Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers

LPF Donation via Stripe | LPF Donation - Other Methods

Links below open in new window

ArcticMyst Security by Avery

Buck drivers with a single battery for low power

Joined
Jun 22, 2011
Messages
2,431
Points
83
Many lasers are built with buck drivers that are supposed to take two batteries in order to maintain regulation.

I have tested a few of them with a single battery and I often use my 445nm C6 with a single battery to achieve a lower power. It does about 1.3W with two 16340 and around 100-300mW with a single 18650. The power level varies wildly between runs but is very stable after you turn it on (i.e. sometimes it will turn on doing 200mW and sometimes 250mW, but it will maintain that power level as long as it's kept on).

I also added a switch that series a diode with the battery on a 532nm laser and managed to get a low power mode without modifying the module/driver.

I still haven't tried this on my new 500mW 405nm and since the diode is sensitive and the Vf is higher I thought I should ask...

Is this practice safe?
Can it damage the driver or the diode?
 





Garoq

0
Joined
Aug 27, 2010
Messages
1,525
Points
83
On the 445nm diodes, it is safe as far as I know. I have used it numerous times and I know many others have as well.
 
Joined
Dec 29, 2009
Messages
3,136
Points
63
regulation basically means it keeps spikes, noise, and overall current below a certain threshold. If the supply can't supply more than what it requires, the battery just gives it all it's got.

So, it goes from taking an input that is too much, bucking what isn't needed, and giving what's left to the diode, to taking an input that isn't enough, bucking nothing, and just passing it on to the diode. Pretty much like direct drive, but with a bit of resistance from the fet and circuitry.

I've run my 1st gen A140 just wired to an 18650. Never used a driver for my 445nm, I've no need for a stable output power or anything. Not that I use it all the time or anything. Last time I ran it was almost a year ago :(
 
Joined
Sep 12, 2007
Messages
9,399
Points
113
The power level varies wildly between runs but is very stable after you turn it on

Physics says this won't be the case. As the cell drains, the Vf lasing threshold will eventually be higher than the cell voltage. Power will decrease. Simply put, it isn't in regulation, and as bshan says, it's electrically similar to using a resistor to limit the current. It's safe, but not in regulation.
 

Garoq

0
Joined
Aug 27, 2010
Messages
1,525
Points
83
The 18650 battery needs to be very close to full charge (4.1-4.2V) for this "low mode" to work.
 
Joined
Dec 6, 2008
Messages
1,581
Points
63
Many lasers are built with buck drivers that are supposed to take two batteries in order to maintain regulation.

I have tested a few of them with a single battery and I often use my 445nm C6 with a single battery to achieve a lower power. It does about 1.3W with two 16340 and around 100-300mW with a single 18650. The power level varies wildly between runs but is very stable after you turn it on (i.e. sometimes it will turn on doing 200mW and sometimes 250mW, but it will maintain that power level as long as it's kept on).

I also added a switch that series a diode with the battery on a 532nm laser and managed to get a low power mode without modifying the module/driver.

I still haven't tried this on my new 500mW 405nm and since the diode is sensitive and the Vf is higher I thought I should ask...

Is this practice safe?
Can it damage the driver or the diode?

At a power level of 300mw, it is quite safe as long as you have a reasonable heat sink on the LD.

My 445 LD operates @ 600mw in a direct drive configuration with a 4.35 VDC lithium cell.

http://laserpointerforums.com/f65/direct-drive-445-host-52918.html

LarryDFW
 
Last edited:
Joined
Jun 22, 2011
Messages
2,431
Points
83
Thanks, guys!

Physics says this won't be the case. As the cell drains, the Vf lasing threshold will eventually be higher than the cell voltage. Power will decrease. Simply put, it isn't in regulation, and as bshan says, it's electrically similar to using a resistor to limit the current. It's safe, but not in regulation.

I'm not saying it will be stable forever, but it stays very stable for at least 2min with a 3400mAh Panasonic 18650:
underdriven.png




Still curious to know if anyone ever tried this with the S06J, if you have don't hesitate to bump the thread :)
 




Top