Did I screw my driver??

[amkdeath]

Hi,

I just built daedal's driver circuit, hooked it up to an LED, (i dont have my LD yet) and tha LED turned on.

One problem though...

The potentiometer is doing absolutely nothing. I can turn it violently, or even disconnect it conpletely, and it wont affect the circuit a bit, the LED stays on.
I hooked it up to my voltometer and it showed 5.6 or so volts coming out. I have 4 AAA batteries on that thing, and only 2 of them are new.

I used the 25ohm pot that says is recomended on his page.

Plz help. Thanks.

amk

 

[Gazoo]

Well for one thing, you need a minimum of 6 volts for the regulator to operate properly. Even 4 fresh alkalines will begin sagging as soon as you start to use them. 6 would be much better.

Did you follow Daedal's pin numbering? It is different from the way the regulator should be hooked up. Check with the following link to make sure you have it hooked up properly.

http://users.pandora.be/davshomepage/current-source.htm

Also an LED really isn't a good load to test the circuit with. An 8 ohm resistor or 4 silicon diodes hooked in series would be much better.

 

[amkdeath]

I read the back of my LM chips container and it said: the middle one is ADJ
I built the thing liek that and nothing from the pot.

Then I saw the guide, pic and etc on this website and stuff, and I desoldered everyhting, and re-soildered the LM so that left is ADJ. Still no difference.
Im so confused

It has something about R = U / I
on the link you sent me.
Im using a 10 ohm resistor, and plan on hooking up one of senkat's sony diodes, what resistor do I really need?

thanks

 

[Gazoo]

Where did you get the LM317?

R = U / I .............The U refers to the sense voltage of the regulator which is 1.25 volts. You want to have ~250ma's running to the GB diode...so you would need a 5 ohm resistor.

Measure the voltage between the Adjust and Output...you should always see 1.25 volts there as long as your regulator isn't bad. And use a bigger load on the output as I previously suggested..

 

[amkdeath]

ok, ill get a 5 ohm resistor, some batteries for my now dead voltometer, and a heavier load and test it.

BTW,

Earlier u said use 6 batteries. thats 9 volts! will the regulator take it back down to what it needs to be?
Thanks for all your help.

amk

 

[Gazoo]

Yes, the regulator will provide the same current to the diode. If you use a 5 ohm resistor, which will give you 250ma's going to the diode, the current will remain at 250ma's no matter what the input voltage is, provided it is more than 6 volts. Anything less than 6 volts and the regulator will begin to drop out. You could get by on 5 alkaline batteries. But if you ever want to use NIMH batteries, use 6.

 

[jayrob]

Yes, the regulator will provide the same current to the diode. If you use a 5 ohm resistor, which will give you 250ma's going to the diode, the current will remain at 250ma's no matter what the input voltage is, provided it is more than 6 volts. Anything less than 6 volts and the regulator will begin to drop out. You could get by on 5 alkaline batteries. But if you ever want to use NIMH batteries, use 6.

Gazoo, I am building Daedal's circuit as well....Since the GB diodes needs around 2.5 - 3.0 volts, would it be alright to use two 3.7 rechargeables instead of the 3.0 batts? I know the current won't change, but won't the voltage to the LD be too much?
Thanks,
Jay

 

[Gazoo]

Two Li-ion batteries are ideal for this circuit. The voltage can not change unless the current changes. So say you are running at 2.8 volts with 250ma's of current, that is what you will have regardless of the input voltage.

 

[amkdeath]

ok so, can I just hook up a 9 volt? thats alot easier and cheaper than 6 AAA's... will the current be affected? and BTW, if I want to see if I killed my LM or not, I just check the voltage on the ADJ and output right? thanks gazoo

 

[Gazoo]

A 9 volt battery will sag so fast it is not worth it. In the long run, 6 AAA's will be much cheaper. The voltage between the output and adj. should be 1.25 volts. If it is chances are your LM is ok.

 

[amkdeath]

ok man thanks, will it still be the same (the adj and out volts) if I have a 10 ohm resistor on it at the moment, I havent had time to the the 5 ohm one yet

 

[amkdeath]

OMG

OK BIG PROBLEM:

when hooking up 4 aaa's (mildly not fresh) to the circuit, now this is from the FRONT of the chip, so when looking at the chip from the front:
VOLTOMETER
ADJ and right pin:
1.42 volts

ADJ and left pin:
.05 volts

akward....
according to the back of my LM chip's case, that means ADJ and VIN are showing the 1.42, and the ADJ and VOUT pin are showing .05
None show 1.25, although I dont have 9 volts hooked up yet.
Also, the main point of this thread was why my pot has nothing to to with my circuit what so ever, I can totally disconnect the whole pot and my LED will stay on and wont even change a bit...

plz help. thanks

 

[Gazoo]

Well I am totally confused. For one thing you said the pin labels on the box it came in are different than the 317 as we know it. The only 317 case that would match up with what you have described is the one that comes in the TO-39 case. Something is weird, and this is one reason I asked you where you got it. All LM317T's that come in a TO-220 package have the same pin labels. I have never heard of, or seen anything different.

I would suggest you look at the spec sheet for the regulator which can be downloaded from here:

http://www.angelfire.com/electronic/hayles/downloads/lm317.pdf

 

[amkdeath]

I got mine from radioshack.

BTW, again, Why isnt my pot doing anything???

can I hook up the diode now without screwing it up?

 

[Greyfox]

Okay, I've set up a few circuits of the same, and a single LED -will not be in regulation- with the circuit using the 25ohm pot. Things won't change because the LM317 will never get what it wants until the LED is destroyed. LEDs typically run 20mA, and if you have the 25ohm RadioShack pot in there, the lowest current the regulator can be set to produce is 50mA. I've noticed that in this case, the LEDs I've used draw 20-30mA and won't accept more. This means that the regulator never functions, and because the regulator isn't operating, no adjustment on the pot will show.
Here's a solution to do a field test with a low-end LD equivalent load:

Connect 3 LEDs in parallel as your load, or use a 20-50 ohm 5W wirewound resistor as your load. This way, your load will run under regulation, and you won't be trying to push a component beyond its limits just to operate.

Here's a list of components in my LM317 simple supply I use for benching burning lasers right now:

LM317 chip with 2.2ohm resistor and 25ohm pot between Vout and Vadj lines.
9V battery + to Vin on the LM317. 9V battery - on GND line.
10uF capacitor between Vadj and GND lines.
Load between Vadj and GND lines.

I doubt you've wired it incorrectly, but the only way to be sure is to give yours a more power-hungry load than a single LED. Until the regulator chip sees a load big enough for it to kick in, you won't see anything happening on your output.

 

[Gazoo]

I got mine from radioshack.

Interesting...and that is how they have it labeled? Well like I always say, I learn something new every day.

I bet it is labeled in a confusing way, I see one customer reviewed it and stated.."Confusing pin-out diagram".

Can you take a picture of the diagram and post it please?