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09182007, 01:52 AM  #289  
 
Class 1 Laser Join Date: Sep 2007
Posts: 51
Rep Power: 16 
Second pic...
 
09182007, 01:53 AM  #290  
 
Class 1 Laser Join Date: Sep 2007
Posts: 51
Rep Power: 16 
And last but not least:
 
09182007, 03:07 AM  #291  
 
Class 2M Laser Join Date: Jun 2007
Posts: 650
Rep Power: 16  Quote:
It looks like a 22 ohm resistor so,if you supply the LM317 with enough voltage overhead, the LM317 will adjust its output current so that the voltage drop between the Out and Adj pins equals 1.25V. *1.25V/22 ohms = 56.8mA The way you measured current is not the way to do it. There is a reason why it worked out this time, but I caution you that this method will only work in certain circumstances (in others, it will blow the fuse in your multimeter!). There are several other ways to measure current, but the BEST and easiest way in this case is to measure the voltage drop through a known resistance. *You already have the resistance (22 ohm resistor). Measure the voltage drop on it and calculate the current (I=V/R). Another way is to insert the multimeter in SERIES with the load. *Use the highest current setting on the multimeter (and the correct jacks) to minimize the meter's effect on the circuit. *This method works OK to check battery current by using the meter in current mode to complete a light/laser's tailcap circuit.  
09182007, 05:50 AM  #292  
 
Class 3R Laser Join Date: May 2007
Posts: 2,277
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Mountaineer, your circuit appears to be configured properly. Although, with 22 Ohms of resistance you are only permitting 56.818mA through, which is what you got there on the meter. As chimo said, you do not measure current across the load. You measure the voltage like that and that is ok, but to measure the current you have to make the current forcefully flow through the DMM. I suggest testing the circuit again with a reliable 6V supply, and using 2 of the diodes you have there. The diode you have there will not read more than the voltage that it needs to operate, is you use 2 of them, then the voltage reading is well past that of the LD and you get a better picture/idea of your supply voltage to the diode. As about the current, I suggest using a 5Ohm resistor for use with one of the GB diodes GL; DDL
__________________ ____________________________________________ Daedal Lasers... NEW LOWER PRICES... LPF Coupon = LPF10OFF ________________________________ CLICK ME  LASORB is now available for immediate purchase ________________________________  
09182007, 07:17 AM  #293  
 
Class 1 Laser Join Date: Sep 2007
Posts: 51
Rep Power: 16 
Thanks for the help guys. Would a 4.7ohm resistor give me 266mA (1.25V/4.7ohm), and is that too much? What would the mW be then? I'm still trying to figure out all the math and stuff involved in figuring this out. Kinda makes a guy's eyes want to cross... Sorry if all this is beating a dead horse, but I'm just not quite getting it yet. Thanks again chimo and DDL [smiley=dankk2.gif], now it's time for me to take my helmet off and go to bed, I've got to catch the short bus early in the morning haha .
 
09182007, 07:32 AM  #294  
 
Class 3R Laser Join Date: May 2007
Posts: 2,277
Rep Power: 1331 
If you're going to be using .25 or .5 Watt resistors from RS, I suggest using 2 X 10Ohm resistors in series. Just twist them onto each other. That'll give you double the rating and half the resistance That's what I use On the other hand, I think you'd be alright with 266mA. That should get you anything from 150mW to about 250mW ;D That's a big range and it all depends on the temperature of the diode. GL; DDL
__________________ ____________________________________________ Daedal Lasers... NEW LOWER PRICES... LPF Coupon = LPF10OFF ________________________________ CLICK ME  LASORB is now available for immediate purchase ________________________________  
09182007, 07:51 AM  #295  
 
Class 3B Laser Join Date: Jun 2007 Location: Dallas Tx
Posts: 3,199
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I wish I was good at drawing... ;D But here is what I use. The only resistor I use is a 1 ohm resistor connected in series with the diode. This is used to measure current. Measuring voltage across the resistor will give the same readings as measuring current, and will be safer as there is less chance of ruining the diode on account of accidentally discharging the voltage built up in the capacitor..... into the diode. In series with the resistor I have a RS 25 ohm 3 watt rheostat. This allows me to adjust the current as needed. Of course this will not fit into a flashlight but is a nice way to begin experimenting.  
09182007, 08:38 AM  #296  
 
Junior Member Join Date: Aug 2007
Posts: 25
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09182007, 08:08 PM  #297  
 
Class 3R Laser Join Date: Sep 2007
Posts: 1,591
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daedal i hooked up the diode to the circuit but it shines dim but i put and LED on and bam light up the blue LED when i added the 5 ohm did it need to be in series or paralel
 
09192007, 01:12 AM  #298  
 
Class 2 Laser Join Date: Sep 2007
Posts: 415
Rep Power: 12 
Well, I came to this thread to complain (nah, rather ask for help politely) because my circuit doesn't work. Problem was, I thought "123" on the circuit on p.1 referred to legs 1,2,3 on the LM317. Unfortunately, with the LM317 T, this is not the case, instead of "inadjout", it is "adjoutin". Now gotta go and see if it works Just if that helped anyone.  
09192007, 01:22 AM  #299  
 
Class 3B Laser Join Date: Jun 2007 Location: Dallas Tx
Posts: 3,199
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Good point. As many times as I have looked at that circuit diagram I never noticed it.. :P
 
09192007, 02:03 AM  #300  
 
Class 2M Laser 
last week I decided to not be such a noob * i started figuring out how this works and I finished the driver last night! but today i realized i didnt use 2.2ohm resistors, i put in two 2.2k ohm resistors in a series; 4400 ohm! i kno i have to replace these guys but just want to kno how would that have effected the laser diode  
09192007, 03:45 AM  #301  
 
Class 1 Laser Join Date: Sep 2007
Posts: 51
Rep Power: 16 
Would a 10uF 16V capacitor handle the spikes OK? I don't figure it will since the recommended capacity is almost 5X that, but I just thought I would make sure. The reason I'm asking is because I'm trying to find a tiny capacitor to fit into the Aixiz module that I can get at the local Radio Shack. Would this one work?: http://www.radioshack.com/product/in...entPage=family Thanks!  
09192007, 04:48 AM  #302  
 
Class 3R Laser Join Date: May 2007
Posts: 2,277
Rep Power: 1331  Quote:
GL and I hope you managed to get it working; DDL
__________________ ____________________________________________ Daedal Lasers... NEW LOWER PRICES... LPF Coupon = LPF10OFF ________________________________ CLICK ME  LASORB is now available for immediate purchase ________________________________  
09192007, 04:50 AM  #303  
 
Class 3R Laser Join Date: May 2007
Posts: 2,277
Rep Power: 1331  Quote:
GL; DDL
__________________ ____________________________________________ Daedal Lasers... NEW LOWER PRICES... LPF Coupon = LPF10OFF ________________________________ CLICK ME  LASORB is now available for immediate purchase ________________________________  
09192007, 04:54 AM  #304  
 
Class 3R Laser Join Date: May 2007
Posts: 2,277
Rep Power: 1331  Quote:
Do you have a V and I measurement? Try and get a 1Ohm resistor in series with the diode as Gazoo did and let us know what the voltage across it is. It should be outside of the circuit and should pretty much act as one of the LD pins. Also, do you know if the LD itself is still ok? Measuring the voltage across the diode itself and then across the resistor should give you an idea what this thing is taking. If it is in fact drawing ~2.8V and 250mA (because of the 5Ohm resistance) and it's still dim, you may have a COD diode there GL; DDL
__________________ ____________________________________________ Daedal Lasers... NEW LOWER PRICES... LPF Coupon = LPF10OFF ________________________________ CLICK ME  LASORB is now available for immediate purchase ________________________________  
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