Re: WN4ISX made a mistake!!!!
¿ªÔÆÌåÓýOne more detail: You previously mentioned that you replaced the resistor with a fuse. You ought to have a small value resistor there. If the power is switched on at the peak of the sine wave, an extremely high current, narrow pulse will happen trying to charge the capacitor instantaneously.? The current is basically only limited by the bridge diodes¡¯ internal resistance and the LEDs resistance. The series resistor is chosen to limit that turn on transient current. Bertho ? From: [email protected] <[email protected]> On Behalf Of wn4isx via groups.io
Sent: 17 December, 2024 16:17 To: [email protected] Subject: [electronics101] WN4ISX made a mistake!!!! ? I made a mistake, in my description of a ultra simple current limited LED driver. Call the cyber police to take my PCs from me. ? [Me making a mistake ought to make at least one person in this group smile. I live to please.] ? I transposed the position of two components. ? The capacitor goes between the AC Hot and full wave bridge, not the other way around. ? The AC from the mains passes through the capacitor, the current is determined by the capacitor value (Xc) and mains frequency. ? Higher capacitance equals higher current. ? The now current limited AC passes through the full wave bridge producing 120Hz pulses of DC (100Hz pulses of DC in 50Hz nations] ? This safely (if the capacitor value isn't too large) provides current to power/drive a LED or LEDs. My fake florescent LED replacement tubes have a lot of small SMD LEDs. I quit counting at 50ish. I'd guess there are about 200. ? Note that is a guess and I won't pretend it is "mainly accurate," don't know, don't care. ? |
Bertho