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Thorlabs L658P040 Driver Construction/Selection

berget2

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I've got a thorlabs L658P040 laser diode that I'd like to turn on. I'm considering 2 options:

1. The simplest possible circuit to drive this LD without blowing it up

2. A cheap off the shelf driver that can be integrated with some microcontroller

Any starting points on either of these paths is greatly appreciated.
 
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Immo1282

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  1. LM317 set up in constant current mode, set at an appropriate limit (30-50mA? pulled this figure out of thin air but it seems reasonable).
  2. "Integrated with some microcontroller? What do you mean. Do you want to be able to turn it on and off rapidly (PWM for modulation), or do you want analog modulation (i.e. signals from the microcontroller adjust the actual current setting of the driver). Look for laser drivers with a TTL control pin and reading up on them is your best bet.
 

berget2

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How do I account for the monitor photodiode for a basic LM317 constant-current circuit?
 

Immo1282

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You can ignore it if you want to - you'd likely need more complicated circuitry than a basic LM317 CC circuit if you wanted to use the monitor photodiode. Provided you only drive the diode at safe current limits (according to it's datasheet) you dont strictly need to regulate it using feedback from the photodiode.
 

berget2

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So the photodiode mostly corrects for temperature drift, correct? If this trend is largely an exponential decay with reasonable lifetime I can just wait until its stable within 1% or something, but a linear drift will affect the measurement I'm trying to make.

I'll start with the basic LM317 CC and measure the output, but if I need PD feedback is there some cheap controller I can just purchase?
 

Cyparagon

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Yes, it would be an exponential decay, and would stabilize within a few minutes at most.

I'm not aware of a standard driver that utilizes photodiode feedback, but this is likely because no one around here cares about stability. There are schematics available you could build from, but a standard constant current source sounds like it will be enough for you.

What are you building?
 




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