User:Matthew Stannard/projects
Lampshade Project
[edit]Background, Objectives and Constraints
[edit]Background
[edit]I use LEDs packaged so as to make them plug-compatible with halogen lamps. When these went on sale a few years ago the idea was that, because they use much less electricity, people would be motivated to replace existing halogens with LED equivalents. They fit in the same sockets, are rated at 12V, and take far less current. Unfortunately, many people returned them complaining that they didn't work. The problem was that the 12V switched mode power supplies used for halogen bulbs have open circuit protection, which means that they stop delivering any appreciable current when the load has too high a resistance, as is the case with an LED. This was exactly what happened, so if you really want to replace your halogens with LEDs, you also have to change the power supply to one with no minimum current limit. This acted as a deterrent to people purchasing these packages and resulted in most electrical suppliers ceasing to stock them. However you can still get them; the prices aren't going up and the CRI is ever improving.
I decided to use these LED packages and build them into lamps that could be used as bedside lights, worklights, etc., anywhere one wanted a small cool lamp. Whilst the light source in an LED lamp is an intensely bright point source of light, the illumination from them is generally a 45-degree cone. Compared with traditional lighting, a room illuminated entirely with such lamps has light in places where you want it, but is quite dark in other places. The result is a lower overall level of illumination, but one's eyes adjust so that the dark doesn't seem quite so dark. For most of human history, night-time was mainly dark, with perhaps just a camp fire or lantern for illumination - not like today, where we tend to make night as bright as day in our homes. Why waste electricity making our environments so bright that our irises have to compensate for it?
LED spotlamps are great insofar as they illuminate almost as well as sunlight at close range. The problem is mainly that they are too bright; looking into them is like looking into a torch. Therefore I need to have a lampshade that funnels the light. The Koch snowflake design is graceful and would seem to suit the requirement for making an attractive object. That's not to say there aren't even better shapes to use. The character of the finished lamp is largely determined by the lampshade and I would love to find other organic shapes based on nature or mathematics that make attractive objects.
Issues acting as Constraints
[edit]The issues to do with using these ready-made LED packages in a desk-top lamp (for which they aren't designed) include:
- the bulb, whilst providing a beam of great power that is equally fabulous for illumination at close quarters or to spotight objects further away, is so bright that looking at it from even quite a wide angle is quite distracting and not pleasant
- if used in a confined space the temperature of the LED package increases, i.e. the thing needs to be reasonably well ventilated. The temperature isn't a particular problem per se as it never gets nearly as hot as a halogen, but the LED becomes less bright over time at a rate proportional to its operating temperature, i.e. the hotter you run it the less long it lasts.
- nobody supplies attractive holders for the LED package. All you can get are rather clunky sockets made of ceramic designed for halogen bulbs with the same fitting.
- my desklamp/worklamp design uses "stay-put" (aka "gooseneck") tubing, which only works reliably to let you keep the light pointing in the direction you choose if the bulb, housing and any lampshade aren't too heavy. If they are too heavy then the lamp will tend to droop and not stay pointing where you want.
Objectives
[edit]The overall objectives are to produce a desklamp/worklamp where:
- the beam is shielded so it only hurts your eyes if you point it directly at them
- the lamp holder/lampshade allows air to circulate around the LED package
- the lamp holder allows easy insertion of the LED package and is reliably connected to a length of stay-put tubing
- the overall weight of the bulb, housing and lampshade doesn't exceed 70 grams
The objective of this project is to produce a lampshade, either 3D printed or moulded, that allows the overall objectives to be met and results in an attractive functional object.
Parts
[edit]LED package
[edit]
I tend to use the LED packages indicated as having the MR11 fitting, shown here. These are about 35mm at the widest diameter, considerably smaller than the popular MR16 packages that are commonly used in domestic ceiling-mounted spotlights. The one with the striated heatsink (on the left of the photo) emits light between the fins, which produce lined shadows on any surrounding structure.
Lamp stem
[edit]I'm using an existing design comprising a length of brass tube into one end of which I've inserted a short length of stay-put flexible steel tube. The whole of this assembly is pushed inside a length of white silicone sleeving. On the end of the flexible end I've attached a holder that accommodates the LED package.
Koch Snowflake-based lampshade
[edit]
The piece shown here was kindly supplied by fellow SLMS member, Laurent Muchacho. It's based on a design published in thingiverse.
I attached to the narrow end a piece of plywood with a round-cornered rectagular hole intended to take the pronged end of the LED package. With the LED package inserted inside, it meets all the design objectives except one: there isn't enough space inside this form to allow air to circulate freely around the LED package.
Therefore I rejected this idea and instead decided to cut down a copy of the part supplied to make an opening at the narrow end that was large enough for the LED package to go through, thereby:
- allowing air to circulate without restriction around the LED package, and
- allowing the lampshade to be removed without removing the LED package.
I then designed and made a 'collar' to attach to the snowflake object. It contains three prongs, which are intended to grip the LED package at the place where it is joined to its holder. These prongs are made out of enamelled copper wire one end of which has been dipped in white epoxy, making them look a bit like the little matches that restaurants give to smokers.
The picture above shows the collar with copper wires inserted though not yet stuck in place.
I stuck the collar to the cut-down Koch smowflake object using polyester resin, which holds the copper wires in place and makes a firm bond with the collar.
Assembly
[edit]Assembly is a matter of bending the copper wires so they grip the the holder at its waist, but can be bent back so that the lampshade can be taken off.
The whole lampshade assembly is light enough not to cause the gooseneck to droop, regardless of the direction it's pointed.
Refinements
[edit]I was relatively pleased with the look of the result shown here, though I'm looking at a better method of attaching the shade to the lamp.
Using copper wire for the prongs means that a pair of fine pliers is needed to make the shade fit tightly over the LED package, which implies supplying a pair of such pliers with each lampshade I make. Whilst it is entirely part of the makers' ethos to possess such a tool, it occurs to me that the fitting process would be made trivial if the prongs were made of something springy. So that's my current quest.
Materials I've experimented with include:
- 0.2mm cheesewire, which tended to incur permanent bending too easily. Even when I doubled the number of prongs to six, it wasn't strong enough to hold the lamp in place without drooping. However the collar does make a remarkable ring, which I can put on my middle finger and in the right light with my hand splayed it appears to stay suspended round my finger as if by magic
- hairclips, which were too stiff
- unravelled springs, which also were too stiff and difficult to attach to the collar
- cut up cable ties, which would be an effort to attach to the collar
- the nylon line used in a strimmer
Using wire makes construction less fiddly because one can wind it round a groove on the outside of the collar and use one piece of wire to go through every hole. After it's glued in place I can cut the wires to the right length. However, I haven't found a wire with correct degree of springiness and whilst not being easy to deform, though I'm sure such a material must exist.
Cable ties are made of nylon, which is good in terms of its flexibility, strength and the fact that it doesn't tend to get a permanent set. But strimmer line is also made out of nylon and is of circular section, so it was going to be much easier to fit.
Now I only needed small holes in the rim to stick some strimmer cord through, like the spokes of a wheel. Attaching it was going to be an issue, though, until I discovered that I could use thin nosed pliers to deform the nylon on each side of the hole, thereby preventing the spokes from falling out, though leaving them a bit wobbly.
The collar needs to be stuck to a koch snowflake object but in the mean time I can check out how long to make the spokes with a lamp, as the picture below shows.
Review
[edit]Polyester resin is rather brittle, or else the stuff I'm using has got past its sell-by date. Several of the shades I've made have smashed by being dropped. I'm ordering some fresh resin to see if I can make them more robust. A better solution than using a mould seems to be to 3D print each one individually. This will require mastering some 3D CAD package producing, for example, an .stl file that can be sent to a 3D hub for printing. The nylon spokes that hold the lampshade in place are quite successful. I use six spokes, and they need to be accurately placed and cut so that the lampshade is balanced and central when it's fitted to the lamp. I milled a cap out of MDF that fits over the narrow end of the lampshade and allows me accurately to drill the lampshade and to position the nylon spokes.
Next Step
[edit]Try out Tinkercad to see if I can use it to manipulate the thingiverse Kock Snowflake object and design a lampshade which can be 3D printed. Alternatively, find a fellow SLMS member with whom to collaborate and who could generate the requisite .stl file more easily than I could.
The dimensions I require are, with the lampshade sitting on its narrow end:
- Height: 66mm
- Top (maximum) diameter: 75mm
- Base (minimum) diameter: 41.5mm
- Base (maximum) diameter: 45mm
- Collar height: 5mm
- Collar inner diameter: 39mm
Note that the Koch snowflake nowhere has a circular perimeter, which is why I've user the terms 'minimum' and 'maximum' when referring to diameter.
Perhaps it would be simpler to say that the item comprises:
- a 'snowflakey' bit, which is 66mm tall and has an opening (where the light comes out) the outside of which would just fit into a 75mm diameter circular hole. The narrow end of the 'snowflakey' bit would just fit into a 45mm diameter circular hole.
- a collar, which is a 5mm tall fill and has a circular cylindrical hole of 39mm diameter, giving it a minimum wall thickness of (41.5-39)/2 = 1.25mm and a maximum wall thickness of (45-39)/2 = 3mm
The collar merges with the 'snowflakey' bit such that the height remains as 66mm and the outside perimeter of the narrow end of the 'snowflakey' remains the same as if the collar weren't there, i.e. the collar fits inside the 'snowflakey' bit and acts as rim for the spokes that are needed to hold the lampshade in place.
Tinkercad Log
[edit]I'm recording here what I do in Tinkercad so I can refer to it after I've forgotten what I did!
- The URL is https://tinkercad.com/. One needs to register to use it
- Click on + Create Project and Add a description.... I'm calling it Koch Snowflake Lampshade
- Click on Create New Design. The screen changes to show the work plane
- In a new browser tab, go to http://www.thingiverse.com/thing:37117/#files and download the file called Koch_SnowflakeTwistRound .stl
- Back in Tinkercad, click on Import, select File and upload the file downloaded in the previous step. After quite a wait, an image of the thingiverse object appeared.
- tbc
Diversions
[edit]Invitation
[edit]Please visit my Facebook page if you'd like to see some of my other work and do give the page a Like if you like it.