ddl circuit on 7.2 lithium

[Kenneth_v]

Should I just wire it up and hope for the best ???

 

[chido]

Hold on, be patient, you don't want to mess anything up just because you rushed to it, lets see what Gazoo has to say about this.

 

[Kenneth_v]

I plan on waiting!! nothing to be in a hurry about.

 

[Gazoo]

Well here is what I think...with your pot turned to the least resistance you should be getting close to 250ma's. I have a SenKat diode running with 250ma's and the voltage across it is 3 volts.

 

[Gazoo]

It shouldn't matter cause if I was running fresh 4 AA's id be putting 3.2v into it as well

And here is my canned response for you.. ;D

The LM317 is no mystery and very easy to work with. The following calculations always apply since it uses 1.25 volts for its reference voltage, and ohms's laws don't lie.

To calculate the resistor needed for a given current, take 1.25 and divide it by the current. So say you want to drive a SenKat diode with 250 ma's. 1.25 divided by .250 = a 5 ohm resistor.

Another way you could do this is to take 1.25 and divide it by the resistance. 1.25 divided by 5 = .250.

Next you will want to calculate the wattage of the resister needed. We know 1/2 watt resistors are common for use with the regulator. But to figure it out, simply take the 1.25 and multiply it times the current. 1.25 times .250 =.3125 watts.

The rule of thumb for the voltage going into the regulator is it should be 3 volts more than the voltage going to the diode. A SenKat diode running at 250ma's will have about 3 volts across it. Therefore a minimum if 6 volts is needed.
I recommend 6 nimh batteries or 2 RCR123's for use with Daedal's driver.

This is why you need at least 8 volts to run the blu-ray. You will find when you have it hooked up, the voltage across it will be appx. 5 volts. But since it will only draw ~38ma's, you can run it with a 9 volt battery.

To learn more about ohms law go here:

http://www.the12volt.com/ohm/ohmslaw.asp

 

[Kenneth_v]

I know my calculations are correct according to ohms law

full open pot is 1.25 / 4.3 ohm resistor = 290
actual reading = 282

looks perfect

My concern was that I was putting more than 3 volts through and that I my damage the LD but I should be fine with the settings

I have turned the pot so I'm putting out 185ma current across the resistor and 3.17 volts is the reading across the 4 diode dummy load. I set it low because of what I have been reading about the quality of this batch of diodes.

Thanks

Ken

 

[SargeMX5]

Dont take my word, but im putting my 2c in. I had an older diode from i think a sony drive that my mate gave me for nothing. I ripped it open and hooked it up straight to 4xAA batteries but just put a 10ohm resistor in series with the diode. Worked fine and i think it was running of 5.x volts. The sony diodes i believe can take up to 5 volts. You shouldnt fry your diode.

Ive noticed that when i dummy load my circuit with the 4 1n4004(same as 4001) the reading is always abit different when actually using a dead diode(LED'ed) as the load. Do you have a blown diode to test the driver with?