Micro-Drive laser driver by rkcstr

[robjdixon]

On the positive side, before the driver.

 

[rkcstr]

Depending on how much extra voltage you have to the driver, it may not do anything to change the current. That would effectively drop a voltage and lower the input to the driver. As you drop below the threshold voltage for current regulation, current output would begin to drop, but it also would not be regulated, so it would continue to drop as the battery voltage changed as it discharged.

Also, you would have to be careful with how much current you're running since as you drop more voltage, it will dissipate heat. You should make sure your pot is rated to handle the power at it's maximum resistance and the maximum current you intend to run.

 

[gbl]

rkcstr, so where can we find a host for the 3 batteries we need for the driver ?

 

[pwNd]

you can get mxdl 3*AAA flashlight and some AAA size but higher voltage batteries. You can get it all on dealextreme.com

 

[rkcstr]

Hey gbl, sorry for the delay. Actually I typed up a response shortly after you posted that, but I was at work on my phone and got an error when I went to post and lost what I typed. Meant to come back, then forgot to do it, haha.

Anyway, as pwNd said, a 3xAAA host is what you need. You can use the 10440 sized lithium batteries, which are the same size as a AAA. Dealextreme is one source, but you can also find them at other various Chinese retailers and even locally. Jayrob makes heatsinks that fit specific models from Dealextreme and I believe other members on here also offer other DIY hosts that use 3xAAAs; just look around the B/S/T forum.

 

[daguin]

Did you ever get a chance to do this test? I use a bench PSU for my diode tests (and your driver).

Peace,
dave

For 7V output you'll need at least 9.25V input voltage, ideally over 10V to allow some overhead, especially with batteries. Theoretically, 3x 3.7V lithiums should be enough voltage, but I haven't tried it personally to tell you for sure they will work. It could be that the dropout voltage of the driver increases at that high of an output voltage and therefore the input voltage requirements of the driver also increases. It could also be that the lithium batteries voltage is dropping while under load, enough so to drop below the minimum required voltage for the driver.

If I get a chance on Sunday, I'll see if I can test a driver out with a >10VDC wall adapter on a load that is ~7V and see what happens. If it works fine, then it is probably the batteries, if not, then the driver.

Or, if you're not happy with the driver, you are welcome to return it for a refund.

 

[rkcstr]

Oh, yeah... I forgot about that. I did test out a ~6.5V load with a 9V input and it seemed to max out around 300mA. I wasn't able to test much more than that, though.

I suspect that what is happening is that the IC chip's required overhead voltage needs (the dropout voltage) are increased with that high power of a load (remember, 6V at 300mA is TWICE the power of 3V at 300mA). So, I'm guessing that there may be a decrease in efficiency at that kind of load. I had never tested (nor expected) that high of output voltage, but it is within the limits of the IC.

I didn't check to see if a 12V load made a difference or not, though. I suspect higher input voltages could allow for the full output current from the driver, but I didn't have a 12V power source readily available.

 

[Mohrenberg]

i drove the BDR-203 with the rckstr at 325mA without any problems, using two CR123 batteries, (4.25v at full charge)
no idea what kind of load it was pulling though. check out brew's 8x black/blue marble kryton

 

[rkcstr]

If the forward voltage of the diode is close to 5V, then you might have no problem getting away with two 3.7V lithiums.

Do I remember correctly that the "true" 8x diodes (salvaged from the actual drives) had a relatively low Vf, but the "sourced" 8x sleds tended to run higher? Like around 5V compared to 6-7V at higher currents like >250mA?

Forgive my lack of knowledge at this point, school has kept me from staying up to date on the ever changing world of DIY lasering

 

[daguin]

If the forward voltage of the diode is close to 5V, then you might have no problem getting away with two 3.7V lithiums.
Do I remember correctly that the "true" 8x diodes (salvaged from the actual drives) had a relatively low Vf, but the "sourced" 8x sleds tended to run higher? Like around 5V compared to 6-7V at higher currents like >250mA?
Forgive my lack of knowledge at this point, school has kept me from staying up to date on the ever changing world of DIY lasering

The diode with the high voltage need was harvested from a Pioneer BDR-203. What we were sold as an S03 has pretty much been proven not to be an 8X diode. People using the LG BH08 are not reporting such a high voltage requirement.

I have harvested both now. The diodes from the Pioneer BDR-203 and the LG BH08 are the same diodes. The exceptional voltage requirement may have just been my first diode and/or it only occurs well above 365mA

I'm not quite sure what happened during the test. It does not appear that anyone else took it as high as I. The problems began above 365mA. I took the diode up to ~400mA, but lowered it back to 365mA for the finished laser.

365mA was NOT a decision based on some kink or problem. It was simply the point where the diode was producing 400mW after acrylic lens. It was just a nice round number and well below where the problems started. It wasn't until I replaced the acrylic with the 405-G that the output went to >500mW. That was a very pleasant surprise. It was NOT a plan.

Peace,
dave

 

[rkcstr]

Cool. I'm glad to hear that people are having success with the 8x and my driver, though. I have yet to try one, sadly. Maybe after I finish up my internal medicine block this week...

 

[Darkarmyofone]

I have had perfect success with the V3 rkcstr driver and 8x diodes since the V3 came out.

@rkcstr - i got the broken drivers today, (and the 10 pack) and 3 of the broken drivers work, the rest either dont, or the current drops FAST to nothing. thought you'd wanna know. their pretty much toast. dont know what you want done with them. let me know via PM.

Tyler - Dark Lasers

 

[matrixcs]

anyone wanna send me a defective rckstr driver??? thanks!

 

[IgorT]

• Advanced protection for the laser diode and driver function against reverse polarity and voltage spikes.

I was there when Rkcstr designed his protection, and i must say it really is ADVANCED!


I tested it with three full Li-Ion voltage (3 x 4.2V = 12.6V) from my adjustable Lab-PSU, and it worked just fine.

Regular Li-Ions will sag under load, so the most the driver will ever see is 3x 3.9V = 11.7V which is within the protecting MOSFET's official range..



The MOSFET fully protects against wrong polarity, and creates a fool proof "shield", even if someone was dumb enough to turn all three Li-Ions around.....

Then there is a Schottky, which shields the last 47uF Tantalum directly across the diode, by creating a short if all else fails, but the MOSFET can't possibly fail.



You need TWO Li-Ions for reds, THREE for BluRays, NOT TWO!!!

You also need a big heatsink...


But this affordable driver is more stable than the FlexDrive and better suited for big heatsink lasers.



There are good three AAA hosts out there, so use those for BluRay diodes with a room for a large heatsink from Jay, with tutorials....



Just a little info...

Some people probably don't realize what a service by Rkcstr it is to sell drivers so cheap, that were made to be this good, and tested by an electronics engineer for stability...


He used to etch these by hand, and then solder the kits too!
And for barelly any money too!


You should all give him some rep for this....


Otherwise everyone would have to solder these by hand themselves!

I used kits, so i know how much work it is to solder them. I never asked Rkcstr to solder them for me by hand, i would feel silly. :angel:

 

[IgorT]

I have had perfect success with the V3 rkcstr driver and 8x diodes since the V3 came out.

@rkcstr - i got the broken drivers today, (and the 10 pack) and 3 of the broken drivers work, the rest either dont, or the current drops FAST to nothing. thought you'd wanna know. their pretty much toast. dont know what you want done with them. let me know via PM.

Tyler - Dark Lasers

Send them to me, i'll fix them for free..

How about that dummy i asked for?

 

[IgorT]

The diode with the high voltage need was harvested from a Pioneer BDR-203. What we were sold as an S03 has pretty much been proven not to be an 8X diode. People using the LG BH08 are not reporting such a high voltage requirement.

Did you measure the voltage directly from diode with two wires and another DMM?