0-5 V LM317

Thread Starter

mahmut_kelesoglu

Joined Aug 12, 2022
60
Hi again,

I have designed something that supply 0 to 5 volt by using LM317 and LM337. Details are given in attached files.
My question is:
When I built this circuit on Porteus, it works very well. Proteus ss is attached. But when I create this in real life, it does not work. Why? Where and what is the problem/s?
I must supply everything with one 9 V battery or adaptor. How should I connect all grounds including Arduino's ground?
After getting 0 to 5 V, I am gonig to connect 3 diodes and a 8.2 ohm resistor at the output. I need 250 mA through this circuit (3 diodes and a 8.2 ohm resistor) when output of LM317 is 5 V. Where can I connect this circuint's (3 diodes and a 8.2 ohm resistor) gnd?

Thanks in advance.
Note: The potanitometer in Proteus represents output of DAC.
 

Attachments

Thread Starter

mahmut_kelesoglu

Joined Aug 12, 2022
60
Hi again,

I have designed something that supply 0 to 5 volt by using LM317 and LM337. Details are given in attached files.
My question is:
When I built this circuit on Porteus, it works very well. Proteus ss is attached. But when I create this in real life, it does not work. Why? Where and what is the problem/s?
I must supply everything with one 9 V battery or adaptor. How should I connect all grounds including Arduino's ground?
After getting 0 to 5 V, I am gonig to connect 3 diodes and a 8.2 ohm resistor at the output. I need 250 mA through this circuit (3 diodes and a 8.2 ohm resistor) when output of LM317 is 5 V. Where can I connect this circuint's (3 diodes and a 8.2 ohm resistor) gnd?

Thanks in advance.
Note: The potanitometer in Proteus represents output of DAC.
Attached a helper schematic. But the quesiton is how to get +V, -V, and a ground with only one battery.
When I connect 3 diodes and a 8.2 ohm resistor at the output, it need voltage drop of 5V across it to consuming at least 250mA.
 

Attachments

dl324

Joined Mar 30, 2015
15,455
actually I do not want to use this complexity because I am just a student.
Do you really need the output to be adjustable to 0V?

There are inverting voltage doublers that only require capacitors. Here's an obsolete part:
1669739341984.png
Since the adjust current from LM317 is only 5uA, you can use a charge pump design.
 

Thread Starter

mahmut_kelesoglu

Joined Aug 12, 2022
60
If you tell us exactly what you are trying to do instead of your solution for what you are trying to do, we could likely be of more help.
I want to built digital controlled laser diode driver up to 250 mA. I connect my laser diode at the output of the driver that supply 0-5 V. This 0-5 V have to controlled DAC. I have to use these components.
 

Papabravo

Joined Feb 24, 2006
19,580
I do not believe that it is possible to generate very low voltages with an LM317 from a positive voltage source. The device operates in such a way that the output is 1.25 volts above the ADJ pin.
 
I want to built digital controlled laser diode driver up to 250 mA. I connect my laser diode at the output of the driver that supply 0-5 V. This 0-5 V have to controlled DAC. I have to use these components.
Connect the laser diode to the 9V positive rail, via the collector/emitter of an NPN power transistor and a 10 ohm resistor to ground. The Arduino also connected to 9V makes its own 5V giving you the 0 to 5V you need for the DAC. From your first post it looks like you are expecting around 3V across the laser diode? At 250mA the volts across the resistor will be 2.5V. A/D this with the arduino and close the loop to drive the DAC into the base of the transistor (via a resistor) to control the current. You could use analogWrite instead of the DAC (which would use less power) but if you have to use it... Maybe there is a way to use the LM317 instead of the transistor but I can't see how or why you need the LM337.
 

BobTPH

Joined Jun 5, 2013
6,078
How did you get from needing to drive a laser diode at 250mA to needing a 0-5V supply?

If this is an assignment, please post the actual assignment so we can distinguish between the requirements and your own assumptions.
 
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