Testing Power supplys

Discussion in 'Hardware' started by unholy, Feb 18, 2006.

  1. unholy

    bigal

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    bigal, Mar 5, 2006
    #21
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  2. unholy

    The Modfather

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    Forum bug here Ian, the list shows this thread as having 2 pages, it actually has 3 but I can't get to the 3rd page, I can only get to the 2nd one, if I click the 3rd page (once entering the thread) it just loads the 2nd page. Will you see this post? Who knows? I doubt it.
     
    The Modfather, Mar 5, 2006
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  3. unholy

    XhArD

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    I see it :)
     
    XhArD, Mar 6, 2006
    #23
  4. unholy

    unholy

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    me too, maybe theres something wrong with your head modfather :p

    That review explains the effc. But i wanna know what their home made load tester is :p
     
    unholy, Mar 6, 2006
    #24
  5. unholy

    The Modfather

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    Whose home made load tester???

    Um, no the bug was here, I swear.
     
    The Modfather, Mar 6, 2006
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  6. unholy

    bigal

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    Read the PSU review and you shall see what they're talking about.:handkiss:
     
    bigal, Mar 6, 2006
    #26
  7. unholy

    The Modfather

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    Oh, the review, er, yeah, I thought we were still talking about the whole effeciency thing. :)
     
    The Modfather, Mar 7, 2006
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  8. unholy

    unholy

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    Lol, i have no idea where i am going o get a reistor that will do more then 10 Watts :|
     
    unholy, Mar 7, 2006
    #28
  9. unholy

    bigal

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    Look for power resistors.
    [​IMG]
     
    bigal, Mar 7, 2006
    #29
  10. unholy

    unholy

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    Ok, so i get like 10 of the same reistor and hook it up like this

    .|
    /|\
    012
    \|/
    .|

    0 being reistor 1 and 2 being reistor 3. "/,\,|" being wires, "." being Spaces to fill in gaps

    12v/5a = Ohm = 125, round off to 120.

    120OHM 5 WATT WIRE WOUND RESISTOR, or should i be looking at Ceramic?
    100+ $0.18

    What about..

    Nichrome Resistance Wire - 4 metre pack

    Used for wiring heating elements etc. 80% nickel, 20% chromium. - Resistance 13.77 ohm per metre.- Size 28 B&S (0.315mm).Pack of 4 metres.
     
    Last edited: Mar 7, 2006
    unholy, Mar 7, 2006
    #30
  11. unholy

    bigal

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    You are looking to dissipate 60Watts of power (P = V * I, or 60 = 12 * 5), and you increase the power handling by putting the resistors in parallel. However, the resistance also decreases when you put the resistors in parallel. For example, two 10-ohm resistors in parallel give the equivalent of 5-ohms resistance, but with the power capacity of the two resistors. See this page for a handy calculator for resistors in parallel: http://www.1728.com/resistrs.htm
     
    bigal, Mar 7, 2006
    #31
  12. unholy

    unholy

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    So if i have 10 120 OHM 10 Watt Resistors i would get 100 Watts of Power ability and 10ohms of Resistance? and 1 amp of load on 12volt
     
    unholy, Mar 8, 2006
    #32
  13. unholy

    bigal

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    Almost. No to 100 Watts. Yes to 10 ohms, and yes to a 1 AMP loading. Each branch would provide 100 mA (I = 12/120), each branch would dissipate 1.2 Watts (12V * 100 mA). You have 10 branches, so you will draw 1 AMP, and you will dissipate 12.2 Watts. Now you see that you need to adjust your resistor size and the number of resistors.
     
    bigal, Mar 8, 2006
    #33
  14. unholy

    unholy

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    So Dissapation is the amount of power that still travels through the Resistors?

    I will make a little program to calculate this.
     
    unholy, Mar 9, 2006
    #34
  15. unholy

    bigal

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    I would say that dissipation is the heat energy released by the current flowing through the resistor. Power is a measurement of that effect. Since each branch sees the 12 volts, each branch will dissipate the same amount of power, assuming the resistor values are accurate and they all drift in their resistance values equally over temperature.
     
    bigal, Mar 9, 2006
    #35
  16. unholy

    unholy

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    But its all Still Load am i correct? or is the Dissipation no considered in the factor, or is it more energy loaded onto each resistor?

    If i have read and understood al correctly do you mean that dsspation is the Load kept in the resistors. aka the amount of power that is being used.


    Included is the Calculator so far, there is not dissapation calulations, because i dont understand what this dissiaption factor Al is talking really is.

    It has Calculate Resisotrs required to Load x Amp at y Volts when u have z watts max per reistor. And it also functions to get the ohms from the resistor count.
     

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    unholy, Mar 9, 2006
    #36
  17. unholy

    bigal

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    Dissipation is the power consumed by the device under test (DUT). It's a general term meant to account for the heat energy given off as waste heat. Obviously there is energy used to switch transistors and perform other functions within devices; I would say we generally look at power dissipation as a measure of how much energy you must put into a DUT to have it function for your design. Just concern yourself with calculating power as voltage times current.
     
    bigal, Mar 10, 2006
    #37
  18. unholy

    unholy

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    So this Dissipation Has nothing to do with the Load put on the PSU? or does it have part to do with the load in general nothing to do with changing it.

    Is it just the Heat Energy Put off by the resistors.

    I have included a diagram with this post, its off the Loader. u Might be able to read them but heres the info :)
    Code:
    12volt= 24Amps
    200 120 Ohm 5 Watt Resistors ~$36
    10 Per Amp
    
    Load 12v Cost = ~$53.28
    --------------------------------------------------
    5v = 46amps
    90 10 Ohm 5Watt Resistors ~$18
    2 Per Amp
    
    Load 5v Cost = ~$32.4
    --------------------------------------------------
    3.3volts = 20Amps
    20 3.3 Ohm 5 Watt Resisitors ~$4
    1 Per Amp
    
    Load 3.3v Cost = ~$18.4
     

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    unholy, Mar 10, 2006
    #38
  19. unholy

    bigal

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    Loader diagram...

    ...is kind of small for reading, but I get the idea. You are basically making a setup to switch in and out different loads for the PSU (our DUT in this case). What you are finding is that it takes lots of resistors to come up with maximum loading if you can't get high-current or high-wattage power resistors. I think it's gonna be cheaper to go with fewer high-wattage resistors in your situation, since your listed prices are quite high.

    For example, use 45 20-ohm 5-Watt resistors in the 5 Volt test loop. It would be nice to have higher-wattage resistors, but you won't be leaving this on too long, right? It's like turning on a heater element.:bandit:

    The dissipation of the load is the heat energy released. You could compute this in several units, even joules. Stick with Power (Watts) = Voltage (Volts) times Current (Amps)
     
    Last edited: Mar 10, 2006
    bigal, Mar 10, 2006
    #39
  20. unholy

    unholy

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    10 Minutes to 11 Minutes Load. I will Be putting the Ressistors onto a Curcuit Board and a heatsink to keep them cooooool, :) thats if i need too :p

    i Could get the 10 Watt resistors but they cost like 20 cents more per resistor
    I will mention though these prices are in AU Dollars :p and from a wholesaler, aka where Jaycar gets their stuff.
     
    unholy, Mar 11, 2006
    #40
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