experiment 6 - report

8/3/2019 Experiment 6 - Report

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Build and test a basic voltmeter with the following specifications:

o Voltage to be measured: 0V ± 5Vo Display: One seven segment display without a display driver. Use a lookuptable to display the correct value on the seven segment display.

o Output Response Time: Voltage measured should be displayed real time.o The circuit must be constructed on Veroboard.o Measuring leads must be fixed onto the board

y The input probes relegate the measured voltage.

y The ADC converts the voltage into a binary number

y The PIC decodes the number

y The display relays the converted and decoded number in recognizable format

InputProbes

ADC PIC Display



y

V

eroboardy 7805CT 5V Voltage regulator

y PIC16F628A

y ADC0804LCN

y ELS-505 Common cathode Display

y LM336Z25 2.5 volt Zener Diode

y Multi-meter Probes

y 10k Resistor x 1

y 330Ohm Resistor x 8

y 100pF Capacitor

y 3 channels SPST switch

y 2 Channel Cable junction Block

y IC Sockets x 2

y Ethernet Cable Cores

y 9V Duracell Battery

y 9V Battery Connector



Lookup-Table For converting Binary Values

RB0 RB1 RB2 RB3 RB4 RB5 RB6 RB7

E D C DP B A F G HEX

0 1 1 1 0 1 1 1 0 77h

1 0 0 1 0 1 0 0 0 14h

2 1 1 0 0 1 1 0 1 B3h

3 0 1 1 0 1 1 0 1 B6h

4 0 0 1 0 1 0 1 1 D4h

5 0 1 1 0 0 1 1 1 E6h

6 1 1 1 0 0 1 1 1 E7h7 0 0 1 0 1 1 0 0 34h

8 1 1 1 0 1 1 1 1 F7h

9 0 1 1 0 1 1 1 1 F6h

For 1 Hz



Circuit operates in the following manner1. ADC is given a reference voltage of 5 volts full scale = 255 Binary Output

2. Comparative voltage is then connected via the probes from an external source

3. This voltage is measured against the reference voltage and a scale output of 5V vs.

Input voltage is displayed on the D0-D7 Output pins

4. This binary number is relayed to the PIC16F628A Microprocessor

5. The processor decodes the binary input numbers connected to PORT-A and

relegates a decoded signal to PORT-B.

6. Port B sends the signals to a 7-segment display via 330 resistors

7. The measured voltage is displayed on the seven-segment display.



Start

Disable Comparator

Set I/O

Move Port A value to storage Register

Load d'51" to decrement register

Subtract 51 from storage-register

Remainde Positive ?

Load d'5' to decrement register

Subtract 5 from storage-register

Remainde Positive ?

Next Page

Increment

Voltage-Main

File

Increment

Voltage-

Decimal File

Yes

Yes

No

No



CompareVolt -Main fileto lookup table

Return Lookup Tablenumber to Port B

Display number

1 Second Delay

CompareVolt -Decimalfile to lookup table

Return Lookup Tablenumber to Port B

Display number

1 Second Delay

Goto: Move Port A valueto storage Register

End



Circuit operates in the following manner1. ADC is given a reference voltage of 5 volts full scale = 255 Binary Output

2. Comparative voltage is then connected via the probes from an external source

3. This voltage is measured against the reference voltage and a scale output of 5V vs.

Input voltage is displayed on the D0-D7 Output pins

4. This binary number is relayed to the PIC16F628A Microprocessor

5. The processor decodes the binary input numbers connected to PORT-A and

relegates a decoded signal to PORT-B.

6. Port B sends the signals to a 7-segment display via 330 resistors

7. The measured voltage is displayed on the seven-segment display.

Shortcomings.

1. Shelf Volt-meters can measure AC+DC voltage we can only measure DC Voltage.

2. This meter cant measure current or resistance.

3. This meter can only measure up to 5-volts.

4. This meter has only one-digit display.

5. This meter is not isolated from measured supply.

Improvements.

1. LCD-interface instead of 7-segment display.

2. Larger voltage measuring range.

3. Place control board in an enclosure.

4. Use printed circuit board instead of Veroboard.

5. Incorporate a logic probe option.

experiment 6 - report

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