The 555 timer is one of the most successful integrated circuit (IC) designs of all time. Developed in the 1970s, this inexpensive 8-pin chip continues to be popular today. The 555 is a source of timing pulses and can be run in astable, bistable or monostable modes. To build a circuit with it, study its data sheet and examine the formulas used to determine its timing network. Look at the 555's pin-out diagram and see where to connect power, ground and components. Enjoy exploring different circuits with the chip, a breadboard and a few external parts.
Instructions
1. Examine the 555 timer's data sheet. Note that you connect positive power to pin 8 and ground to pin 1. A timing network, made of two resistors and a capacitor, connects to pins 7, 6 and 2. Formulas to determine the chip's timing are given on the data sheet. Note that the output's on time and off time are determined separately by the two resistors. Note also that, depending on the operating mode, some of the 555's pins are shorted together.
2. Insert a 555 chip into your breadboard. Note that the breadboard has a special channel for the ICs to straddle. Wire your DC power supply to the breadboard and connect the positive and ground pins of the 555 as described in Step 1.
3. Connect the 555 for astable mode. Determine values for the timing network R1, R2 and C1. If you just want to try a circuit, R1 and R2 can be the same value, i.e., 1,000 ohms. Pick a capacitor in the .001-to-1 range. You can choose other values and learn their effects at any time.
4. Plug one lead from the mini speaker to the 555 output at pin 3 and the other lead to power supply ground. When you turn the circuit on, you should hear the speaker make a clicking or buzzing indicating that it is working.
Tags: data sheet, Note that, timing network, connect positive, data sheet Note, power ground