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.

I word to the wise/ stupid(like me): 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.

The Point(s) 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 letters (actually, you probably started at ‘a’) and ‘1’ starts the numbers and you 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 and branchlets (a quaint word for twigs, but with alliteration)

Top-Downers: You are outside the tree, you just see the leaves. If you want to know more then you go a little deeper from out to in. Consequently, your knowledge is kind of upside down. You don’t really have an in-depth understanding of what you know and you don’t really know what you don’t know either unless you stumble across it as you move into the centre.

My real point is, I have no idea what I am doing – 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 (Molices?) seem to be a good option, in a no-more-burning-plastic-smell-as-verification way.

Of course, I didn’t need to go all trial and error in it in my top-downness, 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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