Handheld housing and driver

[Litleck]

Hello,

For a couple of months now I've been trying to design my first handheld laser and it's been slow. Currently, I have a 445nm 1.8W diode pressed into a small housing and a heatsink which I got both from DTR's laser shop. I'm also using the DTR-3E-B lens since it's the cheapest. I'm don't have any high power resistors for the driver that im using right now so what I have is just an LM317 constant current with no resistor (I know it isn't the best). What I want to do is take the next steps to get this into a handheld form so I won't need my power supply. The beam is also really spread out, and changing the focus doesn't help. There's a strong point in the middle then horizontal lines coming out. I don't know if it's from the cheaper lens or if it's normal.

Thanks.

Diode: On eBay BOGO SALE!!! A140 / M140 A-Type Laser Diode * 445nm * 5.6mm * 1.6W * TO-18 *

I can't post links yet, unfortunately.

 

[paul1598419]

You won't be able to get 1.8 watts out using an LM317 for a driver. IIRC, you can only set them to a maximum current of 1 amp. I would go for the SXD driver that DTR sells set at 1.8 amps. You should get around 1.6 watts with that using the 3 element lens. You can buy a single element aspheric lens with a FL of ~2.39 mm for less than $8.00 on eBay and that will give you at least 2 watts if not more. that is assuming you use the M140 diode.

 

[Litleck]

You won't be able to get 1.8 watts out using an LM317 for a driver. IIRC, you can only set them to a maximum current of 1 amp. I would go for the SXD driver that DTR sells set at 1.8 amps. You should get around 1.6 watts with that using the 3 element lens. You can buy a single element aspheric lens with a FL of ~2.39 mm for less than $8.00 on eBay and that will give you at least 2 watts if not more. that is assuming you use the M140 diode.

Can I make my own driver to stay cheap? I have a whole collection of components that I could use.

 

[paul1598419]

To keep it efficient you will need a switching driver and those are not easily built. In the end it would be cheaper and much less of a hassle to just buy one.

 

[BillClinton1]

A lm317 will convert a huge amount of your battery into heat, your laser's worst enemy. I tried for weeks, months, to make a compact driver that would supply the needed current, it is a losing battle. The best thing I have ever done in my years making lasers was buying an x-drive from DTR. It's not that expensive, it doesn't get burning hot as soon as you turn it on, it's got a soft start, trust me, just buy one and try it out. It will even fit INSIDE the aixiz housing. Think how easy that will be? It's a no-brainer.

 

[MrCool]

If you're not into electronics then just buy one from DTR. If you have the skills to build a step-down constant current buck driver then you can start searching your buck regulator ic, it's not impossible at all. I like the texasinstruments site, they have a lot of good regulators, and the webench tool can generate you a circuit, some useful charts and it can even run some simulations, so it can help you start designing your own driver.
You can also check the LED2001 ic from ST, it seems good for the job and the footprint for an optimized PCB can even be smaller than the DTR x-drive. My only problem is, that the LED2001 can only drive 4A, I have an XHP70.2 LED which requires 4.8A to operate at full power but I was unable to design a circuit - so far - that can fit in 150mm^2 and can drive 5A.

 

[aaronnoraa]

You won't be able to get 1.8 watts out using an LM317 for a driver. IIRC, you can only set them to a maximum current of 1 amp.

I had to look this up because I wasn't sure certain but it turns out that a properly heatsinked TO-220 LM-317 is specified as a "minimum" max output of 1.5A and a "typical" maximum continuous output of 2.2A.. For your 1.8 watt 445nm diode you can feed it 1.6 amps by running a 0.8 ohm load between the adjust and output pins using resistors rated at least 2 watts. To make it easier to get that load you can put two 1.5 ohm resistors in parallel to achieve .75 ohms which is close enough and should result in 1.7A to the diode which should be within it's tolorance. Best just use 5 watt resistors to keep the resistor temp down. You can put a small ferrite bead on the output of the LM317 between the regulator and the diode if you're concerned about power spikes.

http://www.ti.com/slvs044-aaj LM317 datasheet
http://www.reuk.co.uk/wordpress/electric-circuit/lm317-current-calculator/ Handy LM317/LM350 current-resistor calculator
https://diyaudioprojects.com/Technical/Current-Regulator/ Same idea as above but reverse to get the output for a specefied resistance

 

[paul1598419]

That would certainly make for an interesting handheld laser. Imagine the heat that thing will generate at 1.7 amps.

 

[Lifetime17]

Hi,
Save yourself all the aggravation and get a preset SXD driver from DTR . The members here giving you great advice and in the long run save you money. The SXD is time proven over the years , you get what you pay for . I won't use Chinese drivers for laser diodes and most of them are for Led's.
Rich