Circuit board 2

Component list
Diodes x2
LED
Capacitors x2
Zener diode 22v
Resistors carbon film resistor x3 160, 270 and 820 ohms.
LM317 Regulator
Red and black wires.

To find R1
5-1.8=3.2
3.2/0.02=160 ohms.

To find R2 and R3
5=1.25(1+R3/R2)
5/1.25=1+R3/R2
4=1+R3/R2
3=R3/R2
R2x3=R3
This is a 3:1 ratio.
I used a 270 ohm for R2 and a 820 ohm for R3. It is the closest 3:1 ratio I could get.

The circuits aim is to regulate 12v into 5v.
The Zener diode and normal diode act to protect the regulator by controlling voltage spikes and smooths the input voltage. They also protect the regulator incase of shorts, giving easier paths to earth. The capacitors also work in the same way by absorbing voltage spikes. The D12 diode protects the output of the regulator. The adjustment or negative side of the regulator controls the output voltage by the resistors on the negative side and across the negative and output. The LED shows that the circuits in on.

Vd readings,
D12=6.3 This is the difference between supply voltage and output voltage.
D13=0.7 This is the knee voltage of the diode.
D15=11.5 This is the voltage supply minus the knee voltage being regulated by the zener.
Vin to output=7.56 This is how much the regulator regulates to get to 5V from Vs.
R1=2.87 This uses up the leftover 5V that the LED doesnt use.
R2=1.25 Is the how much the resistor uses to flow through it.
R3=3.84 Is 3 times the voltage of R2 to adjust the output voltage to 5V.
LED=2.22 Knee voltage for the LED.


I had some problems with this circuit.
First of all I had a 220 ohm resistor in, instead of a 270 ohm.
Secondly I misunderstood how a regulator works. I thought that the output was negative and adj was the 5v. Because I misunderstood this, I then wired in the regulator the wrong way, but thinking it was the right way I spent all day trying to figure out the problem with this board. Once I realised that the Output is the signal and not the negative I fixed the problem in 5min.

If I were to redo this board i would compact the board, and I find out exactly how the components work that I'm not sure about.