White laser *now with host* :)

How about adding a microcontroller with 3 logic level power mosfets, one for each color, and add PWM control for them, to achieve much more different colors? I actually don't know how drivers would handle PWM... but i think there should be a way to achieve it. I have a DIY laser with a rkcstr driver which i can use for testing.
I have to check if there's any small PIC model with 3 hardware PWM modules and i could program it for you. It's not a difficult task. I could also make a 7 colors only switch using a tiny SOT-23 PIC , 3 power mosfets and 3 push switches in a small area.
Imagine making a laser spyrograph with slow fading color changes...

Click to expand...

That certainly would be cool, there have been others elsewhere on the web who have come to the same conclusion, as I said to them electronics/programing is very much my short suit.

The only thing that has been pointed out is that with moving images you would see the beams as a series of dots, it depends a lot on the frequency.

Regards rog8811

erdabyz said:

How about adding a microcontroller with 3 logic level power mosfets, one for each color, and add PWM control for them, to achieve much more different colors? I actually don't know how drivers would handle PWM... but i think there should be a way to achieve it. I have a DIY laser with a rkcstr driver which i can use for testing.
I have to check if there's any small PIC model with 3 hardware PWM modules and i could program it for you. It's not a difficult task. I could also make a 7 colors only switch using a tiny SOT-23 PIC , 3 power mosfets and 3 push switches in a small area.
Imagine making a laser spyrograph with slow fading color changes...

Click to expand...

I'm interested in this. But I'm no good at it.

http://www.laserpointerforums.com/forums/YaBB.pl?num=1214844611/0#0

I had forgotten all about that thread erdabyz is discussing something much more grand than our attempt on that one....

It would certainly be interesting to see something like that working.

Regards rog8811

rog8811 said:

I had forgotten all about that thread erdabyz is discussing something much more grand than our attempt on that one....

It would certainly be interesting to see something like that working.

Regards rog8811

Click to expand...

ç

frequency may be low, not because the pic can't give high frequencies (up to aprox 32khz), but because there's an output capacitor in the driver that should be at last a bit discharged to notice the on/off effect. Linear regulator drivers may work better than switching ones (lavdrive) for this task.

The lowest PWM frequency for a PIC running at 4mhz is 145hz, 489 for 8mhz. I've found a pic with only 14 leads and 4 channel hardware PWM. Must read the datasheet to ensure it'll be suitable, and then just prgram it. It's an easy program

just prgram it. It's an easy program

Click to expand...

Thats it...I am now totaly out of my depth

I await developments.....

Regards rog8811

Yeah, it's actually not a difficult one. For now i'll probably have to use a PIC16F877, which is kind of huge (40 leads, 44 in TQFP version) because microchip samples program is not available ATM for europe (greetz from spain ). If i can get it working, i'll do it with a smaller PIC which needs less extra parts and SMT mosfets. Mosfets have a very low internal resistance, using them with PWM doesn't require any heatsink. they are slower than bjt's, but fast enough for this.

Let's see what happens. I've read your thread with the led fader driver, and i've seen that this will probably have some problems. Let's see what happens at lower frequencies.
hope it works!!! i'll do it probably this weekend.

I would just toss in an arduino nano (overkill) but I'm wondering if pwm will show really visible blinking no matter what you do. If you are shining it a hundred meters or so the end of the beam could be moving extremely fast.

I don't know explicit equations or anything, but the 2nd motor's rpm (the variable speed one, the slower one [assuming no resistor between power and first motor]) would be the deciding factor for how fast the the pulses would need to be. I don't know how PWM works, so I can't really help figure out how fast the pulses would need to go. Maybe if we used a lm317 to regulate voltage, and another to regulate current, we could eliminate the output cap, and maybe then we could put the transistor? between the driver and the LD.

rog8811 said:

I had forgotten all about that thread erdabyz is discussing something much more grand than our attempt on that one....

It would certainly be interesting to see something like that working.

Regards rog8811

Click to expand...

wel thats no problem i can provide anyone with a 3 channel pwm controller that can handle 500 mA per channel.
Should be enouch for most laser modules / pointers
Can even controll the colors using a computer or presets.

I must see if there's a way to directly control the diode, not the driver.
I know that, as is, the diode would get burned by the capacitor discharge every time we turn it on, and the driver isn't designed to work without load. So, i think a possible solution would be a resistor in paralel with the diode, that way, then the diode is turnd off, the resistor acts as a load (because it's always connected) to discharge avoid frying the diode when it turns on. Must check this with a cheap 5mw diode from an aixiz module to see what happens. Also, when the diode is turned on, the resistor won't affect very much because the diode has less resistance.

If this works, we could achieve frequencies up to 32khz. I think that that way dots would be unnoticeable. (32000 cycles per second....)

PWM means Pulse Width Modulation. It is a train of pulses at a determined frequency, with a dutycycle which is the time on a period that the output is at low or high level (depending on pwm config). that's basically the concept of it. Means turning something on an off a lot of times per second, varying the amount of time it's turned on and off every cycle.

PWM with not so high frequency would make an awesome timetunnel or spirograph together with RGB.

How about applying the pwm after the current regulation but before the capacitors?

If it was done before the capacitors, the caps would filter it, and it would thus be ineffective. What is the reason for the cap, is it just for voltage spikes? If it is, you could make a voltage regulation circuit as well as a current regulation circuit (use a pair of lm317s or a lm317 and a 7809). Then you could directly control the diode without worrying about the cap frying it (because it wouldn't be there).

edit: After browsing around for a while, I found jayrob's green laser build ( http://www.laserpointerforums.com/forums/YaBB.pl?num=1227233016 ). In that he uses the case of the module as the positive contact point to the battery. Since this is the case, it seems that using a common terminal for all 3 won't fry any diodes, but I'll have to play around a little once I get some more parts. I am now thinking that the green and red won't be independent (if red is on, green is on, and vice versa) because of the common terminal.

why do you need a dead green module exactly, i get the red and blu-ray part.

can i just get a working dx 5mW to use instead of the sandstone module.

laserwanabe said:

why do you need a dead green module exactly, i get the red and blu-ray part.

can i just get a working dx 5mW to use instead of the sandstone module.

Click to expand...

You could, but it'd be more difficult. The sandstone module has a threaded front barrel. The back of the DX module where the IR diode goes is the same size and has the same threading on it. You use that part from the DX module (thus ruining it if it isn't dead) to screw on to the front of the sandstone module, then put the brass adapter in the part from the DX module to connect it to the ps3 sled. Here's a basic drawing of it:
____________
____________________ _____ |
Sandstone module DX ---- ps3 sled
____________________ _____----
|____________
Brass adapter ^

The DX is the adapter from the DX. The ps3 sled isnt that shape, but hopefully this will help you get the gist of how it goes together now.

Good text drawing adcurtin that is exactly right I will not even bother attaching my picture.

@laserwanabe, I have been doing this long enough to have a graveyard of parts from experiments that went wrong : I had a couple of standstone greens and just found that the DX part screwed in so I used it.
When modding nothing is set in stone, you just need to find something that will hold the module in place rigidly, had I not had the DX module I would have found something else to use.

Regards rog8811