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12 or 6 VDC to 5 VDC using diodes
- Thread starter sajib
- Start date
We'll need a bit more information. As kubeek said, by themselves they won't regulate, just drop around .6V each, more or less.
There are classes of diodes that will regulate, but not quite the way I think you're thinking of. They are Zener diodes, and can be found in the AAC eBook here. Matter of fact, reviewing the chapter, a lot of it will answer your questions.
There are classes of diodes that will regulate, but not quite the way I think you're thinking of. They are Zener diodes, and can be found in the AAC eBook here. Matter of fact, reviewing the chapter, a lot of it will answer your questions.
Ahh, I think you're a bit off, Bill.
I graphed the response of a 1N4002 over a range of currents several months back.
I only went from 10uA to 100mA, but a simple extrapolation of the results I received tells me that with 750mA current, our OP would likely see more like a 0.9v drop across a 1N4001 through 1N4007 diode. The datasheet specifies a 1.1V drop with a 1A current, which also agrees with the extrapolation; particularly when you consider that when you're approaching the high end of the diode's rating, the Vf increases more rapidly.
So with a supply that was 6V even, with a 750mA load, one 1N4002 diode would have a Vf of around 0.9V for 5.1V out, and two 1N4002 diodes in series would give 4.2V out.
If the load varies, the Vf of the diode will vary.
I graphed the response of a 1N4002 over a range of currents several months back.
I only went from 10uA to 100mA, but a simple extrapolation of the results I received tells me that with 750mA current, our OP would likely see more like a 0.9v drop across a 1N4001 through 1N4007 diode. The datasheet specifies a 1.1V drop with a 1A current, which also agrees with the extrapolation; particularly when you consider that when you're approaching the high end of the diode's rating, the Vf increases more rapidly.
So with a supply that was 6V even, with a 750mA load, one 1N4002 diode would have a Vf of around 0.9V for 5.1V out, and two 1N4002 diodes in series would give 4.2V out.
If the load varies, the Vf of the diode will vary.
Wouldn't you just be as well off to use a 3 terminal voltage regulator such as a 7805 ?
Feed it 12 volts, get out 5 :
http://www.national.com/mpf/LM/LM78M05.html
Almost the same parts count, although there would be a little more expense involved. Are you going to be doing this in a production run, or just making up an individual device ?
Good luck, Jim
Feed it 12 volts, get out 5 :
http://www.national.com/mpf/LM/LM78M05.html
Almost the same parts count, although there would be a little more expense involved. Are you going to be doing this in a production run, or just making up an individual device ?
Good luck, Jim
That's true if you're trying to go from 12v to 5v. Can't go from 6v to 5v with a 7805 though; as dropout is 2v.
