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

2 diodes on 1 driver?

Mohrenberg

Mohrenberg

0
Joined
Aug 30, 2008
Messages
6,891
Points
83
say i wanted to run 2 diodes at the same time at......lets say 200ma, would it work to hook both of them up to a 400ma driver?
 





K

k-shell

0
Joined
Sep 5, 2008
Messages
164
Points
0
maybe in series, but if they are in parallel then one might pull more current than the other.
 
billg519

billg519

0
Joined
Feb 21, 2008
Messages
1,056
Points
0
In series, they won't divide the voltage evenly, unless they are known to be a very well matched pair of diodes.
If one diode was to drop too much voltage, it could fail. Differences in diode resistance are at the root of this.
Usually one diode per driver. The obvious exception is the diode bar, which of course has many identical matched emitters side by side. I can't remember having seen on this site one driver attached to several laser diodes at once.
 
billg519

billg519

0
Joined
Feb 21, 2008
Messages
1,056
Points
0
Even if the diodes were the "same", namely purchased at the same time, same lot#, etc., they can display markedly different electrical characteristics between individuals. PHR-803T blurays are a good example. Some take 150ma, some don't. Bottom line is if you have enough diodes around, go for it.
 
K

kernelpanic

0
Joined
Sep 8, 2008
Messages
182
Points
0
Mohrenberg said:
i mean like the same exact diodes just soldered to the driver.....
Click to expand...

The problem with that is that no 2 diodes are exactly alike. Any variance in resistance will cause the load to each diode to differ. In practice, if one diode blows, it might take the other one with it. If you decide to do it anyway, you should test as many diodes as possible and select the 2 that are most alike. Also, remember that in series you'll double voltage but in parallel, you'll double current. This means that if you're using 650nm diodes, you'll need to supply ~6v at the rated current for one diode. If you're in parallel you'll need ~3v at twice the rated current for one diode. Since we're using current regulators, You'll just need to make sure that you're supply can give the diodes the voltage needed.

In any case, I wouldn't do it. (If you do, test your setup with the IR diodes that we all have piles of laying around... )

Good luck! And If your sig changes to '6x Sony diodes destroyed so far.' we'll know what happened ;)

cheers,
kernelpanic
 
K

k-shell

0
Joined
Sep 5, 2008
Messages
164
Points
0
kernelpanic said:
Good luck! And If your sig changes to '6x Sony diodes destroyed so far.' we'll know what happened ;)

cheers,
kernelpanic
Click to expand...
:eek: That sux dude. i didnt realize how bad you had it.

We're rooting for ya  :)
 
Mohrenberg

Mohrenberg

0
Joined
Aug 30, 2008
Messages
6,891
Points
83
:) i'm not going to try it....i'm trading these diodes off for another 16x sony diode.
 
thesk8nmidget

thesk8nmidget

0
Joined
Jul 24, 2008
Messages
1,415
Points
36
the flexmod1 driver dr lava makes can be used with multiple diodes.



drlava said:
Hi, yes you can run many diodes of the same type from one driver, just stay within the current limitations of the driver (5A max)

Each diode is slightly different so to even out the current draw between the diodes when they are in parallel, you should put a (thick) metal film resistor in series with each diode. This is true for driving parallel diodes no matter which driver you use.

Let's say you are making a super red and want to use as many red diodes as possible, and you want the max current to be 350mA to each diode, and the lasing threshold is 75mA. Choose a resistor so that it drops about 10% of the diode voltage at the idle current, or 0.3V at 75mA: 4 ohms. Then calculate its voltage drop and power disipation at full power: 4 ohms*350mA = 1.4V; 1.4V*350mA= 0.49W

So, for an array of open can diodes you should use 4 ohm, 3/4 or 1W resistors in series with each diode. Maximum number of diodes on one driver is 5A/350mA = 14 diodes.

Minimum power supply voltage for the driver would be 3V (diode voltage) + 1.4V (resistor voltage) + 2.5V (Driver requirement when delivering 5A) = 6.9V

Finally, your diodes should be of the same make and model, and thermally coupled so they stay close to the same temperature. They should be connected to the same size heatsink block and with the same length and type of wire.
Click to expand...
 
You must log in or register to reply here.




Top