12.5mA in a 100 ohms load needs 12.5V that you do not have.

You slipped a decimal point. It would be 1.25V for 12.5mA.
And the 100 ohms is not the load (in his latest post), it's the current sense resistor.

 

Yes, you are right! I found the problem today after receiving a reply from crutchow yesterday. I mistakenly hooked up the LED light to the output of the LM317 instead of to the ADJ. pin of the LM317. So that now, one side of the LED lights is connected to ground and the other side of the LED lights connect to the ADJ. pin. instead of the output pin of the IC. Now it works great. Thank you for your informative feedback. I appreciate it.

 

Thank you for your reply. I quadrupled checked the connections very carefully. I even tried 3 other new LM317s' and still the same unwanted results. I have a batch of 20 new LM317s and will try the other new ones in the morning and see the results.

why don't you test them? it is not inconceivable that you got fake ones... no point in building and frying things if you cannot get it to work. when Vadj is connected to 0V, you should get 1.2V output.

chances are you are doing something wrong but the message does not get across. so why don't you show a picture of your assembled circuit? perhaps shorting output to 0VDC through tab to a heatsink?

 

why don't you test them? it is not inconceivable that you got fake ones... no point in building and frying things if you cannot get it to work. when Vadj is connected to 0V, you should get 1.2V output.

chances are you are doing something wrong but the message does not get across. so why don't you show a picture of your assembled circuit? perhaps shorting output to 0VDC through tab to a heatsink?

Great suggestion.




This is where I made the error and why it did not work for me. The schematic above showed the Anode of the LED diode connected to the junction of the 10 ohm resistor and the ADJ. pin. The error I made is when instead of connecting the Anode of the LED diode to the proper junction mentioned as shown on the schematic, I connected it to the Output pin of the LM317 directly. That is why it did not work. Thanks again for your feedback. I appreciate it.

 

no... that is only symbolic representation, not actual construction. it does not allow us to see what connection methods you used (breadboard, soldering, alligator clips etc.) and if you really connected things correctly.

example schematic:


and different examples of construction methods (actual implementations). some are more robust than others and allow one to see actual wire size, polarity of components etc. - something that every user could do wrong by misinterpreting schematic or datasheets.