I want to create a Regulated 5V Supply for upcoming projects. I decided to try out the "LM317A" here are my schematics. **broken link removed**
The one on top is the default way i seen in the data sheet
The one on bottom i made after reading PAGE 1 PARAGRAPH 3
"The adjustment terminal can be bypassed to achieve very high
ripple rejection ratios which are difficult to achieve with standard
3-terminal regulators."
My Question is will either or both work? (don't have parts yet to physically test it) Just got paid today going shopping tomorrow
Reason for bottom circuit is the wrong interpretation of the term "bypass" in datasheet, which here means connecting an additional capacitor between the ADJ pin and 0V.
Edit: Of course one still have to use the two usual resistors as they are needed to setup the correct output voltage.
Why do you need 317 for constant 5v supply instead 7805?..
Anyway 317 is used for variable supplies..
Just put a variable resistor around 2k/4.7k instead 360.. by varying you can obtain 5v..
The LM317 has a higher output current than the LM7805 and can drop 40V which the LM7805 can't do.
The LM317 doesn't have to be used in variable supplies, it can be used in a fixed supply if you use the correct resistor values.
For 5V use any of the folowing combinations of R1 and R2.
R1 = 100hm:
R2 = 300hm:
R1 = 110hm:
R2 = 330hm:
R1 = 82hm:
R2 = 240hm:
R1 = 68hm:
R2 = 200hm:
R1 = 56hm:
R2 = 180hm:
The above are all standard values that will give you 5V with a reasonable accuracy. Be warned about making R1 too low as the quiescent current will become excessive.
Yes i agree.. but in the above circuits it shows 9v input, thats why i told 7805..
Anyways thank for your good infos.. probably all our infos would help atom..
It won't last for long as it will stop regulating when the voltage drops below between 7V and 7.5V (depending on the current draw and how good your LM317 is) which isn't very long in to the discharge.
If you're using a 9V battery, then you need a low dropout regulator like the LM2936-5.0, LM3940, LM2937 etc. to maximise the battery life.
Be warned that the output from your 9V adaptor could be much higher than 9V when there's no load connected so make sure the input capacitor is rated to 16V minimum, 25V recommended.
Im waiting to get my hand on some new tools because mines are a pain. When i get them and am sure i can accurately measure my projects right ill keep posting lol but i just went shopping and forgot to buy a new multimeter. Gonna go out again in like 30 min so.. ill get it then