Browsing Posts published on 09/09/2010

From the sublime…

…to the ridiculous.

So, these last few days have been er, interesting.

(…’Interesting’ as the Chinese curse: ‘May you live in interesting times’…)

There’ve been some excellent moments -like when I first sat on the bike and saw the meter move to show I was putting charge back into the battery; and there’ve been some awful moments -like when I realised that it had unaccountably stopped working.

There’ve been some pretty good bits in between -like today viewing that other community allotment project.

SO, when I got in tonight, I had in mind some more coding to get more lights flashing to tell me when various things were happening with the circuit.

BUT, then I thought no, I’ll do something different.

I knew that at some point I would have to build the circuit that actually monitors the current going into the battery.  I would have done this with discrete components, and was prepared to do so, but Dave mentioned some excellent chips from Maxim that do it all for you.

All you need do is put a ‘known’ low value resistor in the circuit’s power lines, and the chip reads the voltages either side (…there’s a really really small difference…), amplifies that voltage and gives it you in a useable format.

There was, however one snag.  (…Isn’t there always?..)

Normal integrated circuits come in ‘standard’ DIL (Direct In Line) packages with the pins spaced at 0.1″ pitch between legs.

When you’re a ‘Newbie’, this can present quite a challenge as you have to solder the legs to the circuit board, not each other, but you soon learn how to solder properly, and after only a short while, it almost becomes second nature.

Now, prototyping, which is essentially what we’re doing here, should always be done on 0.1″ pitch.  Rule of thumb.

Except of course, unless you’re my old boss at Computer Science who insisted that I prototype using the smallest components known to man.  Just for a laugh.

Still, apart from my muttered curses, this wasn’t much of a problem because he very kindly equipped me with the best equipment I have ever used -hyper-small soldering iron bits and an awesome magnifying/light thing that meant I could see -and work with- anything!

(…No joke here.  Its a good job I didn’t have dandruff, because some of the resistors and capacitors I had to solder were smaller than your average dandruff flake.  Honest…)

So, back to this evening, and the ‘snag’.

Take a look at this:-

The chip, the circuit board and a penny.

The chip, the circuit board and a penny.

From this shot, you can see the kind of size I’m talking about here.

The penny was just there to give you a sense of scale.

The chip had to be soldered (…that’s all eight legs!..) onto that tiny piece of ‘veroboard’ used for prototyping.

The veroboard has ‘standard’ 0.1″ pitch holes in, by the way.

The first job was to cut away some of the verboard tracks to give the chip room to be glued on and to prevent any short-circuits. Thus:-

Veroboard with tracks cut.

Veroboard with tracks cut.

You can see I’ve cut away the copper cladding from eight of the centre-most holes.

In itself, this was pretty fiddly!

Chip prior to soldering.

Chip prior to soldering.

In the shot on the right here, you can see the chip ‘sat’ in its final resting place, but before it could be mounted, I had to ‘cut the corners off’ the four innermost tracks so I could spread the outer legs and them not short back onto the inner four tracks.

Very, very fiddly!

Then came the real ‘fun’ of the operation as I had to mount the chip using superglue (…which promptly dripped through onto the tabletop and stuck the board to the desk!..), then put through two rows of four ‘terminal strips’ to make the ‘legs’ of the new 0.1″ pitch chip so it would fit onto my circuit board, thus:-

Soldered and IN!

Soldered and IN!

This shot shows the final finished ‘chip’ with the correct 0.1″ spacing courtesy of the white ‘breadboard’ often used for ‘rough’ prototyping, with all eight legs of the i.c. soldered without short circuits, to the veroboard and the two four-way terminal strips.

Now the ridiculous bit:

This was all done at my bench with no hyper-bright lighting, a standard soldering iron and certainly NO magnification whatsoever.

So, tomorrow, I will mount this onto my existing circuit board so the PIC will be able to tell how much current is being drawn.

Of course, this is assuming I haven’t over-heated it in soldering it in.

Well, I just read back what I wrote this morning, and all I can ask is just how wrong can one man be?

Yes, when I wrote that, it was dull and foggy and grey and miserable, but almost as soon as I’d left my flat (…with the extra pullover on…), I realised what a mistake I’d made!

If the day didn’t turn out ‘glorious’, then given the time of year and all, it was very close to it.

Myself, Diane and Ian (…no relation…) had been invited out to another growing project quite near to ours.  They were having an ‘open day’ to show visitors round, and this included a barbeque.

How could we not go?!

It was great to meet new people and put faces to names that have been bandied about, and on the whole, it appeared to be a very well run and organised project.  Their food was pretty good too!

All too soon, it was time to come back to our project, and aside from quite a bit of harvesting, counting and weighing, not a big lot else was done.  Still, this is often the way, and we’re not really bothered by that.

So, I’ve just got back from the monthly Management Meeting, and its time to don my electronics and computering head and crack on.

More soon  in the ‘Power’ blog.

That Thursday feeling. 09/09/10

Today will be a day of ‘Plotting’.

After the huge rollercoaster of emotions of the last few days back here at ‘The Workshop’ (…or ‘The Cave’ as some have called it…), its time to get back to The Plots and see how everything is going down there.

It doesn’t matter that the weather is now dull and grey and that the temperature is getting lower and lower as the days progress; as summer inexonerably progresses in autumn; as it gets darker in the mornings and darker earlier and earlier in the evenings.

Glorious and beautiful though summer was, with it’s long, hot, carefree, balmy days of shorts, t-shirts and strawberries, it must soon end.

But before we curse as we put on another pullover, let’s not forget all the work we put in and the rewards we have reaped.

This year really has been a ‘Bumper Year'; not only in the crops we have planted -and harvested- but in the infrastructure work carried out.

Don’t forget, we now have a fully functioning greenhouse!

If we dismiss everything else we did this year, this, this has to be the year-defining moment for us.

So, I’ll lace up my boots, put on another jumper, and see what the day will bring…

…It has to be better than being sat here watching for the plumes of blue smoke!


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