need help with lm317 driver

[ndrew2505]

change the resistor value to something lower and try again.

edit: try a 1ohm 1/4 or 1/2w resistor(or similar). that should give you more room for adjustment than you need.

 

[pumie3]

it is already 3,7ohm, can I also just remove the resistor?

 

[HIMNL9]

3,7 ohm must be 325mA ..... what is the input voltage, with the test load connected ?

 

[pumie3]

6,4V , how do you mean with the test load connected? there is going 3V trough the 4 diodes in the test load

 

[HIMNL9]

No, no, i mean, measuring the battery voltage at the input of the module, with the test load connected and the module powered up, not just the battery voltage itself ..... for see if it drop down too much, when the driver is connected.

 

[pumie3]

I'm only measuring 0.05V at the adj- and out-pin

 

[HIMNL9]

Uhm, ok, let me try to say it in a different way

Connect the load to the driver, then connect the battery to the driver ..... with all connected, how much volts you measure ON THE BATTERY ?

 

[pumie3]

now I got it, ... : 5,67V

 

[HIMNL9]

Uh, it's a bit too low ..... sure that your batteries are good, and that can give you all the needed current ?

As example, a good pair of lithium cells, must be 7 to 7,5 volt, if charged, also under load (until 8,4V, just after a full charge) ..... 5,67V looks as almost discharged batteries ..... or there are other 2 possibilities:

1) one of the 2 batteries is not fully charged, or is damaged

2) the batteries are too small (in current capacity) for give you all the energy needed (like, trying to use 200mA batteries)

can you check for this ? ..... or, better, try with a power supply that can put out 7 V, in place of the batteries, for check if the problem is in the battery pack or in the circuit ?


Edit: also one of these cheap "universal" power supplies with 7,5V and 500mA can be ok for do a test

 

[pumie3]

i am using now some 3V cr123a batteries you can't charge. But i have ordered a pair of rechargeble cr123a of 3,6V 580mAh each. I think i dont have an 7V power supply, but i have to look.

 

[HIMNL9]

This may be part of the problem ..... non rechargeable batteries can be too low for this, remember that you need at least 2,5V more than the output voltage, but is always better considerate also the dropout and loosing of other components, not just the regulator ..... say, at least 3,5V, so, better use 2 rechargeable ones (or, just for the test, 3 of the non rechargeable ones, just for see if the driver works) .

 

[pumie3]

couldn't find a 7V power supply so i hooked it up to an 12V 1000mA adaptor, and Poof... now it isn't working at all. What could be broken?

 

[HIMNL9]

Are you sure you not connected it wrong ? ..... i'm using LM317 for my lab style heatsink, and they works at 12V without problems (with heatsink, anyway)

Can you post some pics of the assembly, too ?

 

[pumie3]

here is a pic of it. Hope you can see it, it was taken with the camera of my laptop.

 

[HIMNL9]

Uh, i don't see too much there ..... anyway, i hope that regulator is seen from back, otherwise it's connected in reverse

Anyway, have you checked that there is no short circuits or bad connections ?

 

[rog8811]

Could you try again with a better photo, I cannot see that one clearly enough to check it out.
As HIMNL9 says 12v should not cause any problems, the extra voltage will just be turned into heat by the LM317, it does have an auto shutdown function that kicks in if it gets too hot.

Regards rog8811