales, ranging from the individual button press to global policy. A convenient example of a multi-scale problem which is in nearly every living room is the cable box.


It seems innocuous enough, the cable, satellite, or telecom company rents it to you and it makes the telly gets a crisp HD signal. Sure it complicates the remote situation, and it adds a few bucks to the cable bill and the electric bill every month … wait, how much does it tack on to the electric bill? About 25-50W, continuously, 8760 hours a year, which adds up to about 200kWh/year, or at my rate of about 10c/kWh I pay about $2/month for the cable box electricity consumption (that’s a slightly more stinging $24/year, per box). Two of them consume as much electricity as the fridge! (which consumes an average of 415kWh/yr, or $45.65). And all it’s doing is … a lot.

What the cable box is not so silently doing

If it’s a DVR, it has a hard drive in it, which you can often hear spin up and hack away while recording, or at conveniently quiet times to defragment or update the guide. That uses energy. It also has a nice little clock, and a few LEDs to tell you it’s on or (still on but pretending to be) off. It never really turns off, and most don’t even throttle back a significant amount. The reasons it stays powered up all the time is that it has a lot of communicating to do, and people expect near instant action when they turn the TV and the box on.

It has to stay in contact with the cable office or satellite, and keep the channel and program listing synced up. It has to record when you want it to record (and therefore it needs to keep the hard drive defragmented (if you haven’t defragmented your computer’s drive lately, you should do that soon). It may have to do other things too—like get real time messages from upstream—some can be controlled from the web or from a smartphone application, or offer other features.

Why does it use so much electricity?

The quick answer is the most telling quote in the article: “Nobody asked us to use less.” Now, engineers shave grams off bike frames and milliwatts off the draw of cell phones, but without external pressure on multiple levels—from the government (105), on the corporation (103), to the boss (102), to the engineers (101) things won’t be prioritized. A cable box has to offer at least acceptable ergonomics, high reliability, and *instant performance*. People expect it to start instantly—and certainly not take an hour to update. If you’ve ever plugged in a factory fresh one, it can take up to an hour to set itself up—not exactly useful.

The system itself operates at multiple levels, which is why it has to stay booted (sort-of). The cable box (100) has to communicate with the local network (103), and possibly with a higher level network (104) or satellite network (106). That’s a little more complexity than just picking up the carrier wave from the local network affiliate and demodulating the Indian Head.

What to do

The engineers at Motorola or Cisco or Samsung (large manufacturers of set-top boxes all) need to work with the network designers to design more efficient ways to get the data to the box so that it doesn’t need to download so much data to get itself ready to go, and can power up and down as needed, such as waking on external signal or having a higher data rate to get its work done faster before powering back down. And of course better electronics can help to some degree.

One partial solution is to get rid of the cable box, and make the television smarter—modern TVs already have some equipment that’s always powered on—the remote receiver, possibly some other functionality—1..5W worth of something, which isn’t inconsequential when summed over the whole of the US. This would require a better solution than the failed CableCard, but something modular like that would be a start, eliminating a separate remote and batteries, power supply, cabling, box, and some circuitry.

There’s a behavioral component here as well—can you train users to expect a few second delay between button press and when the picture appears? That’s a fundamental human factors issue, fortunately people can put up with a few seconds of delay, although now being accustomed to instant action makes it harder to go to a less ‘perfect’ model of operation. The other part of the human dimension of this problem is that due to the delay in and diffuse nature of the feedback on power consumption (you get a single number at the end of a month), unless you read the Times or use an electric meter to figure out the STB is unobtrusively drawing a constant 25-50W, and then put that into context—and then get riled up enough to petition the government for redress.

Fortunately the EPA is extending the Energy Star guidelines to cover the set-top box, but that will take some time to come into force—and as consumers have almost no say over which box they get, the cable utility providers may not opt for newer higher efficiency units—it’s not their cost, so they don’t care other than wanting to be good corporate citizens.

What can you do, now?

You can try to see what happens if you power off the cable box with a power strip physical switch—some may resume quickly, some may take an hour. There’s going to be a lot of variability. And you can petition the government… or get rid of your cable/satellite service and read more books!

A Follow Up


Their estimate of 25 billion kWh of annual consumption, is incredible, especially if that results in 9 power plants worth of draw.   I’ve heard the figure bandied around of 5 power plants powering all of the devices which aren’t doing anything useful (like the charger not charging your cell-phone).  If it really is fourteen (14) power plants powering things which aren’t doing useful work, there’s a huge problem, and opportunity for electronics design and user education.


Datasurfer Surface Plot Tool

Corner View of surface plot


Datasurfer is a four-dimensional surface plot developed in Processing, for Introduction to Computational Media.  Datasurfer takes a two-dimensional spreadsheet (CSV) and translates values into a 3D surface, which can be manipulated by moving the viewpoint, or by shrinking or growing a two-dimensional window (in the case of the NYISO Grid Data, hours of the day/days of the year) of which blocks are plotted.  Moving the viewpoint changes the apparent representation of the data, allowing for a wider set of conclusions to be made–in this case, it is easy to see that there is substantial variation in the load both over the course of the year, and over the course of the day.


The processing sketch is based on a two-dimensional parsing algorithm from Jonathan Cousins and Nick Sears, and adapted with help from Zannah Marsh.  The interface buttons and sliders come from the spectacular plugin set ControlP5, and the 3-D manipulation is provided by PeasyCam (much easier than writing my own manipulation with the Processing Camera commands).  Of course, neither ControlP5 nor PeasyCam are perfect, but they do work quite well.  A special thanks is due to Andreas Schlegel, author of ControlP5, for modifying the library to allow for changing the slider edge width – right when I needed it at the Ebay Design Expo.

At the ITP show, this is being displayed on a giant touchscreen, which is really a lot of fun, but unfortunately is a little hard to manipulate due to being only single-touch.  Multitouch (which everyone loves on tablets, phones, and now laptops) is going to really extend the computing experience, much more than it has already.


As a programmable interface, there is nearly infinite ability for customization of the tool to different datasets–half the work of information visualization is setting up the tool in such a way as to yield valid conclusions and minimize artifacts.  One of the goals of this project is to build a real-time interface for data from a feed, such as a Tweet-A-Watt.

Special Thanks

Thanks to Jonathan Cousins and Nick Sears for a great fall introduction to information visualization and the seed of this project (and the start of the code), Zannah Marsh for the opportunity (need) to develop this for ICM, the Processing community for developing great plugins (ControlP5, PeasyCam), and of course ITP (specifically George Agudow and Red Burns).


Have heat, need electricity?


The thermoelectric effect has been used since the 1930’s to generate electric power, but it really hasn’t been used widely in consumer products to generate electricity.  While inefficient, this are suitable for some applications with relatively low electrical power requirements, combined with extreme environmental conditions.

Historical Background

In the 1940’s, the Soviet government produced kerosene-thermocouple generators to power radio amplifiers.  Fuel up, Plug in, Tune in!


The Soviets also have used radioisotope thermoelectric generators as power supplies in remote locations, such as lighthouses and navigation beacons in far Siberia.  The US used them for remotely located radar stations in Alaska and probably northern Canada.  If you see one of these, don’t bust it open.  Inside there’s a slug of strontium-90 or plutonium, and you’ll likely die of radiation poisoning from exposure to the source inside.


Thermoelectric generators have also been a mainstay of the space program, powering deep space probes where the solar flux won’t yield much energy.


The black tubes are the RTG’s

Principle of Operation



the principle of operation is incredibly simple.  With power supplied as shown above, one side gets cold and the other gets hot.  Run in reverse, heating one side and cooling the other side, a voltage is generated.  N and P typed doped bismuth telluride (Bi2Te3) is the most efficient semiconductor for this application, but other materials have been used in the past.





From the first version, I added a 3-Farad ultracapacitor and Pololu boost regulator, which acts as a DC-DC converter, stepping up voltage from 1.5V to 2.8V, the minimum forward voltage for the LEDs.  The capacitor smoothes out the voltage supplied to the boost regulator, and provides about a minute of light with no input from the thermoelectric elements.





As assembled, the stack is as thermally efficient as possible, with a copper base plate, and thermally conductive matting between the copper substrate and the thermoelectric element.  Unfortunately, a double-sided adhesive film was only available in a product with a relatively low thermal conductivity, but the impedance is not terrible considering its thickness.

The heat sinks used here are relatively dense for the application, being intended for use in forced-convection applications.  They do dissipate enough heat to provide significant energy flow under natural convection in this arrangement.


Most of the energy is dissipated as heat, but a small amount is converted to electricity.


Based on this chart from the manufacturer, CUI, the theoretical efficiency of the elements used is 1.25%, given the temperature difference.  That’s not very good compared with even low-efficiency PV panels, but PV’s don’t work at night, requiring battery or capacitor storage.  As the thermoelectric elements work directly from heat, this is a fine solution for the application.

Doing some calculus yields the theoretical voltage of the assembly, based on the electrochemical properties of doped bismuth telluride.


Experimental tests yielded a lower output than predicted, but that is expected due to system inefficiencies.


Cost Analysis




Gasoline Generator

PbA Battery

Marine Deep Cycle

Kerosene Lantern

Lighting system

LED lights

Fluorescent Lights

Fluorescent Lights, Inverter

Kerosene Lantern

Associated Hardware

LED lights




Recurring Needs


gasoline, oil

battery replacement

kerosene, mantles

Expected Life

20 years

10 years

3 years

(900 cycles)

20 years+

electrical Power Output (W)





Initial Cost





recurring costs


$2/day for fuel

$0.25/ day for recharging

$1/day for fuel

(US white gas price)

First year cost





Second+ year cost





5 Year Cost





toxic impact


gasoline, oil

Lead, Sulfuric Acid

Mantles, Hydrocarbon Fuel




 Sulfuric Acid



The total cost of the thermoelectric system is about $200 US, substantially less than the other options for portable electrical power/lighting used in food carts.  The cost breakdown above does not include lighting for the gasoline generator and lead-acid battery installations, which would total about $100-200 more.  The amount of electrical power generated is orders of magnitude greater for the gasoline generator and battery arrangements, making those suitable for more power-intensive situations like an ice cream truck.  But if all you have is a griddle, and all you need is some light, thermoelectric is the way to go.



This is a promising technology with many potential applications.  While not in wide use, it could be used to good effect to provide lighting, displacing other energy sources which are highly polluting and have relatively high costs.  The barrier to entry into the market is not insurmountable with a kit solution, and in volume the cost of devices would drop.

An issue is the fragility of the commercial elements I used – they can be overheated, which was a problem I ran in to, but there are higher temperature rated elements available.


Insolation is measured in terms of radiant flux, measured in Watts.  This little gadget stores energy in a set of capacitors, so yes, Dr. Brown, there are flux and capacitors here.  But alas, very little time travel.


For the midterm project for Sustainable Energy, I made a rather crude, yet elegant (in a prototype sort of way) voltmeteter.  With a 12” square high-efficiency photovoltaic panel formerly of Cornell’s Hybrid Electric Vehicle project (material diverted from waste), some 1F ultracapacitors, and an NTE 1508 bar graph driver, it’s not a particularly complex circuit to make.


The NTE 1508 bar graph driver chip is nearly identical to the National Semiconductor LM3914.  The documentation for that chip is much better, so follow the wiring diagram for that chip (PDF).  Instructables’ LM3916 driven VU meter instruction set is also a good resource, the LM3916 being very similar to the LM3914 and LM3915.

The NTE 1508 + LED set draws a surprising amount of power.  The capacitor bank drains pretty fast when the PV is detached.  But it works quite well when in partial or direct sun.

The trim potentiometer on the wiring diagram above is really useful, allowing easy calibration to suit the light.  In the 3914/3915/3916 the voltage divider has fixed resistors, replacing those with a variable resistor is a much better arrangement, given the different use of the chip.

Helpful hints:

  1. the chip is ‘sinking’ power from the LEDs, which have their positive leg on the power rail (+3.3V +/-)
  2. the NTE 1508 works with either +5V or +20V supply voltage.
  3. use the potentiometer to trim the scale for full reading on the bar graph/LED set.  if you like, connect pin 9 (MODE) to pin 3 (V+) for bar mode, leave open for dot mode)


What do you want for breakfast?  How about a nice bowl of Crummy Crunchies?

DSC_0079 DSC_0080 DSC_0085DSC_0083

… as in the infamous fake cereal from Haredevil Hare (the Definitive Bugs Bunny cartoon)

(see 5:20)

The CrunchBox is a talking cereal box.  It’s self powered, with three shake flashlight generators embedded in a foam block charging a 3.6v Ni-MH battery.  A bridge rectifier converts the alternating current induced by passing the magnet through the coil (left side of the diagram below), to direct current to charge the battery.


This powers the Radioshack voice recorder/player (catalog number 276-1323)  which is rated 50mA @ 9V, but runs nicely on 2.2V, although the pitch rises as the voltage drops.  Below 2V, the player doesn’t function at all.  Note: you have to carefully solder to the switch on the circuit board: the play button is integrated on the board.  Make sure not to bridge the terminals!  I covered the wires with some hot glue to make sure the leads didn’t break off.

A microswitch glued to the box side closes when the top is opened, triggering playback.




To add the coup de grace, some real cereal is in a shortened bag in the top, covering up the electronics, and a witty graphics package covers the (by comparison) pedestrian Weetabix box.

NB: don’t take this on the subway or ship it, as it does look rather suspicious. (see above)

Eco-Jam report

The IBM Ecojam brought together some of the best minds in the world on the topic of environmental sustainability in an environment where everyone can contribute to topic threads and push forward best practices.


The Eco-Jam covered a wide variety of topics.  As most of the attendees were in the IT field, there was a heavy concentration on the IBM-related smarter planet theme.
One of the important topics was negawatts–electricity that doesn’t have to be generated.  I’ve heard that the equivalent of three full sized powerplants are required to run all of the transformers that are just quietly heating the atmosphere and not powering any device.  That’s serious business.  Another thing brought up was nonessential loads, like the lights in a vending machine.  No one likes the dingy and dim half the bulbs in the fluorescent fixture look (remember that from high school?), but not lighting the vending machine is a fine thing to do.


Smart grid is coming to your home soon, I hope