Handcrafted Scope Clocks with circle graphics
In Transformer Corner Part 3, I looked at how to choose materials for a custom HV transformer. One way was to pull stuff from the junk-box – I did this in my early Prototype. The much, much better way was to use an off-the-shelf core with documented specs.
Let’s look at winding up the transformer. It’s amazingly easy to get a workable result!
In Transformer Corner Part 2, I looked at the power supply used in my early Prototype, and showed how to determine the key requirements for the HV transformer.
Now, let’s see how I could choose the materials and design the transformer – without any pesky mathematical formulae!
The first challenge was to find a suitable core from my junk box. First off, recall from Part 1 that this couldn’t be iron (too ‘slow’ for 151 kHz), and it couldn’t be air (too ‘weak’ for 25mA). I suppose I could have tried plastic, milk, or even beer – but I knew better. I knew about a substance called Ferrite.
(more…)In Transformer Corner part 1, I introduced one of the key parts of the Oscilloclock – the HV transformer, and tried to illustrate some of the concepts and history behind it.
Next, let’s explore the Prototype’s power supply configuration. This will tell us a lot more about the transformer I had to wind!
My greedy little Oscilloclock wanted lots of different voltages…
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There are probably many people who think that microcontrollers are bug-free. After all, they are glorified integrated circuits; a hard-wired jumble of infinitesimal transistor logic gates. There should be no unexpected behavior, as long as you operate the device within the rated voltage and temperature parameters….
Wrong!
What we tend to forget from our CPU architecture classes is that a CPU actually has a program inside. Known as microcode, its primary function is to interpret each instruction into the right electrical signals to drive the various parts of the CPU. For example, an addlw 0x7F instruction might involve directing the ALU’s input to the next word in program memory (0x7F), and then telling the ALU to add it to WREG, with output set back in WREG. The microcode for addwf MyVar would be different again; it needs to get a value in RAM, and set the result back there too.
Well, where there is a program, there will definitely be bugs.
My first experience with a microcontroller bug cost me several weekends of frustration, fretting, and frantic but fruitless rework. Here’s how it happened:
It was the early days of the Prototype, And things were looking great! My dream was coming to fruition! Except… every once in a while, the clock would go absolutely berserk. Seemingly at random, it would start displaying crazy, meaningless images, and controls would cease to function. Sometimes it would recover; other times, it would exhibit brain death – requiring a hard reset.
No amount of testing or experimentation could tell me what the problem was. I rewrote huge blocks of code. I removed massive chunks to simplify the code. I drank more and more coffee. Sleepless nights and grumpy days ensued, wasting my precious youth!
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Those of you who own, or are building, an Oscilloclock may have realized how tedious it is to create a new character or drawing. My little Casper (October, Seasonal Treats post) required a grueling 5 hours to get him looking good!
I have another blog post series in progress describing the theory behind Circle Graphics figure display, so I won’t elaborate on details, but the current process of getting a figure from paper to screen is very much manual:
Easy?
NO.The figure looks NOTHING like you expect. The size is wrong. The edges don’t meet up. The curvature is out. The thing is upside down. All of the above!
The new Oscilloclock Figure Creator utility allows you to easily create and modify font characters, graphic images, and sprites – interactively.
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