Lab number four.
555 astable timer
components:
1) B1: 9 volt battery
2) R1: 100 k ohm resistor
3) R2: 10 k ohm resistor
4) R3: 100 ohm resistor
5) C1: 0.1 uF capacitor
6) C2: 4.7 uF capacitor
7) IC1: 555 timer
8) SPK: 8 ohm speaker
notes:
1) Adjusting R1 will change oscillation rate
2) Replace C1 with a 10 uF cap and SPK with an LED for a flashing light.