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1 battery for 7 lasers...

zxn474l

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If I want to power seven 20x dvd laser diodes just using one 9.6volt power drill battery...amps(? maybe 4-5 amps) would I install a momentary switch to activate the circuit on and off ,and wire the diodes with a longer wires from the bread board wired in "paralell" so the voltage stays the same 9.6 volts and set the current on the drivers for 450ma each? Would the drivers each still get enough current to work at that setting or would they start to drop off? Also just curious can a 20x dvd red long open can laser diode survive straight off a 9 volt regular battery for short pulses for maximum power with 5-10 second burn times and about 30 seconds off? I realize that a driver would be best but just how many milliamps does a small 9 volt battery have anyway...say an "energizer" brand? Has any ever survived being straight wired with no driver for such short burn times?
 

billg519

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Laser diodes are current sensitive devices and require a driver. The diode has a very low internal resistance and will try to draw far more than its' rated current. As the diode heats, the internal resistance can drop, increasing the current draw. (Thermal runaway) There is a member here, Switch, who has a 20x DVD diode running off 2 x 1.2V nimh batteries, no driver. The red needs about 3V to deliver full power, giving 2.4 V doesn't let it draw enough current to die. If 1.5V energizers were substituted here, the laser would die. Not the best way to run a diode, not giving full power withoout a driver. A red diode directly connected to a 9V battery will be instantly burned by excess voltage and current. By instantly, I mean dead in milliseconds, no run time at all.

For your seven red lasers off one battery, use a driver for each diode, your large battery should be able to run all seven no problem. At 9.6V, use a DDL driver you make yourself (cheap, since you need seven), or get rkcstr drivers. Lavadrive is a boost drive and 9.6V is too much for it, I believe.

Hope this helps ...

Bill.
 
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Bill, your explanation is correct, but you didn't mention that using ONE battery for SEVEN laser diodes will consume the battery very fast, he'll have to change the battery every five seconds..
 

billg519

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He says he has a drill battery. Drills draw a fair current when running, and last a while on the job site. He will get more than a few seconds of run time, for sure. 7 x 450mA is 3150mA drawn off the battery. Depending on the quality of the battery, if it is rated "1C", it could last even an hour or so. If my cordless drills were not all at the machine shop, I'd measure the motor current draw and be able to give a better answer regarding battery life. At least its' rechargeable ..
 

LarryDFW

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zxn474l;

The DVD red lasers require about 3 volts to operate.

A good regulator will need about 2 volts of headroom.

So, I would look for a 6VDC battery to begin with.

Setting the currents equal in each diode will be the challenge.

A five-amp regulator and individual resistors for each diode is one solution.

You may need some electronics help to set it up.

LarryDFW
 

HIMNL9

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just wondering, if the diodes are all identical units (and i mean IDENTICAL :p), he can connect them in series, using a single 324 and a 24V battery pack, drawing from the battery just the current of a single LD ..... :)

Just supposing we're speaking about usual 2,8V LD's, ofcourse ;)
 

billg519

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So, I would look for a 6VDC battery to begin with.

Good idea, this would put less heat stress on the linear regulators. There are 6V cordless batteries around.

A five-amp regulator and individual resistors for each diode is one solution.

Five amp regulators are not common. Could be made from an LM338, though. Probably easier to make 7 DDL's at 450mA each. No need then to worry if one diode has a lower resistance than the others and is therefore trying to "hog" the current and no need for balancing resistors on each diode. LM317's are dirt cheap on the web ...

just wondering, if the diodes are all identical units (and i mean IDENTICAL :p), he can connect them in series, using a single 324 and a 24V battery pack, drawing from the battery just the current of a single LD ..... :)

Just supposing we're speaking about usual 2,8V LD's, ofcourse ;)


This is how many IR diode high power arrays are made. You probably need good equipment to assure that the dies selected for the array are actually functionally identical.




 




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