Oxygen Sensor Circuit

Oxygen Sensor Circuit:

Oxygen Sensor using the flowing Components:
12V Battery
1x op Amp LM 324
1x Zener diode 9v1
2x Capacitors 0.1uF
3 LED: 1x Green LED; 1x Yellow LED; 1x Red LED
7x Resistors: R2=1KΩ; R3=1KΩ; R4=1KΩ; R5=380Ω; R6=10KΩ; R7=270Ω; R8=470Ω

Calculation:
I=9.5mA=0.0095

Power supply voltage is 12V, Vd of crossing diode D2=0.6Vd, Vd of zener diode D1=9.1V

R2:
Vd=12-0.6-1.8=9.6V
R2=V/I=9.6/ 0.0095=1010.5Ω

R3:
Vd=12-0.6-0.6-1.8=9V
R3=V/I=9/0.0095=947Ω

R4:
Vd=12-0.6-1.8=9.6V
R4=V/I=9.6/0.0095=1010.5Ω

R5:
I=5.6mA=0.0056A
Vd=12-0.6-9.1=2.3V
R5=V/I=2.3/0.0056=411Ω

R6=10K
The voltage befor R6: 12-0.6-2.3=9.1V
The voltage after R6: 0.63V
Voltage drop of R6=9.1-0.63=8.47V
I=V/R=8.47/10000=0.000847A

R7:
Vd=0.23V
R7=V/I=0.23/0.000847=271.5Ω

R8:
Vd=0.63-0.23=0.4V
R8=V/I=0.4/0.000847=472Ω

There is some photo of I built it on  breed board and pcb board.

breed board

Oxygen Sensor

Oxygen Sensor

Red LED shows when the car is running its rich mixture

Yellowe LED shows when the car is running its normal mixture

Green LED shows when the car is running its lean mixture

Oxygen sensor:


An oxygen sensor is an electronic device that measures the proportion of oxygen in the gas or liquid being analyzed. It was developed by the Robert Bosch GmbH company during the late 1960s under the supervision of Dr. Günter Bauman.  The most common application is to measure the exhaust gas concentration of oxygen for internal combustion engines in automobiles and other vehicles. Divers also use a similar device to measure the partial pressure of oxygen in their breathing gas.
Scientists use oxygen sensors to measure respiration or production of oxygen and use a different approach. Oxygen sensors are used in oxygen analyzers which find a lot of use in medical applications such as anesthesia monitors, respirators and oxygen concentrators.
There are many different ways of measuring oxygen and these include technologies such as zirconia, electrochemical, infrared, ultrasonic and very recently laser methods. Each method has its own advantages and disadvantages.

Automotive applications
Automotive oxygen sensors, colloquially known as O₂ sensors, make modern electronic fuel injection and emission control possible. They help determine, in real time, if the air fuel ratio of a combustion engine is rich or lean. Since oxygen sensors are located in the exhaust stream, they do not directly measure the air or the fuel entering the engine. But when information from oxygen sensors is coupled with information from other sources, it can be used to indirectly determine the air-to-fuel ratio. Closed-loop feedback-controlled fuel injection varies the fuel injector output according to real-time sensor data rather than operating with a predetermined (open-loop) fuel map. . Rich mixture causes an oxygen demand. This demand causes a voltage to build up, due to transportation of oxygen ions through the sensor layer. Lean mixture causes low voltage, since there is an oxygen excess.
Modern spark-ignited combustion engines use oxygen sensors and catalytic converters in order to reduce exhaust emissions. Information on oxygen concentration is sent to the engine management computer or ECU, which adjusts the amount of fuel injected into the engine to compensate for excess air or excess fuel. The ECU attempts to maintain, on average, a certain air-fuel ratio by interpreting the information it gains from the oxygen sensor.Reference:
http://en.wikipedia.org/wiki/Oxygen_sensor