DIY CNC Router – Post 7: (Hot and Melting) Wires


CNC Wiring: What I Thought Was a Good Idea

I had neatly done all my wiring using old-style computer serial leads and plugs (technically called a DE-9 D-Subminiature connector).

The serial connectors have nine pins so I was using four for the two stepper motor coils and the remainder for end-stops switches etc.  I had even devised a cunning way to avoid soldering using jumper wires: It was all about avoiding soldering as I hate it.

I did everything very neatly and I was quite pleased with myself until I got everything working and powered up. The plastic insulator on my stepper motor power wires started to melt and smoke.

This will make people who know such things cringe, so You: just turn away. I did not think about what wire gauge I needed for such-and-such a current. I just thought you connect A to B with a wire (in retrospect hopelessly inadequate) and you are good to go.

Not so. Hence the smoke.

Takeaways of this Post

Point #1: Top-Down vs Bottom-Up Learning

After an epiphany, I wrote a small thesis on top-down vs. bottom-up learning…and then deleted it. In summary:

Bottom-Uppers: you learnt that ‘A’ starts the alphabet (actually, you probably started at ‘a’) and ‘1’ starts the numbers and you slowly built on that through pre-school, school, university and beyond. You climbed a tree and you know, to some extent, of many of its boughs, branches.

Top-Downers: (ie Me) don’t know much about the tree. We don’t really have an understanding of what we are doing – we are winging it.

My real point is, I have no idea what I am doing and I am top-downing when it comes to anything electrical/ electronic. I jumped out of that tree about a foot up the trunk around Ohms Law at school.

Point #2: The correct wire gauge

If you google ‘AWG selection tool‘ bottom-uppers have helped out: I found this website where you put in your current and voltage and it spits out the appropriate wire gauge…18 AWG for me (~36V 4A).

Point #3: 4-pin Molex

Looking around for a cheap-and-easy remedy I decided to use 4-pin Molex plugs – the type that used to put power into computer CD-ROMs, hard drives etc. The reason for this is that I had lots of them old computer bits and I am trying to stick to my ‘built from scrap’ mantra.

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