Thursday, September 27, 2012

diy testing of led lamps

I had done some testing of LED lamps available to me to rank them for brightness and efficiency. I went through several interations of a DIY test method to help me select a lamp for my 1 watt DIY garden lamp project. Here is a part of the assortment that I tested back in February. I have a few more I'd like to try so this is ongoing.

I wouldn't normally do this for just one lamp, but the idea is to create a prototype for something that could be reproduced on a limited "craft" scale as a DIY project. Perhaps a dozen or so to surround a garden or guide a walkway? Or even a hundred?

My goal of making the maximum attractive light from only 1 watt of power is arbitrary. 1 Watt is an impressively sounding small number but it could be any amount. As it turns out, 1 watt can produce a very impressive amount of light. I will describe a simple but effective test method that helped me to rank LED's.

You can modify this any way that makes sense to you. It does not become dangerous until you start looking at the line voltage 110/220 operated bulbs. I don't think you need to involve line voltage in powering an outdoor system except where it plugs in to keep it safe - so all of the LEDs I tested were of the "12 volt DC", automotive or flashlight type.

I had gathered LEDs from various sources and I wanted to be able to compare them in some semi-organized fashion. I wanted to be able to measure the amount of light produced and the power used by each one. I wanted to observe the light they produced in as objective a manner as possible, but simply.

click any pic to enlarge

There is a bit of basic electronics and physics involved but it is pretty easy stuff. The equipment you can usually borrow or get used what you need at low cost. You don't need it very long, just for the tests. This is a schematic of my LED test setup. The variable power supply allowed me to vary the electrical input to the LED in a smooth manner. I don't say whether it is AC or DC since either could be used. I'll talk more about that later.

Two of the meters allow me to measure the VOLTAGE and CURRENT flowing in the circuit loop, through the LED and back to the supply. From the voltage and current, I can calculate the POWER (the watts) used by the LED. With a ideal variable supply, I can vary either the voltage or the current or both.

The lightmeter lets me measure the light produced. There are different types of light meters and I will talk a bit about that. I was lucky to have a very nice old instrument from Tektronix called the J16 that allowed me to measure either foot-lamberts or mW/

This is the actual test setup. I took this picture in the daytime but daylight through the window affected the tests, particularly when I used the ft-lambert sensor so all of my later testing was done in the dark. The cardboard box is around the J16 lightmeter and the variable supply and the meters are to the right.

You will see that the LED I am testing is mounted on a little frame above the J16 and both of them "look" the same way, towards a bright white sheet of paper taped to the wall in front of them, inside the cardboard light box. In the first pic above, you will see a number of LEDs mounted in these frames. I made them out of scrap wood, all the same size (about 15x8cm)so that they would clip onto the J16 easily and could be swapped around. I tried to mount the LEDs (which were all shapes and sizes) so that the main emitting surface was about level with the surface of the frame and mounted at its center.

In this way, I tried to have a similar environment for all of the LEDs. The LED and light meter are about 55cm from the white paper which is tabloid or north america B size paper. It is what I had available. You can use whatever size of sheet and setup that makes sense for you, but the idea is to keep it the same for all of the LEDs as much as possible.

Thank you for your interest.

George Plhak

diy landscape lamp reading list
a very bright 1 watt diy led garden light
making a lamp from a 2x4
best light at least cost - about testing bright diy leds at home
diy testing of led lamps - this article
diy 1 watt led update
diy garden lamp progress
a shielded low power diy garden lamp
diy lamp update

Related: Fixing LED Strings (Christmas Lights)

Thursday, September 06, 2012

diy solar reflector squeegee from a car wiper

I get questions about cleaning my parabolic solar concentrators.

Concentrating collectors might have a mystique about them that because they use mirrors, these mirrors have to be perfectly clean. This is not possible in the real world and not really necessary I have found. As with a flat plate type collector, the reduction of output due to atmospheric grime might be in the order of 10% if the equipment is really dirty.

Adding a transparent cover over a parabolic collector does not solve the problem since the grime accumulates on the cover instead. Adding a cover means that some energy is always lost by the cover, even if it is clean, since the cover will absorb some of the heat and re-radiate it so that heat does not make it to the collector.

Here in my northern climate (Toronto Canada area) rain water cleans my solar concentrator reasonably well. My array is at an angle to the ground and most of the grime just slides away with the rain runoff. I have not cleaned them myself until now.

To maintain peak efficiency ALL types of solar collectors benefit from manual cleaning, even if only once a year, a concentrator is no different. Some atmospheric deposited grime does not wash off with the rainwater and a mild mechanical cleaning is required. If you are in a dry climate, you might need to manually clean your solar collectors more often.

If the concentrator mirror is on the backside of the sheet as it is with a plastic mirror, a squeegee is perfect.

This is about my DIY tool for cleaning concentrating parabolic solar collectors similar to my DIY design very easily. Like using a regular straight squeegee on a flat plate collector.

Recently I noticed the shape formed by the windshield wiper on my car when I pulled it away from the glass. It was almost perfect - a backwards parabola of almost the right size. But the rubber blade was on the wrong side!

click any pic to enlarge

I disassembled a standard auto wiper to invert the blade and mounted it on a pole. As you will see in the video below, it is now almost a perfect fit with my parabolic collectors.

Above is a closeup to show the swivel pin which holds the wiper to the curved arm. I looked at four types of car wiper blades to check for curvature and length. A friend came up with this rather ingenious method of fastening the blade to the arm. thank you Peter! Simple yet very tough, it allows the blade just the right degree of support and a small amount of give. Details will be in the upcoming book.

If you want to make one of these cleaners, you will need to look at the type of wiper blades you have available.

I tried OEM blades (my drive is a Ford product) and universal replacement blades I bought from an auto supply. I found that by removing the end caps (twisting and pulling) each blade could be easily disassembled. With all but one of them, the blade could be reversed.

If you are in Canada, the one I finished with and show in these pictures is the "Horizon" by rain-x available in various lengths from Canadian Tire.

I ignored the packet of rain-x that they suggest I apply to the glass prior to wiping. I didn't think it was necessary. I used a 22 inch blade for my 24 inch collectors. I am surprised that this product is sold here in inch lengths with no metric marking at all on the package? Canada is metric I think

Getting the center pivot onto the other side proved the most challenging. Of the four types of wipers I looked at, they all had removable end caps but all differed in their details. All but one could be reversed. One had too much curvature. One was too short. It was difficult to remove the center pivot and involved gently bending metal fingers and breaking a spot weld but I did it.

This cleaner works very well. The reflector must be wet before using it. You can do it after a rainfall or use the morning dew. Otherwise you will need to mist with a water spray to the point that water droplets start running down the surface.

This is the parabolic squeegee in action. The pole it is attached to is the common expandable type sold in the home centers for applying paint. The arm is bent in an arc to miss the collector tube. Only light pressure is needed to keep it in contact with almost the entire reflector surface. You can make another two passes to catch the very edges of the reflector sheet if you want to do that.

I don't see many people on their roofs cleaning their collectors - maybe that's a business idea for someone?

DIY concentrating solar reflector squeegee from a car wiper from George Plhak on Vimeo.

Thank you for your interest
George Plhak

[to the gen2 intro and reading list]

Saturday, September 01, 2012

new uses for old tv towers 2

Old television tower sections are low- or no- cost structural components that can be re-used for horizontal spans like this small footbridge that was made over a single weekend. The boards I used for the top and sides are salvaged 2x4's that otherwise would have been scrap.

(click any pic to enlarge it)

Many of the towers around here were made by the Delhi Metal Products company (now Wade Antenna), manufactured in Delhi, Ontario. Typical towers are bolted together of sections that are each 10 feet (300cm) in length. The top section is different and has the antenna mount platform. The sections are made of 18 ga. steel tubing with welded rungs. If they are in good condition, they are very strong, even if used sideways.

The galvanized zinc coating has probably mostly dissolved away in it's mission to protect the steel. Many of these old towers are standing un-used as we've switched, most of us, away from off-the-air TV.

I wanted a small footbridge across what we call here the "seasonal stream". The amount of water varies but at wettest is more than we can jump. It seemed a perfect place for a small bridge. Two or three of us can stand on it and it does not sag at all. Not unpleasant to look at and certainly functional.

The sections I used for this bridge had been sitting by the family cottage for years since being taken down. There were two of the regular sections and a top section. I took the top section to the metal scrap dump and took the other two home.

In a tall tower, you may have more sections. These towers with guy wires sometimes reached four or five sections. If still standing, towers are extremely dangerous to take down and if they are to be re-used, some care is required so that there is no damage. The bolts are rusty and the task is not fun if you have vertigo. There are people who do this sort of work and you probably should hire someone with insurance to do it.

Tower guys are also a good source of supply. For another project, a sun deck, I needed four tower sections and those came from a tower guy. He even let me pick very nice ones from his stock yard that matched.

With tower sections at hand my first step was to clean them with coarse steel wool and wet sand paper and examine them carefully, rung by rung to see if there was any damage. I wanted them strong. In my case, I had to have a couple rungs re-welded to the tubes as they had been broken loose.

I then moved the towers to the bridge site and primed, painted and let them dry in the sun while I thought about the foundations.

The foundations were simple. The tower legs rest on a patio "stone" of precast concrete, the pair cost about $10 and were the first of only three things I had to buy for the project. The rest of the material was recycled.

I did have some loose gravel and bedded the stones on about six inches. I also placed some loose real stones against the stream side to slow the erosion a bit. Three years later, that has held up fairly well. I will probably rework the foundations a bit. Maintenance is easy. With two people, one at each end, the bridge can simply be lifted off its foundations and moved aside.

Here is a view from underneath to help me explain the mounting system for the planks. With the Delhi towers with the round tubes, I used plastic clamps of the kind used to hold down plastic conduit. The planks don't actually get screwed to the tower but are captured by the clamps. This seemed easier than trying to drill into or through the tower tubes. I measured the diameter and then went looking for clamps to fit. I splurged on stainless steel screws to hold the clamps to the planks. The clamps and screws where another $15. I thought that the plastic clamps would be good underneath where they aren't so exposed to sunlight so even if they are not listed as UV safe, they should be fine. The plastic won't rust.

I realized at about this point that I would have to watch for rungs as I spaced out the planks since they might interfere with the clamps. So I did a mock up and laid the planks and slid them around. The clamps could go towards one edge of a plank if necessary yet still keep the plank tied to the tower. When I had an arrangement that seemed to work, I fastened the two end planks at both ends of the bridge with their clamps and worked inward toward the center.

I used a string attached to the two end planks and stretched it to form a guideline. You can see how that helped me in this view. Without the string, it would have been uneven at the edges.

I cut all planks in the shop on a crosscut saw set with a length stop. Working from a pile of salvaged 2x4s, I selected sections that were sturdy and cut them out of the scrap, all to the same length. Some had been painted, some not. Some pressure treated, some not. The best of the pile. The balance now was firewood. The pressure treated cuttings went to the landfill (I always keep PT separate), but so much less. Most of the scrap was used in the bridge.

The finishing touch is a strip of wood down each side fastened to each plank with a stainless steel screw. These tie the planks together so they don't move when you walk on them and also help define the edge. I had tried it before these were added and it just didn't seem as safe.

These strips are cut from the scrap 2x4s like the planks except in this case, the scrap wood is sawn lengthwise.

Probably I should add a kick board at the end and a yellow hazard strip? So the fox and coyotes can see it. They do use it. I see their trails over it in the snow.

This small footbridge has been weathering nicely here for three years. The most of the old paint has fallen off the recycled planks and the bridge is starting to look uniformly gray. It feels sturdy and safe to walk on. The old tower sections look like they will useful for at least the next 20 or 30 years or so.

Thanks for your interest!

To the first new uses for old TV towers

You may like another bridge project.