SDIY Building Blocks

Appearance

555 timer circuits ​

What It Does

The 555 timer is a very popular chip with a little circuit inside. With just a few extra components you can create different configurations for different functionalities.

Overview ​

Pinout

  1. Ground.
  2. Trigger. A negative pulse on this pin sets the SR Flip-flop when the voltage drops below 1/3 * Vcc.
  3. Output. The output can source up to 200mA of current.
  4. Reset. Optional reset for the SR Flip-flop. This input is generally connected to a logic HIGH level when not used to prevent any unwanted resetting.
  5. Control Voltage. This pin controls the timing of the 555 by overriding the 2/3 * Vcc level of the voltage divider network.
  6. Threshold. This pin controls the threshold level for resetting the SR flip-flop.
  7. Discharge, Controls the “discharge” of the timing capacitor.
  8. +Vcc, Power supply between 4.5V and 15V.

Monostable mode ​

  • Notice after pressing the button the LED lids up for a short period.

Astable mode ​

  • Notice the oscillating LED.

Bistable mode ​

  • Notice you can set and reset the LED with the two buttons.