----- Original Message ----- From: "John H. DuBois III" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Saturday, January 24, 2004 11:29 AM Subject: Re: EOS 550EX, flat batteries if left on ?
> On Fri, Jan 23, 2004 at 02:34:22AM -0000, Konstantinos Bibis wrote: > > I understand that. What i dont get is why and how is the unit > > consuming energy by doing nothing. After the tube is charged, does it > > need more power to conserve this charge ? > > It's not like let's say a capacitor where when it's charged it's > > charged? > > Yes, it's storing charge in a capacitor, and yes, you would think that it > wouldn't require much power to maintain it, since the self-discharge of the > capacitor should occur very, very slowly. But no matter how slowly, it will > require a periodic recharge to keep it "topped off". Also, the type of > charging circuit used in modern flashes depends on monitoring the voltage on > the main capacitor so that it knows when the capacitor is fully charged - but > the monitoring circuit itself drains charge from the capacitor, increasing the > standby discharge rate. > > The Canon approach to keeping the capacitor charged seems to be a bit > aggressive; it fires off several times a second. Once the capacitor is mostly > charged, the charging circuit probably isn't very efficient, so most of the > power it consumes is wasted. > > In the case of the 540EZ, after the capacitor is fully charged, the baseline > current drain is about 50mA. The charging circuit kicks in at 100ms intervals > for about 7ms (7% duty cycle), drawing about 800mA, which accounts for another > 50+mA on average. > > So, about half of the standy current consumption is used to maintain the > capacitor charge and about half by the rest of the circuitry - the flash's CPU, > monitoring circuitry, indicators, and such. > > Note, all of above is based on watching the battery current with an > oscilloscope and having designed & built many many xenon strobe circuits, so it > isn't neccessarily correct :) > > John > -- > John DuBois [EMAIL PROTECTED] KC6QKZ/AE http://www.armory.com/~spcecdt/ Thanks a lot John - that was the type of answer i was hoping for. It covers me 100%. Cheers. Konstantinos * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
