Re: Question for Dave regarding DROK


Joe Zeglinski
 

Woody,
 
    That’s impressive. Your example shows how the DROK compensates for the voltage IT IS BEING SUPPLIED, and “boosts” its conversion level to maintain an OUTPUT set point voltage (under or over) ... based on its own INPUT. This will work great for a battery supply, which gradually loses power. However, if the DROK supply is from say an AC/DC supply, and the household power dips a bit – for reasons I stated previously – I would assume that a well regulated AC/DC supply would likewise maintain voltage for the DROK, in this chain.
 
    My “feedback loop” was more about voltage drop in the resistance of wires from the DROK to the telescope stuff. Would the DROK still provide a steady 12 vdc output during load changes – CCD cooling variable load, or mount slews, where more amps are drawn and some voltage is lost to the cable resistance?
 
    The DROK maintains its own output steady, even as it is supplied by weak or spikey  power. But without a feedback line, the DROK wouldn’t know about raising its preset 12 vdc slightly, to account for the equipment load it is supplying. Then again, DC cables are 2-wire, so a feedback compensation would require a third wire, which means special 3-wire cable if we wanted compensated output.
 
    Anyway,  it is probably not that much of a problem, unless the DROK is driving an accessory at borderline voltage levels. If the equipment loads the DROK output, so that a bit more is lost along the DC cable, then the CCD might only be running with 11.5 VDC (even though the DROK is putting out 12 vdc at its output terminals).
 
    The DROK supplying reliably consistent 12.0 vdc to the CCD depends somewhat on the cable length joining them, and the size of the load variability. The DROK can provide “reliable power” BELOW a user set maximum level, but not compensate for lost power actually delivered at the load.
 
    I’ll leave it at that, since this is more of a “theoretical” possibility.
Must say, based on its reasonable  price and excellent user feedback, the DROK is a really nice device for supplying varied levels of voltage to our diverse accessories.
 
*****
 
    One other thing came to mind, while viewing that “bulky” oversized  DROK case’s  assembly video.
In the interests of saving scope space needed for DROK enclosures, for say,  TWO different voltage levels controlled by individual DROK’s - I was wondering if it would be possible to “stack” two DROK boards inside the same case.
Would be nice to have just one (switchable) DROK meter for both – using something similar to the old PC’s (parallel port “printer sharing”)  switch for its two IDC cable connectors. But, I suspect the meter itself holds dedicated parameters for just one DROK - thus not switchable. In such case, a second DROK panel meter might still  be attached to the back end, with the  fan(s) and output posts, relocated to the enclosure side panel(s).
 
Joe

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