Circuit board 1

Components for this circuit board:

Resistor R1/R2 : 560 ohm's

Resistor R3/R4 : 1000 ohm's

2x 1.8v/20ma L.e.d's

2x c547w64 NPN transistors

With a Vs of 12v.

pwn : 5v

Calculations to finding out what type of resistors to use:

R1/R2 = (12v-1.8v/20ma) =10.2v/.020 = 510 ohm's

R3/R4 = 5-0.7/5ma

=4.3/0.005 = 860 ohm's

In this circuit we have the 12v power supply connected to the collector of the transistors, the 5v PWN signals which are low current flow through the base of the emitter, which then opens a the gate and allows the high current in the circuit to go through the collector then to the emitter, to ground.

To test if the circuit is working up to scratch a volt drop test can be done across the components of the circuit board

(You can Look up data sheets for all different types of transistors).....

I found Vce= 0.05V and Vbe= 0.08V. I also knew that the L.e.d's are 1.8volts.

Then i checked these 3 points with my multimeter and found that...

(Vce) was 0.04V for the two transistors.

(Vbe) was 0.84V= L.e.d 1 and 0.79V= L.e.d 2.

The voltage drop across L.e.d 1 was 1.84V, and L.e.d 2 was 2.12V.

In the end I think my experiment all went fine, the only real thing i could have changed would be to use less soldier for a cleaner looking circuit board, but it did what it was meant to do and everything functioned upto standard. For the first time making one the only down fall was putting one transistor in the wrong way but you learn from your mistakes so this could be expected from a first timer, all specifications were met without having to go back and change any major components though so am happy with end results.