2 diodes on 1 driver?

[Mohrenberg]

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-shell]

maybe in series, but if they are in parallel then one might pull more current than the other.

 

[billg519]

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.

 

[Mohrenberg]

i mean like the same exact diodes just soldered to the driver.....

 

[billg519]

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.

 

[kernelpanic]

i mean like the same exact diodes just soldered to the driver.....

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-shell]

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

cheers,
kernelpanic

That sux dude. i didnt realize how bad you had it.

We're rooting for ya  

 

[pocketfluff]

Series should be ok since current through the diodes will be the same.

 

[Mohrenberg]

i'm not going to try it....i'm trading these diodes off for another 16x sony diode.

 

[thesk8nmidget]

the flexmod1 driver dr lava makes can be used with multiple diodes.

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.