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Go Back   Laser Pointer Forums - Discuss Laser Pointers > Lasers > Drivers, Test-load, Power Supply, & Batteries



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Old 01-07-2014, 04:05 PM #1
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Default 2w m140 test load?

Can anyone suggest a test load to mimic a 2w m140 diode (in the mail from dtr at the moment!)? If anyone knows the resistance that would be best, so I can just eBay a resistor for it. Any input appreciated! Steve.


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Old 01-07-2014, 04:43 PM #2
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Default Re: 2w m140 test load?

Use a bunch of diodes in series and an ammeter, no need for a resistor
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Old 01-07-2014, 05:57 PM #3
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Default Re: 2w m140 test load?

I'll only have the 1 diode when it arrives so I'm just looking to buy the appropriate resistors from eBay, since they're dirt cheap. I want to make sure my driver is putting out only 1.7amps before I put my diode on it (it's an adjustable jobby). Even if I had multiple diodes though, wouldn't that increase the resistance and thereby lower the amps? So I'd measure my 1.7 amps with multiple, then when I put just 1 diode on have more than 1.7 amps flowing. If I remember my Ohm's law anyway...
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Old 01-07-2014, 06:41 PM #4
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Default Re: 2w m140 test load?

You are assuming that your driver is a constant voltage source. It is a constant current source, so more diodes increases the load's Vf, and would lower the current if the driver's output voltage stayed the same. Therefore, the driver ups its voltage output until it is putting out its set current.

You are also assuming that all diodes have the same Vf. A typical silicon diode has a Vf of 1V. It also doesn't put out near as much light as a laser diode ;-)
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Old 01-07-2014, 10:52 PM #5
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Default Re: 2w m140 test load?

Aha, thanks, that makes sense. These regulators are smarter than I thought (yes, assumed ) So basically I can use anything that won't require morev volts than the driver can put out... I'm thinking flashlight bulb.
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