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.

circuit board 2

The second circuit is made to regulate voltage.In the second circuitboard i made a circuit containing two rectifying diodes a zener diode two capasitors three resistors a led and a voltage regulator the circuit has a 12v iput and a 5v and 12 v output.I had to calclate the resistors, the first resistor circuit as the 5v supply and a led the led is 1.7v and 20ma so i worked it out as:
5-1.7=3.3
3.3/0.02=165
R1=165ohm
the second and third resistor has a formula of vref(1+R3/R2)
vref=1.25
5/1.25=4
3R2=R3
i checked on the datasheet and found R2=240ohm
240x3=720
R3=720
After I worked out the resistor I designd the circuit on lochmaster

I had some trouble with this circuit and after diagnosing it I found that my diode was the wrong way around and caused it to blow up and also caused my zener diode to bloow up.After i reaplaced the diodes i tested it and found that i was geting 9v output instead of the 5 that i had to get.1 did visual inspection first and comparing my circuit to my design.I found i was missin a jumper wire from R2 to the adjustment of the voltage regulator this was cuting my resistor out of the circuit. After puting the wire in and testing it I got 2v wich is to low.i checked all my values of my resistors and tested my resistors I found one of my resistors was to small after replacing it with the right size resistor i was geting a voltage of 5.09volts so it was working perfectly.

the photo above shows my circuit working.The way to test this circuit is to have a 12v supply put the positve of the circuit in the positive supply and the negative in the negative then get a multimeter put it on the volts scale put the black terminal in the negative of the supply and the red on the wire when on the 12v (red wire in this case) shoul give 12v wen on the 5v(white wire)should give 5v.

circuit board 1

i built a circuit board with diferent components the circuit I had to build was a circuit containing four resistors 2 leds and two npn transistors the circuit has a 12V supply and two 5V supplys and a ground.I had to work out the resistors the first resitors i worked out was R14 and R15 they were in paralel series with a led each and they used the 12V supply and a transistor I measured the led it is 1.7V and the transistor is 0.5V and the led has amprege of 20ma so it is:
12-1.7-0.5=9.8
=9.8/0.02
=490
therefor R14 and R15=490ohm
next i worked out R13 and R16 both has a transistor wich is also same transistor as for the other two.
I looked at the datasheet and found beta=100
Ib=Ic/B=0.02/100=.0002
Ib=.0002=.2ma
I checked the datasheet and found .2mA is not enough i have to use 5mA
5-.6=4.4
4.4/.005=880
R13 and R16=880ohm
I had to design the circuit first using lochmaster

The picture above here shows my design of the first circuit.the circuit i built is made fore injection because it gets earth trigerd.I had some problems with my circuit,when i tested it i found only one of my lights was working after diagnosing it by first visual inspection i saw my soldering was touching after i cleared it i tested my circuit again and found it was stil not working so i checked the voltage drop at the working led and found it had a voltage of 11.4 volts wich is realy high.Then after loocking at my diagram i found my resistors was on the rong side of my leds and it was cuting out the resitors after puting two new resistors in front of the leds my circuit was workin perfectly.

The photo above is showing the circuit works as it should (showing the red light).The way to test this circuit is to have the 12v positve wire in the 12v supply aswel as the negative then have a bridge wire going from the negative of the 12v supply to the negative of the 5vsupply then the 12v and 5v has to be turned on then take the one 5v wire and put it in the 5v positive and the one light has to cme on do the sam with the other 5v wire and other light should come on.

photo above shows the green light working.