From: ehsjr@verizon.net   
      
   On 12/26/2025 12:56 PM, Cursitor Doom wrote:   
   > Gentlemen (IOW not you, Bill),   
   >   
   > I've got a bunch of green laser diodes which are specified for 370mA   
   > current draw. I've been using a straight 5 ohm WW resistor rated at   
   > 10W as a dummy load, but it's crude and inaccurate. Is there something   
   > better I should be using? I've got some 2W blue ones to do later on as   
   > well so something which could be adapted for those would be a plus.   
   > Ideally something which mimics the knee you get as it starts to   
   > conduct.   
   >   
   > Cheers,   
   >   
   > CD   
      
   If you want something better than a 5 ohm resistor dummy   
   load, see the LM317 datasheet figure 8.8   
      
   As you did not specify your supply voltage, I don't know   
   how close your 5 ohm resistor dummy load is to drawing   
   370 mA when connected directly across the supply.   
      
   If you put the LM317 circuit in series with your 5 ohm resistor,   
   you compute the current drawn by by  1.2/R1.  So, for example,   
   if R1 is 3.25 ohms the current drawn will be ~369 mA.  This of   
   course assumes a supply of enough "grunt" and within Vmax   
   for the 317.   
      
   Some more detail:   
   R1, at 3.25 ohms, will dissipate around half a watt. Use   
   at least 1 watt. I don't know what you have on hand - I'd   
   use power resistors - a 3 ohm in series with a .25 ohm.   
      
   Ed   
      
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