Homebrew PCBs

On 10. 12. 2014 12:05, Cristian crissstian@... [Homebrew_PCBs] wrote:
>> With 100mW laser I
>> need to switch it on and off at 1MHz rate.
> BJT is slow. Use  fets.
Well I dissagre. BJT when used right can be pretty fast. At least 1MHz 
should be no problem.
> Also, "pre-heat" the laser diode with some 10% current with a resistor.
That's the question. I didn't find any data how fast is laser response 
to current. Is in real beter to have "preheated" laser or is same? With 
new driver I wan't to have ability to set current too.

>
>
> Why that speed? I guess you expose point by point.
Yes. I do raster imaging and one dot lasting 1.5 us. (calculated for new 
system right now is 15us)
I try with vector imaging but came out just to slow. And when trace is 
bent at 90 degre the laser motion need decelerate and then accelerate in 
other direction. And thus point in corner get more laser energy and burn 
bigger spot. It works but result is not so good as raster imaging. I 
tried both.

>
> I suggest you to convert the normal Gerber output to HPGL (that means
> lines instead of points)
> and to use it as in a plotter. No speed problem here.
Why to complicate? Gerber is already vector format. Just need to make 
some subs for flash items and to manage line thickness correctly. Of 
course HPGL is even better for that and most PCB programs can do output 
to HPGL directly. For now I export image in bitmap image at resolution 
at least 800DPI.
>
> I've bought such a program. If you think to go that way, you can mail
> me your Gerber and I'll send you
> back, for free, the converted HPGL.
Thanks for offer but I don't need that (at least not now)

> By your name you are from ex-Jugoslavia. I'm Rumanian.
> Cristian
The answer is yes.. I'm from Slovenia.
Slavko.