Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers

LPF Donation via Stripe | LPF Donation - Other Methods

Links below open in new window

ArcticMyst Security by Avery

Need help with modwerx adjustable driver/LPC-815

Z

Z_mnypit

0
Joined
Jan 14, 2009
Messages
30
Points
0
I recently purchased a modwerx adjustable driver to run my LPC-815. Im having a hard time getting this thing adjusted correctly and dont want to LED my LPC before I hook it up. Im using a 9v battery for the power source. With the driver disconnected from the power source, Im mearsuring the restisance between the "thru Holes" on the board. Currently Im reading 22.5ohms. So 22.5ohms and 9v if the online calculator Im using is correct should be .4A X 1000 is 400mA correct?

Turned all the way counter clockwise I get around 30ohm so, .3A X 1000 = 300mA

Turned all the way clockwise I get 20ohm. .45 X 1000 = 450mA

Now according to the specs of the driver its suppose to be 30mA-470mA.. No matter what I do I cannot get these #'s. I do not have a dummy load, but according to the directions I can use an LED (which I have plenty of) or the "thru holes"

I did hook a white LED to the driver then adjust the pot until the color starting changing to a purplish color, then backed off a bit. Then measure the thro hole resitance and got 22.5ohms. I want to run the LPC around 400-420mA.

Am I missing something or does all this sound right?

(So much easier when you could buy the rckstr non adjustable drivers lol)
 





Benm

Benm

0
Joined
Aug 16, 2007
Messages
7,896
Points
113
Are you feeding it enough voltage?

You can use leds as dummyloads if you like - they arent perfect, but good enough for any adjustments. I often use luxeon star leds as dummy loads since i have plenty of those, and they emulate a laser diode rather well.
 
ndrew2505

ndrew2505

0
Joined
Feb 23, 2008
Messages
2,832
Points
48
i believe the dropout voltage is 1.25v so you need that much more V than your laser will draw. most people use 2x 3.6v batteries. a 9v will work but the amp/voltage draw will kill a 9v battery pretty quickly.

edit: you also have to be missing something.. all the rkcstr drivers are ~30-430ma +/- a few ma. if you have a 1ohm resistor you can use that for a test load. hook the ends to where the diode + and - go then test mv on each side of the resistor with the lowest v setting on your dmm.
 
Last edited:
Kevlar

Kevlar

0
Joined
Apr 26, 2010
Messages
1,353
Points
48
Z_mnypit said:
I recently purchased a modwerx adjustable driver to run my LPC-815. Im having a hard time getting this thing adjusted correctly and dont want to LED my LPC before I hook it up. Im using a 9v battery for the power source. With the driver disconnected from the power source, Im mearsuring the restisance between the "thru Holes" on the board. Currently Im reading 22.5ohms. So 22.5ohms and 9v if the online calculator Im using is correct should be .4A X 1000 is 400mA correct?

Turned all the way counter clockwise I get around 30ohm so, .3A X 1000 = 300mA

Turned all the way clockwise I get 20ohm. .45 X 1000 = 450mA

Now according to the specs of the driver its suppose to be 30mA-470mA.. No matter what I do I cannot get these #'s. I do not have a dummy load, but according to the directions I can use an LED (which I have plenty of) or the "thru holes"

I did hook a white LED to the driver then adjust the pot until the color starting changing to a purplish color, then backed off a bit. Then measure the thro hole resitance and got 22.5ohms. I want to run the LPC around 400-420mA.

Am I missing something or does all this sound right?

(So much easier when you could buy the rckstr non adjustable drivers lol)
Click to expand...

I believe this is incorrect.

I believe your calculations are wrong. If you want to set the rckstr driver by measuring the setting resistance between the thru-holes you use the following formula 1.25/Ohm reading on your DMM X 1000 = mA

I have a couple of these drivers and thought instructions say these is the least accurate to set your driver I found it off by only a couple mAs as I tested it both with this method and with a test load.
 
Last edited:
Z

Z_mnypit

0
Joined
Jan 14, 2009
Messages
30
Points
0
Kevlar said:
I believe this is incorrect.

I believe your calculations are wrong. If you want to set the rckstr driver by measuring the setting resistance between the thru-holes you use the following formula 1.25/Ohm reading on your DMM X 1000 = mA
Click to expand...

Thanks for the quick replies. so I divide 1.25/30=0.04166666 x 1000 is 41.6?????



So using 9v and measuring the thru holes what resistance should I see to get around 400-420mA?
 
Kevlar

Kevlar

0
Joined
Apr 26, 2010
Messages
1,353
Points
48
For setting the driver with this method, using the 9V battery doesn't become a factor because as you said in your OP, you don't power the driver when setting it this way.

So if you turn the pot until it reads 300 ohms that would give you about 416mA.
 
Z

Z_mnypit

0
Joined
Jan 14, 2009
Messages
30
Points
0
Kevlar said:
For setting the driver with this method, using the 9V battery doesn't become a factor because as you said in your OP, you don't power the driver when setting it this way.

So if you turn the pot until it reads 300 ohms that would give you about 416mA.
Click to expand...

Sorry, I was throwing that out there as the power I will be using. Ok, Ill try 300ohms or little less and see what it does.

Also going to pick up a 1ohm resistor and try that to verify
 
Last edited:
Z

Z_mnypit

0
Joined
Jan 14, 2009
Messages
30
Points
0
Just LED'd two LPCs. Set it 3.4 (same as the rckstr) and worked fine for a sec then went out. The other LED'd as soon as I turned it on. Guess its back to ordering more LPC's.
 
Kevlar

Kevlar

0
Joined
Apr 26, 2010
Messages
1,353
Points
48
Aw man, that sucks!!! Sorry about you loss. That is weird for 2 LED on you. I've had my LPC set wit the rckstr driver all the way to max for a while now (pot turned to least resistance) and it works fine.

Are you powering it with a 9V battery? If so, as Andrew said, it will kill you battery pretty fast. Those 9V batteries don't have enough capacity. Maybe you didn't LED you diodes. If you using a 9V battery, maybe it just drained the battery. Do you have any other power source with more capacity like 2 X 3.6V Li Ions?
 
Z

Z_mnypit

0
Joined
Jan 14, 2009
Messages
30
Points
0
Yeah 9v. It shouldnt drain it after like 30secs. My rckstr driver on a 9v will run about 30min total run time. I dont know what the deal is, Maybe I got a bad driver. I ordered a new driver and some more LPC's last night.
 
gillza

gillza

0
Joined
Jul 26, 2010
Messages
583
Points
28
Kevlar said:
For setting the driver with this method, using the 9V battery doesn't become a factor because as you said in your OP, you don't power the driver when setting it this way.

So if you turn the pot until it reads 300 ohms that would give you about 416mA.
Click to expand...

Kevlar I might be totally wrong here so please correct a n00b, but if you set the R to 300ohm and the Vout of the regulator on the circuit is only 1.25v so 1.25v/300ohm=0.00416A 0.00416A*1000=4.16mA .... So what did I do wrong :undecided: ?

Thank you.
 
Last edited:
ndrew2505

ndrew2505

0
Joined
Feb 23, 2008
Messages
2,832
Points
48
if your not trying to read the V out and just measure the current you can use a 1ohm resistor to measure current. just hook the resistor leads to the + and - and measure mV on each side of the resistor..

actually you can use any type of resistor.. just divide the output by the value of the resistor and you get your current. with a 1ohm resistor there is not math.. 1mv will equal 1ma
 
You must log in or register to reply here.




Top