The Call of the Open Sidewalk

In a previous post I talked about a public input meeting I attended that was about a footbridge. I ended by expressing some confusion about the scoring of a survey handed out at the meeting. The survey had participants rank a series of options but in the end only the first choices were reported.

I chatted briefly with the Active Transportation Coordinator. When pressed lightly about the thinking behind the survey he attempted to change the subject to the validity of the decision to cancel the bridge. Struck with the sudden fear that I might accidentally cause The Great Footbridge Survey Scandal I quickly bailed out of the conversation.

I don't think I really understand the point of public consultation. You hold a meeting and the people who come to the meeting line up and say stuff. Some of the people who say stuff do not have to stand in line and have access to a projector. Sometimes the people talking will express an opinion on the issue that caused the meeting. Often times people will talk about unrelated things. Sometimes there are pieces of paper distributed. Sometimes you are expected to write stuff on the distributed paper. Some of the people there are there simply to be seen to be there (usually local politicians).

Public consultation is all the rage these days. In general the results of these things are used a bit like the conclusions of consultants. If the result matches the politically determined conclusion it is used as support of that conclusion. Otherwise it is ignored. That is OK as far as it goes. The problem is that these things are touted as a way for non-politicians to participate in the process for the small cost of an evening. The actual participation is at at level of the employee who submits an idea to the suggestion box only to have that suggestion dumped in the trash at the end of the month. In this way I think that the participants in public consultation meetings are being deliberately misled. Rather than helping the process such meetings are harmful in that they tend to distract people from participating in a more effective and difficult political process. A thoughtful letter to a city councillor is a much better use of a citizens time then sitting around listening to people go on about random stuff.

If politicians really want to make it easy for citizens to participate in low level decisions there are better ways to do so. They could just hold a poll. Give everyone enumerated in the civic election a long random number. Post the arguments for and against something on a website somewhere. Let people insult each other on a forum for a while and if any actual new arguments arise from the chaos post them too. Post this all various places offline and see if any offline people can add to the arguments. People would vote by quoting their numbers either on-line or in the form of a letter. Votes with duplicate numbers would be quietly discarded unless there were an excessive number of them. If there were multiple options then the voters would rank them and an appropriate form of preferential voting would be used. If it was felt that such a system would lead to some sort of tyranny of the majority at the expense of local interests voting could be restricted to a particular area or the value of votes could be geographically weighted. Raw data would be made public as well as any complaints of vote buying and/or other coercion.

I feel that the system described in the previous paragraph would be a lot better than holding public meetings. As a bonus the professional politicians would not have to waste their evenings sitting in an uncomfortable chair. The results of such polls could still be ignored if required. The results would be of higher quality than a bunch of rambling speeches.

In the end the process with repect to the footbridge sort of worked. I am just not sure exactly what that process was. The dangerous metal posts on the existing bridge were removed. One day they were just gone. I like to think that some low level civic employee with access to an angle grinder heard about the controversy and just decided to deal with the issue. More romantically; a rouge individual somewhere out there in the dark who believes in direct action against civic infrastructure for the greater good. Perhaps we need such a hero...

Speaking of direct action... Most of these stimulus projects are funded by three levels of government. The tradition is to identify tax money going to any generally popular and non-controversial project by erecting a sign. As a result each of these projects ends up with 3 signs. There are many small projects so the city now has a lot of these signs everywhere. Sort of the most boring Burma-Shave campaign imaginable. I was delighted to see that someone has given the now irrelevant signs at the footbridge site purpose with the creation of some textual art. Sometimes anarchy makes the world a better place.

posted at: 13:09 | path: /politics | permanent link to this entry | Comments (0)

The small area of LED light emitters makes it somewhat challenging to use them effectively in low level lighting applications. The light is hard to shade and diffuse efficiently. In the past I have used light coloured ceilings and walls as diffuse reflectors. This works fairly well but it can be a problem avoiding a bright area on the wall/ceiling where the light is mounted. Here is a description of a light I built that physically moves the light emitters away from the wall to deal with this issue. This works but the resulting fixture is quite large.

The ideal angle of the wedge of light from a wall mounted fixture is something a bit under 90 degrees. We want to avoid illuminating the wall behind the fixture while preventing people from seeing the small bright emitters directly. We also do not want a lot of light on the ceiling closest to the fixture as this tends to make a bright spot, particularly if the fixture is close to the ceiling. The raw LED chip itself emits light from a flat surface. This means that the light distribution tends to be proportional to the cosine of the angle from the normal. Cutting this distribution in half would produce a fairly good light distribution for the application. That could be done by adding a horizontal reflector. Since we have no need for optics other than the reflector we might as well use surface mount LEDs and make the fixture small.

I wanted to experiment with monochrome light as we are targeting night vision here. This plot:

from here suggests that the best wavelength for night (scotopic) vision would be 505 nm. That by coincidence is the wavelength that is perceived as the North American traffic signal "green" colour. As a result LEDs that emit this odd wavelength are relatively easy to find. The colour ends up being sort of a cyanish green. Light with a wavelength of 505 nm is fairly active as circadian light but the light levels achieved here are much too low to be disruptive.

My thinking up to this point inspired me to go out and buy these from here. I ended up with the larger 1206 packages because the supplier I ordered from would only provide the wavelength I wanted in that size. The extra width (1.6mm) ended up not being a problem and they were easier to handle than the 0805 packages I normally prefer for hand made surface mount based prototypes.

I spent some time planning to use a thin sheet of stainless steel as a reflector until I stumbled on this at a local home improvement store:

It was originally intended as an edging for a counter top. It was made out of a shiny alloy and was close to the desired shape. It comes with a prefabricated wall shade in the form of the overhang.

The use of the surface mount devices pretty much mandated the use of the PCB. Rather than measure anything I made a drawing at 5X scale:

and then printed it at 20% to use as a guide. Much to my surprise the Xfig program on Linux got it exactly right with no fiddling. That's not all that expected for a mere figure creation program. Here is the drawing in various formats: fig, postscript, pdf, svg, png.

A sharp tool was used to transfer the dimensions from the 1X scale drawing to the copper:

followed by a layout:

followed by some use of a cutting disk:

Note that the edges of the copper have been ground off to prevent shorts through the metal reflector. I just dragged the cutting disk along the sides. A more appropriate tool would make for a straighter edge.

I first applied liquid flux to the PCB. This is probably optional for such a simple assembly but I had it available and it did make things easier. A popular method of hand soldering surface mount devices starts by adding solder to just one pad. In my case this meant I would first add solder to each alternate area of copper like this:

Then the device is moved into position and held in place with something like a round toothpick. Heat from a soldering iron is applied to the solder (but not directly to the device) to sweat solder the device in place. Then it is fairly easy to solder the other pins. Once the device is well secured the original pin can have solder added if needed. This was the scene after soldering was complete:

I have ended up with 3 LEDs and 2 resistors. When I made the drawing I was enough of an engineer to want to cover the case where 4 LEDs were required to make up the voltage. The idea was to just skip one cut for the 3 LED case. When I made the board I was apparently enough of a technician to be compelled to make things as shown on the drawing. Thus I managed to make a classic error involving an ambiguous drawing in a way that normally requires two people. Using 2 resistors solved the problem in the assembly phase which meant I had also achieved pointless symmetry which is another sort of classic error. There is probably some insightful observation on the human condition available to me here but it escapes me.

I picked a LED current of half the normal specification based on the hope that it might increase the lifetime of the fixture. I have no idea if that makes sense with LEDs. Heat might not be an issue. LED manufacturers like to quote a lifetime of 100,000 hours (11 years) which really just means they think their product might last a long time. With a target current of 10 mA we end up with (12V-(3.2V*3))/0.01A = 240 ohms of resistance. I ended up using two 110 ohm resistors.

After soldering the wire connections and cleaning off the rosin based flux with pure isopropyl alcohol I was done with the electrical assembly:

I used a small amount of RTV silicone sealant to glue the board in place in the reflector. The board would not stay where it was supposed to go. I ended up using the weight of the wires to keep it in place:

The preceding image shows that the reflector is quite a lot wider than would be required just to reflect the light from the LEDs. The idea was to prevent light from escaping from the ends of the channel without any extra fabrication. This worked but the channel itself was still a bit bright where it could be seen on the ends.

Testing the light distribution against a white surface showed some problems:

To prevent light from projecting below the horizontal plane the assembly had to be tilted back towards the LED side. This is inconvenient for the eventual installation of the fixture and caused two other problems. The largest amount of light was going more or less directly up to the ceiling above the fixture creating a bright spot. The other problem was that a significant amount of light was finding its way to the wall directly behind the fixture which created another bright area. Blackening the top of the channel helped but I eventually took a different approach and bent the end of the reflector up like this:

The edge of the reflector is bent up enough to be in the same plane as the top of the channel. This means that there is no light projected below the horizontal plane when the fixture is sitting flat against a horizontal surface. The result was:

This is much better. I consider the design complete.

Next I'll go into the various thoughts and observations that came out of this activity...

When using monochromatic light even illumination can create a situation that destroys visual information. The light from the designed fixture is very uniform. Evenly illuminating large areas of the ceiling results in a situation related to an outdoors whiteout condition. Objects are still visible but with little detail. I suspect that this would only be an issue in rooms small enough to allow a single fixture to evenly illuminate the entire ceiling. A fix is to move the fixture closer to the ceiling to produce sharper shadows at the cost of a more intense hot spot.

The Homo sapiens sapiens set depend on visual transitions in their peripheral vision to help with things like walking around. The sharp vertical light transition produced by the reflector means that a strong cue should exist for orientation and balance. This artificial horizon effect might end up being the more important visual information. This system is after all intended to improve navigation. I am not sure how well this actually works at low light levels. There is probably a research opportunity here.

An important performance feature of a low level lighting system is the length of time it takes for vision to adapt enough to navigate after the high level lighting is turned off. Testing this produced a result that initially seemed odd. It seemed that the nighttime vision system (rod based) was adapting significantly faster than the daytime vision system (cone based). I would see a monochrome image before I could perceive the colour of the light. This lag was something like 5 seconds. The oddness here came from the impression that nighttime vision takes a much longer time to adapt to darkness than daytime vision. Some research revealed that this isn't really true in general. It turns out that the traditional way to check the time it takes people to adapt to the dark is to expose them to really bright light for a long time and then plunge them into complete darkness. This presumably is to simulate the common situation where one is walking along in a sunlit meadow before falling into a fast moving underground river. In more reasonable transitions from light to dark it is the nighttime vision that kicks in first (Ref, See Figure 2). At the light levels I am using the effect would be close to the maximum. The daytime vision system has to adapt to a level close to the daytime minimum while the nighttime vision system only has to adapt to a light level 100 times higher than the nighttime minimum. The transition is driven harder for the nighttime system. This I think strengthens the contention that 505 nm is the magic wavelength for low level lighting.

Since the edge of the reflector is to be bent up it might make sense to cut the reflector in such a way as to allow the bent up part to shade the bright ends of the channel. In other words, the reflector could be cut off at an angle to make the LED side shorter than the bent side. This could also hide associated wiring.

Light fixtures that point upward accumulate dirt. This creates a maintenance issue. For some applications it might be better to put the light sources below eye level pointing downward. Hallways and walkways are sometimes lit this way.

Blue LEDs at 470 nm are fairly effective for nighttime vision but are a lot less visible to daytime vision than 505 nm LEDs. This might make blue LEDs preferable where it is important for the night lighting to be invisible during the day.

The next step is to make some of these and deploy them around the house to try out the low level lighting lifestyle for myself. I should be able to hide the fixtures on the top of door and window frames. This will make it possible to hook the wires up into the attic for an easy installation. I will report on the results when and if there are any.

EDIT: proceeding -> preceding

posted at: 15:49 | path: /ledlight | permanent link to this entry | Comments (0)

According to a local Winnipeg newspaper the Omand Park footbridge proposal is effectively dead. I found some of the background and subsequent discussion interesting.

Apparently the federal government is keen to spend money because of the economic crisis or something. They needed to spend it fast so they went around and asked various other levels of government if they could manage to spend some money relatively quickly on infrastructure. One of the things the city of Winnipeg asked for was money for a new footbridge in Omand's Park.

You can see the Google Maps satellite view of the disputed area here. The existing footbridge crosses the creek that goes from north to south to the river. The proposed footbridge is shown on this drawing.

The existing bridge has become part of a sort of bicycle green-way for that part of town. Bicycle commuter traffic comes from the west and a nearby footbridge over the river on the way to downtown to the east. The problems with it are:

• It floods every spring (recently for an extended period). It is flooded as I write this. Bicycle traffic has to detour 0.8km when the bridge is out. The detour is not that great. Part of the detour involves a steep hill to a blind T intersection. Another part of the detour involves illegally riding on the sidewalk. Not that people seem to mind the illegality...
• The approach to the bridge on the east side with the switchback up the hill is not done very well. People often walk their bicycles to avoid dealing with it. Those that can will sometimes just go cross country to avoid it. It somehow manages to be bad both going up and coming down the hill (Pic).
• Physics. Bicycles basically work by conserving energy. They speed up going down hills which provides kinetic energy to help get up the next hill. The approaches to the bridge are reasonably steep. As a result bicycles are going at maximum speed going over the bridge. It is a mixed use path. Pedestrians do not conserve energy going down the hill and as a result are moving relatively slowly. The speed difference causes problems. A past attempt was made to improve things by installing barriers in the middle of the ends of the bridge (Pic). The barriers work the first few times but the bike rider eventually learns how to avoid injury and manages to retain some precious speed going on to the bridge. At this point the rider has dealt with a hill, a turn, and the barrier in quick succession. They sometimes have nothing left to deal with any semi-stationary people and/or animals and/or things on the bridge.

In cities there is a natural tension between people in local neighbourhoods and people who are simply interested in getting to the other side of those neighbourhoods. The neighbourhood in question has some interesting history with respect to transportation policy in the story of the Wolseley Elm. These sorts of things normally do not end in the wildly irresponsible use of high explosives, but, well Winnipeg is special that way. People can stay really wound up about things that people in other parts of the world might perhaps eventually let go of. At any rate the Wolseley residents lost the tree but won the battle. The street in question now has four-way stops every few blocks. In the summer cars are not even allowed on it Sundays.

Which brings us to politics. The Wolseley area is famous for a high level of community consciousness and activism. When some of the local residents found out there was to be a bridge they had the city hold another meeting to talk about the bridge. I attended that meeting.

At the "community meeting" there were four alternative proposals to look at (most of which really didn't make a lot of sense). There were places to write comments on the proposals. There was a sign in sheet. There were forms you could fill out with your comments and a ranking of the five options. Some people talked for a while. The people who made the proposals mentioned that they did not think two of them were actually practical. There were people from the local community. There was a person who talked about the bicycle issues. After a while a line formed and then a whole lot of people talked.

The most compelling argument against the bridge was made by the the "too young to vote" crowd. Some of the neighbourhood children stood up and more or less said "Don't build the bridge. It would ruin our toboggan hill.". In other words, building the bridge would destroy a rare resource: an inclined surface on the prairies. Their directness was refreshing as many of the adults triggered a pet peeve of mine. When addressing an issue like the bridge it is really nice if at some point you tell the audience:

• What you think should be done.
• Why.

Those two points make the rest of what you might say much easier to understand. Particularly for members of the audience that do not know you.

What I think should be done

I was actually part of the 4% who voted for the bridge as originally proposed in the drawing. So build the bridge.

Why

I really think the engineering types got it right this time. All the other proposals seem worse in some way. Using the existing bridge in any reasonable way does not solve the physics issue. Improving the approaches makes the speed issue worse. The proposed road level bridge solves all the mixed use traffic problems permanently.

Raising/moving the existing bridge would tend to block the flow of the creek due to the required earthworks. That would be at a time when culverts upstream on the very same creek are being replaced with bridges. A watercourse is a classic example of how local changes can have non-local effects. The proposed bridge almost entirely avoids unanticipated changes to the creek environment. For what it is worth I think that a long narrow bridge as proposed would look pretty good.

As for the toboggan hill issue. There are other places to slide in the park. A few minutes with a front end loader would produce an even better hill.

Unless a grassroots "Save Our Bridge!" movement emerges in the next few weeks arguments for and against the bridge are moot. The bigger question is how much control should a local community have over things of value to the larger community. I tend to the progressive side, I really hate to see things left broken. Obviously a local community can not have complete control of all aspects of their area. As an semi-absurd example, I could get together with my neighbours and insist that the street on our block be converted to a playground and parking for the residents. It would remove the risk that the local kids have to face from the large high speed traffic our street tends to get. When ignored we could then complain we were not being consulted on the parking/playground issue. I think most people would consider us to be quite unreasonable in our desire.

So, yeah, in the case of the Omand's Park bridge I think the residents were being a bit unreasonable. For a very small local cost we could of had something of great general value. The process was quite bad. The people from outside of the area who would of gotten the most benefit from the bridge would not of seen the postings for the meeting because it took place in the winter. Even if a whole bunch of bicycle types had shown up and won the vote for the bridge would it really of mattered? I don't see how these sorts of issues can be resolved by majority rules. Someone has to decide at a level of government beyond the community in the end.

Just a comment on the local media coverage. The Free Press is the more respectable looking print newspaper in Winnipeg. They were being deliberately misleading when covering this issue. In this article they state "Only four per cent approved of the hilltop-spanning bridge.". The actual results are here. There is no "hilltop-spanning" bridge mentioned here. Which kind of makes sense as there are no actual hills in the area. A better way to put it might of been to say that 27% wanted a bridge as their first choice and 68% wanted an option that did not involve a bridge. It still sounds negative toward the bridge but it at least is sort of correct. In defence of the Free Press they were reporting on something that kind of sounded odd. The survey report said that people were asked to rank preference (I was) but then they decided to just count the first choice. It might be good at this point to ask for the raw ballots and do the ranking as the people at the meeting expected.

I would be amiss if I did not reference a local blog that normally covers this sort of thing, and did. Here.

posted at: 18:56 | path: /politics | permanent link to this entry | Comments (0)

Did you ever watch a moth express a unnatural and disturbing desire to become one with the filament of a light bulb? I tend to feel sorry for the moth and, I must confess, a little bit superior. After spending way too much time reading about circadian light I think that in the future I will feel a little less superior.

In a previous post I mentioned something about blue light and circadian rhythm. It turns out that mammals have an entire separate visual system devoted to synchronizing circadian rhythm to the local light/dark cycle. The existence of this system was entirely unknown until recently. I would like to state at this point that I think that the people who figured all this out are awesome. All the important stuff was worked over a period of less than 10 years. It was definitely a triumph. I suspect that even now it is still pretty difficult to get funding to study something no one learned about in school. Imagine what it was like to propose that there was this huge thing that everyone else had missed in the beginning.

Basically there are slow ambient light sensors in the eye that are connected directly to a biological oscillator with a period of 24 hours. This oscillator is phase locked to the light/dark cycle and in turn locks various systems to the light/dark cycle. The system is most sensitive to light in the range from 450 to 480 nm. Light of this wavelength is perceived by the daytime visual system as blue. Here is a nice summary of what was known in 2003. Check out the figures.

Following this I will freely mix the ideas of myself and others in infotainment style.

Much of this is still not understood

... least of all by me. Even the reasons for having a circadian rhythm at all are not clear. The explanations I have seen state something to the effect that the circadian rhythm is important because it regulates important stuff. Some arctic animals get rid of of it entirely in the dark months but start it up when the light returns ((Ref)Thanks Gord). This implies that maintaining a circadian rhythm is expensive. At the same time it implies that the cost is worth it somehow.

The thing with these systems created by evolution is that evolution can't actually design anything. It doesn't matter that no one can understand it or even that it makes sense. It just has to work. Stuff like this is why I avoided taking anything like biology in school. Every path leads down the rabbit hole. I strongly prefer things that make sense in a simple way. Evolution sucks.

What is understood is that people are directly controlled by light levels in a very direct way. We just don't know what all the implications of this are.

"Wait, how many marks do I get for this?"

While reading through related papers I was struck by the apparent level of dedication shown by the human experimental subjects. These sort of things are mostly inflicted on students. Students tend to think that the most outrageous form of physical humour involves drawing stuff on drunk people. Thus it must of seemed that they were part of someone else's hilarious practical joke. When pushing back the frontiers of this particular bit of science you get to:

• Put up with people shining bright lights directly in your face.
• Sit alone in the dark for hours extending to days ... often with a thermometer in your butt.
• Stare at an illuminated surface ... without moving your eyes ... for up to 6 hours. At least one experiment had a video system to allow someone to yell at you if you attempted to move your eyes.
• Wear incredibly dorky glasses in public. Funniest when applied to teenagers (Ref).

Melatonin

Circadian light significantly reduces the level of a hormone called melatonin. The hormone is reasonably easy to measure and is dramatically effected by light exposure. Thus people like to use it as an indicator that circadian light is being detected. Since it is the thing everyone is measuring people tend to fixate on it when coming up with theories. Light makes it go away fairly fast (15min) but it can take 3 hours to return in darkness.

Age

Older people are significantly less sensitive to circadian light than younger people. In an analogous way to the way people loose the ability to hear short wavelength sounds as they grow older they also lose the ability to sense shorter wavelengths of light. Circadian light is at the short wavelength end of the spectrum and gets attenuated. The first graph from this shows the spectral characteristic of the lens of the eye with respect to age. Fluorescent lighting has a large spike of energy at 435nm. This would be effective as circadian light. Past the age of 20 this wavelength is strongly attenuated. It might be reasonable to assume that children and teenagers are much more effected than adults by fluorescent lighting. I suspect that is part of the reasoning that led to studies like this.

Circadian light is good

People living close to the poles tend to live without much natural light for much of the year. This can lead to various problems. The most famous of these is seasonal affective disorder (SAD). A common treatment involves sitting in front of a box full of fluorescent lights for a while in the early morning. Circadian light is generally assumed to be involved somehow. One idea is that melatonin prevents the production of serotonin which in turn prevents the person involved from feeling good. So... circadian light can make you happy...

In general people like brightly lighted places. I bemoaned that fact in this post when I was discussing low level lighting. Those people back in the day were not just wasting energy with their extravagant light levels. They were possibly improving the mood and health of the people who worked there. The present standard for office lighting calls for 500 lux. You need 1000-2000 lux to get a reasonable circadian effect. Typical factories and warehouses tend to be dimmer than offices.

Circadian light is bad

Bright light in the evening can retard the circadian cycle in people. The effect can be increased where there is no exposure to light in the morning. This could mean that the affected person would stay up later and have trouble getting up for work/school in the morning. The net effect would be a general lack of sleep.

The question of "How much light is too much?" is a bit complicated. Fluorescent lighting at 2000 lux would certainly have an effect after sundown. The traditional well shaded 60W incandescent sitting on an end table in a living room is not likely to make much difference. TVs and computer monitors might have an effect. For example, my monitor is rated at 300 nit. That is equivalent to 940 lux. That sounds a bit bright but the monitor only occupies maybe 1/4 of my visual field. That is important because the circadian light sensors are well scattered in the retina. We can't stop here because when people say that 2000 lux is significant they mean illumination. Only the light that is reflected from the surroundings ends up on retinas. The rule of thumb seems to be a factor of 5. So we are down by 4 and up by 5 which may mean an equivalent of 1200 lux of fluorescent lighting. That still sounds a bit high.

There are of course programs to play with for people that want to experiment with reducing evening light exposure caused by their monitors. A program like Redshift that adjusts to a warmer colour temperature at night might help. The idea is that warmer means less blue light from the screen. For those trapped in the MS Windows environment F.Lux does the same sort of thing. The less technical solution for those concerned is just to turn down the brightness of the monitor/TV at night.

The "C" word

This section could be subtitled "Circadian light is real bad". I get the impression that there is a relatively large amount of money available for cancer related studies. When you look harder you find more stuff. It is then no surprise that there is a theory linking circadian light to cancer.

A study showed that women that work night shifts tend to have more breast cancer. Also, people in developed countries tend to have more cancer than people in less developed countries (citation needed). What do night shift workers and people in more developed countries have more of? One thing is artificial light. The growth of at least some cancers has been shown to be reduced by the hormone melatonin. More light means less melatonin so we end up with more cancer.

I am sceptical myself. As mentioned earlier, most workplace artificial light environments do not count that highly as circadian light. Since shift workers tend to create a dark environment to sleep in (and close their eyes) the extra melatonin suppression could only be what counts as the evening hours for the particular person. That would be only something like 3 hours down from the normal 8 or 9 hours of high melatonin levels. Significant, but most of it is still there. If artificial light does in fact cause cancer this would be one of the most significant unintended effects related to a technology in human history.

Nightlights make no difference

This all started with a night night that had bluish/white LED's. This well done experiment shows that a lower limit of 0.01 W/m2 for circadian effect would be reasonable. My calculations were quite rough. I assumed that someone managed to stimulate their entire visual field for 15 min (the time used in the study) with the light from my night light. I also assumed that all the light energy was moved to the circadian wavelengths. Since that light energy ended up being less than 0.01 W/m2 I think it is safe to say that my night light was not going to disrupt anyone's circadian stuff. It would be hard to think of a reasonable night light that would. From time to time the news media does a popular science article on the circadian light thing. Sometimes this gets livened up to "Is your childs night light harmful? Find out at 9!". For extra excitement they throw in the "C" word. So to that I say, no, it isn't. If it bothers anyone they can just stick the thing behind a dresser. "For extra safety!".

There is a lot of bogosity here

One of the nice things about writing articles about things wildly outside my expertise is that I can say things that might be a lot more insulting coming from someone more knowledgeable. Anyone with a light meter, access to a freezer, and a test lab can do a study involving circadian light. The catch is that a lot of this stuff is wildly unknown and it is hard to know what needs to be controlled. That does not mean that I think that the simple studies are worthless. It is just that they should not be used to back up things like news articles, wikipedia entries, and products.

Let's play along at home...

It might be fun do some some wild speculation of our own. For extra fun let's be slightly political.

Daylight savings time causes unhappy/tired people! This applies to the situation where just as the day becomes long enough to see light in the morning daylight savings time kicks in plunging morning commuters back into darkness. Since the lack of morning light is bad then daylight savings time is bad for a few months in the spring. In the height of summer daylight savings time results in a lot more light late in the evening. Also bad.

The ban on incandescent bulbs will cause tired/unhappy people! Canada is planing to ban light sources that use hot filaments. Incandescent bulbs create relatively little blue (circadian) light. Compact fluoresents could be expected to have more of a disruptive effect in the evening. Children/teens would be more affected by this. The "Find out at 9!" article writes itself at this point. If you dim an incandescent it produces virtually no circadian light. This option does not exist with compact fluorescents.

With great knowledge comes great responsibility

People are already trying to use this new found knowledge to abuse the working class. Yes, 3% extra productivity justifies any means. Employers have been fiddling with lighting for years. The problem is that now lighting at work is known to have an effect on life outside of work. I would not be surprised to see circadian light issues show up in future employment contracts. Even if an employee accepts a particular situation is it then ethical to fiddle with stuff that might conceivably have an effect on things like reproduction (Ref1, Ref2)?

What should we do?

I don't know about other people. Poorly understood? Potentially powerful and/or dangerous? Great! Let's try to hack it! More later...

posted at: 16:40 | path: /ledlight | permanent link to this entry | Comments (0)

We had a wet spring and as a result my bedroom window looked like this;

It and some of my other windows of that type had looked like that in the past but this seemed a bit extreme. Some hunting around on the web revealed that people were sometimes managing to dry out multipane windows by drilling holes in them. Most were making 2 holes. I thought it might be interesting to just make one hole and see the results.

The thinking here is that I live in a cold and dry climate that has wide temperature swings. The water vapour might get pumped out by the trapped air expanding and contracting over each day-cycle. After all, that is likely how the water got in there in the first place.

The window is triple-pane and the fogged bit was of course on the other side from the drier environment outside. This meant drilling through two panes. I used this;

I would not recommend this tool for this application. It grabbed badly when clearing the hole on the outside pane. I did take reasonable precautions but this was still a bit scary with all that breakable heavy glass above the work area. There is some potential for serious injury with this activity. Something like a small diamond core drill would of been better as the hole can be made quite small. Using such a large tool wasted much time.

I used the felt like material from an old floppy disk as the filter. What is needed is something to keep small insects out that will not rot. I used a piece of a plastic pipe end cap as the rain cover. I used clear RTV sealant to hold everything to the window after cleaning the surfaces with alcohol.

I first put a thin coating of sealant on the edges of the filter. Using the point of a knife I positioned it over the hole. The rain cover then had a thin layer of sealant applied before it was placed on the window. A bit of duct tape held it in place while the sealant dried. Some glass dust ended up between the window panes. I wasted some time with a tube trying to vacuum the dust out. The dust fell to the bottom after the static electricity discharged.

The window took about a month to clear. I was left with very small water droplets that were mostly invisible in the summer. They froze in the winter and are a bit obvious now at 4 months into the experiment;

I am happy with the result and have no plan to add a second vent. If I do this again with another window I will put the vent at the top of the window in the centre. This would be better because;

• The vent would be better shielded from rain by the eave and window frame.
• The vent would be out of the reach of curious people.
• Drilling the vent would be safer as the glass would be below the work area.
• The window would defog from the centre top which might look nicer.

posted at: 13:52 | path: /house | permanent link to this entry | Comments (0)