I'm in high school computer engineering, and I'm experimenting with the 555 Timer chip on my own. I'm using the Electronic Experimenter Box.

  • Pin 8 is connected to +5V
  • Pin 1 connected to ground
  • LED1 is connected to Pin 3 and +5V
  • LED2 is connected to Pin 3 and ground

At first, LED1 is off and LED2 is on. When I connect pin 6 to +5V, LED1 turns on and LED2 turns off. When I connect pin 5 to +5V, LED1 turns off and LED2 turns on.

The weird thing is that when I touch pin 6 with only 1 end of a wire, it produces the same results as if I connected pin 6 to +5V. The other end isn't connected to anything either and I'm not touching any metallic part of the wire. What's going on here?

  • 3
    \$\begingroup\$ I would love it if you drew a schematic. \$\endgroup\$
    – Kortuk
    Commented Apr 15, 2012 at 4:32
  • \$\begingroup\$ What are some free/open source tools that I can use for that? \$\endgroup\$
    – Alex
    Commented Apr 15, 2012 at 19:16
  • \$\begingroup\$ Quite a few answers to that. The tool I suggest is from circuitlab \$\endgroup\$
    – Kortuk
    Commented Apr 15, 2012 at 22:01
  • \$\begingroup\$ @AlexYan Pencil, paper, camera. \$\endgroup\$ Commented Apr 16, 2012 at 19:41
  • \$\begingroup\$ Camera batteries are empty and can't charge \$\endgroup\$
    – Alex
    Commented Apr 18, 2012 at 2:35

1 Answer 1


Try holding the wire in an insulating holder - say on the end of a toothpick or wooden chopstick etc. Results are likely to be different.

You should provide a circuit diagram of EXACTLY what you are doing BUT if pin 6 is "floating" normally then your body will pick up mains hum capacitively from the surroundings and couple it into the pin. ALL input pins must ALWAYS have defined conditions if you want defined operation to happen. If you don't want defined operation then you can connect them any way you wish :-).

  • \$\begingroup\$ Yeah it's probably this. Plastic doesn't work, Some shiny reflective plastic (Probably have some bits of metals in it) works, and metals definitely work so I assume it's my body picking up charges \$\endgroup\$
    – Alex
    Commented Apr 18, 2012 at 2:37

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