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



Laser Pointer Store

M140: Powering with USB?

TimTom

New member
Joined
Jan 20, 2014
Messages
136
Likes
15
Points
0
Hi guys,

today I got the idea to power up a M140 diode with a USB from my pc, because I don't have a driver atm. that is working and I want some fun with my lazor's.

I heard, that they give me about 500mA up to 1,5A. Is it true, if yes, useful or possible for the diode?

Would be cool ^-^

Thank you,

Tim
 

jimdt7

Well-known member
Joined
Feb 5, 2011
Messages
1,899
Likes
69
Points
48
That's not a good idea nor for the PC nor for the diode...it could damage both! :beer:
I suggest you buy a boost driver if you plan to power your diode from a USB port! ;)

Jim
 

ARG

New member
Joined
Feb 27, 2011
Messages
6,987
Likes
576
Points
0
You can't hook it up directly as USB is constant voltage and you need constant current.
 

LarryDFW

New member
Joined
Dec 6, 2008
Messages
1,577
Likes
108
Points
0
TimTom;

In spite of the comments, your diode can be hooked up directly to a USB voltage source.

1. You must have the diode in a good heat sink.

2. Then you must check the current when hooked up to your 5 VDC USB port (they will vary) If current is too high for the diode, then you will need a resistor to lower the current.

I have a 445nm diode hooked up to a new 4.35 VDC lithium cell for a direct drive @ 700ma. It has been operated that way for over 1 year.

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

LarryDFW
 

ARG

New member
Joined
Feb 27, 2011
Messages
6,987
Likes
576
Points
0
In spite of the comments, your diode can be hooked up directly to a USB voltage source.

1. You must have the diode in a good heat sink.

2. Then you must check the current when hooked up to your 5 VDC USB port (they will vary) If current is too high for the diode, then you will need a resistor to lower the current.

I have a 445nm diode hooked up to a new 4.35 VDC lithium cell for a direct drive @ 700ma. It has been operated that way for over 1 year.
Just because something can be done does not mean it's a good idea ;)
If you must hook up the diode directly to a voltage source at least use a resistor to drop the excess voltage, 5V is too high for an M140.
 

chipdouglas

Well-known member
Joined
Dec 23, 2008
Messages
4,011
Likes
190
Points
63
and this is why we have dialog. whether some thing is safe or not is now up to the op to decide =p
 

jimdt7

Well-known member
Joined
Feb 5, 2011
Messages
1,899
Likes
69
Points
48
I once tried powering my A-140 straight from a 9V battery....it WORKED! (for a week) :shhh:

Jim
 

NKO29

Active member
Joined
Jun 6, 2013
Messages
871
Likes
70
Points
28
I have powered a 300mW red off of USB WITH DRIVER just fine :) However you'd probably want a high end desktop motherboard to do higher currents.
 

BShanahan14rulz

Well-known member
Joined
Dec 29, 2009
Messages
3,175
Likes
151
Points
63
At 5V, the M140 would allow ~3.5-4A, which is too much for this little beastie, and definitely would either trip a temporary fuse on your computer or just burn up that USB port. Visually extrapolated from this graph: http://cms.diodenring.de/images/stories/electronic/laser_diode/diode_1-3_voltage.png


A blu-ray diode is a different story, with a higher Vf range within which 5V falls fairly comfortably.

I have an A140 build (well, I used to, can't find it right now :( ) that is direct driven from an 18650, but even at 4.2V, a typical 445nm diode will only allow ~800mA, which is easy peasy for an 18650.
 

LarryDFW

New member
Joined
Dec 6, 2008
Messages
1,577
Likes
108
Points
0
If you must hook up the diode directly to a voltage source at least use a resistor to drop the excess voltage, 5V is too high for an M140.
It depends on the source of the USB power and the wiring.

Most USB sources will sag ~ 1/2 volt under that load (several amps).

My 445nm direct drive runs @ 4.4 VDC and only delivers 650 ma.

A 0.22 ohm resistor would be a good idea, to test the current with.

LarryDFW
 
Last edited:




Top