Function Generator using 8051

Prepared by

Mr. Paresh R. Kamble

Guided by

Prof. Anish Goel

Overview• Aim: To generate sine, rectangular and triangular waveforms using 8051.

• DAC 0808 will convert 8-bit digital output of 8051 to analog value.

• It uses R/2R ladder method for conversion from D 2 A.

• Iout = Iref {(D7/2)+(D6/4)+(D5/8)+(D4/16)+(D3/32)+(D2/64)+(D1/128)+(D0/256)}

where, D0 – LSB, D7 – MSB, Iref – 2mA fixed current

• Output is available in the form of current at Iout pin of DAC.

• After amplification it is provided to the Oscilloscope.

Block Diagram

P1.0

P1.7

8051

Vcc

D0

D7

GND

DAC 0808

+5v

1k1.5k

Vref(+)

Vref(-)

2.5k CRO

Iout Vout = 0 – 10v

Comp. 5k pot

100pFVee

-12v

Sine wave details:Angle θ (Degrees) Sin θ Vout (Voltage Magnitude)

5v +(5v x sin θ)Decimal values sent to DAC

(V magnitude x 25.6)

0 0 5 128

30 0.5 7.5 192

60 0.866 9.33 238

90 1.0 10 255

120 0.866 9.33 238

150 0.5 7.5 192

180 0 5 128

210 - 0.5 2.5 64

240 - 0.866 0.669 17

270 - 1.0 0 0

300 - 0.866 0.669 17

330 - 0.5 2.5 64

360 0 5 128

WavefromVolts

109

87

654

32

1

0 30 60 90 120 150 180 210 240 270 300 330 360 Degrees

Angle vs Voltage Magnitude for Sine wave

Thank you !