Construction part four- improvementation

Take experiences from last time, we were going to use thinker pencil leads. 

These pencils were purchased by Yinxin in a convince store and cost at 2 dollars(including tax).

We used a sharp knife to cut off the wood part of the pencil and carefully took out the thicker pencil lead. It was an excitement when we cut the pencil perfectly in half without breaking the lead.  

Since the lead is thick enough to afford the wires' weight. This time, we achieved successful connection between the copper wires and pencil leads without any damage.