0-5V voltage regulator

[Sauerkret]

Hello,

I need a schematic of a 0 to +5V voltage regulator, where the voltage output is controled with a potentiometer.
I can only find 1.25 to 3 volts or higher voltage regulators. I hope someone can help.



Kind regards, Eric

[Minion]

As Far as adjustable regulators go the lowest you will get is 1.25v as with the LM317 , what you can do is put a Pot at the output as a Voltage divider and get lower than 1.25v ......

[earthtonesaudio]

How about a generic 5V regulator into a potentiometer, with an op-amp buffer?

[JKowalski]

If you are running it off of a transformer you can build a diode/filter cap arrangement to create +5VDC, GND, and -1.25VDC and then you can reference the LM317 off of the negative voltage instead of ground - giving you adjustable voltage down to zero.

The buffered pot is another idea. Without the buffer it would not be a good idea.

[PRR]

Why do you need to go to zero?

How much Current do you need?

Do you need 5.0V MAXimum, or can it be a bit more and you will adjust it?

[Sauerkret]

It will be used to controle an effect pedal. Much like a wah pedal.

[Johan]

j

[puretube]

j

Leave out the transistor...
1k pot
0.1µF from wiper to ground for "crackle not OK"
(wiper=outputvoltage)

[PRR]

What Johan and puretube said. Control voltages are usually "no current", or 100K impedance and <50uA current. They are designed to be "easy".

If it really has to be 0.0V - 5.0V, you get a good 5.0V source, add a pot much less than 100K across it. 10K pot is often fine. The wiper will tap-off 0.0V to 5.0V. The mid-point won't be exactly 2.500V, but that rarely matters (real pots have worse errors; you will turn the knob to get what you want). If it gets scratchy, a cap across the output slows-down and muffles the scratch.

If the load is heavier or your 5V source is weak, Johan's buffer is handy. In simple form, nothing happens for the first 1/8th rotation, and the top is about 4.5V; also if the output can be shorted the transistor may die. Still a useful idea with many variants.

[Sauerkret]

THX

[Sauerkret]

I think this will be a good 5V source.