question about laser driver

I was wondering whether someone might be able to tell me if these laser diode drivers are any good?

http://www.k3pgp.org/laserbias.htm

http://www.die4laser.com/dvd-rec/Die4Drive.htm

I got on a group buy for a couple of 80-100mw 650nm laser diodes and need a means of powering them. If I can do that with some sort of modulation that would be a big plus :wink: .

From the descriptions, I like the second link's option better, but I can't build it as I have no source for SMD components (are there any non SMD alternatives to those?). The first link seems a bit easier to build, but I can't tell for sure if the modulation circuitry is what's needed for TTL or analog modulation.

Any help appreciated

The second one is designed by Robin Bowden who is a member of this forum - he trades under the name uk-laser on ebay and I think thats his ID on here. His circuit is pretty much like many drivers provided by some manufacturers and you dont need smd bits.
I have built similar circuits for a number of years using LM358 (or half of one actually) and for the output transistor I have used BC337 transitor (or bigger if more current is needed but this BC337 is fine for DVD diodes). Some of the resitor values will be different or need tweaking but you could easily build one 'based' on Robins circuit - or just buy one ready built off him.
Im away on hoiday now for a week so if i dont answer your response - if you have one - its cos im not here :)
see ya'll when I return

Rob

Enjoy yourself Rob.
Where are you going?

Jim

We are off to Andorra Skiing - if there is any snow :(

Gonna have to wait a week for all the FLEM news and hopefully pictures....
something to look forward to when I get back

See ya

R

I bought a couple of the Die4Drive boards and soldered the components on myself. It was fun soldering those itty bitty components. :) The board works as advertised. I really don't have anything else to say about it but if I will definitely buy from him again if I need more.

i have a page on the die4laser driver, not much info on there yet as ive not really played with it

www.laser-man.co.uk

Thanks for the answers. I do have one more question, though, if I use the lm358 and BC337, what changes do I need to make to the resistors?, and which resistors do I change?

As you can see, I'm no EE, but I can follow a diagram and build it if I can find the parts. The lm358 and bc337 are easy for me to find, in fact I have a couple lying around in my junk box already :wink: . I like to keep my junk box well stocked :lol:

Hi jkaiser,

I am an EE, I'm just lazy and impatient! :)

I couldn't wait for new parts to come in, so I just used an LM358 and a TIP121 transistor without changing anything else and it works nicely. TTL modulation is flawless from what I can tell. Analog modulation works good too, but it isn't totally linear (i.e. it is fully off below ~2v). Maybe that's the way it supposed to work, but I've never played with a "real" die4drive driver...

-Andy C.

Well, I don't have the TIP121, but I think I can find one on my local store (I got a TIP50 a while ago, hopefully they carry the 121 as well). The 358 I do have, so no worries there.

As soon as I find the 121 I'll give it a try and see what happens. I still don't have red diodes at my disposal, so i will try with a couple of IR ones (from a CD drives).

P.S.: I do have eye protection, as well as an IR capable digital camera :wink:

kaiser,

I should have mentioned - I actually started out using a 2n3904 transistor in the circuit, and it also worked well! :) It got pretty hot, though, so I just reached for something in a TO220 package and stuck it in. I'm real scientific when it comes to these things! :lol:

It is a pretty good circuit, too - it pumped the correct current through a single diode (0.7v drop), 4 diodes in series, and two laser diodes that I tried...

-Andy

Well, the only TO220 things I have at the moment are the tip50 and some voltage regulators (7805, lm317 and such). I will try the tip50 when I get a chance and see what happens, it's a NPN transistor like the 3904. So, one more question for now, how should I connect it?, what's the equivalent for EBC to DSG? My guess is that E=D, B=S and C=G

where:

E: emitter,
B: base,
C: collector,
D: drain,
S: source,
G: gate

I just found a IRFZ20 chip that is quite close to the one used originally (IRLR3105) so I will use that instead.

There is, however, one question I forgot to ask before, will everything remain the same regarding the volts to ma reading? (1mv=1ma on the MON pads)

Hi jkaiser,

I bet the TIP50 would work pretty good, but I'm guessing the IRFZ20 would be even better!

For future reference the Bipoler-to-MOSFET equivalents are

Bipolar_____MOSFET
Emitter (E) = Source (S)
Collector (C) = Drain (D)
Base (B) = Gate (G)

Always check the datasheet for which pin is which.... a lot of the TO220 devices go BCE (or GDS) from left to right when looking at the front, but not always!

As long as you use a 1 ohm resistor as shown, then 1mv=1ma. That's the beauty of a 1 ohm resistor... since V=I*R and R = 1, then the voltage across the resistor will equal the current through the resistor (V=I). :)

-Andy C.