Melting a strand of wire

Projects General Guidance
1

Hello everyone,

I've been trying to do this for weeks but in vain.

You guys know the jumper wires you use on breadboards? If you cut them, there are small, thin strands of copper wires in them (like less than 0.1mm diameter each). For part of a project, I want to pass enough current through ONE such strand to melt it.

The strand is about 4cm in length and has a resistance of around 2 Ohms. If I connect the strand to the terminals of a fully charged 9V alkaline battery, it melts in about 1-2 seconds. However, I want it to be faster and need to control it using Arduino as I need to also add LEDs. From what I've read, you can use a capacitor to do that.

In the diagram, I have represented the wire that needs to be melted by an Inductor. Also, I need to use a 9V battery to power everything (NOT the 2 AA batteries in the diagram).

Now, here's how the operation of the circuit should be:

As soon as the circuit is switched on, the program is loaded and the Red LED will turn on (Pin 2 on Arduino), indicating that the circuit is ready.
The capacitor will be charged.
Then I can connect the wire that needs to be melted. As soon as I do, using DigitalRead or AnalogRead, I need to check if a wire is really connected (Pin 3).
If the wire is really connected, I need to switch ON the Green LED (Pin 4), indicating that I can start the melting process.
When the push button is activated, a large current is supposed to flow into the wire, causing it to melt. The Green LED turns off as the circuit is now open. Then I can remove the remnants of the melted wire and place another wire and repeat the process.

The problem I'm getting is that the wire is not melting, actually not even heating up. I am using a 100 microFarad Electrolytic capacitor. I am not sure what's wrong. Should I use something more powerful like a 2S battery?

Also, I have tried melting the wire using the output from the Arduino pins but the current is too low to do so. That's why I chose the 9V Alkaline battery.

Any help would be greatly appreciated.

Thanks

Wire meltingwith arduino_bb.jpg
Wire meltingwith arduino_bb.jpg2760×1524 418 KB

2

Have you ever measured the current necessary to melt you wire? That should have been you very first step in your project. If you didn't measure it, do it now!!!!

Paul

3

Paul_KD7HB:
Have you ever measured the current necessary to melt you wire? That should have been you very first step in your project. If you didn't measure it, do it now!!!!

Good idea. It's probably too late to measure the current required to melt the Arduino though...

4

Also, I need to use a 9V battery to power everything

9V block batteries are for smoke alarms. They have very little capacity and cannot supply much current.

5

Try a pack of NiMh rechargeable cells - they can produce a high current.

A lead-acid battery would be even better. It could probably melt the entire jumper, not just a single strand.

You won't need much voltage to produce a current that can overheat a wire - you just need a power source capable of producing a high current - 10 or 20 amps.

Wear eye protection. With a high current the wire will probably explode

...R

6

I suspect that’s what the OP wants...
A DIY igniter.

7

A capacitor stores a truly tiny amount of energy. The capacities are measured in microfarads or nanofarads. Like 0.0000000001 of a useful amount of energy.

Look up "quarter shrinker" those guys use capacitors that are almost suitcase-sized.

8

melting wire requires significant current source... it can be done with as little as 1-2A with right materials.

Copper is too conductive... your jumper wires use 0.15-0.2mm strands and does not provide enough resistance You should be measuring 0.2 Ohms or less so if you're measuring 2 Ohm's it is too high and something is not right.

Try Nichrome has about 50-100 times the resistance of copper.

Material Resistivity ρ (Ω/m)
Copper 1.68 x10-8
Nichrome 100 x10-8

get a real current source.

9

Thanks a million for the replies everyone. I never though so many people would try to help. I ended up using a Lead Acid battery and with some changes to the circuit, I was able to get exactly what I wanted.