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- 1. Digital Design Project BinaryTemperature Monitor Utilizing 8-Bit A-D Converter Denis P. Cote
- 2. Binary Temperature Monitor Overview TemperatureMonitor : -100º to 90ºC 8 Bit Binary Output Display (0-255) Core: ADC0808 8-Bit A/D IC – National Semiconductor A/D Utilizes Successive Approximation Single Supply (Vcc) Referenced to Ground Conditioned Analog Input: AD594 Type J Thermocouple Amp IC A/D Clocked via 555 Timer Configured as Astable Multivibrator Simple Design, Low Cost & Expandable
- 3. Circuit Block Diagram Voltage Regulator (7805) ADC 0808 LED Output Resistor ICAD594 Thermocouple & HeatSource Supply Voltage 12V Clock LM555 Analog In Digital Out Vref (+) = 5 Vdc Vref (-) = GND
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- 5. Model Simulation -MULTISIM A1 ADC Vin Vref+ Vref- D0 D1 D2 D3 D4 D5 D6 D7 SOC EOCOE 11 U1 DCD_HEX_BLUE U2 DCD_HEX_BLUE LED1 A R2 180 Ω RPACK8 17 16 18 19 1 2 3 4 5 6 7 8 0 A2 555_VIRTUAL GND DIS OUTRST VCC THR CON TRI R3 100Ω R4 100Ω VCC 5V C1 100nF XFC1 123 23 22 0 VCC 14 15 20 21 U5 DC 10MW 3.000 V + - 0 0 VDD 3V VDD VCC 5V VCC 24 555 Timer Model: Freq Out - ~29.6KHz Square Wave at Vcc Fout =1.44/(R3+2R4)C1 LSB Analog In Simulation: Vdd = Output of T/C Amp
- 6. Circuit Prototype Clock Pulse Freq.~30KHz Binary Out: 10010111 Top = MSB
- 7. Parts List &Cost Item Tag Qty Part No. Vendor Description Unit Price 1 U1 1 ADC0808CCN- ND Digi Key / Kit IC ADC 8BIT MPU 8CH MUX 28-DIP $ 5.40 2 U2 1 AD594AQ-ND Digi Key IC THERMOCOUPLE A W/COMP 14CDIP $ 11.48 3 U3 1 LM555CNFS-ND Digi Key IC TIMER SINGLE 0-70DEG C 8-DIP $ 0.44 4 U4 1 NJM78L05A-ND Digi Key 5 Volt Positive Regulator $ 0.12 5 LED 1 67-1009-ND Digi Key LED ARRAY 10X25MM 10SEG RED DIFF $ 2.13 6 TC 1 JMTSS-062G-6 Omega Type J Junction Thermocouple Probe $ 24.95 7 R9 1 Resistor KIT 100 Ohm 1/8 watt carbon film resistor $ - 8 R1-R7 1 Resistor IC KIT 300 Ohm Resistor IC $ - 9 R11 1 Resistor KIT 1K Ohm 1/4 watt resistor $ - 10 R10, R12 1 Trimmer KIT 2K Ohm trimmer potentiometer $ - 11 C1, C3, C4, C5 1 Capacitor Radio Shack 0.1 uF ceramic capacitor $ 1.18 12 C2 1 Capacitor KIT 10 uF 25VDC elecrolytic capacitor $ - 13 D1 1 Rectifier Diode KIT 1N4007 Rectifier Diode $ - 14 S1 1 Dip Switch KIT Dip Switch $ - Misc Total $ 45.70 Hook Up Wire breadboard
- 8. Measured Performance MultiSIM Model VinBinary Out Dec Hex 0 0 0 00 0.500 11001 25 19 1.000 110011 51 33 1.500 1001100 76 4C 2.000 1100110 102 66 2.500 1111111 127 7F 3.000 10011001 153 99 3.500 10110011 179 B3 4.000 11001100 204 CC 4.500 11100110 230 E6 5.000 11111111 255 FF Sensitivity: 5 volts / 255points = 0.019607 V/Point ~20mV/Point Error: 1/2 LSB & 1 LSB Circuit Vin Vin Actual Volts Lo Hi Binary Dec Hex Calculated Vout Comment 0 0 0.009 0 0 00 0.00 0.500 0.487 0.497 11010 26 1A 0.51 1.000 0.986 1.003 110011 51 33 1.00 1.500 1.479 1.492 1001101 77 4D 1.51 2.000 1.983 2.002 1100110 102 66 2.00 2.500 2.471 2.49 10000000 128 80 2.51 3.000 2.982 3 10011001 153 99 3.00 3.400 3.392 3.404 10101110 174 AE 3.41 (Limit of trimmer pot reached) 0.00 0.00 5.000 5.000 5.010 11111111 255 FF 5.00 Vcc minmax DD Dx VzVfs Vin Comparison of Model Vs. Circuit Output
- 9. Measured Performance ADC0808 -Actual Vs Model Linearity 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 0 1 2 3 4 5 6 Input Voltage BinaryOutput(0-255) MultiSIM Model Circuit
- 10. Future Improvements Increase numberof Analog Inputs (0-7) Robust Display: Decimal or Hex Enable Multiplexing of Inputs Parallel DIO output to PC – Data Logger Disadvantages: – Low Resolution (256 points) – Limited to Max input equivalent to Vcc – Higher Resolution = Chip Replacement
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- 12. Back Up 1 815 22 29 5 12 19 26 3 10 17 24 31 7 14 21 28 Project Research (3/10 - 3/30/2008) Project Selection (3/30/2008) Project Approval Design / Model Part Procurement Construction Commission Final Report Out 8-Bit ADC Digital Design Project (Digital Circuits 2) Project Timeline - 3 month outlook Denis Cote Task March April May June ADC0808 Datasheet Data Sheets: Analog Devices AD594 LM555 Datasheet Schedule: