PIANO using IC-555 timerBy:(ECE-B) * N.AJAY KUMAR(478) * M.MOUNIKA(476) *BHARANI KUMAR(4A2) * N.DINESH(482) Circuit diagram: Components required: 1. bread board. 2. IC-555. 3. resistors ( 1k=10, 10k =1, 330=1). 4. capacitors(0.1uf=2). 5. speaker. 6. battery(9v). 7. connecting wires. IC 555 INTERNAL CIRCUIT OF 555-IC PIN DIAGRAM OF 555 TIMER 1 Pin specifications: Pin Name Purpose 1 GND : Ground reference voltage, low level (0 V) 2 TRIG : The OUT pin goes high and a timing interval starts when this input falls below 1/2 of CTRL voltage (which is typically 1/3 of VCC, when CTRL is open). OUT : This output is driven to approximately 1.7 V below +VCC or GND. 3 4 RESET :A timing interval may be reset by driving this input to GND, but the timing does not begin again until RESET rises above approximately 0.7 volts. Overrides TRIG which overrides THR. CTRL : Provides "control" access to the internal voltage divider (by default, 2/3 VCC). THR : The timing (OUT high) interval ends when the voltage at THR is greater than that at CTRL (2/3 VCC if CTRL is open). Open collector output which may discharge a capacitor between intervals. In phase with output. Positive supply voltage, which is usually between 3 and 15 V depending on the variation. 5 6 7 DIS : 8 VCC : Working: ASTABLE MODE: In astable mode, the 555 timer puts out a continuous stream of rectangular pulses having a specified frequency. Resistor R1 is connected between VCCand the discharge pin (pin 7) and another resistor (R2) is connected between the discharge pin (pin 7), and the trigger (pin 2) and threshold (pin 6) pins that share a common node. Hence the capacitor is charged through R1 and R2, and discharged only through R2, since pin 7 has low impedance to ground during output low intervals of the cycle, therefore discharging the capacitor. In the astable mode, the frequency of the pulse stream depends on the values of R 1, R2 and C: Standard 555 astable circuit 2 Procedure: connect the components as shown in the circuit diagram. connect the input i.e positive of battery to pin8. take the output from pin8.i.e to the speaker. in the circuit diagram,we have resistors R1,R2,R3,R4....so on. to generate a tone as in a piano,we need to switch at different positions ie after R1 or after R2... Clearly saying if we on switch after R1,R2,R3,R4,R5.. so on respectively, we get different tones.. as the resistors are connected in series , we get resistence values of 1,2,3,4,5,6 after R1,R2,R3,R4,R5,R6 respectively.. this is how we can make a piano using 555 timer. =====================================***======================================== 3