I realized recently that you can make non-dimmable LED strands dimmable by replacing one LED bulb with a traditional incandescent. Why is this?

 

All I want is english subtitles.

 

Incandescent is basically a giant multiwatt resistor - a resistor bleeds off excess current as heat, a bulb turns heat into light (very inefficiently). Depending on how its wired (parallel, series) and your power source (wall wart, battery) is why it's dimming. It's inefficient as hell for dimming.

 

I watched video and still don't know why adding a resistor in parallel with a bunch of commercial non-dimmable LED bulbs makes the frequency generator work properly.

The particular 'non dimmable' LEDs I'm using do not have enough resistance to trigger the frequency generator?

Whatever brand/design frequency generators I tried (Lutron wall dimmer & IKEA slider dimmer) just need a certain resistance to function I assume.

 

So (old school) wall dimmers are basically giant potentiometers wired as variable resistors.I'm making lots of assumptions here - but this makes sense to me.

You've got your typical 60watt bulb LED replacements and a newer PWM-generating wall dimmer. LED Bulbs need a much smaller current. There are two ways to limit current - you have your resistor as listed above which is a dead simple and cheap way to limit current. Your LED bulb needs a little bit more to work in A/C. It has to be rectified - and you could easily use a half wave rectifier and capacitor to generate DC (and maintain DC charge through the negative portion of the A/C waveform), then a resistor to limit current across the LED. Dead simple, but inefficient. A more efficient method is to make a small half wave buck power supply - this is basically the same thing that's inside a wall wart.


^ he's got the guts apart in that one, and yeap, looks like a wall wart.

So you're generating a A/C waveform that's being split into A/C PWM (I have no idea if those do rectification) - but the LED needs a very small amount of the current even after being split up in the PWM - and is able to maintain full brightness across the PWM and A/C peaks. Adding an incandescent bulb is adding a load to the circuit - so the charge that was being stored in the capacitor (or inductor) is being sucked out of the LED bulbs by the incandescent, and dimming finally works.

I'm no electrician - but I do play with 12v all day long and know enough to be dangerous.

 

Typically not. Most of these dimmers use Triacs, which are basically two SCRs in parallel with a common gate, with their polarities reversed. They conduct AC just fine.


The rest of your analysis is basically correct. Most electronic dimmers cannot operate linearly at the extreme bottom end of their range.


In a residential context, there are also a bunch of other options. This paper gives a good overview: http://www.awlights.com/files/1414/0...01_revised.pdf

This page gives detail on how PWM dimmers work: http://ecmweb.com/lighting-control/s...-light-dimming

 

I'm getting a prizewheel but want to rice it out. I'd like to get it to have a low frequency beep like the Price is Right wheel.

So far the best idea is getting Reed switches and pasting magnets to the rear of the wheel.

1) Can I modify the sound of a piezo buzzer to be low frequency?
2) Are piezo's fast enough to react to for a full beep?
3) Would Sonalert buzzer work? Needs to be kind of loud.

 

So.. yes and no. Piezo's are self oscillating based on voltage, so you can lower the voltage to lower the tone - but you'll lose your loudness. I think your limit would be the reed switch - might be better using a microswitch and some pegs on the board. You could drive the tone lower with some more fun fun PWM action, but that gets into the realm of microcontrollers.Lemme see if I can find a piezo here in my box 'o' stuff.

 

What about buying one of those super-cheap Stylophone knockoffs, and just wiring a reed switch across one of the keys? This way you can custom-tailor the note to your liking.

 

Joe, I like that option. Is it as simple as soldering one end of the reed to the stylus and the other end to a key?

 

You can cut the stylus off and solder directly to the wire (or open the case, de-solder the wire, and solder to its pad) but otherwise, yes.

I don't know what sort of plating / coating is applied to the keys. I'd hit 'em with a scotchbrite pad and isopropyl first, and use liquid flux if you have it.

 

Excellent, thank you for this. Makes sense to me now!

 

/shameless plug

 

I love how he's using the product to test a computer motherboard which does not have a power supply connected to it.


Looks like a baller UI, though.

 

Testing the new wireless power standard. Duh

 

Yeah, I've been telling the hardware guys for years that all they need to do is merge 802.3at and 802.11.

--Ian

 

FWIW, Ip Man 1, 2, & 3 are on netflix.

Another Donnie Yen flick on there is "Kung Fu Killer" - Watched that last night and was not disappointed. I highly recommend.

Jackie Chan has 2 on there as well... Legend of the Drunken Master, and Skiptrace. Skiptrace is something new, more so a comedy as it has Johnny Knoxville in it. He does quite well in his role. Wasn't sure what to expect but it wasn't too terrible.

 

Racing community mourns Gainesville woman killed in Road Atlanta accident

Hazel Harrell recalled as ‘strong-willed’ person who ‘put everybody in front of herself’
By Norm Cannada ncannada@gainesvilletimes.com
POSTED: June 5, 2017 5:05 p.m.

Hazel Harrell

Flaggers at Road Atlanta’s Turn 7 were back at work Sunday in memory of Hazel Harrell, a friend and co-worker who died trying to help an injured motorcycle rider just one day before.

“We were the very best flaggers we could be,” Sandy Lewis said. “She was in the forefront of our thoughts the whole time.”

Harrell, 60, of Gainesville, was at her usual Turn 7 at the track Saturday, working an event for the Western Eastern Racing Association’s Motorcycle Roadracing.

Deputy Stephen Wilbanks, a spokesman for the Hall County Sheriff’s Office, said Harrell “was attempting to cross the track to assist an injured rider who’d gone down in a turn,” when the accident occurred.
Wilbanks said the track was under a yellow flag, telling riders to slow down, and was in the process of going to a red flag, where riders stop. He added that not all of the riders had come to a stop when Harrell went to help the injured rider.

Wilbanks said a witness reported that Harrell “either stumbled and fell or possibly twisted an ankle while crossing the track. One motorcycle was able to swerve and avoid her, but the rider immediately behind that one was unable to see her until the first bike took evasive action; there wasn’t enough time for that rider to react, and that bike is the one that struck the victim.”

Wilbanks said the case is being investigated as an accidental death.

Lewis, who said she had known Harrell for six or seven years, was working at the same turn with Harrell Saturday and said the fact Harrell died trying to help someone else was “as her personality would dictate. She was always putting someone in front of herself.”

“She was strong-headed, strong-willed, put everybody in front of herself, sweet, feisty,” Lewis said. “I absolutely adored her, and everybody who knew her did. She trained almost every flagger that’s at Road Atlanta right now. It’s going to take a while for all of us to process it and get to the point when we can accept it,” Lewis said of her friend’s death.
Harrell was engaged to Kory Chandler, also of Gainesville, according to Lewis.

Harrell’s death grieved many others at Road Atlanta. Geoff Lee, president and general manager of Road Atlanta, said he was not at the track when the accident occurred but arrived after hearing the news.

“It’s a sad day for all of us,” Lee said. “Hazel had been an institution here for almost 20 years.”
Lewis added that tentative plans call for a memorial service to be held at Turn 7 at Road Atlanta, but a date and time have not been set.

Lewis started a Gofundme page that had already raised nearly $16,000 by Monday afternoon.

“I am just absolutely amazed, and I feel like we are truly blessed with having so many kind, sweet, wonderful people within the racing community,” Lewis said.”I knew that the family could use the help financially to pay off any final medical bills and funeral expenses and stuff like that.”

 

You realize that was a 6 year old post you replied to, right?

For the record, Ip Man (#1) was clearly the best, 2 was barely ok, 3 wasn't even worth watching.

 

Payday 2 is free on Steam. Add it to your account before they take down the giveaway.