flexmod and blue 445 no dark

[michelrietveld]

Hi, i tried to setup my 445 with a flexmod and so far so good only it doesn't go dark/out completely, it doesn't laser but it shows a bright blue light. i turned down the potentionmeter for the low current but this doesn't seem to go down enough.
any suggestions? is this where the balance comes in?
Michel

[allthatwhichis]

Most of them do that; both of the DIY 445 blues I have do. That's what a shutter is for I guess.

[300EVIL]

Turning the bias adjustment low enough on the flexmod will surely extinguish any output from the diode. They are 15 or 25 turn pots; are you sure you're turning them far enough? I usually leave mine just below lasing threshold to get better response.

[dnar]

I am surprised by the recent posts regarding Flexmod's. I am running 445 and 660's with them (P3 model), with the modulation signal at 0V I am able to set the bias for zero output. I set my 445 just below lasing however, which results in a weak blue "LED".

[drlava]

dnar, no biggie, it's just people getting used to building lasers and the technology behind it.

Michel, as 300evil suggested, if the diode's LED glow bothers you, you can decrease the bias current you set it to until the level is low enough that you can't see it. Everyone has their own preference about where to bias 445 diodes.

[dnar]

I am yet to complete my projector, still need a case.

I am guessing the final 445 and 660 bias will be determined by the linearity of the 532 which I can't (or don't want to) adjust.

[michelrietveld]

well i thought it was led glow at first too but when i was out yesterday evening, in complete darknes,s i couldn't help to see a beam, turning the bias down did not make the beam more faint. turning it up definately showed a more laser like beam.
I can turn it some more, can i turn it too far or will it just hit the limit?
Michel

[300EVIL]

I can turn it some more, can i turn it too far or will it just hit the limit?
Michel

Like I said, It's a 15 turn pot. That means it will turn 360 degrees many times. Turn it further.

[norty303]

I run my bias at 20mA on my FM2's when driving 445 diodes. Even then I get a faint blue output, but this is not visible in a gig situation.

Rather than just 'turn the pot some more' why not actually connect your multimeter and set it to a specific level - this strikes me as a more scientific approach. Don't forget that you'll need to re-adjust your main output as pulling the bias down will affect the output mA. Thats why you set the bias first.

[michelrietveld]

it's the amount of current measured when shorting the diode pins with a multimeter set to current right, not the amount of current measured as provided by the power supply.
i will readjust it tomorrow.
let you know how it went.

thanks for the reply.

Michel