blue ray driver options??

[Benny_Hill]

I have run harvested reds and IR's from LG burners with no regulator with no problems. I typicaly use 2x33ohm resistors a cap and a diode for polarity reversal. If I do the same with the blues, and restrict the current, what type of voltage should I use 4xaaa for 6v or higher? I was also thinking of using some LR44 button cells instead, seeing as the current draw for the diode is 50ma. Using Gazoo's circuit is probably the safer bet, but its too bulky for what I want to do. If these diodes can handle up to 9v do I have to worry about voltage spikes when using 4 or 5, 1.5v cells?

 

[Benny_Hill]

So the batteries im thinking of trying are 1.4v (zinc air) energizers, meant for hearing aids. Hopefully they have enough juice when 5 are used in series, has anyone tried this type of config?

 

[Benny_Hill]

Also, on a spec sheet for BR, I noticed that the wavelength begins to increase from the 405nm area and approaches the 473nm rehlm when the voltage to the diode is increased. Does this same rule apply to the ps3 sleds from psxboy.com?

 

[Benny_Hill]

anyone?

 

[rkcstr]

I have run harvested reds and IR's from LG burners with no regulator with no problems. I typicaly use 2x33ohm resistors a cap and a diode for polarity reversal. If I do the same with the blues, and restrict the current, what type of voltage should I use 4xaaa for 6v or higher? I was also thinking of using some LR44 button cells instead, seeing as the current draw for the diode is 50ma. Using Gazoo's circuit is probably the safer bet, but its too bulky for what I want to do. If these diodes can handle up to 9v do I have to worry about voltage spikes when using 4 or 5, 1.5v cells?  

The blu-ray diodes are very sensitive, I wouldn't chance it with a questionable driver.  And, what exactly are you doing that a regulated driver is too big for?  If we had more details on your intended application, it would be helpful.

Also, try the "Modify" button instead of replying to yourself

 

[Benny_Hill]

Im trying to fit it in something handheld, like a pointer. I dont want to spend "wicked dollars" to get a nice pointer. Also a collegue of mine has a birthday coming up and hes a science teacher who loves anything unique. But I dont want to give him something bulky and lobsided, so im trying to cut the size to minimal as possible. Ive noticed after playing with the proto. that it has a tendancy of getting warm, but the output hasnt been affected. Is this normal, or am I missing something? (probably)

 

[rkcstr]

I suppose you could use a cap, diode and resistor to run it, but the problem would be the output wouldn't be constant and would decrease output as the batteries lose voltage. And, make sure you choose a resistor for the highest voltage output of the battery, which for alkalines tends to be slightly higher than their rated output.

And the "tendancy to get warm" is that refering to the diode? I'm not sure I understand what you're asking.

When are you wanting to have something for? I'm working on some drivers that are really small, I may be able to help you, but it won't be for a few weeks.

 

[Benny_Hill]

Yes the diode in the current config. gets warm, but the output doesn’t seem to be affected. I placed the axiz barrel inside a larger heatsink, and it seems to be a valid option whilst the details are worked out. With the setup I am trying, the max voltage on fresh cells is 5.5vdc 250ma which drops rapidly due to the button cells being used. I am new to the circuit aspect right now, so please bare with my bouts of ignorance. With the supplied numbers what do you think would be a suitable resistor? I don’t mind a lower output, of say 7mw? And is the standard 103 cap good for this? My problem is that I don’t fully comprehend the slight variations in the components used and why, this is where I tend to get confused

Thanks again for your help, if it weren’t for this forum, I probably would have blown at least one by now


PS im trying for Mar. 04th as his biirthday is on the 6th

 

[rkcstr]

Well, the reason it's getting warm may have to do with the current it's being driven at. As for the proper resistance, I believe you can use a standard "LED calculator" to get the resistance you need, just search Google for it. Basically, you put in the highest input voltage, the forward voltage of the diode (should be somewhere between 4.25-5V) and your intended current (around 35-40ma should be good).

A 103 capacitor is only 10nf, which is pretty small. Comparatively, I usually use a 47uf cap, which is 47,000nf. I'd say find a small tantalum or electrolytic cap to use, they'll have a much higher capacitance and you can usually find pretty small ones, just make sure the voltage rating is higher than 10V. Even it's only 1uf, that's better than what you're using. The reason for using a cap is that voltage from batteries isn't just off and on, when you first connect the battery, there tends to be a very brief, but large jump in voltage before it settles to it's average output. The capacitor absorbs the spike as it charges up as the capacitor will draw the current from the source first because it's resistance is low when discharged and increases as it charges to a very high resistance when it reaches it's full capacity. It kind of works like a buffer for voltage preventing a spikes and smoothing the voltage reaching the diode, preventing damage.

There is also a circuit I've seen mentioned that uses a small TO-92 sized voltage regulator, the 7805 (?), that should also be pretty small and would provide some actual regulation for the diode. You can try looking into that as well.

 

[jayrob]

Im trying to fit it in something handheld, like a pointer. I dont want to spend "wicked dollars" to get a nice pointer. Also a collegue of mine has a birthday coming up and hes a science teacher who loves anything unique. But I dont want to give him something bulky and lobsided, so im trying to cut the size to minimal as possible. Ive noticed after playing with the proto. that it has a tendancy of getting warm, but the output hasnt been affected. Is this normal, or am I missing something? (probably)

I found this host to be an excellent host for a blu-ray:
http://www.laserpointerforums.com/forums/YaBB.pl?num=1202168096/0
Take a close read at that thread. There are links to parts too...
Jay

 

[toked323]

i would suggest 6volts and a 47ohm resistor

 

[Benny_Hill]

While waiting for a response, i tried to use two of the microresistors found on the driver board from a small radioshack pointer. Its labeled 151 and when measured read 151ohm. I placed two of these in paralel and was getting 40ma, but the diode wont lase. Im thinking that they also may regulate voltage, as the original diode the 151 is used on measured 20ma and 2.5v across the diode. Wouldnt a 47ohm resistor give close to 80ma @ 6v? The other problem is that the usual resistors i use are too big and have to go with something smaller, but im kinda nervous going lower than 75ohm seing that its 40ma. Im probably missing something here, but if your sure that 47ohm isnt too low ill give it a shot.


Added--- Also the button cells are rated 1.4v each, but on the meter show 1.35 im using 4 of these comes to 5.4 @ 250ma, is this the numbers that would suit a 47ohm resistor?

Thanks

 

[rkcstr]

OK... I'm guessing you didn't look for the site I was talking about earlier.  Go here:

http://www.hebeiltd.com.cn/?p=zz.led.resistor.calculator

Inputing 5.6V (that is 4 x 1.4V), with estimating a forward voltage for the laser diode of 4.5V and outputing 40ma, the calculator predicts a 27ohm resistor should be put in series with the laser diode, 33ohms is the nearest standard value.

The resistor acts to drop the excess voltage from the battery to the diode while at the same time limiting current.  As I said before, though, this voltage and current regulation is entirely dependent on the supply voltage, meaning that as the battery loses voltage, the voltage and current to the laser diode will also drop.  

I don't know the lasing threshold of voltage for the diode, but for current, it's somewhere around 25ma, so once the output is limited to below 25ma, the diode may not lase anymore, but just give off a dim violet light.  An easy way to determine the driving current is to measure the voltage across the resistor (say 1.32V) and measure the EXACT resistance of the resistor (say 33.0ohms), that equates (using Ohm's law, I=V/R) to 0.04A or 40mA.  But once the voltage drops to around 0.825, that means the output is only around 25mA and possibly below the threshold for the diode.

Unfortunately, the Blu-Ray diodes are pretty variable in their forward voltage (I measured 10 of them, and they ranged from 4.33V to 4.98V at the same driving current).  And since your battery voltage input will constantly change, the output will probably drop off quickly with use, especially using the button cells.  

All I can tell you is to experiment around and see what you can get out of it.  Just be careful, the diodes are sensitive to voltage spikes caused by static discharge and if you connect a charged capacitor to them.  So, always ground yourself to prevent static and always short out the capacitor before connecting AND disconnecting it from the laser diode.

 

[Benny_Hill]

Thank you for your response, the link you provided was very helpful and will definately aid in my understanding of things. I have a background in computer repair, automotive electronics etc, but all of that is pretty straight forward in comparison to the sensative nature of the components used here. I am looking at different options, and trying to figure out the best path to take. So far everything is pointing to sticking with a regulator, but I will try both and see what result is the more suitable for my application. Over the next couple of days I plan on spending more time reading, and less time doing. I will post my results from the different methods tried, and hopefully have only working diodes in the end.

Thanks,

Benny.