circuit board 3

The third circuit was designed to work with a oxygen sensor to tell us if the car is runing rich or lean.This circuit contains an four opamp chip 7 resistors two rectifying diodes one zenner diode two capasitors and three leds with a 12v input and a sensor input with a earth.I had to work out the resistors in this circuit before building it.To work out the first three resistors it is 12-.6 because it goes through a diode
12-0.6=11.4 each has a led
11.4-1.8=9.6
9,6/0.0095=1010ohm
R2=1010ohm
R4=1010ohm
R3 has diode
1.8+.6=2.4
11.4-2.4=9
9/0.0095=947
R3=947ohm
working out R5.there is a 9.1v zenner diode in reverse bias
9.1-11.4=2.3 zenner=5.6mA
2.3/0.0056=410
R5=410ohm
R6 is given to us
R6=10kohm
working out R8after R6 there is .63v in the circuit
9.1-.63=8.47 after R8 there is .23v
.63-.23=.04
.04/.000847=472
R8=472ohm
working out R7
.23-0=.23
.23/0.000847=272
R7=272ohm

After working out the resistors I designed the circuit.

After building this circuit  i had alot of problems first time i tested it all my light was working but then my one led caught on fire i did a visual inspection and found i didnt put the breaks in properly so i was get to high voltage.I made the breakes replaced the led and only one light was working i checked the votage drop across my led and it was working I compared the design with the crcuit and it the same acept for some jumper wires that I had to move because the board realy small and I cant fit them in like origenal design.I checked all the soldering to make sure nothing touches. i checked my resistors they are all corect I ran out of time but I think it might be a lose conection in the circuit.

The photo above shows only one light is workin the yellow one.The way to test this circuit is to put the positive and egative in a 12v supply and bridge a wire from negative 12 to a negative 5v supply and put the sensor positive and negative in 5v and conect the output of the sensor with the circuit sensor wire.When working  the diferent lights should come on when you turn the sensor.