Roithner drivers

[Morgan]

Hi all,

I'm wondering if anyone can shed some light on this tiny driver drivers for laser diode driver ICs for laser diodes Lasermodul lasermodule laserdiode Lasertechnik Laserdioden laserdiodes optic lasermodules laserbeam

I'm mainly interested in the EU-42 as it is, "modulable". Up to 120mA, (which if anyone could suggest a way of upping to above at least 200mA, I'd be grateful too).

The thing I can't get my head around is the photodiode connections. I'm aware that many commercial diodes have a built in photodiode for live monitoring but is there a simple way round this to run a 6x or LOC from one of these?

I've also got a EU-37 but will have the same problem as it seems to require a photdiode also. If I were to include a fixed diode, would this be a fix?

I bought both these drivers early on when I knew even less about electronics than I do now, (if that's at all possible!!!! )

Looking for an expert to chime in here I think!

Many thanks,

M


(P.S. I can take some better macro photos if needs be. I can't read the values on the Roithner site but maybe you get a crisper image)

 

[lasersbee]

First... NO... a 6X (unless you are running it low powered)
will require more current than the Driver can supply...
Second... the data sheet only states the Input Voltage at a
max of 6 Volts... but does not state the output voltage..
This is NOT a Boost Driver... and without schematics we
don't know if it has enough output voltage to drive any Blu-Rays.

I think that Driver was designed for Red LDs...

As to the photodiode input... it is looking for a voltage level
produced by the photosensitive area of the photodiode by
the energy of the laser's beam...
Again... without the Schematic... you will need to experiment..
Maybe... another member has a trick to bypass it...


Jerry

 

[HIMNL9]

Yes, as lasersbee said, they are linear drivers ..... about the photodiode, if you want to "fool" the control circuit (using it with a red diode), you can just connect an 1N4148 or a 100 ohm resistor in place of it (just for not use a direct bridge ), but if they cannot drive a BR, is unhelpful.

And with a red diode, having the PD inside, just connect it, is the more easy thing

 

[Morgan]

Okay, that's helpful. Thanks guys

A few thoughts then...

I realised it was not a boost driver and was sceptical if it had the power to run a BR, (although of course this would have to be proved by trying it!), but, if I were able to insert a resistor in parallel with the pot, would I be right in thinking this may increase the output current, (Let's assume for the moment that designed output will only be able to drive a lower power red LD)?

Could a boost driver be connected in series to raise a 3.7V battery to 6V for maximum input? (Not sure why I'd want to do that but, in theory would that be feasible)

The fact that it will take a modulated input means it should be possible to control the LD brightness with a PWM input, right?

I do know my knowledge is limited but have just started studying a BTEC National Certificate in Electonic Engineering at college so have come back to relook at these things, (only 3 weeks in so please don't expect too much of me regards pure theory!). My project is to build a 7-colour handheld with smooth cycling through the spectrum so I'm trying to think of ways to use PWM to control brightness but keep power consumption to a minimum. I've been talking to FireMyLaser who has been very helpful with schematics but I want to try and avoid 5+V inputs. This might be difficult but I do best when things are that way. I thought a flexdrive might be good but apparently they may not like a modulated input.

As I said to FML, I'm not looking for someone to do the work for me, just a point in the right direction. Drlava has given me this link, ( http://laserpointerforums.com/f42/erdabyzs-switching-laser-drivers-41820.html#post563777 ), and I've PM Erdabyz for info too, so the more leads I get the better the finished article will be.

I appreciate all posts.

Thanks again guys.


M

 

[HIMNL9]

Uhm, i'm not sure if i've understood your question correctly, but if you mean connect in series the output of two linear drivers used as constant current drivers, like normally is done in laser diodes power sections, i'm sorry to say you that the reply is no ..... is not possible to do this and have them working correctly. (overall, using a single battery, ofcourse ..... but also with 2 separate batteries, it don't work as you want)

 

[lasersbee]

Hey Morgan...

I think your best bet would be to build a DIY DDL current Driver...
or you can get a prebuilt rkctster or FexDrive Driver...


Jerry

 

[Morgan]

Hey,

HIMNL9 - I was wondering whether a boost driver can power a linear driver from a 3.7V battery. E.g. could a flexdrive boost 1 x 3.7V battery to run a RCKSTR, (or other driver), + LD? I know you would never do this because you'd just use the flexdrive but would it work? Hyperthetically? I'm expecting it to be a resounding, "NOOOO!", but had to ask. It would seem too easy if it were that simple. (+2.25V above running voltage for a RCKSTR etc. is understood)

Jerry - I think you're right. I have already put in an order for a few flexdrives. I'm hoping drlava will tell me that a modulated input will work too. If not I'll use them for fixed current builds. I'm still exploring this one and the project is only in the research stage at the moment. I have no doubts regards my mechanical engineering skills, it's the electronics that is the hard part and that'll take effort. I won't be satisfied if I don't meet the specs I've already set out for myself.

I seem to have some knack of finding different applications for current bits of kit so was just sounding out about these Roithner drivers but will experiment as well.

Off back to college in a while so I'll catch up next weekend.

Your input always improves my output!!!

Ta...


M

 

[dr-ebert]

The flexdriver output voltage is limited to <6V. You can have boost drivers with much higher output voltages (probably even using the same IC, the limiting factor is the Schottky diode), but still combining a boost driver+linear driver would make absolutely no sense. All the linear driver in such a setup would be doing is burn off energy. But YES, it would work.

Modulating the power supply input to a flexdriver is probably not a good idea. Better get a boost driver chip which has a modulation input pin.

Also, connecting a standard diode to the photodiode input of a circuit most likely won't work. That's because a photodiode is a current source (like a solar cell).

 

[HIMNL9]

@ Morgan: no, cause, as dr-ebert also said, you can't get enough voltage from it ..... you can use a DC-DC converter, but probably you need to build one yourself, and this don't worth the effort.

If you have a flexdrive, just use it directly, is the better solution.


@ dr-ebert: no, i was not suggesting him to use a common diode for make the circuit work as a photodiode ..... just for "fool" (don't know how to say it different) the feedback loop ..... with a common diode, it see no current, so the negative feedback regulation is turned off (or always at the maximum set with the trimmer, if you prefer)