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Help built driver having problems!!!!!!

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drewk302

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Feb 10, 2011
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ok I built a driver using this diagram:
LM317%20components01.jpg

I did not use a pot meter though, for resistors I used a 10ohm and (2) 15ohm to get me 4.2 ohm (i used 1/2 watt 5%). Then rec. diode 1n4001, and a 10mfd 16v cap. heres pics:
http://www.flickr.com/photos/59411845@N03/5449484482/

http://www.flickr.com/photos/59411845@N03/5448876337/

I tested it and was getting just about no voltage through it, and the 3117 was getting very hot. I have read that all the 3117's are the same and just to use the pin layout like rog8811 shows, but the package shows different for the v in, v out, and adjust. It almost seems obvious that i should do it again and follow the package, but do you see anything else that could be wrong???? Thanks in advance!
 





Flaminpyro

Flaminpyro

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I would do like you suggest and follow the package diagram, what do you have to loose ?
 
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drewk302

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yea I am gonna. I just wanted to see if there was anything else wrong that stood out too.
 
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anselm

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hard to tell when one can't see the flipside of your thinggy there
 
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drewk302

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I didnt take a pic before it came apart but I checked it several times, I ran beads of solder cleanly, and I checked for continuity down each bead and at each point of solder.
 
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drewk302

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ok I rebuilt the board. It is working but i am putting in 7-7.5 volts and its giving the 5 volts to the diode? I want between 3-4v right??? wtf I am going nuts.
 
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anselm

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Don't worry about them volts, it doesn't matter if the tension is somewhat over what
the diode needs.
Once you hook up and run the diode, the voltage you'll measure will be just right, magically!
It's the current you need to control.;)

Do you have a testload at all, or how are you measuring the current?

Have you read this?
Laser driver - It can be done
 
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drewk302

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I dont have a test load, I was just hooking up the power and ground from the housing I am using and then testing the output voltage with my multi meter?????
 
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anselm

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Nevermind about voltage, make yourself a test-load like explained and measure
the current your driver is outputting. When you feel it is at a safe level
for your diode, then connect your diode to the driver after shorting the drivers output pins, discharging the capacitor!.
 
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drewk302

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ugh I have everything except the 1 ohm resistor..........also how do you discharge the cap.
 
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anselm

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You can use a different than 1Ohm resistor, but then you'll have to do a little math,
the mV you read are not going to correspond directly to the mA that flow.
The resistor being 1Ohm just makes it faster/easier to read.;)

You discharge the cap by shorting it's pins together, ie touch them both at the same time
with something electrically conductive, a clip or a piece of wire....
 
bluuray

bluuray

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if you dont use a cap , you dont have to discharge anything right?
 
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anselm

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right, no caps -> nothing to discharge, but it's still a good habit to always short the output pins together immediately before connecting the diode!
Doesn't hurt and better making a habit out of it.
 
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drewk302

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ok, so I said screw it and hooked it up to the diode. I had 7v going in and at the diode I was getting a weak laser and under load it was getting around 1.5-1.7v. I didnt test the mA I will again tomm. i didnt want to keep it hooked up to the diode long. What could be the problem?????? Side note I hooked the diode to my 2AA batt box and had a nice very very bright laser, couldnt burn anything though.
 
Scoots

Scoots

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looking at your underside pic it seems you have wired the adjust pin as your V in.
 
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