Go Down

Topic: LM317T voltage regulator project (Read 182 times) previous topic - next topic

ProNewb

I need some assistance with building a power supply. For that I drawed a shematics and would like you to guide me in that. Would it work that way, or have I done some mistakes in it?


allanhurst

Looks more or less OK. The output of the LM317 is always 1.25  volts higher than it's control pin, so your output should be controllable over a 1.25 to 1.25 + (1+R2/R1)*5 volts range

regards

Allan


G7MRV

Yes that looks quite a good circuit. One thing I would point out is that you could of course use a 7805 rather than a 7809 and feed the Arduino with 5v direct, this bypassing the controllers own 5v regulator. Also, if the current needed by the Arduino is small, the 78L09 or 78L05 (100mA) might do and are much smaller packages.

arduinoaleman

A Low-Pass Filter ....

Using an Arduino and PWM and a low-pass filter (resistor and capacitor) is not a good idea.

The LM317 needs 2 resistors to control the output voltage. Your OP-Amp replaces one of the resistors and the low-pass filter will give you an output voltage with a lot of ripples. A filter is just a filter.

Use a digital potentiometer in front of the OP-Amp.

You did not explain at all, why you need an Arduino for a power supply. A simple potentiometer in series with a resistor can do everything you want in a manually controlled power supply.

Or do you want a digitally controlled power supply?
If your questions are not precise, nobody can help you.

allanhurst

There is a lowpass filter - and if the OP ran the PWM at a much higher frequency than normal - 20kHz or more - would be  very effective

Allan

DrDiettrich

You can use a npn power darlington transistor (TIP120...) instead of the LM317. Connect the output to the opamp - input, using a voltage divider (R1/R2). Don't forget a biiiig heat sink (and fan?), the transistor will burn up to 45W!

ProNewb

Yes that looks quite a good circuit. One thing I would point out is that you could of course use a 7805 rather than a 7809 and feed the Arduino with 5v direct, this bypassing the controllers own 5v regulator. Also, if the current needed by the Arduino is small, the 78L09 or 78L05 (100mA) might do and are much smaller packages.
Good idea, thank you!

A Low-Pass Filter ....

You did not explain at all, why you need an Arduino for a power supply. A simple potentiometer in series with a resistor can do everything you want in a manually controlled power supply.

Or do you want a digitally controlled power supply?
Why not? :) I'm just interested in Arduino and in power supplies - I think it will help me to go deepter in unterstanding electronical principles. Later on, I would also try to write a software in C++ (with surface), which could generate different signal types (sinus, rectangle, triangle) to the arduino and output them just by clicking a certain button at the power supply.


There is a lowpass filter - and if the OP ran the PWM at a much higher frequency than normal - 20kHz or more - would be  very effective

Allan
Yes, I think 490 Hz is way too little!
You can use a npn power darlington transistor (TIP120...) instead of the LM317. Connect the output to the opamp - input, using a voltage divider (R1/R2). Don't forget a biiiig heat sink (and fan?), the transistor will burn up to 45W!
If this first version will run well, then I will (maybe) combine the lm317 with a power transistor and change some other components.


Go Up