controlling voltage alternation lasers

[dylangeorge]

Hi all,

I'm trying to control the alternation output of two lasers. A working example - Laser 1 - on for 45us off for 5us then Laser 2 - on for 45us and off for 5us then Laser 1 back on for same times in as loop until I press stop.

The lasers require a modulation voltage of 5V, I have done this with a NI Daqmx board + Labview before but would like to find a cheaper way to allow more access to people who can't afford a daq board.

Basically I need some guidance on how to do this codewise, which ardunio/microcontroller to buy that supports the alternation frequency (1000kHz) and is cheap.

Thanks,

[Semtex9]

Seems a bit much but here, someone tried it

https://forum.arduino.cc/index.php?topic=482817.0

[TheMemberFormerlyKnownAsAWOL]

Basically I need some guidance on how to do this codewise, which ardunio/microcontroller to buy that supports the alternation frequency (1000kHz) and is cheap.

Have we got our powers of ten mixed up?

[jremington]

It would take about ten lines of code to do that with a $2 eBay Arduino Pro Mini, less than the cost of a good cup of cappuccino. Very crudely, you could try something like this. If the timing is critical, there are better solutions.

Code: [Select]


digitalWrite(pin, 1); //turn on laser
delayMicroseconds(45); //wait
digitalWrite(pin, 0); //turn off
delayMicroseconds(5); //etc.
...


[dylangeorge]

Thanks for your suggestions. I'll have a try with an arduino mini. Timing is critical yes. Would combining a arduino with AD9833 DDS work? Or am I just complicating it?

[DrDiettrich]

I'm trying to control the alternation output of two lasers. A working example - Laser 1 - on for 45us off for 5us then Laser 2 - on for 45us and off for 5us then Laser 1 back on for same times in as loop until I press stop.

What's Laser 1 doing while Laser 2 is on? Shouldn't it be 55µs off?

[dylangeorge]

Yes, my description should have been clearer, one lasers would be off while other is on. So both would be off for 55us at different times.

[jremington]

digitalWrite() is slow so for precise timing use direct port access. These instructions set and clear port output bits in a single machine cycle, 62.5 ns on a 16 MHz Arduino.

Code: [Select]

PORTD |= (1<<4); //set bit 4, port D
PORTD  &= ~(1<<4); //clear bit 4, port D

Otherwise, set up a timer with PWM to toggle the bits automatically.

[DrDiettrich]

Slow digitalWrite() does not matter as long as turn on and off are delayed by the same time.

[jremington]

Slow digitalWrite matters for the on/off cycle period, given the delayMicroseconds granularity.

[DrDiettrich]

No problem if the time base is a hardware timer, not a software loop. delayMicroseconds() is somewhat precise but can not take into account the runtime of any code in between two calls.

A very stable solution would generate a sequence of PWM pulses and distribute every other pulse to the other laser. The switch point can be determined by polling or ISR or (foolproof) by an external flip-flop.