N1NKM's solution to flickering LED lights!

N1NKM's Chattering smiley
HOMEBREW gallery!
400Hz squarewave
AC converter
V2.0!

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Ever buy one (or more) of those inexpensive LED Christmas lights, only to discover that they FLICKER like crazy? I bought 6 sets for $1.74, each, in 2011. When I plugged them in, I thought, "NO WAY!" The 60Hz flicker was absolutely awful! These sets are wired with 1/2 of the LEDs in one polarity, 1/2 in the other. That means I couldn't just power them with DC... so this project was born! :) (NOTE: Updated to V2.0 sometime after 2020) This site contains some of the V1.0 pics, but I've added the much better V2.0 info as needed.

Top view of the V2.0 de-flickerer
Overview

The transformer is a rather common dual-primary, dual-secondary type. Since I am only going to draw about 10 watts, it's perfectly fine to use only one of the primaries as the input, and use the other as an output. Wired in series with the two 24v secondaries, it gives me 200V DC after rectification & filtering. (A 100 ohm power R is used between the transformer & rectifier to limit pulse current & max V.) Thus, my 400Hz AC output is fully isolated from the line input.

Closeup of the V2.0 electronics
Electronics closeup

Here is a closeup of the 555 oscillator system, power transistors, filter and output caps. This is V2.0, where I've added some IMPORTANT safety features, like an inline fuse, and a neon lamp that lights if the fuse blows. I've also redesigned the power converter circuit with better transistors, heatsinks, and overall circuitry.

V1.0 Unit powered-up & running a light set!
Operational view

Here is V1.0, doing what it was designed to do! :) With the flicker rate at 400Hz,
it is no longer visible unless you sweep your eyes rapidly across the lights.
SUCCESS! :)
NOTE: V2.0 made little change to the appearance of the lights, but made this unit much safer and more efficient.

Schematic of the V1.0 de-flickerer

The small caps on the input and output of the power stage were necessary to eliminate RFI.
The transistors used in V1.0 were salvaged from computer monitors. They are all rated at 200v
The computer power supply case had a nice RFI filter already built-in, which I included.

Schematic of the V2.0 de-flickerer

The new V2.0 includes better transistors, (300V rated, ceramic case, higher current) and changes to the circuitry to improve performance.
The end result is a more reliable and safer unit.
The heat sinks ensure that these ceramic transistors run much cooler than the old ones did.

V1.0 of this project was completed on 1/7/2011. V2.0 upgrades made after 2020
This unit has been in use every Christmas, since. :)

You are welcome to E-mail me with comments/suggestions.
Constructive messages are welcome.
Abusive messages will be deleted. It's that simple. :)

Here's my HOME page

*** DISCLAIMERS ***
(Keep the lawyers happy.)

Please note: This unit is NOT a "standard" design! It is unorthodox, due to my limited budget and having to work with the stockpile of junk parts that I have on hand. Therefore, even though this unit works quite nicely, please understand that it is NOT a recommended design, and I would NEVER use this kind of "engineering" for any kind of commercial use! This is strictly my HOBBY. :) It's something I do because it's practical and FUN. This information is merely presented for those who are curious... I don't recommend you try this at home! ;)

*ALL* Information presented here is done so without warranty or guarantee of any kind. Author assumes no responsibility for the use or inability to use this information. Author also assumes no responsibility for the ability or inability to complete the project, above. This project uses potentially *LETHAL* voltages! If you are not sure of what you're doing, ask an experienced friend to help. ALWAYS "pull the plug" and ground the caps to make sure there is *NO HIGH VOLTAGE* when working with this unit! Always attach the cover to keep hands away from dangerous voltages.

This information is presented as educational information only. No guarantee is made as to its fitness for any purpose. All risk is assumed by the person who choses to use this information. While the author's experience indicates that this proceedure was effective, any attempt to build/modify these devices IS AT YOUR OWN RISK. Extreme care must always be excercised, this is at the builder's SOLE RISK.