3 ms·
At 120 V that's 0.36 W (if using both halves of the AC wave), if you use that 10 years non-stop you'll burn 31 KWh, a value of 5-20$ or so, thus if you were to
by pflanze 4y ago
At 120 V that's 0.36 W (if using both halves of the AC wave), if you use that 10 years non-stop you'll burn 31 KWh, a value of 5-20$ or so, thus if you were to produce many of these devices it would be worthwhile to lower :). But sure, for a one-off it won't matter.
OTOH I'm wondering how you didn't break the LED during the reverse cycles of the AC wave, if you didn't use either a high-voltage diode in sequence or some random diode or second LED in reverse direction in parallel to the first one to bypass the other half of the wave.
- mindslight 4y agoGood point about needing to plan for both halves of the wave. That's especially true for my capacitor suggestion. Last time I designed something (trickle supply) with line rated capacitors, the DC component was a zener which has that built in. My line capacitor suggestion was really just to get one started thinking about an actual circuit design for longer term. A 1/4 W resistor in serious with line voltage works fine on the test bench, but for longer term non-attended usage I would think about the various ways things could go wrong. And if you're going to spec a special resistor, then you might as well spec a special capacitor instead. If I had to guess about why the LED wasn't destroyed, it's because the reverse breakdown voltage is low enough that significant heat does not build up in the LED. A reverse avalanche isn't necessarily destructive.