FlexMod N2 Laser diode drivers have now arrived :)

[Laserman532]

Haha worked as intended

Hi, I'll post here what I posted in the V1 thread:

Hi, yes you can run many diodes of the same type from one driver, just stay within the current limitations of the driver (8A 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 300mA 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*300mA = 1.2V; 1.2V*300mA= 0.36W

So, for an array of open can diodes you should use 4 ohm, 1/2W or 1W resistors in series with each diode. Maximum number of diodes on one driver is 8A/300mA = 25 diodes.

Minimum power supply voltage for the driver would be 3V (diode voltage) + 1.2V (resistor voltage) + 2.0V (Driver requirement when delivering 8A (0.25V per amp)) = 6.2V. If you are only driving 2 diodes in parallel then a supply voltage of 5V is fine.

Finally, your diodes should be of the same make and model, and thermally coupled so they stay close to the same temperature, and electrically isolated. They should be connected to the same size heatsink block and with the same length and type of wire.

Typically if a red diode dies, it dies of optical failure and so will maintain virtually the same output voltage drop, saving the other diode it he pair. However if it fails open circuit via some mechanical abuse (I have never seen this happen after a diode was installed in a mount, but have seen it happen AS a diode was being installed, so test!) then the other diode will take double the current.

or you could buy two drivers

[DjDevNull]

I was wondering the same thing. But it sound like the $35 extra would be worth it.

[sbk]

Hi, I'll post here what I posted in the V1 thread:

Oh, I should have re-read the V1 thread, I wasn't remember me that

So ok for the parallel mode. But what's about putting the diodes in series? This will correct the diodes irregularities (at least for the current, not for the different efficiency of each diode but I think that's not very noticeable in use), and protect the others diodes if one gets shorted.

Of course it requires an input voltage to the driver at least equal to the sum of the dropout voltages of all the diodes in the circuit, plus a little extra voltage for the circuit operations... I don't know if the driver is ok for that. And I don't know too, if there's modulation slowdown or other problems, when drived in series?

or you could buy two drivers

I was wondering the same thing. But it sound like the $35 extra would be worth it.

I'll be fair, I'll let some drivers for the other members (otherwise I'll need at least 8 drivers!)

[drlava]

I'll give it a try and let you know..

[greeklaserist]

have made an order of one of these driver circuits for trying like 2 weeks ago still waiting for it

[Lasernerd]

Last I heard was a new batch is going out Monday,

[ImageLight]

Got mine.. Thanks DL

[keeperx]

lava.. im interested in the "in series" experiment as well... please post results if you get any

[300EVIL]

Got mine! Looks great! Can't wait to try it out.
Thanks!
Adam

[SideFX]

I just ordered two. hope they arrive soon.. I can't wait to get my open can red fired up!