Electronics - New revised layout

After a great deal of re-thinking (the shop didn't have the stock so I went with the old plan) I've decided against adding a second section of board at 90 degrees to the first.

My demand fish feeder will have to have it's original layout after all.

But I did manage to buy some 10k trim pots.

When you fry around in a plane, there is a way to make the plane do things like turn to the right, and a way to set the plane so it always turns a bit to the right. This allows you to keep the plane pointed slightly into the side wind so you keep going straight. This is called adjusting the trim.

I think.

I read that somewhere.

I cant fly planes or anything.

I just read about trim.

I think.

Anyway, I also think that's the kind of reason trim pots are called trim pots.

The pot bit is potentiometer (volume knob, variable resistor) and what they do is change the amount of resistance they offer depending on the position they are set at. These ones are set with a screwdriver and are normally used to fine tune or trim something before you close up the case and use the controls designed to be used by hand rather than a screw driver.

The 10k stands for 10,000 ohm.

Ohm is a measurement of resistance.


Wire has a low resistance, air has a high resistance, and people have a resistance somewhere in between. That's why we use wires to carry our electricity, and try to keep some air between the power lines and the people.

So when I set the dial on my trim pot with a screwdriver, my PICAXE chip sees a value based on the amount of resistance. The chip translates that into a number between 0 and 255. And then I write some software that says something like...

if its 0 to 9 then theNumberOfFeedsPerDay is 1

if its 10 to 19 then theNumberOfFeedsPerDay is 2

if its 20 to 29 then theNumberOfFeedsPerDay is 3

etc

This gives the user the option to set up to 25 feeds per day.

So the device can be told that the user wants their fish to be fed, say, twelve times a day. As the user turns the dial, a light flashes out the value with a long flash for 10's and a short flash for units. So 12 would flash..

    Long   short  short

The device knows what the human wants, and the human knows where the device is at.

As for the new layout, it looks like the original planned layout.

The three trim pots are on the left with their LED's behind them.

Next is the mode button to switch between normal operation, setting the number of feeds in a day, setting the size of each feed, and setting how much light will be named as dawn, where the user happens to live.

Dawn will be the reset time each day based on light levels.

The last of the new components will be the power switch seen standing upright in the centre at the front.

Electronics - A most productive day

So far electronics has been quite a frustrating "thing".

I've found a few quirks with some software that cost me hours, I've found an error in a catalogue that cost me hours, I had an intermittent fault in my motor due to me melting it as it was the first thing I soldered. That one cost me days. And a stack of me just doing thing incorrectly, and not being able to follow instructions.

The problem with these frustrations is the same problem beginners at anything have, and that the experts in that same thing don't every quite understand.

The beginner cant tell if the fault is in their knowledge, or in something external. Anyone with experience would have looked at my stereo jack, and said, "That catalogue is wrong!" I on the other hand presume it's me that's wrong (as I of course should), and struggle on trying to figure out whet I'm doing incorrectly.

The reality is most often than not it really is my fault. There have been a zillion times over the last few weeks where I left something out, or stuck it in the wrong way, and managed any number of other errors and omissions.

But today was different.

Today stuff seemed to make sense.

It could be because I spent and hour in the dentist chair breathing happy gas this morning, but I suspect that it's actually because I've been learning these last few weeks.

When people are learning how to type or tap out Morse code, their speed doesn't just gradually improve, it improves in big leaps, steps backwards, and stagnant times where nothing much happens.

Some of what's going on is called chunking by some. In the case of Morse code, the student taps out slow letters. They gradually get faster and faster, then suddenly they ratchet up a notch as they learn a word or two. You only need a few things that you can group together like the word "the" or "and" or even just "th" or "ing" and suddenly you double your speed. A while later and you chunk larger words or even phrases. The final step is when you start thinking in taps.

I find it a bit difficult to type what I'm speaking out loud, but I'm just starting to be able to do it now. In fact these last two sentences where done like that to prove to myself that I could at least do it a bit.

Eventually, if I keep blogging every day, I'll probably be able to type just by thinking it onto the page .

Chunking.

I think I may have just had a bit of a learning chunk with this electronics caper.

I decided to work on a new part of the feeder project. It's actually working as it is.

It's not built, but each bit works.

But if I want to change something within the software, say the number of feeds in a day or something, I have to plug it into a computer.

I'd like to make it so you don't have to do that. So you can adjust such values with a screwdriver.

A few hours ago I started to make such a thing, and with only one error that I found and solved within a few minutes, I managed to make a working version of ...

• a button that shifts you from normal mode to adjust mode
• a light that flashes out the number of feeds per day as you are adjusting it
• a pot or potentiometer (volume knob or variable resistor) that adjusts that number of feeds per day
• some code that divides the pot's min to max into 25 different values to allow you to set the number of feeds between 1 and 25
• and pressing the button again takes you back to normal mode

Now, someone with some skills might have done this in a few minutes, but I only took 3 or 4 hours!

Actually I'm pretty pleased with myself.


120 Things in 20 years - Just a most productive day in electronics