Use 5mW red lasers. Adjust the power of the laser with lens 3mW. My acquaintance bought a couple of dozen laser pointers. In some of them, the power reached 7 mW. At us on a city bazaar cost of 5 mW red lasers $ 180 for 100 pieces (1 packing).

 

Your statement "they should be visible on a wall if it's 15-20 feet away" in not very precise. If this is a white wall in a dark room then an LED and lens will probably work. If it is a dark coloured wall on a sunny day then the power required will be harmfull.

Les.

 

So would these 5 MW (err... I mean mW) laser diodes be safe enough?
https://www.amazon.com/HiLetgo-650n...54277&sr=8-1-spons&keywords=laser+diode&psc=1

You're asking for assurances that none of us here can give you, nor should we give you. What is safe "enough"? Safe enough for whom, for what application and under what circumstances? "Safe enough" depends not just on the parts themselves but also on you, and how you're going to use them.

One thing to consider with these laser diode assemblies is there's nothing that says you have to run them at 5 volts; you can vary the voltage to vary their light output.

The ones I have appear identical to the ones you linked to and the ones I cited in post #2, and they consist of the laser diode itself in series with a 91 Ω resistor for current limiting. At 5 volts, they draw about 30 mA and produce a nice, bright spot of light just like a laser pointer, and you definitely don't want to look directly into the beam.

But by reducing the voltage and/or inserting additional resistance in series with the part you can reduce its light output, all the way down to the threshold of visibility if you want. The lower limit on voltage seems to be about 1.6 volts, at which the part is drawing about 100 μA; below that, I can't detect any light at all. With a 10 kΩ resistor in series, the part draws about 300 μA at 5 volts and produces a spot on the wall which is barely visible in a blacked-out room after giving my eyes a few minutes to acclimate.

 

I'm just surprised Harry is willing to stand in front of a 16-year-old cashier wielding a had-held scanner at Target.

I was a victim of an unfortunate Target scanner accident. Took them to court and end up with a parrot.

 

Also, if I run .2 amps at 5V though a laser, is it equivalent to a 1W laser?

 

Also, if I run .2 amps at 5V though a laser, is it equivalent to a 1W laser?

No, a laser diode is like any other diode. The diode has a forward voltage that you cannot control. Feed it current (about 20mA for a 1mW (emitted power)). So you need a current driver.

 

Where can I get a constant current 20 mA driver for a decent price? I am not knowledgeable enough when it comes to constant current power supplies to make my own.

 

Sink or source?

All it takes is a transistor, two resistors, and a voltage reference (which can be a diode, zener, or LED).

 

Here...

Just used on another laserdiode thread yesterday.