There are three because sometimes you don't want just a variable resistance but a variable voltage - a voltage divider network. If you connect one end to ground, the other to let's say 6V, then by adjusting the pot you can get out a variable voltage from 0 to 6V on the middle one (you can't use this for powering an application, as this voltage source would have high internal resistance, i.e. it would sag under load - but you can use it as the input into an amplifier, for example).

I'd be willing to do this for no less than $100, i know for a fact this build is by FAR the most difficult in sense of fine tuning.

But my offer stands

I'd say its a reasonable one.

I am building one of my own very soon ^_^

Dark

I'd say that's almost free! This build is a ton of work. It's one of those things that you put so much time and effort into making it perfect, that you don't want to part with it after you get it dialed in...






Mounting:

I went with a simple 'foot' or platform to mount the assembly onto... (this will make it easy to mount into an enclosure)





Note: The only thing touching the mount, is some double sided tape to the washers, which of course are connected to the sled. (and one other spot on the sled cover plate) So the adjustable heatsinks/modules, do not have any extra pressure on them except for their own weight. This is important, because the alignment is so critical...

The sled cover plate that is covering the optics, can still be removed if necessary. This is an easy method, and still offers some shock resistance...
Jay

Excelent mount Jay,


That double sided tape will add some cushion to absorb any shock if droped too.


-Ryan

Drop?!? You can't drop art, lol.

Simple but effective...

Had to look good too, being near your awesome adjustable sled mounts!

Drop it? Oh man, may that never happen.
Jay

The Supper Sized Green will purdy that up some more I would think when you get it.

Can't wait to see it when it is all finished.

-Ryan

a note on using the trimmer to control the output power. The combination of a 100ohm trimmer and 10 ohm resister doesn't give you much control.
trimmer value~net resistence
10~5
30~7.5
40~8
70~8.75
90~9

the change is basically going from full to half power almost instantly (assuming 5ohm cuts output in half).

Does anybody know if there is a voltage regulator that can be used?

Something similar to a 7805 voltage regulator, which will regulate voltage to 5 volts.

Except one that will regulate to 3 volts. Or better yet, adjustable voltage!

Maybe 2.9 or so...

That way, you could use the 3.6 volt (4.2) rechargeable batteries in parallel for good capacity for the green, but adjust the voltage to the module to control the output...
Jay

^ I heard about a new product, it's called LM317 ..... (sorry, can't resist j/k )

Seriously, a lot of peoples are so used to use it as current regulator, that forgot that it's also a good voltage regulator, with a maximum current of 1,5A (but better keep it to 1A max and with a good heatsink), have an internal protection against short circuit and overload, a stability of 1% to over 70 C, and overall can regulate from a minimum of 1,2V (37 V max, but better not go over 30, and always try to keep input voltage only 3 or 4 V more than the desired output voltage, if possible, for reduce power dissipation) ..... and LM1117 is also better

Or, also L200 is a good choice, it can't go under 2,85V output, but at least all the ones i used, was very stable.

Edit: datasheet of the L200, if someone need it ( i suppose all knows the 317, LOL)
http://www.datasheetcatalog.org/data...onics/1318.pdf

Show us how!

I have plenty of LM317's, and I understand how to use them for regulating current using a resistor between the sense pins. And in that case, the diode takes what ever voltage it needs, as long as the supply voltage is available...

But if you could give an example, or ohms law on how to use it to regulate voltage, I think that it would do what I want to use it for. How about an example of how to set it up?

I have used the 7805 to regulate 5 volts output.

Can the LM317 regulate 3 volts from a 3.6 - 4.2 input supply. I would like to do something like this to power a stock O-like module with it's own driver.

Am I thinking correctly here?? It seems that if I could regulate the voltage to the module, then I could get an output power adjustment in the module...
Jay

No, the LM317 can't regulate 3 V starting from 3,6, you need a switching or LDO type for that, cause the dropout (the internal voltage drop of the regulator) is almost 3 V, so the input voltage must be at least 3 V more high than desired output voltage.

The better and cheaper one, if you can grant 4,2V, is the LM1117, that have a typical dropout of 950mV, so 3,9 / 4 V can be enough for grant you 3 V output (but also this, if the Vin fall under this limit, can't regulate in the right way, and also increasing the current, the dropout increase a little bit ..... btw, LM1117 it's 1A max, not 1,5A like 317)

The most difficult thing, about LDO regulators, is finding models that carry a decent amount of current, cause 99% of this market is made with the goal of fit them in low power devices, so almost all have very low maximum current, like, 100 mA to 250 mA ..... few exceptions.

There is a new line of very efficent LDO linear regulators, actually on the market, that have typically from 180 to 500 mV of dropout, so can do that what you want, but for them i only have the part numbers and datasheets links, cause til now i had no possibility to get some samples for make my tests ..... if you want to try to see if you can get samples (probably in any other country out Italy, it's much more easy ), here are some datasheets with part numbers

LM1117/NCP1117 (1A)

NCP69X serie (1A)

CAT6219 (500mA)

TPS725XX family (1A, the 72501 is the adjustable one)

UCC281/381 (1A)

Or do you need schematics ?

What I am trying to do specifically, is to control the voltage supply to a stock O-like green module.

Now I have used a 7805 voltage regulator to regulate 5 volts supply to a FlexDrive, so it seems that it would be a good way to adjust output power of a green module by controlling the input voltage to the stock driver??

Does this thinking make sense? Since the module gives more power with a 3.6 volt battery, than it does with a 3 volt battery...

In this set up, I have two batteries that I can run in parallel, or in series. So If I need to, I can use 2 X 3.6 volt batteries in series to supply the voltage regulator.

It would be nice to have a pot, and be able to adjust for voltage output. I'm sure the module will not be using more than 400mA's or so for current...
Jay

Uhm, i need to see the schematic of the driver of the o-like module, for say you if it's possible or not in a safe way, but, basically, i think it can be done, also if is not the better way for do something similar .....

I mean, the driver on the o-like module is built for keep the current regulated til a certain limit, so it probably try to compensate a bit, increasing it, when you lower the voltage at the input ..... til when you reach the lower limit of regulation, then the diode just receive less current cause the voltage at the input is less than the needed for keep the regulator working correctly, and the LD just receive less current and dim .....

I think, anyway, that it can work good enough ..... basically, in the way you want to use it, the original driver just acts as "maximum current limiter", for the maximum voltage you put at the input, where instead the regulation is just done decreasing the input voltage through the voltage regulator ..... i advise you, the assembly will be not much linear, in regulation, so if you're planning to use it with a driver like in a scanner assembly, may not be the better solution ..... but for manual regulation, yes, it can work.


Edit, let me go for lunch, then i post you a schematic, if you want, cause with the 2 batteries in serie, you can use also the common 317

After talking with Igor, I understand where the flaw in my thinking is...

All o-like modules that I have tried will give more power with a 3.6 volt rechargeable battery, than a 3 volt primary. That is where the problem is...

This made me think that I could just adjust the voltage going to the module with stock driver.

But Igor helped me to understand that if this is the case, then the driver on the cheap module is not really working properly in the first place. If it was, then it would regulate constant current with either battery, just like a FlexDrive does.

So with in mind, it's back to my original idea of replacing the module's stock driver with a DDL driver using a 1/2 watt pot like I did on my other module. (which died on me)

Anyway, everything makes more sense now. I was confused about how the modules give more power with the different voltage of the two batteries mentioned...
Jay

Then you can use the L200 and build custom drivers, if you want ..... they regulate both the current and the voltage, so you can preset the maximum current that you want for the diode, and set the pot for regulate the voltage to it (maybe keeping a 10 ohm 2W resistor in series to the diode, so the entire system become also less critical about the regulation) ..... this way, you can still vary the voltage, and the current preset prevent you from fry the diode for a wrong regulation or pot misfunction

Ok... thanks for your help.

According to Igor, the DDL driver should work the same way with the IR pump diode, as it does for a red. Except we know that the diode is case positive.

And this is what I have already tried, but for some reason my module did not last even at a lower output using the DDL driver.

So I scrapped that idea. But it must have just been a bad pump diode or something...
Jay

That's strange, I've been running a green module (from dx) way above it's stock current with a DDL-driver without any problems for 5 months.

Good to know! What current? Did you use a test load to set the driver?
Jay

I did use a test load, I always use a HP-LED to test the current. The current is 500 or 520mA, I ran it at 480 until a few weeks ago tho. The stock current was 400-something.

The laser:
DealExtreme: $57.20 35mW Green Laser Module (5V Input)

Thanks for sharing!
Jay

Hi, sorry yesterday was in hurry, and forgot to post also the schematic

You can preset the maximum current with Ri, where the current is 0,45/Ri in ohm (so, as example, 450 mA for 1 ohm, 375mA for 1,2 ohm, 300 mA for 1,5 ohm, and so on), and also you increase too much the voltage, it self limit it.

The 1 Kohm pot is for the voltage regulation, and the 10Kohm trimmer in parallel is for preset the maximum voltage ..... just turn pot for the maximum resistance, then adjust the trimmer for the maximum voltage you want (can also use 4,7Kohm or 10Kohm pot, if the maximum voltage don't reach the one you want)

The 2,2 ohm resistor is just for make the regulation on the LD a little more "smooth", as you know, LD's are eager devices in fact of current, and not exactly linears ..... but can also be not used, if you want.

The diodes are for drop a bit down the output voltage, cause the L200 can't go under 2,85V, without a negative reference (and for a LD driver, building a negative reference maybe don't worth the effort ) ..... with the diodes, you start from approximatively 1,4V

And if possible, better dissipate the L200 with a heatsink

No problem!

wow, i just learned allot!

I may try this myslef,

Tyler

Great job Jay! It's really looking fantastic.

Also, I just realized that this trick quoted below may just be the key to getting long life from our laser diodes in general. Thanks for pointing out something that I knew but hadn't thought of to use for our diodes.