Evaluation (Relating to brief, specs and constraints)

Evaluation (Relating to brief, specs and constraints)

At the beginning of the DTM course, Dr Tony House had made up a brief containing specifications and constraints that we had to follow. The brief stated that the solar garden light had to be resistant to the harsh outdoor conditions especially since the light was going to be placed next to the beach. The light would have to endure harsh winds, rain and the corrosive salt spray. The light had to be camouflage amongst the poacita grass and it shouldn’t cost any more than $30.

My light’s measurements are 160mm high and 150mm in diameter so it can be easily camouflaged amongst the poacita. My light is made of aluminium and is in the shape of a cylinder. My light shouldn’t get blown over in the wind if it was to be planted in the ground firmly. If the light was to blow over, it wouldn’t matter that much as the light is durable and strong. However, Dr Tony House would have to waste time making it stand back up again. A good thing with aluminium is that it is cheap and it is easy to work with since it is malleable and soft. Another benefit with aluminium is that it won’t corrode and it will always stay nice and shiny unlike steel. My light has been sealed so rain and moisture can’t enter the inside of the box damaging the delicate electronic components of the circuit. An additional feature that I have found out recently is that my light is mostly resilient to a lightning storm as the aluminium acts as a conductive outer shell and the power surge is earthed through the ground so the circuit is not damaged. This prevents Dr Tony House having to buy another light when the current light gets struck by lightning.

My garden light has a very bright lightbulb inside so it will put out adequate lighting unlike LED’s. The only problem with the light I used is that Dr tony house will have to waste time changing the light every now and then as the light does not have much of a long life expectancy. This would not have been a problem if the CCFL had survived. The top part of my light is made mostly out of vacuum form plastic and acrylic. This is good because it has extremely high transparency to minimise waste light. These two plastics that I used are resistant to wind, rain, salt spray and being knocked around. I have also sealed up my light so it won’t leak resulting in a build up of condensation and damaging the internal electronic components.

My light has got a few problems with the circuit when the batteries go flat. Considering my circuit contains a relay, the light starts repeatedly flashing no and off for about 5 minutes. After that, the relay turns on and off extremely fast resulting in a rather loud humming sound. After a minute or so, the light will start making clunking noises slowly working down to a clicking noise. This is a very good indication that the batteries need to be charged up. A solid state relay would fix most of these problems.

Overall, my light has met most of the specs and it cost less than $30. The specs that it did not meet were things like not having a dimmer knob and on/off switch. My light has met all of the main specifications that Dr Tony House has stated in order for it to last.

Evaluation (design process)

11dtm final design evaluation                                     Jamie Stenhouse

 

I have put a lot of time and effort into my solar garden light to make it work and look good. I am happy with it but given the time, I could make it look a lot better and could have had a much better design. Throughout the year, I have encountered many problems and challenges to get it to work. My light design had to be changed a number of times due to it being too complicated and not having the time.

Our class went on a field trip to the Unknown Soldier, Waitangi Park and Civic Square. At those three places, we all studied and sketched the outdoor lights. We listed down things such as what they were made of, how they were mounted and what lighting effect they would have on the surroundings. This gave me an idea on what my light was going to look like. After that, we all did some research on the internet about different materials such as aluminum, brass, acrylic, etc.

Dr Tony House (our client) had a brief for us all to follow. He wanted a small, low maintenance outdoor solar garden light that was bright at night. He lived in the Coromandel (opposite the beach). Our light had to be made of non-corrosive materials so they wouldn’t corrode from the salt water. Also, our lights had to have a high light output, be self powered, turn on at night and off at day, be low maintenance and cost less than $30. The lights needed to light up Poacita grass at night and be camouflaged at day.

I started out with a very simple design that was drawn on paper of a box that had solar panels on the top and lights on the bottom, then I made some 2D drawings on a computer program called freehand. I had a simple box made of clear plastic with an aluminum bottom. From there on, I had thought that I could make something a lot better and I came up with the idea of having a cylinder shaped light with a LED cluster to illuminate the surroundings. I stuck with this design and had worked on it to make it better. Later on, I had a simple, effective design which I liked and knew that it was easy to build.

I made a cardboard mockup of my light and it looked quite big and bulky. From there on, further modifications were made. My light had two main parts. An aluminum cylinder at the bottom and a plastic cylinder at the top. The aluminum cylinder was where the circuit and batteries would be. I knew that the circuit wouldn’t take up that much space, so I halved the cylinder to make the light look better. The plastic cylinder at the top looked too small for the light I was wanting to use, so I made it a lot bigger. This way, there would be better light output. 

Most people were using transistor oscillator circuits to run little LED lights. In my opinion, they were extremely dim and not effective. So I planned on using a cold cathode fluorescent light (CCFL) as it had a lot of light output and was very effective. I had the light and the ballast (the circuit to create the voltage in order for the light to discharge) all ready but first, I started on my box.

The first thing I did was cut out a circle on the cam machine. This was going to be the very bottom of my light. Once I had done that, I cut a long strip of aluminum on the guillotine. I put this piece of aluminum through the rollers so it would take the shape of a cylinder. This was riveted so it held itself in place. Once I had done that, I made up some brackets using the guillotine and the metal bending machine. These held the bottom plate on so it wouldn’t fall off. I used screws instead of rivets so it could be taken apart in the future if any maintenance needed to be done on the circuit. Then I cut out another circle on the cam machine and made some more brackets up to hold the second circle. This was for the other side of the cylinder. That was the cylinder complete for the circuit to sit into.

I started working on the second cylinder. This one was made out of plastic. I got a piece of vacuum form plastic as it was flexible and completely transparent. I cut it to size using the band saw. Once it was cut to size, I bent it around, overlapped each of the ends, drilled holes in it and riveted it together so it would stick to the shape of a cylinder. I made up some brackets that were straight. I drilled holes in them and then riveted them to the top of the aluminum cylinder. The plastic cylinder would sit in the brackets and be riveted into place. Once I had done that, I drilled holes in the vacuum form plastic and then riveted it into place. One really stupid problem with this was, I realized that the plastic still had its protective layer on and I would have to peel it off when it had already been riveted into place. It could have been worse.

I had finished the box and now I had to make the circuit and set up the solar panels and light. Once I had completed the circuit, I tested it and found out that the ballast was pulling too much current for the transistors. The light would glow very dim and the transistors got far too hot. I fixed this problem by putting a relay where the output was and have the power come directly from the battery through the relay and into the ballast. This solved the problem and the light was working correctly and turning off when it was daylight. I then glued the circuit in place making sure that it would not short circuit on the aluminum. I drilled six holes in the top circle. Four of the holes were used for the solar panels. One hole for the light and the last for the LDR. I soldered wires to the four solar panels and glued them to the box. I then glued the light making sure it was in straight before the hot glue had set and then I glued the LDR in place. My light was all starting to come together. 

An attempt of making my solar panels sit more flush onto the box seemed like a big mistake when I had snapped my light in half. This was not good at all as time was running out and I couldn’t get replacement CCFL lights unless you order them in. also if i was to order a new one, i would have completly blown my budget as the light without the ballast would cost more then the whole solar garden light once complete. I had to change my light. That did not mean that I was going to use LED’s though. In my lunch time, I went to Jaycar and purchased a krypton light. This light still needed the relay but not the ballast. This was good as my circuit just got a whole lot less complicated. I removed the ballast and had the light wired directly to the relay. When I tested the circuit, I found out the krypton light had a higher light output and a nicer colour temperature then the CCFL (it wasn’t at all like the LED’s). I tested the circuit with a multimeter and everything was working great. The LDR was working and the solar panels charged up the batteries. I was very pleased with the light and the way it worked out.

I then cut out a top disc on the cam machine. This is to cover the top cylinder. I was originally going to use aluminum for it but for some reason, the cam machine hated me. It kept on jamming up, so I used transparent acrylic. This was good because it allowed more light to be dispersed. The first piece of plastic had snapped due to the drill. Too much pressure was applied so I had to cut another bit in the cam machine. The second bit of plastic didn’t snap in half as I drilled it with care. This consumed more time which wasn’t very good as I was seriously running out. I then made some brackets to hold the disc into place. I used self tapping screws instead of rivets because if the bulb blows, it can be easily changed by unscrewing the top. The light looks very good and its light output is very, very bright in comparison to the LED’s. It would have been a lot easier for me to use LED’s as they would be very hard to snap in half unlike the CCFL light. However, I have stated my opinion on LED’s. Anyway the bulb I used is a lot brighter.

Overall, I am very pleased with my light. It is very effective and has a great lighting effect. I had a great time designing and assembling the light although there were a few problems along the way. There are a couple things that I would change about the design and if I was to make another one, I would take my time and be more careful with the production of it. However, I am very happy with the progress I have made with it considering it is my first garden light.

 

Tool List

·         Guillotine

·         Cam machine (2mm milling bit)

·         computer

·         Rivet gun

·         Pliers

·         Wire strippers

·         Metal bending machine

·         Soldering iron

·         Solder wick

·         Drill press

·         Hand drill

·         2mm, 3mm, 5mm drill bits

·         Files

·         Band saw

·         Screwdrivers (Philips, flathead)

·         Silicon sealer

·         Hot glue

·         Scissors

·         Cardboard

·         Masking tape

·         Rollers

·         Vice 

Materials List

Casing:

·         1.5mm Acrylic

·         Vacuum form plastic (transparent)

·         Sheet aluminum (transparent)

·         Self tapping screws

·         Rivets

 

 

Circuit:

·         PCB boards

·         CCFL light

·         Krypton light

·         Relay

·         Transistors

·         Diode

·         Resistors

·         Transformer

·         Inductor

·         Capacitors

·         Solar Panels

·         Wires

·         Solder

dtm week 5 term 4 (the final week)

this is the final week. my light was nearly finished but i had all of this glue on the solar panel. i also came in on saturday. when i was taking the glue off to make the light look better, the light had unfortuanely snapped in two. this was not good as there wasnt a replacement light at jaycar. i decided to change my circuit and use a krypton bulb. this still was very bright and it had a better colour temperature. i really need to finish it though. all i have to do is glue the light into place, screw the bottom on and charge the light. i will be done by the end of today.

week 4 term 4

this week has been average. we are running out of time and i need to seriously finish my blog site or i will fail. i am nearly finished on my light. i have glued my circuit to the box. i have also glued the light in and it looks good. i have tested the light and in my opinion, the LDR is not sensitive enough but the light is really bright and that is a great thing