Trying to blow up a night light and failing.
Added 2021-01-02 19:07:43 +0000 UTCThis classic Chinese night light has one very appealing feature that makes it non compliant with most other countries. You can change the LEDs at the risk of exposing small areas of live metal while doing so.
I wondered what would happen if the LEDs were left open circuit. It seems like an ideal application for a zener, but instead they chose to use a resistor with a value juggled between capping the open circuit voltage versus compromising the current available for the LEDs.
I wonder why they didn't use a zener diode. Is it too expensive?
Comments
Yes. Half watt will be fine. It's more for the voltage rating.
Big Clive
2021-02-15 04:38:49 +0000 UTCThanks Clive. I will use part of that circuit to make some LED lights for the house so I can see just enough in the dark when I want a wee in the night, Question the 1 meg resistor across the cap would a half watt work OK?
Nuts 'n' Proud
2021-02-15 01:15:58 +0000 UTCWhen I cut LED wires I still leave the short wire a little shorter (just a mm or so) that way I don't have to "look inside the LED" to get the polarity.
Zeedijk Mike
2021-01-05 09:25:27 +0000 UTCI was wondering when I saw the video. Thanks
Michael Thompson
2021-01-05 09:06:21 +0000 UTCI don't think I did. The current is so limited that it would really take the high open circuit voltage to do the damage.
Big Clive
2021-01-05 03:01:40 +0000 UTCAre you sure you didn't just short the thing with that clip?
Michael Thompson
2021-01-04 19:36:55 +0000 UTCAs the voltage increased the current would drop slightly due to the fixed capacitive reactance. It failed faster than the meter could respond.
Big Clive
2021-01-03 19:51:04 +0000 UTCI was wondering when the transistor VceMax would come into play. Voltage alone doesn't kill them; they avalanche and you probably got a hotspot. If the resistor was up at 180, how hot do you think the silicon got? You could try replacing the transistor and watching it fry on the thermal imager.
Mike Page
2021-01-03 09:41:38 +0000 UTCYou didn’t hear the poor resistor crying as it was being cooked alive? I am pretty sure I heard a scream from the transistor at the end..
Lostngone
2021-01-03 00:24:26 +0000 UTCSometimes things just slip through. Maybe that wasn’t meant for the export market.
Lostngone
2021-01-03 00:21:04 +0000 UTCwe enjoy a good bang but will have to get by just looking at a Chines log. It is a qute log mind. 2x👍
DC Allan
2021-01-02 21:06:40 +0000 UTCNo bang, no magic smoke... Bummer!
Paul Schuur
2021-01-02 20:37:13 +0000 UTCThe Chinese seem to have very little light sensitivity in their eyesight. They seem to believe that LEDs MUST be driven as hard as possible no matter what.
Scott Miller
2021-01-02 20:34:04 +0000 UTCI'm not sure I understand where the Zener diode comes into play into this -- I haven't watched the video yet, maybe it is explained in there.
Raphaël
2021-01-02 20:14:07 +0000 UTCCheap and safe Chinese electronics? ok, I think I lost something in translation :-)
Peter Stevens
2021-01-02 19:43:55 +0000 UTCI'm sorry for the way this sounds, but the Chinese are dicks to zener diodes! Either driving them too hard or ignoring them entirely...dicks!
Michael Thompson
2021-01-02 19:22:55 +0000 UTC
