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Thread: M-140 Diode W/O cooling!?

  1. #11
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    Quote Originally Posted by VDX View Post
    ... I'm driving all my diodes with LM317 or LM338 as current-regulators and max. 12 Volts - the effective voltage will follow the current adjusted by the LM's.
    check out LT1083 too, it is a robust IC, low noise, low ripple, 7.5 amps
    "its called character briggs..."

  2. #12
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    ... I'm using until 5 of the LM317 (fix set up to 1A each continuous) or LM338 (up to 2A) in a driver with 5 jumpers, switches or relays - so it's possible to set the max. current in coarse steps from 0.5A to 9A and fine-tune it by PWM of the source with a MOSFET to any value from 0 to max set without problems.

    With a single LT1083 (I've tested this too) it's more complicated, as here I have to adjust the sense resistor for the max. current ... and with the single TO-220 housing it has a much smaller heat dissipation capability than 5 of the LM's ;-)

    Viktor

  3. #13
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    excellent! thanks

    that would be an interesting setup
    "its called character briggs..."

  4. #14
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    ... in post #3 I've linked to a wiki-page I've set up for some laser-cutter infos ... here the mentioned driver in detail: http://reprap.org/wiki/File:9Amp-driver.jpg

    Using is as easy as shown in the schematics in the wiki, the sense-resistor defines the current per LM ( I[A] = 1,25[V] / Rs[Ohm] ), the 0R22 resistors (smaller for higher currents) 'harmonize' the single LM's, so the summed currents will be averaged without oszillating, and PWM-driving the diode is done by switching the power to the network through a MOSFET (single TO-220 on the left side)

    Viktor

  5. #15
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    so what driver can i make?
    i am not an expert in soldering, but my friend helps me with that

  6. #16
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    Quote Originally Posted by VDX View Post
    ... but with only 500mA or 0.5Watts each, so not really overpowered ;-)

    Viktor
    they put diodes in spec'd at 1watt and run them at half power? that seems a strange thing to do?
    Eat Sleep Lase Repeat

  7. #17
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    ... I think, it's a matter of heat-dissipating (sizes/prices of coolers) and enhanced lifetimes with 'underpowering' the laserdiodes ...

    @mrfloppy - look at the specs of a LM317, decide, which current/power is enough and select the sense-resistor for this ... e.g. a driver for roughly 0.5Watts and 570mA is made with a single LM317 and a resistor with 2.2 Ohms (common used 2Watts or 5Watts-types) ... and an appropriate cooler for the LM ...

    Viktor

  8. #18
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    They're not underpowered per se, but they're pulsed in the projector. Much less heat output. They need to be pulsed because a DLP projector produces different colours by rapidly changing between colours, then rapidly moving the mirror array, turning on the mirrors needed for that colour.
    Last edited by Things; 11-23-2012 at 01:25.

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