Ideal sound card for multichannel scan and modulations.

[James Lehman]

Maybe you could do it sort of like the way I suggested the optional balanced drivers and have an optional power supply section so that if you want to drive it from an external power supply you could just leave the power supply components off and hook into to it external. Or, you could add the components and get power from the USB power. That gives you the best of both worlds so you can either use it externally or internally but without wasting money on components. It just takes a little clever board design.

I can dig it. Come on!

[drlava]

Having balanced outputs within the power budget is already doable within the 150mA left of the 500mA requested by the CM106, using the chips I found. To cope with weak ports from laptops, we just add an external 5V input for a wall wart, that can be used if needed. I'm not a big fan of having 'optional' components because many components come only in surface mount now, and to most people soldering them on is not an option.

[James Lehman]

After some searching I have found some parts that should meet our requirements and stay within the 500mA typical USB power allotment.
Switching DC/DC converter operating at 85% efficiency which produces +/- 6V Rails up to 120mA each.
Quad op-amp 7.5V/us Can drive capacitive loads 2nf stably, 50mV from rails drive at +/-10mA with a 1.3us settling time, when used with a 85 ohm series protection drive resistor, can provide +/-5.2V drive into 600 ohm load. Will probably need a small compensation cap for driving long lines.

"Quad op-amp" so you need two of these, right?
Do you just use 3 and 3?
Or would you make all 8 channels?

"small compensation cap"
Huh?

Another question is about simplicity. If we are going to integrate the USB device with this amp, do we need any pots to trim it in? Or can we just factory fix it?

James.

[drlava]

"Quad op-amp" so you need two of these, right?
Do you just use 3 and 3?
Or would you make all 8 channels?

"small compensation cap"
Huh?

Another question is about simplicity. If we are going to integrate the USB device with this amp, do we need any pots to trim it in? Or can we just factory fix it?

James.

Actually for 6 balanced outputs you'd need 3 quad chips. The compensation cap would be along these lines:
http://www.ecircuitcenter.com/Circui...d/op_cload.htm
it would dhave to be chosen to maximise slew rate without overshoot for a max cable length we decide.
Yes, the gain and probably offset could be fixed.

[James Lehman]

I think it would be good to have a place on the board to put trims (or fixed) on at least the X and Y.

How standard do you think 0 to +5VDC is for real laser mod devices?
Is there ever a good reason to want more volts?

James.

PS. YEAAAAAAAAAAAAAAHHHH! I just got one increadibly boring job that's been bugging me for weeks done!

[drlava]

A question for mixedgas or one with much experience.. balanced outputs for x-y make sense, galvos have them. But for modulation, I have never seen a balanced input. Would it be reasonable to only have balanced outputs for the galvos?

[carmangary]

Yea. Just balanced outputs for XY. 0-5v for modulation.

[mixedgas]

A question for mixedgas or one with much experience.. balanced outputs for x-y make sense, galvos have them. But for modulation, I have never seen a balanced input. Would it be reasonable to only have balanced outputs for the galvos?

Ok, I've seen balenced color inputs on 1. pcaoms (mine) 2. high end hungerian and german RGB DPSS projectors, 3 ADAT and Hard drive show recorders. PCAOm can be wired for single ended. So can the ADAT with care. Your software is designed to eliminate the show recorder, so lets assume nobody using your software is gonna run 500 feet in a pro situation, design the drivers for balenced x,y, and single ended RGBV, @ 50 feet. Make the RGB 0-5.5 or 0-6 to avoid some suprises in how much it takes for some lasers to go full on.

yeah, and bring out that extra color channel if you can, can we do audio at the same time? or AT least CD sync? (ie have the CD in the cdrom drive) The cd rom outputs a time code of sorts.

I got the USB module in the mail today, that was fast, right from pensylvannia.

Steve

[drlava]

Thanks for the info, sounds good to me. This is taking shape in my mind, and looking good! I also thought up some improvements to the driver last night that should be nice when they are implemented.

From PA, eh? we got it from the same seller

[mixedgas]

There is a "green" or "enviromentalist inspired" variable voltage universal wall wart standard with a standardized connector etc on the way, it was mentioned in EDN magazine but I simmed teh first three paragraphs and then ignored it as I will never be a overseas electronics designer.

I know the USB standard says 500 mA, but I've seen quite a few implementations that were loosers, assume you have 200 or so.

Steve