Engineer Zero

Metric Blue is now assembled sufficiently for operational testing. There was a bit of a tense moment when I discovered that I had connected the 9v battery lead to the voltage regulator’s 5v row, but miraculously nothing got fried. Though for a while the LED was remarkably bright!

The wheels are half the radius of the old design. I did that so that the robot would run slower. Slower is better in this case because it’s a table top robot and the old robot was so fast it would often race to the edge almost before I could rescue it.

Also, the older, bigger wheels were wobbly. Metric Blue’s wheels are on tight. I miss the Toyota ‘tire’ gaskets that went on the old wheels, and for these new wheels have been thinking of putting electrical tape on the rims for added traction.

Notice the bottom’s rear edge has a ‘decorative’ pipe cleaner instead of a caster. A caster costs more than a dollar while the segment of pipe cleaner costs a few cents. Since Metric is small and built close to the ground, any old skid might have done, but a pipe cleaner cuts down on the friction.

I’ve tested the new robot on a table top obstacle course, and . . . I need a bigger table top. But it is definitely an improvement in navigational accuracy over the previous model.

The freshly-breadboarded circuit for my new robot, Metric Blue, isn’t working. When the switch is flipped, the servos make a little noise for an instant, indicating that power is getting to them. But the LED never blinks the ‘ready’ signal.

I removed the microcontroller and installed it on the breadboard for my first robot, Babe, and the LED blinks on cue. So the problem has to reside with the other components. So next I made a couple test circuits using Metric Blue’s components:

The LED failed to blink when power was applied to the breadboard of the simplified battery-powered ATMega circuit on the left. (Circuit is partially-disassembled at the time of the photo.)

For the breadboard circuit on the right, as you can see, the LED does indeed light up. That tells us that the battery, switch, voltage regulator, and LED are all fine.

So what does that leave? The fault must reside in the crystal, the capacitors, or the breadboard itself. It could also be that I wired up the breadboard wrong.

(There is also the dark theory that some kind of malevolent supernatural entity is at work. There are times when frustration causes every engineer’s faith in material reality to waver.)

Next stop is a trip to Vetco, to see if I can get some 22uF ceramic caps to change out the electrolytics presently in Metric Blue’s circuit.

In the Japanese writing syllabary known as hiragana, stroke order is important to properly compose the characters. Likewise, in building a bread board circuit, it’s important to figure out the order of installing the wires and components. Otherwise you find that a wire/component you inserted previously is getting in the way of inserting a wire/component now.

In the breadboard shown, I’ve decided it’s best to set down the common voltage and ground wires first.

1. As a general rule, the shorter the connection the earlier it’s set in place.

2. The wires at the bottom of the breadboard are routed over the edge so that they don’t block the holes inbetween.

3. Wires that pass over the microcontroller are made long enough so that they can arch, thereby allowing the microcontroller to be removed and reinserted for reprogramming.

The photo shows the first layer of circuitry completed, now the rest of the circuitry will be layered on top.