Author Topic: Lt317 problems  (Read 6197 times)

0 Members and 1 Guest are viewing this topic.

Offline House91320Topic starter

  • Regular Contributor
  • *
  • Posts: 176
Lt317 problems
« on: May 29, 2011, 11:09:16 pm »
I have a power supply that i built recently before the lt317 is 8 after the lt317 its 4 any one got any ideas.
 

alm

  • Guest
Re: Lt317 problems
« Reply #1 on: May 29, 2011, 11:15:53 pm »
Your schematic appears to have disappeared in thin air, so it's somewhat hard to debug. Dropping voltage is exactly what a linear regulator is supposed to do, so depending on what you connected to the adjust pins, this could be within spec.
 

Offline House91320Topic starter

  • Regular Contributor
  • *
  • Posts: 176
Re: Lt317 problems
« Reply #2 on: May 29, 2011, 11:21:06 pm »
 

Online EEVblog

  • Administrator
  • *****
  • Posts: 37597
  • Country: au
    • EEVblog
Re: Lt317 problems
« Reply #3 on: May 29, 2011, 11:34:15 pm »
http://www.eleccircuit.com/lm317-lm338-lm350-current-regulator-calculator/ its this but the resistor is 1ohm

That's a constant current circuit, not a voltage regulator for a power supply.
I think you have the wrong circuit.
Try:
http://www.electronics-lab.com/articles/LM317/

Dave.
 

Offline House91320Topic starter

  • Regular Contributor
  • *
  • Posts: 176
Re: Lt317 problems
« Reply #4 on: May 29, 2011, 11:38:13 pm »
i know i am using another regulator for the variable out put voltage and that works fine. I am using the 317 as the current regulation
 

Offline Bored@Work

  • Super Contributor
  • ***
  • Posts: 3932
  • Country: 00
Re: Lt317 problems
« Reply #5 on: May 30, 2011, 05:13:09 am »
i know i am using another regulator for the variable out put voltage and that works fine. I am using the 317 as the current regulation

And we are now supposed to beg you to give us the complete schematic? From my point of view, you either show us the real and full schematics, and you write a useful problem description, or you can stick it where the sun doesn't shine.
I delete PMs unread. If you have something to say, say it in public.
For all else: Profile->[Modify Profile]Buddies/Ignore List->Edit Ignore List
 

Offline Simon

  • Global Moderator
  • *****
  • Posts: 17698
  • Country: gb
  • Did that just blow up? No? might work after all !!
    • Simon's Electronics
Re: Lt317 problems
« Reply #6 on: May 30, 2011, 07:45:34 am »
i know i am using another regulator for the variable out put voltage and that works fine. I am using the 317 as the current regulation

And we are now supposed to beg you to give us the complete schematic? From my point of view, you either show us the real and full schematics, and you write a useful problem description, or you can stick it where the sun doesn't shine.

hahaha couldn't have put it better myself  ;D

House: we need to see the full schematic to get an idea of what your up to. My guess is that you have a lower resistance load than the final current regulator can supply current to so there is a massive voltage drop
 

Online Zero999

  • Super Contributor
  • ***
  • Posts: 19217
  • Country: gb
  • 0999
Re: Lt317 problems
« Reply #7 on: May 30, 2011, 05:55:23 pm »
It's not a very good way of doing it. The current limiter circuit drops around 4V just before the current limiting kicks in and the voltage regulator will drop around 2.5V so the input voltage needs to be a whopping 6.5V higher than the output voltage.
 

Offline House91320Topic starter

  • Regular Contributor
  • *
  • Posts: 176
Re: Lt317 problems
« Reply #8 on: May 30, 2011, 07:54:39 pm »
solved it i had the taps on my power supply wrong
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf