LM317 Adjustable Regulator: 0-30 Vdc Output Voltage

[Antonio G]

The LM317 3-TERMINAL ADJUSTABLE REGULATOR has a Output Voltage Range Adjustable From 1.25 V to 37. For the circuit in the attachment, What kind of adaptation or connection must be made for this device to provide an output voltage that starts at 0 volt? Thanks in advance

 

[berkeman]

The LM317 3-TERMINAL ADJUSTABLE REGULATOR has a Output Voltage Range Adjustable From 1.25 V to 37. For the circuit in the attachment, What kind of adaptation or connection must be made for this device to provide an output voltage that starts at 0 volt? Thanks in advance

You should be able to tell us the answer to your question. What can you tell from the datasheet?

Also, is this your schematic or from someone else? A positive regulator should generally not be drawn below the ground rail like it is in this figure. That's very confusing -- looks like a negative voltage rail regultor like a 337.

 

[Averagesupernova]

You need to pull the adj pin 1.2 volts below ground in order to do what you want. A side note, I don't believe I would recommend having that large cap on the adj. pin. I can't recall what the data sheet says but it looks suspicious to me.

 

[schip666!]

You will probably need a floating ground to get the regulator to go below it's speced minimum. I doubt that the circuit you show will help because the 317's ref is still at circuit ground and the control voltage you propose will go negative -- this will either have no effect or else release the smoke from the components.

Why do you want less than 1.2v? If you don't need a lot of current you could just use a resistor divider.

 

[Averagesupernova]

If the bottom of the 2k pot were tied to a -1.2 volt reference instead of ground the circuit would work just fine. Been there, done that. Still wondering about that 10uF cap though...

 

[vk6kro]

http://www.circuit-projects.com/cimg/LM317-Power-Supply.jpg

Found this circuit. The output is from zero to 3 volts but there doesn't seem to be any reason it couldn't go higher. Important bit is the negative supply giving a zero output.

 

[Antonio G]

Thank everyone for their recommendations. thank everyone for their recommendations. This was the result of the regulated power supply. Tested and worked perfectly

 

[ashwingokhale]

Is there any other way to get the ground level shifted to 0v other than using the 2 IC's
can a center tap transformer be used..?/
If yes How...?

 

[Antonio G]

You refer to IC1 and IC3?. If that's the case, the LM-317 IC1 does not give output 0 Vdc, the regulation is from 1.2 Vdc to 37 Vdc. Depending on input voltage, output never gives less than 1.2 Vdc.
The circuit formed by IC3 is responsible for the negative voltage supply that eliminates the 1.2 Vdc LM317 that are fixed in order to get the 0Vdc to the output of IC1. In the example supply, the transformer is working with central, that is, provides 12 - 0 - 12