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FrozenGate by Avery

DIY Homemade laser diode driver

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Is it ok if I do not put in the POT? To me the pot does not seem necessary as long as you have the resistors (around 5 Ohms) there and if you do not plan on modifying it for blue-ray.
 
Well i like the pot because of the ability to adjust the power of the laser. if you just have a 5 ohm resistor or 2, 10 ohm resistors in parallel about 250ma will be going though the diode which is fine to run the senkat gb diode at so i guess it wouldn't really matter
 
How would u make a 4.2ohm resistor ? Ive got two 2.2ohm ones in sereis in there but i want to up the current some so i want to know how to get a 4.2 one, I have 1ohm ones would a 4ohm resistor be good in it, i dont have a pot in it so the current is maxed all the time so would 4ohm break it?





....lazer.... ;D ;D ;D
 
Uh, 2.2 + 1 + 1 ?
Personally I'd rather just go buy a 50 Ohm 25-turn pot, leave in a 1 Ohm resistor for measuring current across, then you can set it at whatever you want.
 
rubberband said:
Well i like the pot because of the ability to adjust the power of the laser. if you just have a 5 ohm resistor or 2, 10 ohm resistors in parallel about 250ma will be going though the diode which is fine to run the senkat gb diode at so i guess it wouldn't really matter
Click to expand...

Yeah, I don't really need it because I am making one for someone who will never need to adjust it. :)
And in order for me to fit it into the unit I will need to exempt simething like that.
 
Hey guys,

I'm about to build Daedal's circuit to drive a Blu-Ray diode, and I wanted to make a few modificiations. I'm going to add a capacitor before the LM317, and an extra cap or two before the laser diode, plus a capacitor soldered directly to the LD. With the extra caps before the LD, would it be better to wire them in series or parallel for the best filtration of the circuit?

Thanks in advance!
 
Um that sounds like 4x times danger to me because if just one of those many caps disconect and reconect there goes ur diode, Just solder the cap right across the diode, I would just use one but you can make it as big as you like like im using a 100uf 25v just one of them and it protects just fine.



....lazer..... ;D ;D ;D
 
Thanks for the input. ;)

Yeah, that was the plan, in addition to extra caps on the board I was going to solder a cap directly across the laser diode. I remember someone saying that some very expensive, industrial laser diodes are driven through what is essentially a series of capacitors. I was just wanting confirm that you do put the caps in series, and not in parallel, or vice versa.

I'll do a little more digging and try to find the post where I read about the series of capacitors.

Edit: I couldn't find that post (maybe I dreamed it?) but I did find a post by chimo that said it was best not to add too much capacitance on the load side of the LM317.
 
yuip said:
I was just wanting confirm that you do put the caps in series, and not in parallel, or vice versa.

I'll do a little more digging and try to find the post where I read about the series of capacitors.

Edit: I couldn't find that post (maybe I dreamed it?) but I did find a post by chimo that said it was best not to add too much capacitance on the load side of the LM317.
Click to expand...

If you put the capacitor in series with the LD, the circuit will not function. It must be in parallel.

With a circuit this LM317 circuit, a large cap is overkill and potentially (no pun intended) less effective than a small cap with a low ESR (equivalent series resistance). The purpose of the cap is to absorb high frequency "spikes" of electricity. The term "high frequency" is important - capacitors are manufactured with different properties. How a capacitor deals with high frequencies depends on its size and type.

Try this analogy: if you think of capacitors as having inertia, a large cap will have greater inertia than a smaller one. The larger cap will be slower to react to block (absorb) the spike than a smaller, more agile one.

Try a 10uF (electrolytic) at the LM317 and a 1uF (Ceramic or tantalum) at the LD.
 
chimo said:
If you put the capacitor in series with the LD, the circuit will not function.  It must be in parallel.  

With a circuit this LM317 circuit, a large cap is overkill and potentially (no pun intended) less effective than a small cap with a low ESR (equivalent series resistance).  The purpose of the cap is to absorb high frequency "spikes" of electricity.  The term "high frequency" is important - capacitors are manufactured with different properties.  How a capacitor deals with high frequencies depends on its size and type.

Try this analogy: if you think of capacitors as having inertia, a large cap will have greater inertia than a smaller one. The larger cap will be slower to react to block (absorb) the spike than a smaller, more agile one.

Try a 10uF (electrolytic) at the LM317 and a 1uF (Ceramic or tantalum) at the LD.
Click to expand...

Hi chimo,

Thanks for the heads up! Very nice analogy, as well. Unfortunately, I already bought some stuff from All Electronics, so I'll probably be stuck with using that, short of being ripped off by RadioShack. :-/

I guess I'll use the smallest capacitors I bought. I can use a 50V 47uF cap in front of the LM317 and a 10uF 50V tantalum soldered to the LD. Does that sound okay?

Many thanks!
 
Dude_With_Lasers said:
Can I run this off of a 9 volt batt?
If so, will the 317 need a heatsink?
:-?
Click to expand...

I could either:
Give you links to several posts in this thread,
Tell you to 'just search for it as this question has beed asked and answered more times than I can count',
Or just say 'if you use a 9V battery the voltage will sag so quickly that you won't need a heatsink if your LM317 is a TO-220 case, and it will only give you a few minutes of burning power. It would be much better to use 6 AA or AAA NiMH cells or 2 LiPo cells to power it.'

I think I'll go with the last one.
 
Ok. Sorry for not reading, but I really dont have the time. :-/
Can I use a 7.2 volt R/C car Batterie?
Do I need a heat-sink?
So, the 317 =-3v and the N40001 =-.2vThat leaves me with an even 3 volts. Is that corect?
I think it is, but I only read to page 7. :-[
 
Well i used a 7.2v ni-cd 500mah and it worked fine for me tho, the lm317 did get pretty warm with only a small heatsink on it tho...



....lazer..... ;D ;D ;D
 
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