Cheap analog driver??

[Elektrotechniker]

Thanks for your input guys. I decided to go for higher quality ones. Prolly gonna order from Dave soon

[flecom]

Well, useless outside of anything but statics.... Beamtables or lumias.

your point? just something else to play with

if I really needed drivers I would just make some more

[absolom7691]

your point?

Just stating that they're not completely useless. Just mostly useless!

"There's a big difference between mostly dead and all dead!"

[flecom]

if it is PWM a low pass filter/RC circuit could be a possible solution

[WolfMax]

Well I just got one of THESE to see if it would work in my modded KAM 170RGY (modded to ILDA RGB with a Chinese 400mW RGB brick). Answer, well sort of.

First impression of the unit was one of pleasant surprise. It took so long to get here (UK), I'd forgotten it came attached to an aluminium mounting bracket plate. So when I saw it I was taken aback as I wasn't expecting it.

After hooking it up and starting with 0v as I ramped up all looked well until I got to max modulation voltage (from an FB3) where upon the Green DPSS blew. Ok I thought, I have a spare. Fitted it, and lowered the max voltage level in QS settings to 50 (minimum level) and started again. Working the max voltage up until the green upper brightness didn't change, I got to 68% of max voltage. With all 3 lasers working I started to get some encouraging results.

The lasers did indeed fade up and down if a little logarithmic (although oddly, linear setting worked best). However in actual operation the output was obviously pulsed as it was flickering like mad and colours requiring variable brightness (like orange) didn't seem to work well (strange given the brightness was variable). Also, the pure diodes (Red and Blue) achieved full brightness way before the DPSS Green so some playing around with the QS settings coupled with the pots on the board (seem to be bias voltage) was needed to get things reasonably synced. Played a few cues (graphics and abstracts) and the results were better than TTL but not what I was hoping for.

So as my KAM 170RGY(RGB) is paired with a KAM 300RGB (TTL), I switched back to TTL. HUGE MISTAKE!!! TTL as I'm sure you all know is 0v or 5v. No settings for max voltage levels. So the full 5v modulation signals went to the driver and blew the Green DPSS laser again!

Without some kind of gain control, these drivers are not a good idea if you don't know what the output is and you don't know what the lasers can handle. A data sheet for these things is a must (just don't ask me where to get one)!

So next purchase now is another cheap China 400mW RGB brick and stick with TTL (no space in the case for anything else).

[Draco]

ok, i am a little lost of this, what is beam suppression? To me that just sounds like it's being held in an off state? why do they call it that?

[WolfMax]

Beam suppression is the ability of a driver circuit to completely turn off the laser at 0v modulation but still be able to ramp it up to full brightness as the modulation voltage rises.

Taking the Flexmod P3 as an example, the diodes can be glowing like an LED (all be it at very low light level) even with the bias voltage pot turned all the way down due to the driver putting a constant low voltage with negligible current on the output when the modulation input is 0v. In this case, the bias setting is not to switch the diode off but to find the point at which it stops being an LED and starts being a laser. The beam suppression version does cut the output voltage and current to 0 at the point set by the bias pot but at the expense of the interlock circuit. With bias set correctly, the output voltage goes from 0v / 0A to whatever voltage and current the laser diode requires for it to be at its lowest output as a laser, as soon as the input voltage rises above 0v. Then on up to the current output set by the gain pot for full 5v modulation (same as the non suppressed version).

Hope that explains it for you. As always guys, if anything I've said above is wrong please correct me, but it is how I understand it to work.