WEBVTT

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One rectifies 12 Volts alternating full-wave alternation before filtering it by taking care of the wiring

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The receiver is the bulb, the oscilloscope displays the rectified voltage and the residual ripple rate

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I now set the oscilloscope in alternate mode to amplify the ripple and measure it peak-to-peak

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The capacitor is marked as 220 μFarad

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3.2 volts peak-to-peak

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For 90 mA current

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I demonstrate that a capacitor is a very inaccurate component: 60% tolerance on it!

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So here about 20% or +/- 10% ripple with respect to U mean

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We will apply C = I * t / U undulation

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Let 90 mA * 10 ms (rounded) / 3.2 V undulated (and especially not 14 V!)

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The capacitor works only under 3.2 V! The rounded result is 280 mA instead of 220 ...

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We will check with the capacitance if this capacitor does well 220 μF

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To be more precise, one should not take t = 10 ms, the period but ...

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But the working period of the capacitor from maxi to mini, here about 7 ms

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3.5 tiles or 7 ms (3.5 * 2 ms) to be precise!

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With the actual value of t = 7 ms, I find 203 μF

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Measurements are made with a receiver generating a lower intensity

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38 mA and only 1.5 V ripple therefore 10% of 15 V or +/- 5%!

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38 mA * 8 ms / 1.5 Volts

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We find 202 μF for 203 μF previously: beautiful precision!

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We will now measure the capacitor:

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At the capacitance we obtain 201 μF, that is 1% error! This unmarked component is at +/- 20% (standard non-marking), it is in the nails and our calculations were good!