The other day I put together a very simple music driven led box, and it occurred to me that the same concept might just work with a laser. Basically it involves a transistor (i used a TIP31) and an audio cable. I originally found the diagram for this setup on instructables, but keep in mind it was designed with LEDs in mind. I haven't been able to find anything on lasers with transistors.

Now as much as I'd like to get a real laser show setup, I'm not wealthy enough, and even if I was my wife would probably gut me in my sleep for buying any toy that expensive... So think of this as a cheapskates alternative to getting a slightly more interesting light show.

Here is a quick diagram of the setup:



What this basically does, is cause the laser to sort of strobe to the beat of the music.

Now I had several cheapie red modules lying around, so I tested this out and it works without a problem. Toss a few mirrors and a refraction grating into the mix and it gets really interesting. I was able to run two modules, one for the left audio channel, and one for the left, which gives it a much thicker effect. I'd imagine a lumia would really be great for this as well, but I haven't played with that yet.

I would also think that more lasers, more colors etc, would be really nice.

Anyhow I'm no electronics expert, and I only have a basic idea of this stuff. So bare with as I ask what may be a stupid question...

As I said I tested this with red modules, but with greens I had absolutely no luck. I tried two green modules, and nothing... I am guessing the voltage needs to be increased? I haven't had the time to sit down and see if there is a ridiculous voltage drop in the transistor. But it would make sense, I think..? Even with the volume at the max, the lasers aren't as bright as they are without the transistor.

The second issue is that the volume literally has to be turned up to 11 for this to work. I am assuming that an audio amp to boost the audio signal would fix this, but as I said, Im just a novice at this stuff and I dont know for sure.

Any ideas or suggestions?

I'd love to see a video of this in action; it looks great!

+1

-Trevor

Ya id like to see this on action

If I can figure out how to either get the green to respond, or how to get more power safely into the reds then I will definitely get some video. As it is now, its just too dim.

You have made the most basic DR_lava fexMod driver...

really? thats interesting, maybe i can solve the power issues by looking over the flexmod specs?

What you've drawn up isn't really a basic FlexMod, a FlexMod can be thought of as an adjustable voltage to current converter, that rendering is a current amplifier. A FlexMod would work to do what you want, but to roll your own, try using a darlington transistor (TIP131 or similar) and a higher battery voltage with current limiting resistor so that the laser isn't blown out.

thanks for the advice, i'll give that a try. I was able to get the greens to run off this, but they were incredibly dim. I'll try the higher transistor and boost the incoming voltage a bit.

This is what i was looking for some time now, let me know on the progress.

The green laser requires a lower voltage than the red lasers, BUT, requires a lot more current!

Those red laser modules you have may only draw 20mA or so, a green laser will (probably) need atleast 100mA before it'll noticeably lase.

Are there drivers on these lasers, or just wires right to the diode?

The green has a normal o-like driver, and the reds drivers appear to be very simple little things.

The operating current on the green is <350mA, which is a bit higher than the reds which are at 25 and 40mA.

I did my best to measure the current, and it was hanging out around 15mA. I had a few random higher spec transistors lying around and was able to get it up to 30 or so mA, but this was the current when pulling the audio from a pc at full volume. And I didn't want this project to rely on a pc with the volume maxed out.

I decided to go ahead and try pulling the audio from a more powerful music source. I had an audio board from one of those z-rocker chairs lying around, so I went with that.

Taking the amped audio through the transistors didn't have much, if any added current.

I was a bit frustrated, and in a whim of desperation I measured the voltage and current that was coming from the actual speaker and sub output wires. The speaker wires were spitting out 3-5v and as much as 50mA. And the sub wires were doing about double that. Of course, this was, once again at full volume. In any case the speaker wires had more than enough to run the reds at full power, and the green was actually working, though it was very dim.

Obviously this worked because the audio board was basically doing what my simple circuit was trying to do, but at a higher level.

So the next step was to pull a small board from one of those neon tubes that reacts to music. I figured that this would be putting out a much thicker current to work with. I've replaced its silly little on-board microphone with a stereo input jack. Of course I then realized that this thing was only working on mono, so I'm currently trying to figure out how to split up the signal so that I can send the audio on to another board, and to a speaker output in stereo. So far I have managed to send the audio out, but as it turns out, any speakers that are hooked up to the stereo output also act as microphones, which really throws off the pulsing.

At this point I've only been testing leds on the output wires. I'll work on tweaking the output current and voltage for lasers (lm317s + resistors?) once I've figured out the darned input/output mess. Im guessing that the current is very high, since it was designed to send its signal to a neon tube.

I might also try a few different audio boards, maybe I've got one with an input/output already built in that I can put in front of the setup. But so far, this neon board is giving me more voltage and current to work with. Not to mention it is already designed to modulate an audio signal into pulses effectively.

I'm also still digging through piles of transistors to find one that works better than the tip31.

Anyhow thats where I'm at on this. If anything its definitely been an interesting way to learn basic electronics.

This is what i was looking for some time now, thank for so many knowledge!

For the greens, after the transistor I think a op amp would increase the current but still let the voltage modulate to let the laser pulse. I would have to study for a while but I think something like this would work. Also you could amplify the signal enough so you don't have to turn it to 11.

11 is one higher than 10, these are 1 louder

Just use darlington transistors to increase the gain on the setup. it worked for me
Its all about getting the transistor fully saturated at a voltage below the peak amplitude of the sound output.

You could probably use a 555 setup as a shmidt trigger with the output going to the transistor as an adjustable way of setting how loud/strong the sound signal has to be before the laser is on.

Glad to see somone experimenting with sound and lasers like me

I've done this same thing with my DX green laser before. I had to use a 9v battery as the input voltage to get enough juice through the transistor to the laser driver. It ends up basically increasing the laser's sensitivity to the signal and overall intensity. I've also tried having the audio signal go through a separate amplifier and using its headphone output to amplify the audio just for the laser. This way, the speakers don't have to be blaring to get the laser to react.

Another thing I've tried is to simply use the AC current from the speaker wires themselves as a DC source by using a bridge rectifier. This works very well except that it's pretty easy to toast a diode by putting the volume too high, there's a lot more room for error with the first method.

Now shine that laser onto an LED of the same color that is connected to an amplifier/speaker and you will be able to hear the music transmitted through the laser beam. It might sound like crap but it will work.

Sorry if this is necroposting--thanks to all the above for the posts and to the OP for the thread-(+rep given)--and updates-

A simple set-up that just plugs into the headphone jack would be nice---K.I.S.S.