Thanks for all your advice.
I agree that it would be much better to do something properly at the start, so I am going to try to find a driver that would give me analogue modulation. I will still be receiving the X-Drive driver, but shall keep it for spares/testing later.
So it would be possible to run my 445nm laser diode with analogue intensity control just by using a driver that supports analogue modulation?
I had better explain my level of knowledge before detailing what I am trying to achieve. Then you can all see where I intend to go!
The photo below shows my experience with laser displays; its of a 4W Argon gas laser...
Attachment 41015Attachment 41016
... This was in 1985 when I worked for an entertainment laser company called Laser Systems of Cwmbran, Wales, here in the UK. The left (1st) photo shows the 4000mW Spectra-Physics Argon laser, which was split by a beam splitter into blue/green & green shown in right (2nd) photo.
This right photo also shows the beam-stop in the blue beam, which is actually an R.S solenoid with a black bit of plastic on the end. This is the only blanking the system had; slow & crude with no means of fast control. So you can see that my experience of blanking is a little simplified. This photo also shows one of the analogue galvanometer driver circuit boards.
The left photo finally shows the pair of General Scanning G120 Galvanometers providing X & Y axis scanning. Of course with no fast blanking, any scanned graphics or text had lines between their parts. We used to have to do text as handwriting as there was no means of blanking the laser between each character.
Control was by special hardware control panel based on a Z80 microprocessor. The software was written in-house in Z80 assembler. The laser was powered from 3 phase mains (415VAc @ 50 Hz) drawing something ridiculous like 45Amps per Phase. Both laser & PSU were water cooled, & if the water was too cold, then condensation could form within the PSU, & if it formed on the pass-banks, then it could cause an explosion.
The fragile argon laser alignment was often affected by the bass in the discos/night clubs, meaning that Service Engineers like me had to travel the globe adjusting the cavity mirrors to get the power back up!
These 4W scanning systems cost approx £25000 in 1985 money, which was a lot! Way beyond my means!
I moved into defence electronics at Westland Helicopters & the UK Ministy of Defence, but always wanted to run a laser Lightshow on the side, but could not afford such expensive systems.
Then I recently discovered DPSS lasers. It seemed that as these operate at 532nm, they are much brighter than argon (watt per watt). And even a 1000mW DPSS laser could appear as bright as a 3 or possibly 4 Watt argon. Trouble is even as recently as 2007 even a 100mW green solid state laser would cost me more than £1000.
However recently I was able to buy a secondhand 100mW green DPSS laser for £40! I didn't think I could afford galvanometer scanning, so I designed an arrangement of mirrors on steerable motors to give me flat scans/liquid ceilings & laser tunnels, & adjustable mirrors on solenoids to give straight beams onto target mirrors. But then someone on here sold be a pair of 15k galvos, complete with driver cards & XY block.
I found a dual channel DAC based on a laptop parallel port, & dusted off an old Pentium laptop that had a parallel port. I found something called Popelscan so thought I have everything I need.
I then discovered it was possible to build a 1000mW or even 2000mW 445nm laser module based on the M140 laser diodes from Casio projectors, which should be bright enough.
I was only going to build a single colour system using my 100mW green laser, but now I am thinking of using the 100mW green laser too, but it might not be bright enough. I think I will probably need 1000mW of green with up to 3 or 4 times that amount of Red & Blue though??
I have been rather wary of my DAC & the freeware Popelscan software though. Maybe it wont be fast enough. What I really need is an affordable DAC & control software. Maybe a more modern DAC, such as the products sold by Pangolin possibly?
Or is there a more affordable open source solution? I have heard about DACs running on computer sound cards for example; but surely these are only AC coupled? I have also read about some LINUX based DAC that is cheap & another DAC by some chap called Fred!
I have the draft ILDA Standard & some of their guidance notes including their pin allocation & design article concerning making the right connections. I will make my projector iaw the ILDA Standard, (athough as i'm working in military avionics & safety-critical electronics I am surprised that there are not more safety features built in, such as dual redundancy of critical signal paths & power supplies, & fast enough scan fail detection/shutdown. It seems if you lose even one of the scanner PSUs, then that galvo goes stationary at dead centre; a double PSU failure could result in a totally static & dangerous unspread beam! And I have always been mis-trusting of D type connectors; maybe I shall use an Amphenol multipin aircraft connector in mine!!)
Not sure about the scan failure detection & how to quickly shutdown the laser. My beam power & safety calculations show that max permissible exposure level could be exceeded in as short a time as 20 micro-seconds; even detecting such a failure in that time would be difficult, let alone also shutting the laser down within that time too. It might be possible using a fast photodiode, coupled with fast TTL or faster ECL logic maybe. ( I don't want to get too tied-up with this though. Even with the way things were done back in 1985 & since has not resulted in many (if any) laser injuries here in the UK, where we permit audience scanning. The few injuries I have heard about over the years are almost certainly due to gross negligence, such as using huge pulsed lasers for example).
So any advice on any of this would be most welcome, especially about analogue modulation of the 445nm blue laser combo I am about to buy from DTRs laser shop, & also any suggestions on the DAC/control software side of things too.
Many thanks,
Simon B.
(P.s sorry if I have rambled on too much, & also if I've mixed mW & W, which is a bad habit of mine!)