2. Nottingham Hackspace – 555 Timer Workshop
What we'll be doing
RC circuits
555 Monostable circuit
555 Astable circuit
“Advanced” circuits
RC circuits: these basic circuits are how basic timing is done in many applications. e.g. microcontrollers often have onboard RC timer as their main clock.
Monostable: one stable state
Astable: no stable states
Advanced circuits (if we have time!)
Nottingham Hackspace – 555 Timer Workshop

3. Nottingham Hackspace – 555 Timer Workshop
RC Circuits
Capacitors can store charge. Think of them as temporary batteries.
Breadboard + scope demo
Nottingham Hackspace – 555 Timer Workshop

4. Nottingham Hackspace – 555 Timer Workshop
555 Timer Pins
Nottingham Hackspace – 555 Timer Workshop

5. Nottingham Hackspace – 555 Timer Workshop
555 Timer “Rules”
Output
Discharge
Trigger below 1/3 Vcc
ON (Vcc)
Floating (unconnected)
Threshold above 2/3 Vcc
Ground
Nottingham Hackspace – 555 Timer Workshop

6. Nottingham Hackspace – 555 Timer Workshop
Monostable Circuits
Monostable – one permanent state.
Nottingham Hackspace – 555 Timer Workshop

7. Nottingham Hackspace – 555 Timer Workshop
Monostable Circuits
Nottingham Hackspace – 555 Timer Workshop

8. Useful monostable equations: Time on =
Monostable Circuits
Useful monostable equations:
Time on =
1.1𝑅𝐶
Nottingham Hackspace – 555 Timer Workshop

9. Nottingham Hackspace – 555 Timer Workshop
Astable Circuits
Astable – no permanent states.
Nottingham Hackspace – 555 Timer Workshop

10. Nottingham Hackspace – 555 Timer Workshop
Astable Circuits
Nottingham Hackspace – 555 Timer Workshop

11. Useful astable equations: Frequency = Duty Cycle =
Astable Circuits
Useful astable equations:
Frequency =
Duty Cycle =
𝑅 1 +2 𝑅 2 𝐶
𝑅 1 + 𝑅 2 𝑅 1 +2 𝑅 2
Nottingham Hackspace – 555 Timer Workshop

12. Nottingham Hackspace – 555 Timer Workshop
“Advanced” Circuits
Astable – low duty cycle
Nottingham Hackspace – 555 Timer Workshop

13. Nottingham Hackspace – 555 Timer Workshop
“Advanced” Circuits
Nottingham Hackspace – 555 Timer Workshop

14. More “Advanced” Circuits
Voltage Controlled Oscillator (VCO)
Pulse Width Modulation (PWM)
Google it!
Nottingham Hackspace – 555 Timer Workshop

15. Nottingham Hackspace – 555 Timer Workshop
Schematic and breadboard images produced using Fritzing: fritzing.org
This work is licensed under a Creative Commons Attribution 3.0 Unported License.
Original author: James Fowkes
Nottingham Hackspace – 555 Timer Workshop