Christmas Light Flicker - Page 1
Forum section: electronics / projects

author: kamocat
author_rank: Newbie
timestamp: November 26, 2023, 09:54:37 pm
content: I have some cheap LED christmas lights from Freddy's. Like all cheap lights, they flicker, and it drives me crazy.Conventional wisdom says that the LEDs are all wired up in series and only driving during half the wave.However, thebrilliantdesigners of these LED strings decided to enhance the flicker effect by alternating the polarity of the LEDs like so:The result is that if I rectify the AC, then every other bulb is darkThus I am left with three options to fix the flicker:Re-wire the string to make all the bulbs the same polarity, and add a bridge rectifierIncrease the frequency of the AC until the flicker is not noticeableBuy a better string of lightsI have chosen option 2.I have nearly everything at my desk except the gate driver. Before I go and buy an ASIC like DSG2003, I thought I would ask for community opinions.

author: Benta
author_rank: Super Contributor
timestamp: November 26, 2023, 09:59:46 pm
content: I'm for option 3.

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 26, 2023, 11:55:49 pm
content: If you have a small inverter or UPS lying around, it's often fairly easy to hack it to increase the frequency.

author: ejeffrey
author_rank: Super Contributor
timestamp: November 27, 2023, 12:15:21 am
content: Quote from: kamocat on November 26, 2023, 09:54:37 pmDespite the implied sarcasm that's dramatically better for flicker given that they are built in soch a cheap way. Of course the individual elements still flicker at 60 Hz but the indirect scatter and total illumination will flicker at 120 Hz. These are often much worse of a problem for people than direct viewing. It's the same way that a lot of people aren't dramatically bothered by CRT displays where every scan line flickers at 60 Hz or whatever, but the average brightness is mostly constant. Compared to a LCD with a cheap backlight where the entire display flickers on and off at 60 Hz together.It's still not good mind you, but it's definitely an improvement for such a cheap light string, and it also happily reduces DC current draw which is a nice benefit. It's certainly worse for the way you want to modify it but it's not surprising that designers aren't thinking about that.

author: wraper
author_rank: Unknown
timestamp: November 27, 2023, 01:09:04 am
content: There is no other way to drive two sets of LED with standard 2 pin connector, the problem is with low switching frequency. Also there are simple DC PSUs and non switchable lights in this form factor too.

author: kamocat
author_rank: Newbie
timestamp: November 27, 2023, 01:13:01 am
content: You're probably right that it looks better from a distanceIt occurred to me that if I use a microcontroller instead of a 555, I can get sparkle effects like the fancy mini-lights do. The only benefit of the 555 is one less voltage regulator.

author: wraper
author_rank: Unknown
timestamp: November 27, 2023, 01:15:12 am
content: Quote from: ejeffrey on November 27, 2023, 12:15:21 amI would not be so sure sure at what exact frequency they flicker as they are SMPS with additional polarity switching/PWM circuit on secondary side.