Troubleshooting and Fault Isolation

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.

About engineerzero

Once and future engineer.
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