Mortimer wrote: ↑
Wed Jul 18, 2018 2:30 pm
tlfong01 wrote: ↑
Wed Jul 18, 2018 2:20 pm
I have recently bought some 220VAC 15W LED lamps. They use transformers (I guess from 220VAC to 12/24DAC) and say they are flicker free.
Unlikely, almost always capacitive-dropper circuits nowadays. BigClive on Youtube does some interesting tear-downs of this sort of thing and reverse engineers the circuits, so you get to see a circuit diagram of typical electrical items. One of his tear-downs of an LED bulb is here : https://youtu.be/a-exD1-6gsY
Ah, I never heard of capacitive-dropper circuits.
I only know two types of 220VAC to low voltage DC power supplies. One type has a transformer and a regulated voltage device (Less than 10 years ago I still used a power BJT NPN called 2N3055 to assemble a regulator, because I found it scary using inductor based LM2596 (I actually bought a couple of LM2596s but never tried it) .
The other is switching power supply which has a oscillating switch, switching on/off to charge/discharge a capacitor to get the desired voltage,...
I guess my power supply knowledge is perhaps 20 years out of date. I need to google to catch up.
I neither heard of BigClive. I watched the video and found it very interesting.
I think he is a very efficient teacher, teaching you things and at the same time entertaining you.
He is not telling any jokes, but he reminds me of Mr Bean.
He made me laugh in the beginning, trying to open the bulb by hand, though like Mr Bean, failed, but then I knew the bulb is make of plastic, ...
At the end, he took out a ugly, stupid looking calculator to do the arithmetic. I closely watched with amusement his perhaps 50 years old ugly calculator and paid no attention what he was calculating.
His other tool, a box with big Brown Green Blue buttons also surprised me. I have never seen such a thing before. My first guess is a mains simulator, using battery and can generate 200VAC but low current, for testing.
Actually I bought such a toy, called an inverter, and hope to simulate mains 200VAC for my experiments.
I have neither seen an electrician using a tool to check the phase angle (or power factor, I forgot). I know what is mains phase, but don't know why he need to check power factor while studying the lamp.
In short, he is telling me many things I don't know. So I am happy to have learned so many new things from him.
I should watch Big Clive's other videos soon.