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ArcticMyst Security by Avery

Problem bucking a PL520

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Hi all. Without going into too much detail, let me explain what I need.

The PL520 has a Vf between 6 and 8VDC, depending on current. I have one of DTR's with the X-Boost set to 300mA.

The host I am using is built specifically for 2X26650 batteries, and I'd like to not throw off the balance w/ a one battery build.

I've tuned a Moh linear for the job to 305mA, but DTR tells me I am only going to get a usable 1 volt out of it to run on, if I can get it to regulate at all.

So, my question is this: Is there a buck driver that can handle the Vf of the diode @ ~8V while taking the 8.4VDC input and allow me to use this diode w/ the 2 X 3.7V batteries?

Thank you all in advance!

SBA
 





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Keep in mind I'm not current (haha) on the latest generation of drivers, but it would seem that you need a Buck-Boost type driver. I know only of the old Flexdrive, and do not know if they are again available or if there is an alternative.

You're not going to find a Buck that only drops <400mV and if you did you would only have 400mV of battery charge before the diode loses power. You could find a LDO linear that drops <400mV (I know of several 5V fixed ones that only drop 160mV but there are variable types too) but again once you go below Vcc=8.4V-Vdrop you won't fully satisfy the Vf of the diode and it will start to crap out.
 
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The problem with the Flexdrive is that its maximum Vin is only 5.5V. So, that wouldn't be appropriate for the desired setup.
 
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The problem with the Flexdrive is that its maximum Vin is only 5.5V. So, that wouldn't be appropriate for the desired setup.

Yes but it is also a boost driver. Unfortunately, the Flex V5 only boosts to 5.5V.
The MicroBoost is a better option.
Input V is 5.8V max so you cannot use 2 LiIons unless a diode is put in series with the driver but it will get your desired output V from one battery.

From the manual: A good rule of thumb to follow for input/output conversion is:
(Vout (Volts) * Iout (Amps) ) / Vin (Volts) < 1.2

According to this, the MicroBoost should be able to handle the diode with a single 4.2V LiIon.

8V x 0.3A / 4.2V = 0.571 < 1.2

http://hacylon.case.edu/ebay/laser_diode/Micro Boost Drive V1 manual.pdf

You should contact Lazeerer. I don't know if he has any X-boosts in stock but his drivers are really good.
EDIT: Just re-read and saw you already have an X-boost. Why not just pick a more practical host?
Alternatively, you could use the boost driver and one 26650 with one spacer.

IMO it seems silly to use a buck driver for a diode with such a high forward voltage. Boost seems much more practical unless you want a ton of batteries in series.
Also, why such a large host for a diode that only outputs 100mW of green?
It doesn't need much heatsinking. 2x26650s seems like overkill... I guess you want to be able to run it for days continuously...
 
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norbyx

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Why not make a dummy (fake) battery and you are set?
 
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You're missing the point. I have an X-Boost on it already. I WANT to use the 2 X 26650s that the host is designed for. That's why I want to buck this diode down to ~300mA.

What diode would I need to add in series to run two batteries?

Why not make a dummy (fake) battery and you are set?

I would really LOVE the run times that I'd get with two 4000mAh batteries!

The reason I am using the host I am is because it is a truly stunning host, and it's never been built with a PL520. The host is overkill for cooling, yes. But the cool factor of the build is worth the trouble.

I could use a slug if need be. But, like I said, I would love the killer capacity of the 2 batteries.

It's a one of a kind. It's worth some extra work.


Yes but it is also a boost driver. Unfortunately, the Flex V5 only boosts to 5.5V.
The MicroBoost is a better option.
Input V is 5.8V max so you cannot use 2 LiIons unless a diode is put in series with the driver but it will get your desired output V from one battery.

From the manual: A good rule of thumb to follow for input/output conversion is:
(Vout (Volts) * Iout (Amps) ) / Vin (Volts) < 1.2

According to this, the MicroBoost should be able to handle the diode with a single 4.2V LiIon.

8V x 0.3A / 4.2V = 0.571 < 1.2

http://hacylon.case.edu/ebay/laser_diode/Micro Boost Drive V1 manual.pdf

You should contact Lazeerer. I don't know if he has any X-boosts in stock but his drivers are really good.
EDIT: Just re-read and saw you already have an X-boost. Why not just pick a more practical host?
Alternatively, you could use the boost driver and one 26650 with one spacer.

IMO it seems silly to use a buck driver for a diode with such a high forward voltage. Boost seems much more practical unless you want a ton of batteries in series.
Also, why such a large host for a diode that only outputs 100mW of green?
It doesn't need much heatsinking. 2x26650s seems like overkill... I guess you want to be able to run it for days continuously...
 
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I guess you could use a 3.1V zener diode on the input of the x-boost. Just be sure to reverse bias the zener. That will drop it down to 5.3V max from 2 series Li-Ions.
 
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I guess you could use a 3.1V zener diode on the input of the x-boost. Just be sure to reverse bias the zener. That will drop it down to 5.3V max from 2 series Li-Ions.

That's not very helpful when you consider his original goal: utilize two cells for longer run-times. Dumping most of the second cell's energy into a zener sorta defeats the purpose.
 

DTR

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That's not very helpful when you consider his original goal: utilize two cells for longer run-times. Dumping most of the second cell's energy into a zener sorta defeats the purpose.

Not to mention it is another item that will be producing a lot of heat that has to be managed.
 
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If you're stuck with a 2 cell host and you can't find a driver which meets your I/O reqs there isn't a whole lot more you can do. I didn't say it was a great idea, lol. I'm not up to date on the current driver market, but a quick search doesn't pull anything up either.
 
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Thanks Sig, I'm afraid that's where I ran into trouble as well. Maybe the FMT will work, I have to check the specs again.

I'll leave this thread up in case some genius on the forum will come to the rescue.
 
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What about the Buckboost? It's Vout is 2.5-.85*Vin. So, that comes to just over 7V...Has anyone tried this combination yet?
 




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