How to obtain a controlled 5 volts supply from a 6v 4.5ah Rechargeable Battery

[rajaram04]

If you want the maximum output V, then you need to toss out the zener diode. Just use the potentiometer to adjust the voltage.

It is not the same as a regulated supply. However if your power source is regulated to 12V then that will have to be good enough.

The maximum voltage you'll get is about 11.3 V. (The 0.6V drop is drop through the NPN bias).

This is similar to the way I constructed my own power supply. It is unregulated. If I draw more than a couple amperes, the voltage sags.

What if we were to put the load in the collector leg? We could get 12V in that case. However the large range of adjustment would be lost. It would want to act more like a current source.

hmm ya i too observed some hours ago what all you said . . .

So now what i observed as per all your explanations & my experiments that , for 12v either we hv to select collector leg or hv to choose a 15v or 17v supply as input . .

so whats your view ?? please comment

 

[BradtheRad]

Yes, your power source needs to have a volt or two of added cushion.

Suppose your transformer is 12V. After rectification and smoothing, you get peaks at 16 V. This can be sufficient to feed a 12V regulator, if you avoid drawing more than the rated current.

 

[rajaram04]

Yes, your power source needs to have a volt or two of added cushion.

Suppose your transformer is 12V. After rectification and smoothing, you get peaks at 16 V. This can be sufficient to feed a 12V regulator, if you avoid drawing more than the rated current.

here "two of added cushion." means ?