I tried to build a lego crane last week, using pulleys and stuff, but it was a depressing failure.
The less said about it, the better.

This week I tried to build a Mindstorms sweetie-sorter. It was also sort of a bust, but at least it was funny, in a 'robots are stupid' kind of way.

First up: the lego colour sensor doesn't recognise orange. It thinks the orange ones are red. So there's that. It DOES has a function to recognise brown, but brown M&Ms aren't the right shade of brown, I guess. They detect as black. Also, grey detects as black, so brown M&Ms are the same colour as my conveyor belt. That sucks.

So, one in six sweets is invisible, and it thinks the orange ones are red. That's not so bad.

My hopper mechanism is cool, extracting one sweet at a time for examination... so long as there's at least a dozen in there. The last few sweets just sorta tumble around and never come out.

But anyway, when a (non-brown) sweet emerges from the hopper, the machine lets it drop into a little carriage, then stops the hopper mechanism.

Then the carriage moves over to my receptacles, and tilts either left or right to tip the sweet into the correct pot. The carriage then rights itself, and returns to the start position to receive the next sweet.

Brown ones screw everything up, of course. I'll have to take those out. And the carriage doesn't so much tip the sweets out as launch them across the table. Also, the carriage traverse mechanism is nice and quick, but tends to explosively disassemble, and then try to drag the carriage around as far as the cable will let it.

So, yeah. It's shit. But it does something, and no individual stage is completely rubbish. I'm not proud, but it's progress.

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