Nichrome wire

Description

Heated Nichrome wire

Nichrome is metal that is usually formed into either wire or a thin strip. It is a resistive heater, meaning that when power is passed through it, the wire heats up. By hooking a circuit with nichrome wire up to a battery, heat can be quickly generated to affect bimetallic strips, melt fishing line, burn string, light candles/matches, and other possible applications.

Acquisition

Nichrome wire is easily obtained from appliances you have in your house, appliances from thrift stores, and online. Appliances can contain multiple gauges and may have something less like a wire and more like a ribbon (perhaps more appropriately termed heat tape, but usage is similar and both will be addressed as wire). Online stores usually offer spools of a single gauge of wire and may mark it as foam cutting wire. You could also buy heat tape and take it apart, but this is more expensive.

Hair Dryers

A $3.25 hair dryer from GoodWill	Looking down the end of it, you can see the Nichrome wire before you even take it apart	It comes with a free fan and switches!
Those Nichrome coils, as viewed from the other end	The complete innards of your average hair dryer	Random: looks like this one has a hot limit switch
I uncoiled one segment to show about how much Nichrome comes out of there (lots)	This is what I kept. Your tastes may vary.

Toasters

A toaster from GoodWill	And it only cost $2.00	Looking in the top, you can already see the objective
The electronics that drive the toaster. You might find a use for the relay or rotary switch...maybe not.	After some disassembly, we have the three heating vanes. One of them is double sided, since it was in the middle.	I wrapped the wire around the guts of a shaker-flashlight because it was handy. There was about 18 feet of the stuff in the toaster.
This is what I kept. Your tastes may vary.

Buying Online

A number of hobby stores sell Nichrome wire. It is often sold as foam cutting wire.

• Pitsco 32 gauge
• Pitsco 18 gauge

Using

The use of nichrome wire has a few challenges associated with it.

• Nichrome wire gets hot
  • You can't have it in direct contact with anything that will burn or melt unless that's your intent. Use fixed alligator clips to hold it or some other metal clamping method.
  • If the wire is left on too long, is provided with too much power for the length of wire in use, or both, the wire will break and you will have to replace it.
• Nichrome wire draws a lot of power
  • If you are not using several batteries in parallel (or a large battery), the nichrome probably just won't work. You need to either provide it with more power or use a shorter wire length.
  • If left on, this power draw will quickly drain your batteries. If you need to start the machine with the nichrome already powered, make sure to only turn it on directly prior to initiating the run. The best policy is to have a transfer turn the nichrome on either as one of the last transfers, or have one of the trasfers immediately following it turn the nichrome back off.

Setups

This setup shows a simple Lego-based mechanism by which a lever arm was suspended by fishing line (running veritcally), which was melted through by nichrome wire (running horizontally). The lever arm fell onto a microswitch to trigger the next action. The round black object on the lever arm is a ball bearing that has been wrapped in elextrical tape to secure it to the arm. The reason for the added weight is twofold: It ensures that the switch is properly depressed and the extra weight puts tension on the fishing line, which pulls it against the nichrome wire more securely, which ensures that the line melts immediately and reliably. The picture shows the post-operation state. You can see the fishing line and its mounting points at the top and bottom of the picture.

This setup was actually designed to satisfy another from 2004 that involved springs, but it works here too.