LM317 Problem with current output

Thread Starter

Alexandru Ioan Danila

Joined Jun 27, 2018
6
Hi, i am working at a project with a Hall efect. (HAH3DR 100)

upload_2018-6-27_10-54-14.png

Because of noise produced by power source, i used a LM317 voltage regulator to reduce noise.
Power source is ajustable, is set to 12V or 9V and 0.5A.

And LM317 setup
upload_2018-6-27_10-59-31.png

LM317 have 5V and 17mA output. (In MultiSim i get 5V and ~450mA)

When i connect the sensor i have voltage drop to 2.9V and sensor is does not work as is should (sensor need 5V to work).
I do not know how to increase output current to work properly.
 
Last edited:

ericgibbs

Joined Jan 29, 2010
8,588
hi Alex,
Have you confirmed that the 9V PSU is supplying 9V when the LM317 and Hall IC is connected.?
ie: the PSU does not have a current limit set.?
E
Post a photo of the LM317 circuit so that we can check your pin connections.
 

Thread Starter

Alexandru Ioan Danila

Joined Jun 27, 2018
6
hi Alex,
Have you confirmed that the 9V PSU is supplying 9V when the LM317 and Hall IC is connected.?
ie: the PSU does not have a current limit set.?
E
Post a photo of the LM317 circuit so that we can check your pin connections.

What i measured:
(LM317 output is same if input is 9V or 12V, but i need 12V)
(PS is set to 12V and 0.5A, Nothing is changed if i modify current, tested at 0.15A, 0.5A, 1A and 2A)
Power Supply --> 12V --> LM317 --> 5V --> Nothing
Power Supply --> 12V --> LM317 --> 2.9V --> Sensor

Sensor need 47-50mA to work but i have only 17mA (Probably from R1 300 ohm)
 
Last edited:

ericgibbs

Joined Jan 29, 2010
8,588
hi Alex,
Some possible problems are:
Instability of the Lm317, missing or incorrect decoupling capacitors.
Defective LM317
Current load in excess of 1.5A, very low load resistance.
or Incorrectly wired.
A photo would help.
E
 

ericgibbs

Joined Jan 29, 2010
8,588
The diode was a quick sketch.
Confirm that the diode is across the two outside pins of the LM317, from the photo's it appears to be so.
If it is across the two outer pins it is incorrect.

EDIT:
Is the plastic body of the LM317 facing towards the marked diode, it appears to be.
@bertus
 
Last edited:

Thread Starter

Alexandru Ioan Danila

Joined Jun 27, 2018
6
The diode was a quick sketch.
Confirm that the diode is across the two outside pins of the LM317, from the photo's it appears to be so.
If it is across the two outer pins it is incorrect.

EDIT:
Is the plastic body of the LM317 facing towards the marked diode, it appears to be.
@bertus
I made it work!!!
 
hi Alex,
Initial checking looks as though you have the LM317 pin out incorrectly wired.??
I will continue checking.
E
View attachment 155157
i had similar issues,i wired mine like regular 7805,etc regulators, it regulated surprisingly, but had very low output current, but while searching for its max output current, i found this article. . .thanks for helping ,you've helped me too.... .
 
Top