blu ray driver not putting out enough mA

[busterhax]

I am using DDL's driver for my blu ray and i cant get more than 22mA into the diode. with the pot fully turned(least resistance) there is a total of 22mA going through the diode. With no diode in the circuit, it outputs about 239mA. Is something wrong here?

btw as you can see in the pic, i amusing two 10 ohm resistors to get 5 ohm resistance considering i couldnt find any 8 ohm resistors to make 4 ohm resistance

 

[a_pyro_is]

OK, a few questions...
What is your supply voltage?
If the supply is a battery, what type and what size?
What resistance is the Pot?
With the supply disconnected, what resistance do you measure across the resistors with the Pot at max?
With the Pot at the minimum?

 

[rog8811]

What is your input voltage? 9v would be about the minimum required....

Regards rog8811

*Edit Too slow and too brief it seems

 

[busterhax]

sorry about the briefness. i'm using 4 lithium AAA's, so 6v input.
the pot is a 100 ohm.
i measure 5ohms of resistance across the resistors with the pot at min and max

 

[a_pyro_is]

sorry about the briefness. i'm using 4 lithium AAA's, so 6v input.
the pot is a 100 ohm.
i measure 5ohms of resistance across the resistors with the pot at min and max

Could you please measure the resistance including the potentiometer? A potentiometer is a resistor, but you can change the resistance by turning it.

 

[a_pyro_is]

busterhax, you're not on the forum now, and I won't be on again for another 9 or 10 hours so I'll add a bit more.

As Rog8811 said, you'll have to supply at least 9V. Just four cells will not work unless they're Li-Ion at 3.6V each.

You're lucky that you've been supplying too little voltage, otherwise you'd have blown your diode already.

So, provided your potentiometer at it's minimum resistance is less than 2 Ohms, change those two 10 Ohm resistors to series from parallel. For a BluRay, you want the range to be from about 20 Ohms to about 120 Ohms, for a range of about 10 mA to about 62 mA.

Good luck, I'll post tomorrow.

 

[busterhax]

well i started off with just the 10 ohm resistor in there and when the diode was hooked up, with the pot at MAX there was a whopping 22mA going through the diode. without the diode i believe it was 125mA.

 

[a_pyro_is]

well i started off with just the 10 ohm resistor in there and when the diode was hooked up, with the pot at MAX there was a whopping 22mA going through the diode. without the diode i believe it was 125mA.

hehe I'm back for a minute.

That's because the regulator is dropping out because you're not giving it enough voltage. Had you done that while giving it enough voltage, you would have hit that diode with 125mA which would have been instant death.
Now, I'll be glad to help you, but you must slow down.
Please measure the resistance between the side of the two parallel resistors connected to the 317, and the side of the potentiometer connected to the regulator. Measure it with the Pot at the minimum resistance, and with the Pot at the max.

 

[Gazoo]

What were you using as a load to measure current with?

You can replace the pot and two resistors with a 33 ohm resistor which will supply 38ma's to the diode. As others have said, you need 9 volts. Otherwise the regulator will begin to drop out.

 

[busterhax]

i was going by

once i get home from work ill look into the stuff further

thanks guys

 

[chimo]

i was going by
////snip////
once i get home from work ill look into the stuff further

thanks guys

You have already been given the explaination to why it did not function as expected.

The difference is that the circuit you posted was for driving a Red LD and you are trying to drive a BLuRay(BR) LD. The BR LD runs at a much higher voltage than the Red LD so the battery voltage needs to be higher.

 

[a_pyro_is]

But, if you put 9V on it how it is now it will kill your diode instantly. Measure the total resistance across the resistor and potentiometer, we need to make sure it can't go lower than about 20 Ohms.
I'd also suggest adding a one Ohm resistor in series with the laser diode across which you can measure the current you're driving the diode with.
I'm really going now and won't be on until early tomorrow morning EST, just listen to Gazoo and Chimo. They'll make sure you get it working without blowing your diode.

 

[BlueFusion]

6V is not enough.... as it seems, the more people say that the more chance you have of believing us. You need to hook up a dummy load, then find out what setting the pot needs to be on to get appropriate current. Otherwise it's almost guaranteed you'll fry that diode.

 

[busterhax]

ok, home from work. across the 10ohm resistor and the pot(turned down) is 10.2 ohms. across with the pot turned up is 104.3 ohms. i hope this helps

edit:with 9v input

 

[busterhax]

with the two 10 ohm resistors in series, im at about 20 ohms and 115.

edit:with 9v input

 

[a_pyro_is]

with the two 10 ohm resistors in series, im at about 20 ohms and 115.

edit:with 9v input

Great! ~20 Ohms - ~115 Ohms sounds perfect for a BluRay. Than gives you a range from ~62mA down to ~11mA.
One last question before you try to power up that BluRay diode. Does the potentiometer change resistance smoothly, or does it jump at all when you're turning it?