Sensor Circuit Board Write-Up

Oxygen Sensor Circuit

Parts Lists

• D1, D2 and D3 1N4001 1000v silicon diode 0.7 forward biased
• Capacitors x2 Monolythic Dip C5K, 1uF
• LEDs Red, Yellow, Green 1.8volts
• R2, R3 and R4 resistor 1k
• R5 resistor 330R
• R6 resistor 10K
• R7 resistor 270R
• R8 resistor 470R
• Zener diode 9V1
• Integrated Circuit LM324AN 14pins
• Jumper wires

Calculations for resistors used in the Sensor Circuit

R2, R3 and R4 = 12- 0.7

= 11.3v - 1.8 = 9.5volts

= 9.5/0.095

= 1000

Therefore the preferred value resistor used is 1k

R5 = 11.3/0.330

=34.24

Therefore the preferred value resistor used is 330R

R6 = 10k

R7 = 0.23v/ 0.00091A

= 252ohms

Therefore the preferred value used resistors is 270R

R8= (0.63-0.23)/0.00091A

= 439.56ohms

Therefore the preferred value used resistor is 470R

How the sensor circuit works

Inorder to get this cicuit operational you need a 12volts power supply with the common or earth to get the first set of LED working (green). As the current flows through the first diode which uses 0.7volts passing through the capacitor(C1). The zener protection resistor (R5) reduces the current flowing to the zener diode which now regulates the voltage down to the 9.1volts. All currents going into the input of the Intergrated Circuit is later limited by the resistors 6, 7 and 8. Pins number 3, 6, 9 and 12 are the input sensor which is from 0.3 to 1.0volts maximum. The pin number 11 from the Intergrated Circuit is connected to the earth whereas the pin number 4 is connected to the 12v power supplied rail. Pins 2, 5, 10 and 13 are the (in) connected between two resistors and to earth. When you connect the input PL2 the green LED goes off and then when you adjust the voltage to 0.3volts the yellow LED lights up as increase from 0.3 to 0.7 volts the yellow LED goes off and the red LED lights up.

Fault Findings

After making this circuit I conected my circuit to the power supply and my circuit did not work because I did not separated the pins 2,5,10 and 13 from the pins 3,6,9 and 12 after fixing all that problem my circuit looked very untidy so I decided to make a new design and new circuit board. After i made my new circuit board i tested it and than it worked.

Test Procedure

To get this circuit working you need to have 12v power supply and additional 0.3 to 0.7volts is required inorder to allow the yellow and red LED to light up as you adjust your additional voltage. This will show you that the yellow LED switches with the red LED as u change the voltage.