Pulsing A Diode Safely

I am in the market for a 405nm laser to expose photo resist. I do know that these modules die if given a voltage spike and want constant clean current.

My question is which is better: A LM315 current regulator with a transistor on/off switch on the battery or a module with a TTL port built in?

I have seen modules with LM317's, X-Drive, Microboost but I don't want to spend $50 on one if I will kill it by just turning it on and off by disconnecting the battery at 5kHz.

The reason I ask this is I found a 10mW lab laser with TTL input and a 100mW with an X-Drive and I don't know which one I should buy!

Photo resist chemistry doesn't need lots of light - right?

In my opinion, 10mws which has TTL should be fine. But, what's your setup? What kind of irradiance do you need? W/cm^2

What kind of pulse widths do you need?

I know of a couple capable drivers if you need more power than 10mws.. just let me know.

Simply disconnecting power from a pulsed driver should NOT be harmful to the diode. If it IS harmful - its a very naughty driver.

I have no clue what kind of W/cm^2 I will need. The kit I use is HERE and the UV source is HERE and it is a 15W 18" tube.

I guess a 18" 15W tube is around 330mW/cm? Totally just guessing there. It takes 20min to expose a board with that tube though and I would like to make a laser based scanline system to expose my pattern on the photo resist in one go.

I can get a 500mW laser system with TTL controller for $100 but I can also get a 1.2W laser with an X-Drive for the same price. The 10mW is $25 though so I don't want to spend 4x the price as this will be a permanently mounted unit.

Well 405 isn't exactly "UV" in the same sense that a tube is. For replacing a tube, I would actually recommend using a string of LEDs. You can modulate them, they can handle a bit of abuse, they're super reliable, widely available, high brightness, <400nm emitters at 1W are available, fairly efficient etc.

Try making LED strings using about 10 of these guys:


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I'm not using the transparency and expose via UV method any more. I want to use a laser and a spinning mirror in sync so I move a sled over one line, modulate the laser and via the mirror project one whole line like a laser printer on the sensitized PCB. Then move to the next line and do the same.

To make the project even slightly useful I would need to be able to expose 3-5mil (0.0762-0.127mm) lines.

Video of what I am trying to do: (Not me BTW) HERE