[FEELER] Cheap, small Laser diode Drivers

[grainde]

There arent many drivers out there that can deliver 6 A. So how about one that can produce 6 A from 2 x Li and with a high and low mode and soft start?

I have been looking for a suitable driver for an MT-G2 build and Im sure, if your driver were adjustable up to 6 A, it could be used for the new 445 diodes too! :beer:

 

[Atomicrox]

The thing I miss the most is a driver that can have the current safely adjusted by an external pot during operation. Something like those "infinitely variable power" flashlights.

 

[amkdeath]

I know Jufran makes and sells some really nice test loads, I got ome from the wandering box of laser stuff and love it. What would be different about your test load from what nearly everyone has now? jufran test load

It looks like that just simulates a certain voltage drop. My test loads would actually simulate laser diode operation. It would basically be the transistor equivalent circuit of a laser diode, with a pot to set the desired "threshold current". If it is really desired, I could probably also make the voltage drop adjustable as well. These boards would also have an LED to inform you when the virtual LD is "Lasing" and when it is not. It would also have PID feedback, if you're using an advanced driver, or doing any frequency tuning.

Oh, and they'd be a lot cheaper.

Ditto. Lol

While some of the suggested features sound cool, they might make the driver too big/costly.

look at rhd's pico that boosts to 2.4A. Parts cost like 5 dollars. Groupbuy for that, maybe?

I really like the idea of buck/boost for a wide range of currents.

Can you make a relatively cheap and small buck/boost that can output 4.2~4.5A?

There are many possibilities and I'd love to see anything you can make, but my priorities would be making the drivers cheap, small, and with wide current ranges, in that order.

This is awesome, thank you for offering to do this! I look forward to whatever comes out of this

There arent many drivers out there that can deliver 6 A. So how about one that can produce 6 A from 2 x Li and with a high and low mode and soft start?

I have been looking for a suitable driver for an MT-G2 build and Im sure, if your driver were adjustable up to 6 A, it could be used for the new 445 diodes too! :beer:

It seems like there is good interest for low input voltages/high currents. I'll prioritize testing some of these as well as some standard lower current designs.

Oh, and no problem This is all just fun for me, really.

The thing I miss the most is a driver that can have the current safely adjusted by an external pot during operation. Something like those "infinitely variable power" flashlights.

Yes, drivers will be current adjustable via pot. Did I understand this question correctly?

 

[vortish]

I am interested in the led dummy load if the price is right

 

[Atomicrox]

Yes, drivers will be current adjustable via pot. Did I understand this question correctly?

I don't know much about drivers, but it seems people use dummy loads because it's unsafe to change the current with the diode attached and lasing. I'm not sure if that's because the tester wouldn't know when the max current has been reached or because messing with the pot it generates noise that kills the diode.

What I'd like to see is a driver with three holes to solder an *external* pot, which would have the knob reacheable from outside the host, so that the user could vary the current with the laser running. This video illustrates what I mean:

Perhaps it could even have another internal pot to set the max allowed current.

Of course for this to be useful the driver would have to support a wide range of currents without soldering anything.

Hope I explained myself well!

 

[amkdeath]

UPDATE: So I received all of the parts a couple of days ago, and I've begun testing some simple boost circuitry.

Does anyone use bench supplies or wall adapters for their laser projects? I can quickly fab out some simple bench-sized filtering driver circuits for running laser diodes off of a wall supply. If you're really interested, I can also add some simple transformers/rectifiers for a straight 110V/220V-to-laser power supply.

I don't know much about drivers, but it seems people use dummy loads because it's unsafe to change the current with the diode attached and lasing. I'm not sure if that's because the tester wouldn't know when the max current has been reached or because messing with the pot it generates noise that kills the diode.

What I'd like to see is a driver with three holes to solder an *external* pot, which would have the knob reacheable from outside the host, so that the user could vary the current with the laser running. This video illustrates what I mean:

Perhaps it could even have another internal pot to set the max allowed current.

Of course for this to be useful the driver would have to support a wide range of currents without soldering anything.

Hope I explained myself well!

I still might be misunderstanding you, but I'll take a shot:

The drivers we use (or at least the ones I use) for laser diodes are the type that force a certain amount of current (set by a pot) through any given load. If this load is purely resistive, it will therefore also generate some sort of voltage drop across that load. Therefore, when I say "Max current set by pot", It means that that exact current will be output by the driver, regardless of the load. either that, or the driver dies.

Other forms of power sources, such as wall adapters for electronics and transformers for household devices come with a set output voltage rating (say, 5V) and a max allowable current rating. So, for example, your 5V 1A phone charger will supply a 5V potential, and the device can draw anywhere from 0mA to 1A of current, depending on its needs.

I dont see how two pots would be of any use, if you need to dim the diode you can set the driver to a max saturation current (something that wont burn the diode) and then use the pot to lower that value when you need to dim.


With LEDs, people tend to dim in two ways. The analog way (like explained above) or the "digital" way, by adjusting the duty cycle. By turning the LED on and off in very short pulses that are faster than the human eye can percieve, you can create the illusion of "dimming". This is done by adjusting the pulses so that if every "pulse" was 100ms, the LED would be off for 80ms and on for 20ms. This creates the same effect visually as dimming the LED to 20% brightness.

We can't do this readily with Lasers, because there is both a threshold current, and the fact that sudden changes in voltage/current can damage the diode itself. You can, however, switch the diode between a "LOW" power mode (Near threshold) and a "HIGH" power mode (near usual operating point) if you are interested in doing some sort of modulation, or communications system.

So, what is the nature of the dimming that interests you? And what will you be using it for?

 

[upaa27]

I am interested. 7.4v input 3.8amps?

 

[Atomicrox]

I dont see how two pots would be of any use, if you need to dim the diode you can set the driver to a max saturation current (something that wont burn the diode) and then use the pot to lower that value when you need to dim.

That's what I meant. Analog dimming by changing the set current. The second pot would be for setting what you call max saturation current - else you'd need to solder a resistor with the correct value. I can't solder SMD stuff properly.

PWM dimming wouldn't be useful because it doesn't necessarily make the laser safe at low brightness.


Let's use a practical example. Say you have this diode:
https://docs.google.com/file/d/0B_6-KC5wFXIJeUQySklvNEt4bHc/edit?pli=1
You'd set this first, on-board pot by using a dummy load at 1.7A (or higher if you want to overdrive). This would be done once during the build process.
The second pot would have the knob outside the host and be used to vary the current between 0 and 1.7A.

I'll be using it to make handheld lasers that have variable power. That way they could be safer when you're using them indoors and brighter when beaming at the sky.

As for form factor, either flashlight hosts or small handheld boxes, like this one:
http://laserpointerforums.com/attachments/f51/37773d1335742602-broken-optics-box.jpg

 

[rhd]

The thing I miss the most is a driver that can have the current safely adjusted by an external pot during operation. Something like those "infinitely variable power" flashlights.

I don't see any reason why this would be problematic. If you are scaling a sense resistor's vdrop, then it's not difficult to tie the scaling resistor to two through-holes that can attach to an external pot. You'd just work out the ratios mathematically such that the max pot value would always result in a current above threshold, and the minimum pot value would be added to a series resistor that kept the current from exceeding your diode's max current.

I don't see any reason why this would be dangerous. If you're concerned about the current monitor reacting to changes with momentary overshoots, that can be handled with some good output caps.

 

[Atomicrox]

Cool, that's exactly the info I was looking for

 

[rhd]

UPDATE: So I received all of the parts a couple of days ago, and I've begun testing some simple boost circuitry.

What IC(s) are you playing with?

 

[amkdeath]

Working with a few, namely LM34xx series chips.

Boards are in! Preliminary testing of my designs showed promising results, but lots of noise. Ready to test the actual small package layout, except I ran out of IC's.. haha. Ordering more as we speak.

Here's some goodies:












Gold plated pads, soldermask, silkscreen. And all Lead solder. Fuck RoHS. I'll post more as I get it.

Regards,

amk

 

[Jstr]

What are the Vi and I ranges?

How many drivers are you making/at what costs? And when do you think these will be available for purchase?

Thanks! I'd love to see a competitor of the xdrives.

 

[crazyspaz]

If they are going to be that long (and have that much unused board space), you may as well make a variation that is ~21mm long, and add a momentary switch so we can use them in pens.

 

[rhd]

Very cool to see this project take form. If you're using LM34XX, you may want to check out the Benboost (the original open boost driver project). I think we used the LM3410 for that driver. You can of course take anything you want from that thread / project, if it's helpful.

There are a few gems in the LM34XX line.

 

[amkdeath]

If they are going to be that long (and have that much unused board space), you may as well make a variation that is ~21mm long, and add a momentary switch so we can use them in pens.

Actually, not a problem. Any examples/dimensions of current boards with this feature would help. Mainly for determining the optimal position of the switch.

The original idea was to make them fit in the aixis modules, the next batch will probably have to run a bit smaller

What are the Vi and I ranges?

How many drivers are you making/at what costs? And when do you think these will be available for purchase?

Thanks! I'd love to see a competitor of the xdrives.

More operating details to come after I do extensive testing. I have a batch of about 20 of these prototypes for now, haven't thought about pricing yet. I'll let you know!

Very cool to see this project take form. If you're using LM34XX, you may want to check out the Benboost (the original open boost driver project). I think we used the LM3410 for that driver. You can of course take anything you want from that thread / project, if it's helpful.

There are a few gems in the LM34XX line.

It'll be awesome to see them working!

Yeah these are pretty cool chips. I believe I skimmed the thread before, I'll definitely take another look, in case there are some dodge-able roadblocks that I missed.

Best,

amk