Started by fly-navy, January 20, 2015, 14:35:08 pm
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Quote from: TonyKing on January 20, 2015, 15:01:42 pmThe capacitor is fitted to prevent brown out on the receiver
Quote from: Phil_G on April 26, 2011, 13:42:58 pmI've posted this a couple of times, but to reiterate:The idea of a capacitor as some sort of reservoir to supply servos during transient current demands is just unfeasible.Take the example of a 4700uF capacitor. How much energy will that store?F = C/V, and V = 5 Volts, F = 0.0047 Farads, thus C = 0.0235 Coulombs = 0.0235 Amp*seconds = 0.00653 mAhA 4700uF capacitor has a A/H capacity of point zero zero six of a milliamp-hour. A perfect 4700uF capacitor would supply 3A for just 7.8 milliseconds. Thats discharging it down to zero volts, not the 3.5v (?) minimum we need, which from BEC voltage would be reached in 2 or 3 ms. Once discharged, it contributes nothing, in fact actually absorbs more current if the voltage recovers, which will very slightly extend the time the supply takes to get back to working voltage.Extra decoupling is usually good thing & wont do any harm, but its not a magic bullet, and it won't prevent brownout or 'take over from the BEC' if the voltage sags. CheersPhil
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