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 I learnt) and my little control boxes made from wine boxes.

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. and future proofing. 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.

The blue wire at the back-right is melting. Note my super organised pi-diagram of the serial connectors. All in vain.

A word to the wise: Shitty jumper wires for breadboard prototyping and 4 amps don’t mix. They were fine when I was running my little stepper motors, but things started to melt when I bumped up my stepper motors and the drivers so they were carrying 4A 36V.

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 the female ones (a harem?) from old computer bits. I bought some male sockets from the local computer shop. (actually 2 x female, 1 x male splitters – a Molex threesome.)

I made my own Molex extension leads using some heavy weight two-wire cable I had (two of them) with a female Molex on one end and a Male on the other end. Each stepper motor has a female socket, and the control box has a male socket coming out of each driver.

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: You don’t know much about the tree. You don’t really have an understanding of what you are doing.

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.

I suppose pre-Google top downing was not really a thing.

Point #2:

The 4-pin Molexes seem to be a good option for my connections.

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).

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