3V input driver DIY

[adgmeijin]

2nd pic...

 

[adgmeijin]

the finished PS3 Bluray, anyway i dont have Laser power meter, but im assuming it i ran it as 10 - 13mW output.

 

[chido]

UNDERPOWER? Okay that's more serious that destroying the diode!
So, how about 3x CR123 batteries? What power source would you reccomend?
Thanx for that

Sure, you can use 3 CR123s, a better choice would be to use 2 rechargeable CR123s, a rechargeable CR123 has a voltage of 3.6v, so two of them should give you 7.2v.
Use whatever you want, as long as it's above 7v and its mAh rating is good, you should be ok.

 

[Eudaimonium]

Thank you guys for all that info, for now I'm using 9V batt, and you are right, it seems that it's more visible now (testing: night sky ) And,
adgmejin, big tnx for trouble with taking pictures, and man, it looks totally awsome, would you have a spare bluray diode?

And I'm still waiting for that scheme

 

[amir1972]

Hi all, I'm havin' a diy red laser (like everyone) but I have a lm317t based driver which requiers an input of 4+V so using the pot I set the proper resistance,
Also power source is a 4.5 V battery, It's really big and doesn't give a felling of portalbe source
LM317T has internal resistance a little too big than I would want it to have
So any of you might know a driver that requires a 3V input and gives diode required output?
I think it would be nice to have my laser power by  2x1.5V  AA batts then a 4.5 huge batt.
Please post a schematic, thanx in advance

I have found a circuit schematics which may interest you.
The link is the following (cut and paste in your browser' address bar):
kmz.altervista.org/doc/laser_CW.jpg

(I hope that admins won't ban me, as I am not allowed to post links yet - not enough posts so far)

It implies the use of an LM285, a 100 ohm pot, a BC639 transistor and a few transistors and capacitors. The good thing is: looks like this circuit only needs a single 3,6 V CR123 battery to give the proper current to a 200 mW or so laser diode.

Note: I must add that, being a noob, I am not fully sure about how this circuit could be built.
I would appreciate it very much if someone could translate the schematics into a "drawing for dummies" like the one made by aaronX987 you can find in the topic "DIY Homemade laser diode driver", in the section "Lasers"-"Experiments and Modifications" of this forum.

 

[Eudaimonium]

OK, somebody with 2 posts so far gave me something that all the 2000posts guys missed
nice job
As soon as I take some pics and find some time I'll will send you a scheme, ok?
big thanx

 

[Benm]

I have found a circuit schematics which may interest you.
The link is the following (cut and paste in your browser' address bar):
kmz.altervista.org/doc/laser_CW.jpg

It implies the use of an LM285, a 100 ohm pot, a BC639 transistor and a few transistors and capacitors. The good thing is: looks like this circuit only needs a single 3,6 V CR123 battery to give the proper current to a 200 mW or so laser diode.

That circuit might work, but it's all very much on the edge - there is just very little voltage to work with in these things. I would recommend leaving out the 5.6 ohm, and replacing the 820 with something around 390 ohm to get a power range that goes all the way to zero.

Still, the transistor and pass resistor will require at least 0.5 volt to work with, so feeding it off 3.6 and running a diode close to 3.0 is cutting it very, very, tight. Expect it to stop working before the battery is half empty, and not at all from a 3.0v primary cell.

 

[Eudaimonium]

Thanx for info up there, I will keep that in mind, but since it's rechargable CR123, this shouldn't be a problem.

 

[toked323]

i just looked for the lm285 and it comes in soic-8 and to-92 package, only 200ma out put

 

[amir1972]

First of all, please keep in mind that I am still the humble noob I told you about in the first post.
I asked the circuit's author about the comment by Benm, and about the meaning of the components.

He answered that Benm's comment is coherent   It depends however on the diode we want to use and the current we need to feed it with. In some extreme cases the 5,6 ohm resistor can be avoided and the 820ohm resistor can be changed with a 390 ohm one. In some cases we could even remove both resistors,using a 470 ohm or a 1000 ohm trimmer.
He adds that his circuit is generic, as it's designed to work with all lasers, but that everyone can modify it as preferred.

About the meaning of the components... He answered me that it's quite difficult to explain such a circuit to someone with so little practice and knowledge about electronics (and he didn't mean to offend: he is just SO right!  ).

However, he gave me a brief description of the components.
The LM285-1.2 is a micropower voltage reference diode, and it's used in the circuit because it generates an extremely stable reference voltage, and the 100 ohm resistor lowers its base voltage.

The rest of the circuit is a constant current generator with a base trimmer stabilized by resistor on the emitter.
(i bet that I've just built an electronics TechLanguage translation blasphemy!).
However it should work thi s way: if the current should grow due to temperature or other causes, the voltage of the emitter resistor (0,47 ohm) should also grow - the base voltage should decrease - consequently adjusting the current to the initial value.
The capacitor connected in parallel  to the laser prevents sudden variation of voltage or current on it (usually due to turning on the device).

By the way. I have read in another topic that capacitors's purpose should be to avoid power bursts when connecting the batteries, as "When a battery is left unused for a while, the first burst of energy dispelled from the battery can spike up to 10 times the average power of the battery! Therefore, for a 1.5V battery, this would add up to approximately 15V. This burst is very small and very short that in most situations would not even kill the laser diode, but there are times when the burst packs some power along with it, supplying well over a watt of energy to the diode. This can spell instant death for most diodes! " (Lasers - Experiments & Modifications - DIY Homemade laser diode driver- 1st page).

When I reported this to the circuit's author... looked like if I had farted at a funeral   .
The fact is - a battery's voltage can decrease, but it NEVER increases. A power burst of 10 times the voltage would really burn everything, even if very short.

 

[Benm]

I have no idea where that 10x voltage idea came from, but i've seen it before too. It's simply not true though, a battery will output the voltage you measure with a multimeter, and less under load.

You do need the capacitor on the output though, as many drivers do require some time to reach proper regulation and can overdrive the LD before that.

 

[Eudaimonium]

When you measure something with a multimeter, it doesn't have to be accurate.
I mean, multimeters refresh measurng every half a second or so, and a power burst is so short it cannot be measured with m meter. I think that you misunderstood the guy.

Have a practical example, take one empty battery and a LED. When you connect the LED, it won't lit up as you would expect, but, disconnect, and connect again. If you wach more closely, LED will give powerfull flash immediatelly after connecting, and then decrease the output.

Same thing with full batteries. You leave them for long and it build up electricity. then you connect something as fragile and sensitive as an Laserdiode, it fries up instantly. amir1972 has a point.

So, no point trying measuring with multimeter, because it's too slow to measure something as fast as this. Even if it had high refresh rate, you still would miss it.

 

[toked323]

well if your gonna go this way might as well use the 7135 as it out puts 350ma and 3.2v input

 

[Eudaimonium]

OK, since I like to pretend senile
I dont remember that
toked323, could you post that scheme?
I would appreciate it

 

[chido]

http://www.laserpointerforums.com/forums/YaBB.pl?num=1191898669/0

 

[chido]

I have no idea where that 10x voltage idea came from, but i've seen it before too. It's simply not true though, a battery will output the voltage you measure with a multimeter, and less under load.

You do need the capacitor on the output though, as many drivers do require some time to reach proper regulation and can overdrive the LD before that.

What????? That's not true. DDL made a big mistake then. ;D It's in the first post of his thread.

Regulate voltage:

What?
The voltage source that this circuit is designed to regulate is one supplied by an alkaline/lithium battery. An AA/AAA/AAAA battery supplies approximately 1.5 Volts DC(usually more around 1.2 for lithiums, but I've had a few at about 1.6-1.8!!). A CR123A battery supplies 3.0 or 3.6 Volts DC depending on the battery. This is very useful and very stable for the most part. When a battery is left unused for a while, the first burst of energy dispelled from the battery can spike up to 10 times the average power of the battery! Therefore, for a 1.5V battery, this would add up to approximately 15V. This burst is very small and very short that in most situations would not even kill the laser diode, but there are times when the burst packs some power along with it, supplying well over a watt of energy to the diode. This can spell instant death for most diodes!

Here's the link to the DDL driver thread.