Page 2 of 5 FirstFirst 12345 LastLast
Results 11 to 20 of 45

Thread: Starting a new project

  1. #11
    Join Date
    Feb 2011
    Location
    New Hampshire
    Posts
    3,513

    Default

    I like your tight build, but the retaining plates appear to back up 4 diodes simultaneously. Having gone this route, this can make fine tuning diode rotation difficult. Am I miss-reading this or have you worked around this alignment challenge?

  2. #12
    Join Date
    Dec 2006
    Location
    Essex, UK
    Posts
    8,616

    Default

    What issues?

    I had a funny diode I had to swap out, only took a few mins and had no rotation issues.

    This method works great for me
    Eat Sleep Lase Repeat


    Aluminium Optic Mounts

    http://www.laser-man.co.uk/opticmounts/

  3. #13
    Join Date
    Dec 2009
    Location
    MI, flint, farmington hills
    Posts
    569

    Default

    Andy i am correct in saying those are balance resistors right?
    You put them on their to make sure each diode gets the same current.

  4. #14
    Join Date
    Jun 2008
    Posts
    286

    Default

    no that can not be correct,. becourse you can not change the risistor so can not balance anything....

  5. #15
    Join Date
    Dec 2009
    Location
    MI, flint, farmington hills
    Posts
    569

    Default

    i am almost positive they are balancing resistors. someone with more of a rep will come in and confirm.
    There is a good reason you dont attach 4 diodes to 1 driver without those resistors.
    I have those same style resistors on my old dual loc build that used 1 driver.

  6. #16
    Join Date
    Feb 2008
    Location
    Northern Indiana
    Posts
    912

    Default

    Diodes are current devices... meaning they don't change there voltage much with current. When putting diodes or transistors is parallel (all + tied together and all - tied together) a balancing resistor is need. With out the resistors the diodes would have the same voltage across them. But due to variations in the VI curve they would all draw different currents from the driver. the resistors act as a equalizer. Joost is correct in thinking a variable resistor would be better. However, its common practice to use a low ohm high tolerance resistor to give satisfactory results.

    If Andy was to wire the diodes in series (+ tied to - to + and so on) the resistors would not be needed because the current in a series circuit is always the same. This lets each diode "set" its own voltage so to speak. In this case the power supply would have to deliver less amps but more voltage.

    Hope this helps.

  7. #17
    Join Date
    Jun 2008
    Posts
    286

    Default

    thanks !

    serie sounds good, my red also in serie!

  8. #18
    Join Date
    Oct 2007
    Location
    Wisconsin
    Posts
    305

    Default

    These resistors (Very Low Ohms) will allow for current monitoring of each of the diodes
    These are not to keep the current the same between all the diodes, the drivers are doing that.
    They balance out the load drawn by each of the drivers, they could be low ohmage fuseable resistors also but I doubt it in this case.

    Edit: Wow this is a great compact job andy!! Thanks for sharing!
    Last edited by LaserCo; 01-26-2012 at 17:41. Reason: Further thinking led me to the conclusion I was wrong in saying that he should have two resistors from drivers to main power

  9. #19
    Join Date
    Feb 2008
    Location
    Northern Indiana
    Posts
    912

    Default

    Look at the third picture in the second post.... Only one set of alligator clips suggesting all are in parallel. My guess would be he is going to use two flexmods with 4 diodes each. Not 8 separate drivers. Could be wrong though.

    Quote Originally Posted by LaserCo View Post
    These resistors (Very Low Ohms) will allow for current monitoring of each of the diodes
    These are not to keep the current the same between all the diodes, the drivers are doing that.
    They balance out the load drawn by each of the drivers, they could be low ohmage fuseable resistors also but I doubt it in this case.

    Edit: Wow this is a great compact job andy!! Thanks for sharing!

    Edit: And he may have 1 resistor for each of the drivers where they connect to the power supply! he should!

  10. #20
    Join Date
    Dec 2006
    Location
    Essex, UK
    Posts
    8,616

    Default

    yes 4 diodes per driver so two drivers in the module

    the next module will be 10 diodes and 10 drivers in the module
    Eat Sleep Lase Repeat


    Aluminium Optic Mounts

    http://www.laser-man.co.uk/opticmounts/

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •