Need help understanding the LM317

Hi guys. I need help understanding the LM317.  I need to know which is Vin~Vout~Adj.


I've been trying to make Daedal's circuit the way it is shown.  I've made it THREE TIMES!!, and it still won't reduce any voltage whatsoever!!  I'm completely confused.  

When I turn the 100ohm pot to max resistance, it only drops the voltage 1 volt.  When I turn it back it goes up 1 volt.

Something is wrong with my LM317 I'm guessing.  Or it might be different than the one used by Daedal.

Could you take a look at mine and tell me which pin is which?

(from left to right)

Left to right: 1. Adjust. 2.Output. 3. Input

you need a load on your circuit before it even starts to regulate anything. you need a good load too. a dead diode, or A LOT of LED's in parallel will do the trick.

thanks all

Howdy,

I'm new here but I think you're talking about Daedal's *current* regulating circuit. It's not going to change the voltage much, just the usual loss from the 317 which is about one volt, which you seem to be experiencing. I had this same problem. Read over the thread about the circuit; somewhere in the 40-some pages it's mentioned...

My solution was to feed the regulated current coming out of Daedal's circuit into a another 317 circuit for voltage regulation. I'm going to start a thread here soon asking other members for input on my schematic. The circuit's working for me right now - I'm able to completely control the current & voltage - but I'm still going to see if any other members have any suggestions as I'm not that experienced with electronics.

Dave

scription said:

Howdy,

I'm new here but I think you're talking about Daedal's *current* regulating circuit. It's not going to change the voltage much, just the usual loss from the 317 which is about one volt, which you seem to be experiencing. I had this same problem. Read over the thread about the circuit; somewhere in the 40-some pages it's mentioned...

My solution was to feed the regulated current coming out of Daedal's circuit into a another 317 circuit for voltage regulation. I'm going to start a thread here soon asking other members for input on my schematic. The circuit's working for me right now - I'm able to completely control the current & voltage - but I'm still going to see if any other members have any suggestions as I'm not that experienced with electronics.

Dave

Click to expand...

dude you are WRONG!!! it doesnt "regulate" voltage, but it does keep it at 3v, or whatever the diode needs, and regulates current. all you need is a GOOD load. Try a 1 ohm resistor, and measure the voltage across that (while its connected to output of circuit). that is your mA.

amkdeath said:

[quote author=scription link=1197437168/0#4 date=1197461512]Howdy,

I'm new here but I think you're talking about Daedal's *current* regulating circuit. It's not going to change the voltage much, just the usual loss from the 317 which is about one volt, which you seem to be experiencing. I had this same problem. Read over the thread about the circuit; somewhere in the 40-some pages it's mentioned...

My solution was to feed the regulated current coming out of Daedal's circuit into a another 317 circuit for voltage regulation. I'm going to start a thread here soon asking other members for input on my schematic. The circuit's working for me right now - I'm able to completely control the current & voltage - but I'm still going to see if any other members have any suggestions as I'm not that experienced with electronics.

Dave

Click to expand...

dude you are WRONG!!! it doesnt "regulate" voltage, but it does keep it at 3v, or whatever the diode needs, and regulates current. all you need is a GOOD load. Try a 1 ohm resistor, and measure the voltage across that (while its connected to output of circuit). that is your mA.[/quote]

amk, there's no need to be an ass about it.

The LM317 DOES regulate voltage. Set up as a current regulator, it raises the voltage to the load until it reached the preset current. This is why only one LM317 is required.

a_pyro_is said:

[quote author=amkdeath link=1197437168/0#5 date=1197524992][quote author=scription link=1197437168/0#4 date=1197461512]Howdy,

I'm new here but I think you're talking about Daedal's *current* regulating circuit. It's not going to change the voltage much, just the usual loss from the 317 which is about one volt, which you seem to be experiencing. I had this same problem. Read over the thread about the circuit; somewhere in the 40-some pages it's mentioned...

My solution was to feed the regulated current coming out of Daedal's circuit into a another 317 circuit for voltage regulation. I'm going to start a thread here soon asking other members for input on my schematic. The circuit's working for me right now - I'm able to completely control the current & voltage - but I'm still going to see if any other members have any suggestions as I'm not that experienced with electronics.

Dave

Click to expand...

dude you are WRONG!!! it doesnt "regulate" voltage, but it does keep it at 3v, or whatever the diode needs, and regulates current. all you need is a GOOD load. Try a 1 ohm resistor, and measure the voltage across that (while its connected to output of circuit). that is your mA.[/quote]

amk, there's no need to be an ass about it.

The LM317 DOES regulate voltage. Set up as a current regulator, it raises the voltage to the load until it reached the preset current. This is why only one LM317 is required.[/quote]

I am sorry, I think there has been a misunderstanding... I am not being an ass, I just use caps and excamations to empahsize things... I was not yelling or anyhting...
what I meant by my post is exactly as you stated, that it will raise voltage to the point that is needed...

Also, there is a schematic somewhere on here with the 2 LM317 setup, I just dont remember where...

regards,

amk