rrmutt
Oh hey another janky AC-DC converter like the one spotted in @mossmann ‘s shredder. How does it work? 1/3
Feb 15 at 11:48pmWeb
Show threadrrmuttFeb 15
You will notice no transformers. That's a 300Ω resistor and the big brown cap is 560nF. That makes a highpass. It's not the L-topology RC filters you may have studied -- the R is not to ground, it's in series. 2/3
Show threadrrmuttFeb 15
The highpass filters the AC and reduces the amplitude by 20dB -- a factor of 10. So 120VAC in becomes 12VAC out. This goes to the classic bridge rectifier and smoothing cap for roughly 12VDC out. 3/3
Show threadMichael OssmannFeb 16
@rrmutt My eyes are cringing from the 60 Hz flicker from here.
Show threadMichael OssmannFeb 16
@rrmutt well, 120 Hz actually
Show threadrrmuttFeb 16
@mossmann To be fair it does have a filter cap, unlike the horrid holiday light strings...
Show threadDen of EarthFeb 16

@rrmutt @mossmann
Has anyone else noticed cars with aftermarket high beams that flicker noticeably if they're in your peripheral vision?

The province I'm in has mandatory daytime running lights which many manufacturers implement (on lower end cars) as half-power high beams, which means if you're unlucky enough to have one behind you...

In related news:
https://www.cbc.ca/news/canada/british-columbia/vancouver-vehicle-headlight-brightness-safety-concerns-9.7061810

Vancouver city council calls on feds to address headlight brightness | CBC News

Advocates say car headlights are not only too bright, but also too high up on larger vehicles, sometimes aiming at eye level. They say the lights blind other drivers, cyclists and pedestrians.

CBC
Show threadClark Breyman (he/him)Feb 16
@rrmutt - whats the power loss to heat from the first resistor? (It’s been decades since I thought about analogs circuits).
Show threadAI6YR BenFeb 15
@rrmutt @mossmann Wow. A lot of faith in that diode rectifier lol.
Show threadrrmuttFeb 16
@ai6yr @mossmann Exactly -- any voltage spikes go right through! The filter cap is rated at 100VDC, but the LEDs are highly susceptible (the one(s) shown here failed pretty quickly). A better design -- like @mossman's shredder -- has a Zener to catch the spikes but even then it's pretty janky.
Show threadChuckFeb 16
@rrmutt @mossmann That should probably get a mention on @lcamtuf's cursed circuits blog entry 😃
Show threadMarkAtMicrochipFeb 16

@rrmutt @mossmann <insert Mal dumbfounded gif here>

But…LEDs are supposed to be more efficient than incandescents!