Old 08-28-2015, 12:31 PM #1
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Default resistance measurement & LD output troubleshooting

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

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resistance measurement & LD output troubleshooting-ld.jpg  


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Old 08-28-2015, 10:20 PM #2
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Default Re: resistance measurement & LD output troubleshooting

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
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Old 08-29-2015, 12:39 PM #3
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Default Re: resistance measurement & LD output troubleshooting

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.
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Last edited by Cyparagon; 08-29-2015 at 12:41 PM.
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