Tuesday, June 30, 2009

Felt pads

I use felt with an adhesive backing on the legs of these pieces. This shows the leg section upside down on another old blanket. I usually wait till delivery to add the felt as it picks up all sorts of grime otherwise, and on this occasion it would have got soaked as well. Even a very heavy piece like this sofa slides around happily on a polished floor.

Monday, June 29, 2009


It was fortunate that there was an abundant supply of floor space. We were able to bring in all three sections and then start on the assembly. I use these old blankets for all the removal jobs. This photo does show more of the intrinsic color the wood has. In most pictures it just shows up as very dark, but there is more luster visible in person.

Sunday, June 28, 2009


In the end we got rain for our journey with the sofa, so we had to put on a lot of tarpaulins to try and keep the worst off. The roads were also very crowded, so it was dark by the time we got to this stage of snaping the sofa bench in its new home. The new owners seemed very happy with it and tried it out with the cushions to see what that would be like. They said it seemed like it was a piece of furniture that already had three hundred years of history. It seems a bit like that to me too, in some ways.
Sammy snapped quite a few shots. We will look through and see if any are suitable to go up on here.
For now the shop seems very spaceous ready for the next project.

Friday, June 26, 2009


Yesterday the bench was in three bits spread around the shop. Today it is standing on big upturned buckets like a rather wide cheeked circus animal.
Many little jobs during the day. Started with Sammy helping to shift all the parts and then a timely visit from a friend in the afternoon to help lift the leg section up to mate with the seat portion so that I could drill some pilot holes. More solitary work and then in the early evening further assistance from my wife as she helped poke bolts up through the legs as I lifted each end. One of the leg joints was showing signs of not having cured properly, so I left the clamp on that. I hope to find all well when I go down tomorrow morning to check that all the parts have spent their first night as one unit without the help of immuno-suppressants. I have one more day to add finishing touches or reinforcements and then the thing is to be rendered in parts once more for transportation out the door on Sunday.
I took the liberty of trying the thing out for a bit of rest as dusk began to draw in.

Thursday, June 25, 2009


Just in case you think I am cribbing, these are my workings on two little memo notes that got me to the calculation for the temperature value I mentioned yesterday.

int Sensor0temp = ((reading0 * 4.883)-600)/10

It was an interesting exercise as I do not often disturb the part of my brain that deals with maths. I am afraid it may have required bandages after the session of prodding I put it through.
If I were a little smarter I could have got it to display the temperature to 0.1 of a degree, but in all decency I had to let the poor thing crawl back under the bed and rest.
I found the problem easier to follow with the three scales in mind, one for the controller, one for the sensor and one for me. It helps one conceptualize the problem of how to get a given value on one scale to mean the same thing on another. It also helped to try and get assistance from other members of the family. Just trying to describe what you are attempting to do makes things clearer, too.

Wednesday, June 24, 2009

Temperature display

Switching from Solar to "simple" control stuff. I have been having a hard time getting things to perform. Today I found out one of the reasons why. I bought 4 temperature sensors that I hoped to connect up to the arduino via a prototyping board that slots into the top. I tried everything I could think of and googled my brains out to find out why I wasn't getting proper readings from the LM61CIZ sensor. In the end by a happy accident I found the problem. I had the sensor connected to analog pin 2, but in my little program I had it marked as being on pin 3. Strangely it was working there, giving numbers that went up and down with changes in temperature. I thought perhaps I had misunderstood the numbering of the pins, but experiments proved that not to be the case, then I whipped the shield off and looked at the pins underneath thinking I would try connecting up directly. There was the answer, the pins on the protoshield from Sparkfun were marked o12345, on the Arduino the pins are 543210.
I am afraid my comments on the Sparkfun website may have been a little ratty after my wasted hours of trial and error. They were very quick to respond and have now offered to ship out two new and correctly labeled boards, which was very nice of them seeing that it was just a labeling problem. The boards will come in handy as I get nearer to a final controller for the solar system.
A long way off being that the system itself does not exist yet, but I reached a small milestone in getting the temperature to display properly in degrees C and to display "Low" when under 25 and "High" when above. The next step was getting some little lights to work on the same switch and my next goal is to control a relay.
The sensor produces what it likes, the board interprets that in its way and I have to get that into something I understand. "reading0" is the boards interpretation of a number of millivolts produced by the sensor. Those have to be multiplied by 4.883 to get them back to what they were before the boards computer translated them. The sensor produces 600 millivolts at zero degrees, so that is subtracted to give the temperature. The sensor produces 10 millivolts per degree, so finally divide by ten to give something centigrade lovers can drink up. That integer value is popped into a bit of memory called "Sensor0temp".

int Sensor0temp = ((reading0 * 4.883)-600)/10

One of the stupid challenges in getting the display to work was figuring out how to display degrees properly. For the arduinauts among you here are the two lines to display just that.
First put the cursor at the right spot, then print the temperature number we just made; Then print the character for the degree sign; Then print a C
lcd.setCursor(7, 0);

Saturday, June 20, 2009

Step back

Here is the schematic from the data sheet that came with the chip. I got five for a hundred yen. Unfortunately that quickly went down to one. I had a bit of a senior moment while building the circuit and forgot that I was now aiming to step up voltage. I had been working on the step down process too long. When I tried the chip on 5Volts it was happy enough as it had no work to do, but then I shifted to 12V and it did a quick hiss pop that was distinctly alarming. I removed it from the circuit after disconnecting. It had the appearance of the command module of the Apollo 13 mission after the incident. Anyway, I shall be more careful with the remaining units.
The circuit works fine and gives more volts out than go in as it should. I tried approximating the values of the capacitors as shown here, but switching them for two of the same value as in yesterday's photo made no difference that I could see on the meter.

Friday, June 19, 2009

Step up close

A closer look at the scrap of board with the 100uH inductor (a coil of wire in a plastic housing). Two little blue ceramic capacitors and an almost hidden diode to their left. In the foreground is the chip that acts as a little switcher to allow bursts of electrons to pass at the appropriate moments. The two little 100K resistors go between the positive red wire of the USB and the white and green wires in the middle. They are only there for the benefit of the ipod, which will not think about sipping from the power without something of the sort in place. Here the board strips on the back are running north to south.

Thursday, June 18, 2009

Step up

Option two with fewer solar cells. Four all wired in parallel. All positives together and all negatives together. This circuit boosts the 2 or 3 volts from the cells up to 4.7 or so and then that is stored up in the capacitor to be fed out to the USB wires beyond.

Wednesday, June 17, 2009

Step down close

This shows the little scrap of strip board with the step down circuit. Strip board has strips of copper that connect rows of holes on the back of the board. Here they are running east to west across the view underneath.
If you are keen, you just look up the datasheet for the XC6202 and the schematic for a similar cicuit is on there. You then figure out how to wire that on whatever media you have. Or even solder up all the components as a free standing unit. I haven't tried that much as I am using second hand parts with very short wires on. I am advancing a little as I have learnt the virtue of things like detachable connections. I used a three pin connector for the little chip, so that I can try a couple of different units that have similar requirements.

Tuesday, June 16, 2009

Step down

The issue with solar energy seems to be that it wiggles up and down on the productivity charts. Sometimes the sun shines sometimes not. I am experimenting with the two alternatives.
1. Use a large number of solar cells and step down the voltage, losing some of the energy as heat from the unit that drops the voltage.
2. Use all the available energy with minimal solar cells and step up the voltage to a useful level. This picture represents the first. The little cells are connected as pairs in series, then all the pairs are connected in parallel. Provided there is sufficient sun, the little chip reduces the voltage down to 5v and feeds it to a connector for a usb line wired to a female usb socket (not shown)
So far this is recognised by the phone etc, the unit lights up and bleeps to say that it has been connected to a charger, but the charge is minimal. I suspect I need to have three or more panels in series and connect the string of them in parallel.

Sunday, June 14, 2009


I have come to realize one of the reasons why I am concerning myself with solar. If I read even a little about the supression of battery technology it fills me with so much bile I have to do something to counteract it. If you are at all interested in how mendacious the United States military industrial complex is, try this. A story I have mentioned before.
Back in 1997 there was a NiMh battery capable of powering a vehicle at normal driving speeds over 150 miles on a single charge. The battery would last over 1000 charges. That is 150, 000 miles. Our truck has not even reached that number in Kilometers and it has seen daily use for around 15 years. With a solar panel that would mean.....best not to think about it too hard or certain blood vessels might pop.
A one page summary of this foul story here
The actual datasheet for the battery by Panasonic here
That should equip any right minded person with sufficient bile to cause a major erruption at the mere mention of the US car industry and the billions devoted to saving it.
Back to work.

Saturday, June 13, 2009


At last a circuit that works, I agree with the sentiment of the person who wrote this page. This is the best little circuit on the web.
I have the tiny solar cells figured and I was able to get my now redundant cell phone to charge off them, but my ipod was refusing everything other than fossil power. I have just breadboarded this and at last got the little bugger to chirp and soak up the juice. This was also thanks to a separate individual on the instructables site who had drawn out how to connect up resistors to the USB socket in order to dupe the ipod into accepting its host.
Today's success was a complete fluke as I was just fondling ICs I had scavanged from other stuff and looking up datasheets at random when this image came up in my search for the 78L05 I had under the lens. The next phase is for me to package this with a piece of old cell phone that will charge lithium ion batteries, then they can charge other devices. I had some batteries I had charged during the day on the solar power, so they were my first electron shot to the ipod.
Why am I bothering? I have no idea, but the little bites of understanding are deeply satisfying to the monkey part of my brain.
Meanwhile down in the shop the first stage of gluing has been completed and that is sitting quietly awaiting the day when it can be released from traction.

Friday, June 12, 2009


My day was spent trimming the joints for the lower part of the back rest to make sure they will all fit nicely for gluing tomorrow.
As soon as my daughter and I saw this weird little towel thing in the shape of a little dress we knew it had but one purpose and the cat became the subject of abuse for our idle hands a few minutes later. He fought a little at first, but somehow he switched and came over all submissive. This allowed my wife to add the final touch with the little hat as he crouched awaiting the fate he had accepted. We whipped the garments off quickly afterwards. I can honestly say that he suffered no pain, but as to humiliation I can offer no such guarantee. He doesn't seem to be suffering much in the way of PTS, running about chasing moths. I suppose cats everywhere are thankful for the invention of the TV and other distractions that keep them safe from the devils servants in these modern times.

Thursday, June 11, 2009

Take away

This is what the ladies went home with after a hard day in the dust and grime. I had made a fork as a sample, but the spoon and fork set seemed to be a good idea. I am afraid I rather used their visit as an opportunity to pack away the sofa bench for a couple of days so that I could have a bit of a tidy up.

Wednesday, June 10, 2009


The general consensus was to make something out of wood, so I thought some utensils might be a good start for the visitors. They each had a block of wood and cut out two curved blanks like the one at the bottom using the bandsaw. Then they cut out the profile from that and set too with the belt sanders to give a shape a little like the one at the top.
I think the ladies must have been tired when they left, all unfamiliar tools and hard work with it.

Tuesday, June 09, 2009


Although it would be nice to get the whole thing spiffy, getting even this arm rest up to spiff represents a significant amount of abuse to the personal arm linkage despite the assistance of power tools.

Monday, June 08, 2009

Back at it

As usual I have completely overestimated my capabilities to complete things on time. I also forgot to factor in a session with the three ladies coming up on wednesday. After devoting Sunday in truly appropriate fashion to solar I got back on the elbow grease routine and polished up the pieces my daughter had scorched the other day. This was a trial assembly.

Friday, June 05, 2009


The last little step in preparing the cell is to make a little rounded kink in each of the tabs. I put a tooth pick under the tab and use the iron to mould the tab around it.
As I mentioned on the soldering step, the cell expands when hot. Out in the sun each cell will expand and contract through the day, so it is important to make these little kinks to allow the tab to flex between the cells, otherwise it would be put under stress and probably eventually snap off.

Thursday, June 04, 2009

Straighten and tin

Having done the six pads on the back turn the cell over and straighten out the factory applied tabs. They have a load of conductive epoxy gunk on them, so I run the soldering iron along them with a little fresh solder on to re-tin them.

Wednesday, June 03, 2009

Applying solder

I have shaped the end of my middle sized soldering iron to make one side a flat surface about the size of the conductive patch. I bought some liquid rosin flux that I apply with the little paintbrush. Dab the iron onto the stick of solder and get it to the pad area as quick as you can so there is still flux from the core burning off of it, then dab it down so that it just touches the pad for an instant. The cell flexes and even crackles a bit sometimes as the heat causes expansion, so I wouldn't try and hold it down too firmly or it will snap.
Applying the iron for too long seems to actually burn off the conductive film and ruin the pad.

Tuesday, June 02, 2009


This week the procedure for preparing one cell. This is the back of the cell with six little conductive patches covered with a protective white substance. I use about six passes with a fine bristled brass wire brush to clean that off. Keeping the cell pressed to the board underneath and applying as little pressure as possible with the brush.

Monday, June 01, 2009

Solar veranda

Two panels with 18 cells each. The cells give 0.5 volts at up to 3 amps in bright sun. Even on cloudy mornings just sitting on the veranda they power the little computer fan OK and in sunshine it blows strong enough to tip itself over. This month looks like being skimpy for bloging too, but I have just realized that it does present an opportunity to use the power of numbers and aim at filling all the squares on the calendar.