loch Master Design :
Schematic :
R1 = 100Ω 25w carbon pile resistor
R2 = 270Ω 25w carbon pile resistor
R3 = 820Ω 25w carbon pile resistor
D12 = 1N4001 50v 1.3w diode
D13 = 1N4001 50v 1.3w diode
D15 = BZX85-C22 22v 1.3w zenea diode
LED1 20mA 1.8v LED (red)
C15 = electroletic 33uf 25v capasitor
C16 = electroletic 33uf 25v capasitor
Voltage regulator LM317
Circuit board 2.54mm grid
Test procedure :
Output voltage test result = 5.129v
volt drop across the LED 1.9v, vd across R1 was 3.181v, vd across R3 was 3.812v
vd C16 was 5.131v, vd C15 11.51v, voltage reg. adj.-in 7.81v, in-out 6.37v, adj.-out 0v,
Calculations :
Vref = 1.25 Vout must = 5v
(1+R3/R2) 5 = 1.25 (1+R3/R2)
5/1.25 = 1+ R3/R2 4 = 1+R3/R2
4 - 1 = R3/R2
3 = R3/R2
3/1 R3/R2
R1 = 5v - 1.8v = 3.2v so 3.2/0.3 = 106Ω R1 = 106Ω
Vout = Vref (1+R3/R2)
5/1.25 = 4 (1+R3/R2) = 3/1 = 1/3
So I used a LM317 calculator at http://www.electronic-lab.com/ and got:
R2 270Ω
R3 820Ω
Circuit Explanation :
The heart of the circuit is the LM317 is an integrated three-terminal adjustable linear voltage regulator it has a input voltage of 3v to 40v and a output voltage between 1.25 and 37v and a current rating of 1.5amps. The voltage between ADJ and OUT terminals is always 1.25v knowing this I used the equation Vout = Vref (1+R3/R2) and a LM317 calculator to calculated the resistors R2 and R3 these would give me the 5v output voltage required for this circuit. The Vin terminal has a 12v supply through diode D13 in forward bias. Then D15 22v 1.3w zena diode in reverse bias in parallel with C15 a 33uf 25v capacitor. D12 is reveres bias and protects the LM317 from C15 discharging into the input.The LED has a resistor R1 with a 5v supply to get the value of R1 = 5v - 1.8v for the LED = 3.2v the LED is 30ma so i used ohms law 3.2/0.03 = 106.6 so R1 = 100Ω.
Reflection :
The circuit was quite easy to design and build but I didn't really know anything about voltage regulators. So I found it difficult to write a circuit explanation, but after doing some research on the Internet I found heaps of information on the LM317 and now understand what was going on.
