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Problems with my LPC-826 build

J

Jwl456

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Hey guys. I recently had a LPC-815 build running with an lm 317 driver at about 270mA. It worked nicely for about 3 months then all of a sudden went dim on me.

I thought the diode went out so I bought a new LPC-826. I modified the driver to give me 380mA (a little below the suggested current just to play it safe) and hooked it up. It worked really well for about 2 minutes then as I was putting it into the flashlight host I had rigged up it went dim as well.

I really hope I didn't burn out another brand new diode. I'm not sure how it happened if it did indeed burn out.

Could it just be a short in the circuit that's causing that to happen? Is there anything I could be doing wrong? Why is it dim just after having it hooked up for a few minutes?
 





bobhaha

bobhaha

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Pictures would really help in this situation....
 
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J

Jwl456

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Here's some pictures of the drivers I've made:
 

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  • LPC-815.jpg
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bobhaha

bobhaha

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Well there are many things that could be causing this. Are you shorting out the output cap before attaching the diode? Any stored current will be dumped straight into the diode if you don't short it.

Also are you checking the output with a dummyload? Are any parts of the driver getting hot while under load? If so, you may have a shift in current. Which can kill a diode.

Lastly are you changing the output current while the driver is powered on? If so the wiper inside the potentiometer can jump causing a rush of high current to run through the diode... also killing it.
 
J

Jwl456

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Yeah, I dialed in the output current with a test load before hooking it up. It was at 366mA.

I did not short out the capacitor though. But if there was stored charge that could kill it would it have run correctly at first like it did? It ran well for a short bit of time. I turned it on and off maybe three times successfully but then the fourth time it was dim.

I didn't adjust the potentionmeter at all. I just set it and left it how it was.
 
bobhaha

bobhaha

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Hmm that is strange. Did you notice any of the components getting hot?

What about the input voltage? Remember there is a drop out voltage of about 1.5V + your diodes forward voltage. What are your batteries reading?
 
J

Jwl456

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Whenever I first hooked it up the batteries read 7.84 V. Should I test them while they are hooked up and it's running?
 
J

Jwl456

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I didn't notice any of the components getting hot either. The lm 317 usually gets pretty hot but I put a homemade heatsink on it. I didn't check it though.

Could the capacitor put out any residual charge DURING its running time? I thought that was more something that happened as soon as you hooked it up if you hadnt discharged it. Because this one worked for at least a few minutes (not of straight run time, I turned it on and off).
 
bobhaha

bobhaha

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As I said it can be many things.

Lets try narrow it down a bit more....

Is the diode heatsinked?
What are the schematics you used to build the driver?
Are all solder joints strong and making full contact?
What dummy load are you using?

-Adrian
 
Ibuprofen200mg

Ibuprofen200mg

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Why not just go with a small linear driver?
The Ghostdrive is really easy to use, or you
could pick something up from Cajun Lasers,
he has a large selection of drivers. A small driver
will open up a lot more host options for you.
 
J

Jwl456

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bobhaha said:
As I said it can be many things.

Lets try narrow it down a bit more....

Is the diode heatsinked?
What are the schematics you used to build the driver?
Are all solder joints strong and making full contact?
What dummy load are you using?

-Adrian
Click to expand...

I have got the diode in a pretty big heatsink. I didn't feel any kind of heat come off it.

Here's the schematic I used:

Step 3: Driver

All the solder joints should be strong. I've had trouble in the past with shorts in my drivers due to the copper strips in the particular board I bought but I cleaned all those out with an exacto knife. I actually went back through and resoldered all the joints that could be questionable and hooked it up again with the same results.

The test load I used was just 4 1N4001 diodes and a 1 ohm resistor to simulate the diode. Come to think of it, that's the test load for the LPC-815. Could the 826 need a different one and that cause my output to not be measured correctly?
 
J

Jwl456

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Ibuprofen200mg said:
Why not just go with a small linear driver?
The Ghostdrive is really easy to use, or you
could pick something up from Cajun Lasers,
he has a large selection of drivers. A small driver
will open up a lot more host options for you.
Click to expand...

A ghostdrive isn't something I can make, is it? I definitely want to buy some kind of small driver to put one in a more elegant host, but right now I just really enjoy building all of it I can. Just for fun. :)
 
Ibuprofen200mg

Ibuprofen200mg

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That's respectable :), the Ghostdrive is available through member Ghostchrome on his
website Lazorlabs.com
 
bobhaha

bobhaha

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Jwl456 said:
I have got the diode in a pretty big heatsink. I didn't feel any kind of heat come off it.

Here's the schematic I used:

Step 3: Driver

All the solder joints should be strong. I've had trouble in the past with shorts in my drivers due to the copper strips in the particular board I bought but I cleaned all those out with an exacto knife. I actually went back through and resoldered all the joints that could be questionable and hooked it up again with the same results.

The test load I used was just 4 1N4001 diodes and a 1 ohm resistor to simulate the diode. Come to think of it, that's the test load for the LPC-815. Could the 826 need a different one and that cause my output to not be measured correctly?
Click to expand...

That all seems fine... and yes you can use the same dummy load for both diodes.

I cant think of anything else that would stand out. I would suggest going over the drive with a magnifying glass and triple check all connections. Then buy a new diode and try again. Remember to short out the output cap and solder the diode securely.

EDIT: I also noticed you are using a tantalum capacitor whereas the schematic calls for an electrolytic capacitor... What capacitance is that cap? Also do you have a 10mf 16V electrolytic that you can try?
 
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AUS

AUS

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I had issues with a commercial linear driver and it turned out to be the trimpot on the board moving. A dob of nailpolish fixed this
 
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