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07-06-2008, 01:10 PM #17
 Class 3B Laser Join Date: Oct 2007 Location: Slovenia, EU Posts: 4,177 Rep Power: 56
IgorT
Class 3B Laser

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Re: My first blu-ray

Quote:
 Originally Posted by jayrob About your driver set up... This is interesting. What's the math there? 12.6/68(ohm) is 185mA's...right? Then, as the voltage drops to say 3.6 X 3 = 10.8 volts/68(ohm) will be about 158mA's... Jay
You have to subtract the Vf of the diode from the battery total voltage, to get the current.. So it's closer to 105mA, if the Vf of the diode is assumed to be 5.4V. But the Vf changes with the current (and heat), and the current changes with the battery voltage, so there are too many factors involved, to calculate the current preciselly this way.

Now this approach can work, if you make sure the max current with full batteries is ALWAYS under the max safe current, but is't not a good approach. The power is different every time you turn the laser on, and drops with the battery voltage. And if you put different batteries in, you can still kill the diode. The internal resistance of the batteries alone influences the current in this setup.

Event Horizon: The money you &quot;saved&quot; on the driver (i read your other thread) killed two of your diodes.. With three Li-Ions, Rkcstr's micro driver for \$5 - \$10 (depending on the version) would work PERFECTLY. Your power would be the same every time you turn the laser on, right down till the batteries would be completelly empty, and your diode would be fully protected, cos the current can not go higher, regardless of the input voltage (up to 35V or so), when you use a linear driver..

And that driver also fits into an AixiZ module, so you can use it wherever you have room for an AixiZ module, as long as you also have room for three Li-Ions for blu rays or two Li-Ions for reds..

Now since this one is already working and isn't in any real danger, you may not want to take it appart to put in a real driver, but next time, spend the few dollars and save a diode or two.
Not only will your power always be the same regardless of the batteries, you can also push the diode harder with a driver, and still be safer!

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07-06-2008, 04:46 PM #18
 Class 2 Laser Join Date: Mar 2008 Location: Toronto, Canada Posts: 477 Rep Power: 39
Event_Horizon
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Re: My first blu-ray

Quote:
 Originally Posted by IgorT Event Horizon: The money you "saved" on the driver (i read your other thread) killed two of your diodes.
I am pretty sure it was negligence that killed the two diodes, not the driver. The first time I left my variable power supply at high voltage when connecting the diode directly, and the second time I forgot to discharge the capacitor in the driver before connection the diode. I am fairly confident that this driver will protect the laser. There no way that the current could exceed 110mA with this setup, as I tested the setup using the maximum possible voltage that the batteries could output. Aside from using completely different batteries or putting the batteries in backwards, I highly doubt much could go wrong.

But I suppose I could be wrong. But if I am, then this diode it going to be toast and I'll do better next time. It's the only way I learn.

Also, I find that there is more personal satisfaction with the final product if you spend more time building it yourself as opposed to buying semi-finished parts and throwing them together in 15 minutes.
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07-06-2008, 05:09 PM #19
 Class 3B Laser Join Date: Oct 2007 Location: Slovenia, EU Posts: 4,177 Rep Power: 56
IgorT
Class 3B Laser

Join Date: Oct 2007
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Rep Power: 56
Re: My first blu-ray

Quote:
 Originally Posted by Event Horizon Also, I find that there is more personal satisfaction with the final product if you spend more time building it yourself as opposed to buying semi-finished parts and throwing them together in 15 minutes.
I agree. That's why i etch and solder my own drivers myself. But buying a kit an soldering it together is not that bad either.

And as long as you don't use different batteries, the current really won't exceed 110mA. And the diode can take more so it's not in any danger.
But as i said, there are other benefits from using a driver. The power of the laser is the same every time you turn it on, and you can even set the current higher with a lower risk.

Otherwise, i made my first red the same way as you made this one - without a driver. But that's because i used a very tiny host, where i didn't have room for more than one tiny Li-Ion, and i didn't have a boost driver back then.

It worked for a very long time, but eventually i put a driver in. Before, the power started at 186mW on full batteries, and dropped to 150mW and lower, as the battery discharged, now it starts at 186mW every time, and the power only varies a little from heat.

If you don't want to buy a driver kit, make a 317 next time. It's really easy to build, and can work a Blu Ray from three Li-Ions perfectly, or a red from two.

You can also put a 1k resistor across the output cap, to discharge it quickly after disconnecting the load, and not lose more than a few mA. If you set the driver to 114mA, you get 109mA, through the diode, with a 1k resistor across the cap.

This is what saved me from killing many diodes when i had to test a large batch in a short time, and had to desolder one and put another one on quickly.
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07-23-2008, 02:54 AM #20
 Member Join Date: Jul 2008 Posts: 40 Rep Power: 0
scareg
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Re: My first blu-ray

Awesome found my way to this as I was looking for a nice looking host for my Blue ray. I'm pretty much just making what you made
would you mind if I ask you a few questions?

what did you use for a heat sink did you make it or order it from someone on here?

you used a Diode from a Xbox 360 was it easy to remove Im afraid of breaking it.

are there any tips you can give me on making mine?

Thanks for your time and help!

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