laser diode driver circuit with 8bit digital control

[Psi]

Hi, does anyone have a circuit diagram for a laser driver that can control the current into the diode from microcontroller digital outputs (8bit).

I need to build three drivers for my three diodes, 20x dvd, 6x bluray and the IR diode in a cheap 100mW green module. They will be controlled from an ATMega.

I'm using the old KES-400A sled to combine the 3 colors and make a very basic microcontroller driven RGV projector.

[mixedgas]

Hi, does anyone have a circuit diagram for a laser driver that can control the current into the diode from microcontroller digital outputs (8bit).

I need to build three drivers for my three diodes, 20x dvd, 6x bluray and the IR diode in a cheap 100mW green module. They will be controlled from an ATMega.

I'm using the old KES-400A sled to combine the 3 colors and make a very basic microcontroller driven RGV projector.

The usual way is a DAC chip to a standard driver. Do you want a parallel or serial input dac? It depends on how much room you have left for overhead in your software?

please note, all 3 dacs must update at the same time, or interesting effects result at high scan speeds. depending on your lasers, you may need to adjust the phase of the different colors in software, blue DPSS and Green DPSS lasers are slow.

You can adjust the frames before downloading them into your controller.

let me know if you want parallel or serial and we will try to help you pick one.

There is a way to do it with PWM as well, but it also requires simple external hardware as the mega cant change PWM that fast. This is unfiltered TTL PWM, adding a filter messes up the phasing of the colors.


Steve

[-bart-]

I think flexmod N2 drive combined with a R/2R resistor ladder network will do just fine.
(Asuming you have enough io)

[mixedgas]

I think flexmod N2 drive combined with a R/2R resistor ladder network will do just fine.
(Asuming you have enough io)

And how is he gonna double buffer it so it looks good?

Then he needs to analog buffer it and level shift it. Easier to grab a jelly bean dac chip needing no opamp etc.

If its worth doing, its worth doing right.

Steve

[drlava]

if the hardware/software PWM isn't fast enough for you,or you don't have the cycles to spare, then the only way to use a pair of external DAC at 2 channels each, or 3 single channel dacs, they are very cheap at 8-12 bits.

[Psi]

Thanks guys,

let me know if you want parallel or serial and we will try to help you pick one.
Steve

either/or, parallel would be easier

use a pair of external DAC at 2 channels each, or 3 single channel dacs, they are very cheap at 8-12 bits.

yeah, that sounds like it would work

[mixedgas]

Some candidates from goofing around at Digikey.

I think at 25$, we can ignore the 505, but I included it for completeness as I used to use it for laser shows with Mamba Lite.

digikey pn part number

296-2296-5-ND TLC7226IN

MAX505ACWG+-ND max505

AD5334-36,44 AD5334

AD7302BNZ-ND AD7302

5334 and max505 and 7302 are double buffered, which is good. 505 is the classic Norm's Laser Software parallel port dac, but has trippled in price at Digikey. Ad7302 is unique in that you can blank it in a set bit instruction, allowing a speed up of your code.

[Psi]

Thanks

I actually have a TLC7226IN somewhere, hadn't thought about using it but yeah, that's an idea.


I was more wondering if there were any current regulator IC's with built in digital control. ie, all on one IC.
Like some sort of advanced digital LM317 where you set the max current with resistors and then feed a digital signal in to select the current within that range.

[-bart-]

I think all our suggestions are prety worthles without you sharing some more details about your "very basic micro controller driven RGV projector". What graphics are you going to produce ? Have you figured out how to drive your xy signals ? What atmel mega are you planning to use ? What language will you be using ? Do you have experience with similar projects ?

Personally I surely would build some kind of proof of concept first.
Something with some 0832 dacs or similar with ttl blanking.
Then enhance it with funky buffering and 24 bit color.

Before reinventing the wheel I surely think that this architecture can simply be modified for your purposes.

[mccarrot]

I have some 0832 8 bit dacs left over from the LPT DAC decennium

if you are interested send me a pm