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Thread: Dual setup resistor values..

  1. #1
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    Default Dual setup resistor values..

    With a dual diode setup and one driver...IE a Flexmod...will a 6 ohm , 1 watt TMF perform a safe balancing act? Pix to follow soon. Thanks in advance....or could I just move along with 8ohms and lose a little voltage in O bias?
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    6 ohms at 1A = 6W of heat dissipated

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    I don't think you want that much resistance, Mike. One or two ohms ought to be enough.

    Even so, as FOurDee already pointed out, you'll probably need to go with a wire-wound or ceramic resistor, since the power requirements are so high. (Even a 2 ohm resistor is going to dissipate 2 watts of heat with 1 amp of current flowing through it.)

    I'd suggest a couple 10 watt sand-filled ceramic resistors...

    Adam

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    .5 ohms per diode should do it. I'd be amazed if you needed more.

    Steve
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    I wanted to try and use parts that were on hand...order time...1 watt resistors sand boxes. Just hate to add things to get a minimum order...oh well. Thanks....Might try rip off shack....may have a couple of items of use besides the junk that is there.
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    Quote Originally Posted by MechEng3 View Post
    I wanted to try and use parts that were on hand...order time...1 watt resistors sand boxes. Just hate to add things to get a minimum order...oh well. Thanks....Might try rip off shack....may have a couple of items of use besides the junk that is there.
    Hey Mike!
    This is what I'm using... http://search.digikey.com/scripts/Dk...29405419176782

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    Could someone explain why you don't use them in series as I have scene done by others? Thanks
    leading in trailing technology

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    Default Can they be monitored?

    With even a low resistance across each diode, I'm running into a problem. I need to accurately monitor the voltage across each diode. But an added resistance in parallel will add to the voltage drop across the LD. How can I still monitor Vd using a panel meter?


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    Quote Originally Posted by Meatball View Post
    With even a low resistance across each diode, I'm running into a problem. I need to accurately monitor the voltage across each diode. But an added resistance in parallel will add to the voltage drop across the LD. How can I still monitor Vd using a panel meter?
    With multiple diodes in parallel and balancing resistors in series with each, Vd will vary between the diodes. That's why the balancing resistors are there. Assuming common cathodes, you could run a ~10k resistor from the anode of each diode to the + input of the meter. It would then read the average of the diode voltages. However, to know the actual voltage on each diode would require a separate meter for each one since they will be different.

    Why do you need to monitor Vd? It's usually not an important enough parameter to monitor. I'm just curious.

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    Quote Originally Posted by mpoulton View Post
    With multiple diodes in parallel and balancing resistors in series with each, Vd will vary between the diodes. That's why the balancing resistors are there. Assuming common cathodes, you could run a ~10k resistor from the anode of each diode to the + input of the meter. It would then read the average of the diode voltages. However, to know the actual voltage on each diode would require a separate meter for each one since they will be different.

    Why do you need to monitor Vd? It's usually not an important enough parameter to monitor. I'm just curious.
    Hey thanks, that's what I needed to know. I'm trying to come up with a testing station for some drivers I want to use for LDs. I want to be able to look at each driver's efficiency, and stability, and make an educated decision for the best driver to use for multiple diode configurations.


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