Hps lights

Discussion in 'Hydroponic Cultivation' started by ThisBudsforYou, Dec 25, 2003.

  1. ThisBudsforYou

    ThisBudsforYou Guest

    I'm building my own ballasts. I was told the capacitor values differ for HPS from MH. They said light output from a switchable ballast is in the wrong spectrum as the capacitor is sized for MH. I can set it up as switchable capacitors also if I know what the optimum values are. Any ideas??
     
    ThisBudsforYou, Dec 25, 2003
    #1
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  2. Smurfy007

    Smurfy007 Veggy Stage

    Hi TBFY, first off I would like to inform you of what a capacitor is and the role it plays in a ballast.  


    What is a capacitor.  A cap is essentially the same as a battery, it's made up primarily of acid, it stores amperage, and discharges it when needed.  Unlike a battery, a cap can dishcarge up to 5 farad's worth of amperage with no resistence while sustaining a tremendous heat load.  If a battery were to do the same feat, it would be dead within a couple of discharges.  This is what makes a cap so desirable in assisting crest factor spikes.  What makes caps undesirable is the fact they are similar to a bomb if charged and discharged improperly.  They will explode, and leave a hole beside your wall if you are lucky.  Ever see a TV or VCR ignite suddenly?  Well that's 99% cap related, a small cap at that I might add.


    Now standard 120 VAC electrity in North America gives  a crest factor of 1.41.  That means the peak RMS voltage coming from your wall for an instant, during an appliance turn on period, is 168 V.  The closer your appliance comes to this crest factor, the more of the dimming of lights effect around your house when the appliances is initially turned on.  The crest factor for HID's exceeds the 1.41 crest factor in standard home AC so a capacitor is required to aid the initial sparking of the bulbs.


    A 1000 watt HPS ballast requires a 26 µF cap while a MH requires a 24 µF cap.  This is because an HPS ballast uses an ignitor to lower the crest factor and runs at 435 volts while a MH doesn't require a ignitor and runs at 425 volts.  It should be worth mentioning that a HPS Bulb requires an initial voltage of 3000 volts to strike the arc inside the gas charged tube.


    As for the light spectrum being different because of different sized caps.....I think you are being taken for a ride since light spectrum is the product of the gas charge inside the bulb and not associated with the mechanisms required to power it up.


    A switchable ballast is a HPS ballast with a switch to bypass the ignitor.  By doing this, the HPS ballast will light up a MH bulb since it has more than enough voltage to arc it.  The downside to this is the bulb will fail prematurely and the Cap is stressed unnessarily.


    For your safety, I don't recommend you screwing with the ballast as I don't believe you know what you are doing.  If you did, you would have been able to calculate the cap values.  Doing it improperly will create a time bomb wired to a timer; and though I don't know you, I hope to see posts from you again.  :wink:


    Hope that helps
     
    Smurfy007, Dec 27, 2003
    #2

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