lasers connected to arduino

ey!

I am building a little laser harp, and I want to know if it is possible to conect 16 lasers in parallel with the 5v pin of the arduino

laser´s specs: 650nm DC 5V 5mW Mini Laser Dot Diode

http://www.ebay.com/itm/New-1PCS-650nm-6mm-DC-5V-5mW-Mini-Laser-Dot-Diode-Module-WL-Red-Copper-Head-Tube-/370924029372?pt=LH_DefaultDomain_0&hash=item565ccb85bc

and if so, why? (I still dont handle electronics 100%)

thanks!

The important part is "Operating Current: less than 40 mA". That means you should allow 640 mA for the 16 lasers. Add about 40 mA for the Arduino. That's too much for USB power (500 mA total) but should be doable with an external supply. The regulator can handle about 1000 mA so there should be plenty left over for lasers.

You should try to keep the supply voltage as close to 7V as you can. As you go higher than 7V the 5V regulator will have to dump more power and may overheat. The supply current (7V) and the regulated current (5V) will be the same. The difference in voltage comes from turning the excess power (2V at 700 mA = 1.4 Watts) into heat.

understood.

I was expecting to feed them via the usb, since I will have it anyway connected for sending midi to the computer. I think I am simply going to connect the lasers to 4AA batteries then.

It sound fairly easier than having an external supply...

640nm (nanometers, not miliAmps) that's the wave length of the LASER emmission, not the power consumed.
But you are still talking about way too much current draw for sixteen 5mW modules.

123Splat:
640nm (nanometers, not miliAmps) that’s the wave length of the LASER emmission, not the power consumed.
But you are still talking about way too much current draw for sixteen 5mW modules.

What part of:

johnwasser:
The important part is “Operating Current: less than 40 mA”. That means you should allow 640 mA for the 16 lasers.

did you not understand?

I was expecting to feed them via the usb, since I will have it anyway connected for sending midi to the computer. I think I am simply going to connect the lasers to 4AA batteries then..

How long do the batteries need to last?

I'd suggest rechargeable batteries, because I'd guess the batteries are only going to last a couple of hours powering all those lasers. And, if you are going to use this thing for anything "critical" (such as live performance) I suggest having a fully-charged back-up battery pack.

I am pretty sure I am going to sort it put with rechargable batteries. for a live performance is more than enough, and for an installation perhaps I use a dc adapter...

123Splat: what jhonwasser meant to say, is that in the specifications of the ebay product, you can clearly see that it says: "Operating Current: less than 40 mA". Its may look that he confused nm with mA, but this is not the case

respect each other und thanks

camilozk:
I am building a little laser harp, and I want to know if it is possible to connect 16 lasers in parallel with the 5v pin of the Arduino

What puzzled me for a start, is why or how you would want to use 16 lasers?

My understanding of a "laser harp" is that it uses a polygon mirror (as in a laser printer) or galvanometer mirror to scan successively into a fan of beams whose light when intercepted by the player, is detected by a photocell and the particular beam identified by its timing in the scan sequence, converted to a MIDI code to key the keyboard or synth.

I suppose you can however do it using 16 separate lasers, which you have to arrange to be keyed on in sequence one at at time, as small lasers are quite cheap in quantity. (Cheaper by the dozen!) You do have to consider how readily they can be (repeatedly) switched - the ones using just a current-limiting resistor - as these do - should be no problem.

The one I have here is using a "910" (91 ohm) resistor (you can see that on the illustration) and draws 25 mA, suggesting the diode is operating at 2.5V. It is quite bright, but I doubt it is actually 5 mW. Sixteen of these would therefore consume 400 mA, which is within the capabilities of a normal USB port, but again, I do not think you want them to be continuous. You probably could get away with driving them each from a port pin on the Arduino, though you will lose some voltage doing so.

ey!

I am using 16 lasers (from this very cheap ones) because it is a much simpler to accomplish project, that the laser harp you mention. Also, I am building it as a kids toy, so I am actually interested in emulating the strings of an harp with the laser beams.

but again, I do not think you want them to be continuous.

yes I do

You probably could get away with driving them each from a port pin on the Arduino, though you will lose some voltage doing so.

What do you mean by port pin? a DIGITAL I/O Pin? In the Mega2560 specs says that each I/O Pin delivers 40 mA, which is enough for each laser. Then, going back to the possibility of feeding this via usb, I´ve read that USB 2.0 standard allows 0.5 Amps, but USB 3.0 standard allows up to 5 Amps. That means that if I feed the arduino from a USB 3 I would have any problem?

Lastly, at arduinomega2560 page says that "DC Current for 3.3V Pin = 50 mA", but it doesnt say anything about the 5v Pins. where can I find this info?

thanks for discussing! :grin:

And how do you enable a single one of them from an arduino?

I’m not sure I quite understand this . But perhaps the OP wants to drive all the lasers fully. and detect interceptions by a hand with an array of sensors… connected to an arduinio

that should be possible. With a suitable separate 0.5a psu for the lasers

regards

Allan

johnwasser:
The important part is "Operating Current: less than 40 mA". That means you should allow 640 mA for the 16 lasers. Add about 40 mA for the Arduino. That's too much for USB power (500 mA total) but should be doable with an external supply. The regulator can handle about 1000 mA so there should be plenty left over for lasers.

You should try to keep the supply voltage as close to 7V as you can. As you go higher than 7V the 5V regulator will have to dump more power and may overheat. The supply current (7V) and the regulated current (5V) will be the same. The difference in voltage comes from turning the excess power (2V at 700 mA = 1.4 Watts) into heat.

And not exceed 200mA total draw through the Arduino.

Why lasers? WHY especially when kids are going to use it do you have to put THESE THINGS CAN BLIND PEOPLE lasers in there?

You won't see the beams without dust, smoke, or something in the air.

IR light and limited view IR detectors will work as well with no potential harm to any user.

Also... You don't have to have all the lights on at the same instant to work the harp. You can literally have each beam ON for under 10 microseconds while reading the matching detector. No human can move fast enough to begin to be missed by that, including black belt monks.

Total current == current of one. Battery life will be > 10x greater.