Use an isolating transformer on audio signal with resistive dividers on both input and output and rectification on output. Make sure rectified output doesn't go over PIC supply voltage even momentarily at peaks. Resulting speed will follow audio amplitude. If that's what you want to do it could be accomplished with simpler cirquits. You don't really need a PIC

i want to keep the pic, the laser show would have two different settings, one where the music controllers the motors speeds, and another where the microcontroller has would be programmed to create random motor speeds.

"Use an isolating transformer on audio signal with resistive dividers on both input and output" sorry i don't understand that, a bit too technical

this is what the unmodified design does, i want to take out the potentiometers and replace it with the audio signal

Since this is a LASER system that uses spinning motors/mirrors to modulate beam position, you will be disappointed with direct audio modulation. The rotational inertia of the motor+mirror will not respond well to the relatively fast audio modulation. You will get much better results using audio speaker voice coils to move or pivot small mirrors in the beam path. This will be much more responsive to audio modulation.

If you must modulate the motor speed, there are MANY different ways to process or condition the audio signal before it is applied.

I've made several spinning mirror LASER displays which could reproduce many of the "Spirograph" patterns some may remember. I used only 2 spinning mirrors with manual or slowly changing speeds. Adding one audio modulated voice coil mirror provided for some really unique geometries. No microprocessor necessary, but one could be used to store specific geometric patterns for a preprogrammed display sequence similar to your link.

This is a fun but somewhat advanced electro-mechanical-optical "home" project. For simplicity, I would try building one without the micro first. Wish you good luck with it.

i know not to use the direct audio signal, i would use a bridge rectifier to do that.

i have built the displays with the mirror on the speaker itself, they don't interest me and i find them way too simple.

i have also built a system where the amp from a set of computer speakers controls the motor speeds, these motors where also synced to music, this system worked great. but i want to advance my collection.

If you want to control the speed of the motors use sensitive input Triacs which your Pic can control with PWM. Some picks have a PWM controller built in.

For the Maveric's advice, he would like you to return his favor by helping him with a small problem concerning a cat...

Triacs can only be used on AC. Aren't you a mile or so off topic

so can anyone help? i really want to keep the functions of the rest of the circuit

What term you don't understant?
a) Isolation transformers: (you don't want laser and pic power supply to mess with yor audio source output?)
b)Voltage resistive dividers (you do want to have some control on the effect and adjust the impedance your source sees.? )The potensiometer used in the original design is a resistive divider with input PIC's supply voltage eg 5V and output 0V-5V depending on it's position
c)Rectification on output of transformer (pretty obvious) except that no big filtering capacitor needed, it would slow the sytem's responce (Don't tell me you don't understand what a filtering capacitor after rectification is)
Now what part of your signal (e.g. left,right,bass,mid,treble) you want to feed at each PIC A/D input is up to you, experiment on that.My guess is it won't be too impressive. Sorry but can't describe a cirquit without basic technical terms

a)no i don't want the signal to provide power to the pic circuit.

b) probably not understanding this correctly, but i don't need any control. aside from volume of the audio source.

c) i understand that. flats out the signal and chops off highs and lows, correct?

i was planing on just taking right audio and replacing the "a" potentiometer. then replacing two remaining pots with the left side audio

a)OK the easiest way to do it is by use of a transformer. Cheap example is a ground loop isolator tranformer (usally used in car stereos) connected at preamp level or amp output after attenuation.(Resistive dividing for attenuation is fine)
b)You'll propubly have to experiment with filt. capacitor value also to adjust responce speed to your needs.
c)More or less since PIC wouldn't respond that fast anyway
Remember PIC can't handle voltage at A/D inputs over supply voltage or under 0 and can be instantly damaged and that there must always be some resistance from capacitor to ground because A/D input is a high impedance load so capacitor voltage will stay high longer than you need (that's why I suggested dividers here too)
Note us on any interesting results
Cheers

A) where can i find these? have looked for "ground loop isolator tranformer" on mouser, not results.

and searched "isolator tranformer" but there are way to many products to find what i need since i know vertualy nothing about it.

B) value suggestions?

C)dividers?

Good readable schematic! Makes a pleasant change on CR4.

A question, are these really motors (ones that turn!), if yes, how will a motor react to music, very badly I feel. Like nothing like the music's beat or sound.....I am also of the opinion that most motors of this type, will not live long either with a music voltage......

Loudspeaker "motors" or something similar would be a different thing of course. Can you give more detail on the motor type and the program that will be running on the PIC please?

heres a link to the instructable from which the schematic came from

Use transistors and resistor in place of the pots!

Use a cap and resistor from the audio to the base of the transistors.

As for values I would have to study it quite a bit before I could say, maybe this will give others an idea and they can suggest values.

You just need to be sure you are not giving it to much current and it should work just fine. For that mater I am wondering what response you would get if you tied it directly to q1, q2 and q3 getting rid of the pic.

thank you very much! this is what i needed to know!

how do you suggest i go about finding the values myself?

I can post as a guest and tell you any crap that you want to hear and you believe me/us....

If I post as myself, you ignore my posts which are accurate and meant to help....I was/am in electronics for many years....

You have absolutely no idea what you need to do, neither do I/we as ANY guest post......be warned!

Sorry for this post and its message, but you need your brains testing if you believe that what you are trying to do in the way you want to do it will ever work......

I am gone, this is my last post in this pitiful blog......try not to kill yourself if you need to work with the mains....

Hey you're not the only one feeling like this. But hey we're here to give some info on other people asking for it, we don't really wait for any rewarding are we? Anyone can get GA ratings by sucking on others. Thank God our income doesn't depend on popularity here. And this can't be done differently since any idiot can rate eitherway. Have done same experiment as yours with same results so don't get too upset about it. What you have posted stays here for good. Doesn't really matter how it's rated or how seriously it's taken.

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Hi SimpleMind!!

Ouch!!!

I looked at the website (instructibles, a really great web site, I follow it often) and the original usage of this was just to control the speed of 3 x 12 volt fans, each with a mirror stuck to it, slightly skewed.

Why are you thinking that putting a music input instead of the potentiometer will bring anything worth having???

I feel that enough posters here have already told you that in a reasonable manner, the motors simply cannot react quickly enough.

To do this with motors, you need (expensive) servos with a (n expensive) feedback system, or at the cheapest level, 3 stepper motors and therefore 3 stepper motor drivers using both step and direction for each motor and a bundle of well written software to take a music input and turn it into step & direction controls, probably best over a parallel printer port and an old laptop that still understands DOS as a basic way to get going.

The ONLY relatively easy way that I know of, that you can use music input to move a laser beam is, as I and at least one other person have already mentioned, is to use Loudspeaker systems, that were designed to reproduce music in the first place, and stick a mirror on the cone. Angle the mirrors so that in and out movement also results in directional movement of the Laser Beam.

These can be driven using an AC output (same as any audio amp). You only need to drive each (of say three) loudspeakers with different frequency areas - Bass, middle tones and treble for example......you can buy finished units to do just that (since many years!).

I have the feeling though, while writing this, that two speakers, say for Bass and middle tones will be enough, that will give you a horizontal and a vertical component.....I cannot see why you would need a third input and speaker.....that will also make the speaker positioning much, much simpler too.

You can even use the loudspeakers to make the music "audible" for the audience, though they do need to be angled towards each other to affect the laser beam correctly......as previously mentioned.

Experiment using old speakers, a cheap way to go.

You can still use the PIC for its original job, but now it will just push and pull the cones under your control with the pots.

Make sure that you can measure the cone coil temperature as misuse will burn the cone coil out eventually.......or watch for the release of smoke signals.....

The suggestions I have made may not be the best in the world, but they have a far better chance of producing a good light show than the direction you seem to want to take, especially as it would appear that your electronic knowledge is very limited.....

Remember, if you want to be the leader in a new system, you first need to understand the basics much better than you appear to at this time......

Understand your limitations and use them to your best advantage.....we all have them, the same as you do.

I am willing to give you as much help as my personal limitations allow, provided you aim in a direction that I can help in. If you persist in cutting a new way through the electronic jungle, then you will require other people with better knowledge than I possess, but that is still your prerogative if you wish it!!

CR4 members tend not to want to give away fantastic new ideas to people like yourself, they appear to want to keep them to themselves, a normal human reaction I feel.....but who knows?

Best wishes.

Hi Andy, top laser projectors use galvano motors, unfortunately not cheap, still trying to get my hands on some used motors. I'm currently working on a 2 axis stepper motor laser projector and enjoying every moment of it.

Regards

Check eBay. I've seen galvos there for low prices.

Thanks for the lead, will do

yeah it is a great site. have done quiet a few projects from there.

well its not a direct music signal, it modified. I have made a music response laser before (previously described).

I'm very aware that a direct audio signal would not be very effective.

also as i stated earlier i dislike the mirror mounted on a speaker coil, its too simple.

Couldn't what you're trying to do be accomplished by a simple Voltage Controlled Amplifier (VCA) or Voltage Controlled Filter (VCF) circuit???

i have no idea, could it?

Look up VCA and VCF and see what you think.

For reliable results and complyment to FCSCF part A,C and D,C rules you could also use the well known VCE (Voltage controlled electrocution) the only difficulty is calibration that takes at least 2 persons able to apply CPR techniques to accomplish safely.