Design stage 2

During the building we discovered we needed 2 input sources, one to deliver a positive voltage and the other to deliver a negative voltage. This was one set back in designing to use two voltage sources to power a single component, as no customer will accept to buy such a component. Our project only deals with the regulating of  the voltage. The regulator needs two input. If our project was to be considered in a large scale we will consider using a transformer. The transformer that will be suitable to use is a transformer with two secondary windings as shown below,

Figure 8: Transformer with two secondary windings

From  figure 8 above, we have 3 output which are; the unregulated VDC, the positive and negative for the op-amp. We can see that instead of using two input voltages, we can just use this transformer to replace them. 

  Another issue discovered was the heating of the pass transistor. The heat dissipated was reduced by adding a large resistor at the load. However, if a smaller load is to be used it is necessary to mount them on a suitable heat sink.  

Designing Stage

In the LAB we built our circuit design as shown in our previous update on a SK10 board, the circuit worked perfectly. However we discovered it was not going below 4V when we vary the transistor R12, so we had to go back to the circuit to know where the problem came from. The circuit was then adjusted to obtain a voltage  below 4V and even up to 0.1V. Below is the edited circuit diagram and  the output waveform.

Figure 6: The new Design

  

Figure 7: Output from the new design.

The output of the new design when compared to that of the older design is better. The two extra voltages provide bipolar voltages to drive the operational amplifier. The negative voltage is used to generate a reference voltage below ground so that the output can be adjusted down to zero.