need help with lm317 driver

hello,
I'm new here and need some help with my first driver. I build the lm317 driver and test load from rog's website. everything was going fine untill i got to the test section. i hooked up my first driver to the test load and connected it with 2 cr123a battery's wich gave me a total of 6,43V.
I first tested the voltage on the test load, it was 5,83V wich is not good i think, it also wasn't changing at all when i turned the pot up/down. then i tested the current in mv on the 1 ohm resistor, but i got no results:undecided:.
And when i connect my multimeter to the regulator i should see 1,25V but i got no result.
I got an lm317 with 8 pins, 4 of them are Vout. Does it matter on wich Vout i connect it? maybe thats the problem. This is the one I got -> Conrad Electronic - Europa's grootste webwinkel in elektronica en techniek

I also broke the positive pin of my 20x LD by bending it accidently, is there a way to fix it? I tried to solder a wire on it, but just it fells off when i touch it

hope to get a reply fast

An LM317 with 8 pins ???

On my datasheets i have it with a lot of cases, but all 3 pins, except a square unit with 20 pins, but none with 8 ..... any pic ?

Your Link Does not work....

We will need the data sheet of the regulator you are using...
or at least the exact part number of your part..

BTW... Welcome to the Forum...


Jerry

here is the data sheet from the lm317, i have the square one with 8 pins

Have you commoned up all of the outputs as per data sheet? This is to carry the current and it uses the copper on the PCB as a heatsink.

Regards rog8811

i have only connected 1 of the outputs, i'll try it with connecting all four of them.

it doesn't matter, I still got the same results: 5,85V and no mv over the resistor:huh:

Now i understand, is the "L" serie, low current (max 100mA) ..... i was thinking to the standard serie.

and connected it with 2 cr123a battery's wich gave me a total of 6,43V.

Click to expand...

Here is the main part of your problem, imho ..... this model have a dropout that go from 1,4 to 2,5V, depending from the current ..... assuming that you are trying it for its maximum current (that in any case cannot be more than 100mA), your output voltage cannot be more than 4 V ..... and, you have not said what load you are using, but, in the case that it's the one with 6 diodes, the total dropout of the load is more than the voltage that the regulator can give you at the output, so it's same as you have not the load connected to the regulator, and ofcourse, in this conditions, no current at all through the resistor.

Try with only 2 diodes and the 1 ohm resistor, and set the current to 50 mA (24 ohm of resistance for the current set resistor) for check that the regulator is working ..... if you get a reading (must be around 50 mV at the sides of the resistor) in this condition, the regulator is still working, if you can't get anything, then there is a good probability that the regulator is dead.

Also, check the polarity of the diodes in the test load ..... one broken or reversed diode, and all is same as an open circuit, no regulation

so i can't get more then 100mA from this driver with this regulator? I wanted to get 380mA from this driver, so i think it's better to just buy another lm317?
I was using 4 1n4001 diodes and an 1W 1Ohm resistor as test load. i tried it with 2 diodes and 1 ohm resistor and set the pot to 24ohm but got no reading, maybe i heated the regulator up to much with soldering.

Well, no, from the L series, you can't pull more than 100mA ..... you need a LM317 or, better if you can find it, an LM1117-adj (low dropout) and not the LM317L or LM317LZ

Anyway, are you sure you connected the test load correctly ? ..... diodes in series all in the same sense (anode-cathode), anode to the +V, and so on ?

Cause the fact that you can measure full, unregulated voltage at the end, and no current, is like if you have the diodes reversed, or one reversed (or also one opened) ..... anyway, is the same that you have the load not connected, as far as i can understand from your measures.

i tried an another driver on the test load and got a reading from 200mV, so i think the test load is working.

the problem was a bad connection... this is the first time i'm soldering
but as what you have said, i can't get more then 123mA out of it, need to buy an normal LM317.
but is there a way to fix the broken pin of my diode?

^ Then was something like i imagined, open circuit

About the diode, i guess not ..... if it was a BD, where the case is indifferent, you had the possibility to just solder the broken pin with the case and then use it, but being a red, with case negative, i don't see too much to do, if the pin is broken just too near the case, i'm sorry.

ok,
i ordered some LM317TG, are those the right ones to get 380mA?

I think yes, as far as i remember, the "T" suffix in TG is for the TO220 packagem that can hold til max 1,5A heatsinked (not sure if the G is for lead free products, but is indifferent), so 380mA cannot be a problem ..... only, remember that the maximum power is also function of the difference from Vin and Vout, and that this regulator have a dropout of, indicatively, 2 V, so if you want, as example, 5V output, you need at least 7V input (if you use it with a red LD, that is usually around 3V of FV, the two Lithium cells must be enough, cause the minimum required is 5 / 5,3 V .

Anyway, building a linear regulator, is always better keep in mind that the power that the case can dissipate, is a different thing than the current for which the regulator is rated ..... i mean, the maximum current that the LM317 can give, is 1,5A, but the maximum power that the TO220 case can dissipate (without heatsink) is usually 1 W or few more, and the power that the regulator must dissipate is function of the difference from Vin and Vout, multiplied from the given current (said in very simple way, can jump over the formulas )

So, as example, for give you 380 mA with a red diode that have a FV of 3V, with an input voltage of 6,4V (i'm using your data just as example), the power that it must dissipate is 3,4V (6,4 - 3) multiplied 0,38 (380mA), that give you 1,29W ..... a little bit too high for a continuous use, but enough if you use it in a handheld unit that is not turned on for long periods (otherwise, you can use it as continuous, but need to put a heatsink on the regulator) ..... anyway, the LM317 is internally limited as power dissipation and junction temperature ..... if the power is too high, or the junction temperature increase too much, it go in protection and stop to work til it's cooled a bit.

recieved the LM317TG's today and made a new driver...
the voltage is good now: 3V , but i still can't get more then 140mA
:wtf: am I doing wrong?