Extension Electronics Lab: 555 Timer Instruments

Integrated Circuits

• A set of electronic circuits embedded into one small chip of semiconductor material.
• Instead of having many discrete components, an IC provides the same functionality in a single package.
• Chips used for many different purposes:
  
  • Amplifiers
  • Voltage regulators
  • Memory
  • Logic gates
  • Processors
  • Microcontrollers – like ARDUINO!

 

555 Timer Background Info

Serial/Parallel Capacitances

• Series Capacitors - combines similarly to parallel resistors -
• Parallel Capacitors - Same as series resistors -

            

 

Comparator

• A device that compares two voltages and outputs a digital signal indicating which is larger. It has two analog input terminals V+ and V-, and one binary digital output Vo.
• Vo = 1; if V+ > V-
• Vo = 0; if V+ < V-

 

S-R Flip Flop

• A "latch" circuit is used to store information. It has two stable states.
  
  • S – Set, drives output Q high
  • R – Reset, drives output Q low
  • R1 - Resets the latch.

 

555 Timer

     

• Green: Between the positive supply voltage VCC and the ground GND is a voltage divider consisting of three identical resistors, which create two reference voltages at ​1/3 VCC and ​2/3 VCC. The latter is connected to the "Control Voltage" pin. All three resistors are 5 kΩ.
• Yellow: The comparator negative input is connected to higher-reference voltage divider of ​2/3 VCC (and "Control" pin), and comparator positive input is connected to the "Threshold" pin.
• Red: The comparator positive input is connected to the lower-reference voltage divider of ​1/3 VCC, and comparator negative input is connected to the "Trigger" pin.
• Purple: An SR flip-flop stores the state of the timer and is controlled by the two comparators. The "Reset" pin overrides the other two inputs, thus the flip-flop (and therefore the entire timer) can be reset at any time.
• Pink: The output of the flip-flop is followed by an output stage with push-pull (P.P.) output drivers that can load the "Output" pin with up to 200 mA (varies by device).
• Cyan: Also, the output of the flip-flop turns on a transistor that connects the "Discharge" pin to ground.

555 timer square wave simulation - http://www.falstad.com/circuit/e-555square.html

555 timer internals simulation - http://www.falstad.com/circuit/e-555int.html

 

555 Timer Operating Modes

• Astable (free-running) mode – the 555 can operate as an electronic oscillator. Uses include LED and lamp flashers, pulse generation, logic clocks, tone generation, security alarms, pulse position modulation and so on.
• Monostable mode – in this mode, the 555 functions as a "one-shot" pulse generator. Applications include timers, missing pulse detection, bounce-free switches, touch switches, frequency divider, capacitance measurement, pulse-width modulation (PWM), and so on.

 

Astable Mode

• Puts out a continuous stream of rectangular pulses having a specific frequency determined by R1, R2, C.
• Output high when trigger less than 1/3 Vcc, low when threshold greater than 2/3 Vcc.
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Monostable Mode

• Similar to astable but requires external trigger (driven by another source).
• Output driven high when trigger drops below 1/3 Vcc, and driven low when the threshold charges to 2/3 Vcc.
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555 Timer Instruments

Full Tutorial: https://www.instructables.com/Battle-of-the-Bands-555-Timer-Edition/ 

Demo: 

 

Theremin

 

Atari Punk Console

 

Organ