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

resistance measurement & LD output troubleshooting

Joined
Feb 25, 2008
Messages
2,128
Points
63
I'd like to verify this to make sure I'm correct in my thinking.

Let's say I have two 1.9 ohm resisters in parallel. The actual resistance would be .95. The multimeter should read .95, right? I get ~2.4 ohms across one pair and about 1.8 across the other. See the diagram below to understand.

The 660 in my projector wasn't working. Turns out both diodes went LED so I replaced them. The output still wasn't anywhere near what it should be. The driver is a Lasever LSR-PS-I. I cna't get the output to go over ~350mA. The voltage is ~3.99 with the laser on. The driver is supposed to put out up to 2A though.

The driver Lasever Inc.-LSR-PS-I

This is the way it was set up when I bought this projector so don't blame me. lol

attachment.php
 

Attachments

  • LD.jpg
    LD.jpg
    13.7 KB · Views: 82





GatoX

0
Joined
Jun 8, 2014
Messages
87
Points
8
I'm thinking... You have 4V, right? And your only limitation are 2Amps from driver and the resistor of 0.95ohms. V=I*R -> 4=I*0.95 -> I = 4.21A... If you're searching 350ma, go to amc7135, is the better option
 
Joined
Sep 12, 2007
Messages
9,399
Points
113
Your resistance measurements are off because of the lead resistance, as well as the contact resistance of your probe/resistor junction. Don't worry about that - it looks close enough.

The issue here might be related to dropout voltage, or possibly a questionable electrical contact somewhere. This is going to be a linear driver, since switching drivers will have a hell of a time with 30k analog input. That means it has a minimum dropout voltage, and cannot supply the output voltage to push the current you want with the load configuration you have.

The following measurements will confirm this: Voltage input, voltage output, and the voltage across the laser diode.
 
Last edited:




Top