Strange behaviour of LM317

[Blord]

I have build a LM317 driver like here, Laser driver - It can be done
For a red laser build I put a resistor of 5.6Ohm as in the picture. It should provide the LD a current of 220mA but I only measure 120mA with the testload. I switch to another LM317 and the same result. How can it be so low ? Are these the real LM317 ?

Btw I have a LM1117 lying around and in the same situation it provides 220mA as it should be.

 

[Cyparagon]

Are you supplying the necessary voltage?

 

[Bionic-Badger]

What's the input power source? Does it have sufficient voltage and current capabilities? Also measure between Output and ADJ to see if you have 1.25V.

 

[Blord]

Here are the spec, http://www.hengsen.cn/bcddata/az317.pdf

I use the bench psu to simulate different voltages. I have set it to 7.2V and 1A and and the output is not as it should be.
I am thinking these are not LM317.

 

[bennett326]

well in my brain a az317 is not a lm317 ?

 

[Blord]

I have ordered LM317 and I get these in the mail. Are they somehow usefull for a driver ?

 

[midias]

I have ordered LM317 and I get these in the mail. Are they somehow usefull for a driver ?

Data sheet is about the same did you try over 7.2V input?

 

[StereoBucket]

I have ordered LM317 and I get these in the mail. Are they somehow usefull for a driver ?

As far as i know they are useful DDL drivers,as long as you know how to use them.

As far as i understand dropout voltage divided by the amps equals Resistance

so for this LM317 1.25/A=R
i am not sure is it dropout voltage or what but this is for LM317 as i heard

EDIT:Tomorrow i have TIME so i'll build this circuit and test it to check for the amps.

BTW how do i check how many amps LM317 is letting trough?
Do i test it with the multimeter at the beginning or after the LM317.
What i mean is do i check the part near the battery or the voltage out of the LM317?

 

[Blord]

What's the input power source? Does it have sufficient voltage and current capabilities? Also measure between Output and ADJ to see if you have 1.25V.

The voltage between Output and ADJ is 0.7V.
If the input voltage is 5.6V ( from the bench PSU ) this voltage is 1.24V.
When the input voltage is increased ( to 7-15V ) this voltage drops to 0.7V. :thinking:

Data sheet is about the same did you try over 7.2V input?

I have set the bench psu to 7.2V and 1A

 

[foulmist]

It looks more like lm1117 than lm317 according to specs.. but It should work fine...

try it with 6V input and see what happens...
there is a current limit at voltage differences between Vin and Vout...
maybe at larger differences the current is limited.? ?? :thinking:

I am not sure about this but try and see what happens... :beer:

 

[Bionic-Badger]

Why don't you take a picture of your setup. If it's dropping only 0.7V, it's not working. 0.7V is more like a rectifier diode voltage drop.

 

[StereoBucket]

Ill redesign the circuit.
Remove the pot and 2 of those 10 ohm resistors and put 3 ohm resistor.