Hook-up wire: AWG, solid or stranded, which insulation

The prototype works on the breadboard, then you move it into an enclosure and a week later a wire comes off right next to the solder joint. The reason is almost always a simple one: solid wire used where something moves. The Alpha Wire range of hook-up wire has just arrived in our catalogue. Alpha Wire is an American brand that has been making wiring cable for decades: hundreds of items across gauges, colours and insulations. Here is how to choose without getting lost in the codes.

The gauge: AWG and mm²

On electronics wire the size is almost always given in AWG, the American Wire Gauge. It works the opposite way to what you might expect: the higher the number, the thinner the wire. Every three numbers the cross-section roughly halves. To help you find your way, here are the corresponding cross-sections (they vary slightly between solid and stranded wire):

• 30 AWG: about 0.05 mm², wire-wrap and tiny connections;
• 26 and 24 AWG: 0.13 to 0.24 mm², signals, sensors, internal wiring;
• 22 AWG: about 0.32-0.38 mm², the all-purpose wire of electronics;
• 20 and 18 AWG: 0.5 to 0.96 mm², light power supplies, small motors, short LED strips;
• 16, 14 and 12 AWG: 1.3, 2.1 and 3.3 mm², where serious currents flow.

And the current? On the data sheets for its hook-up wire Alpha Wire gives voltage and maximum temperature, not current, and there is a reason for that: the current a wire can carry depends on the ambient temperature, on how many wires run together in the same bundle, on how it is laid and on how much voltage drop you can accept over the length. A 22 AWG wire in free air and the same wire packed into a sleeve with twenty others don't behave the same way. For power supplies it pays to leave a generous margin and, if the load is serious, to start from the standard that applies to that equipment.

Solid or stranded

Solid wire has a single copper conductor. It holds its shape, goes into holes easily and stays where you put it: it is the wire for breadboards and jumpers on perfboard. A quality breadboard like the BusBoard BB830, for example, accepts wires from 21 to 26 AWG, i.e. 0.4 to 0.7 mm in diameter. Alpha Wire's 22 AWG solid wire has a 0.64 mm conductor, the 24 AWG one 0.51 mm: both fit.

Stranded wire is made of many thin strands, for example seven 0.25 mm strands in the 22 AWG wire of the 3051 series. It is softer and stands up to repeated bending and vibration: use it for anything that moves or gets opened, so lids, doors, robots, wiring between a board and a panel.

The typical mistake is forcing a wire that is too thick into the breadboard, for example a 20 AWG solid wire, which at 0.81 mm is over the limit, or a stranded wire tinned at the tip, which the solder makes thicker and uneven: the spring contacts inside get stretched, and from then on thin wires make contact only when they feel like it.

For slightly heavier power supplies, 18 AWG stranded is a good size to start from.

Insulation: PVC, mPPE, PTFE

• PVC: the classic insulation, inexpensive and easy to strip. The 3050, 3051 and 3055 series are approved to UL 1007 (80 °C) and UL 1569 (105 °C), both for 300 V. For wiring inside an enclosure it is perfectly fine.
• mPPE (the EcoWire line): the insulation layer is thinner but tougher than PVC. Alpha Wire claims diameters up to 45% smaller and weights up to 40% lower than PVC, halogen-free, rated 600 V and -40 to +105 °C. Handy when there are lots of wires and little space.
• PTFE: the insulation for heat, from -60 to +200 °C. In the 2840 to 2845 series the conductor is silver-plated copper and the insulation wall is thin, less than two tenths of a millimetre on the 2840/7, so the wires stay very slim (250 V). It is used near power resistors, lamps, heated beds and 3D printer nozzles. If you need a higher voltage, the wires in the 5851 to 5858 series, compliant with MIL-W-16878/4, go up to 600 V.

For wire-wrap, the connection made by winding the wire around a square pin with the dedicated tool, you need thin solid wire, usually 30 AWG, which you will find on reels in Cables for Electronics. If instead you need a very supple wire to run through joints, you will also find silicone-insulated wire there.

Colours and reels

Using different colours costs little and saves you time when you have to get back into the wiring months later. The most common convention for DC is red for positive and black for ground; for signals choose one colour per function, for example yellow for the clock and green for data, and stick to the same choice throughout the project. Leave green/yellow for the protective earth: the IEC 60445 standard reserves it for that conductor.

In our catalogue Alpha Wire reels come in two lengths, written in the code: 005 is 100 feet, i.e. 30.5 m, and 001 is 1,000 feet, i.e. 305 m. The letters before it give the colour, BK black, RD red, BL blue and so on. The 30.5 m reel is enough for a few projects; the 305 m one makes sense for schools, labs and anyone wiring in volume.

The whole range is in Hook-up wire; jumpers and leads with connectors are in Cables for Electronics.

Can't find the gauge or colour?

The Alpha Wire catalogue is much larger than what you see on our site. If you need a particular gauge, colour or insulation, send us the part code or a couple of lines on what you need to wire, and we will look for it.