Overclocking LED Christmas lights for fun and profit - Page 1
Forum section: electronics / general

author: Red Squirrel
author_rank: Super Contributor
timestamp: November 24, 2016, 07:30:18 am
content: I hate that Christmas lights don't come with a bridge rectifier built in so they can at very least operate at 120hz instead of 60hz. Even better would be if they had a capacitor, and were sized for that.So I took it upon myself a few years back to build a FULL BRIDGE RECTIFIER box so that anything I plug into gets 120hz pulsed DC. This lets me plug any strand of lights without worrying about over voltage, technically it doubles the duty cycle so if they are undersized it could be an issue but I've been lucky.Today, I ran into a strand of lights that was built differently, well I think it's common, just my first time running into it. It is several strands wired together in groups. And not all groups had the same polarity, so plugging it in my box resulted in some sections not having light.That is when the cutters and soldering iron came out...Bridge rectifier box:With rectification: (camera set to manual, settings unchanged for both photos)Without rectification:Not only does it remove the flicker but it makes them brighter. The 120hz flicker is barely noticeable so not even worth trying to put a capacitor in there.Just need to make an outdoor rated rectification box and I'm set to put these outside! It's for the garlands, still using 7w C9's for the house ones. I need to change those out some time though, I go through bulbs like crazy.

author: Zero999
author_rank: Super Contributor
timestamp: November 24, 2016, 08:47:21 am
content: Just make sure no one plugs something which won't work off a bridge rectifier, like an old fashioned wall wart, into your bridge rectifier box.Personally, I'd prefer to modify the Christmas lights by adding a bridge rectifier.

author: Red Squirrel
author_rank: Super Contributor
timestamp: November 24, 2016, 09:18:14 am
content: Yeah there is a certain risk but I tend to only pull that box out for the Christmas stuff or if I need DC 120v for something and it's never within reach of other people, ex: friends who would randomly decide to plug their phone charger or something. Would probably be a bad idea to plug a vacuum cleaner in there too.Suppose I could have built it into the strand though, but this made it a nice universal solution that I can plug pretty much any strand... except for these pesky ones where they are split on different polarities, then end up having to modify them anyway.

author: Seekonk
author_rank: Super Contributor
timestamp: November 24, 2016, 12:20:43 pm
content: Quote from: Red Squirrel on November 24, 2016, 09:18:14 amI actually run my phone chargers off 60V DC solar feed at camp and DVD player off 140V DC from inverters with damaged H bridges as well as CFL lights. Been a long time since any phone chargers had transformers. They actually sold full wave boxes for higher speeds on universal motors and old shavers.

author: Ampera
author_rank: Super Contributor
timestamp: November 24, 2016, 05:20:27 pm
content: Question: Why don't you just set your camera to 60Hz? I mean stupid question, if you can do it a crazy way, why not do it crazy, engineer motto, but I am struggling to figure out why you want to do this.However higher Hz is always better, so

author: Red Squirrel
author_rank: Super Contributor
timestamp: November 24, 2016, 09:39:29 pm
content: Quote from: TwoOfFive on November 24, 2016, 05:20:27 pmI don't think frame rate matters for a still picture, it was just to show an example of how it makes it brighter by comparing two shots on manual (so shutter speed etc is same)The idea of "overclocking" them is so they look better and don't seem to strobe as much. At 120hz it's not as noticeable as 60hz. Makes them seem brighter too because of the increased duty cycle. Another way to do this without having to modify strings would be a high speed inverter, so still 120v but at say, 1khz or something. Then it would work for the strings that arn't all the same polarity. More complex though, a project for another day.

author: RGB255_0_0
author_rank: Frequent Contributor
timestamp: November 24, 2016, 09:50:51 pm
content: Not sure if it was deliberate but the way you wrote FULL BRIDGE RECTIFIER it was in electroBOOM's voice.And meh Christmas lights that are all white. Sad panda

author: Red Squirrel
author_rank: Super Contributor
timestamp: November 25, 2016, 02:09:09 am
content: Quote from: RGB255_0_0 on November 24, 2016, 09:50:51 pmHaha glad someone picked that upAnd yeah I usually prefer colors but these are to embed in garlands so figured I'd go with something "neutral". The house ones are red and white. Eventually I want some RGB ones that I can control with Arduino or something, probably led strips. Though I like the look of the big bulbs, too.

author: Zero999
author_rank: Super Contributor
timestamp: November 25, 2016, 09:35:39 am
content: It's not only the increase in frequency which makes the LEDs flicker less but the increase in duty cycle, which will be be between 60% and 90% at 120Hz, depending on the voltage drop of the LEDs, rather than half those figures on 60Hz.

author: Red Squirrel
author_rank: Super Contributor
timestamp: November 26, 2016, 01:20:15 am
content: Yeah makes sense as when they are not rectified you basically miss an entire half sine of duty cycle. Then figure that the LEDs only start to turn on at a certain voltage, and you probably get like 30% duty cycle by default.

author: Ampera
author_rank: Super Contributor
timestamp: November 26, 2016, 02:26:12 am
content: Quote from: Red Squirrel on November 24, 2016, 09:39:29 pmJust realized that. Stupid me.And I guess they do seem a bit tough on the eyes.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: November 26, 2016, 02:50:49 am
content: But but... what is the actual voltage output of a FWB connected to an input of 120VAC RMS?Many sources say that it is ((root 2) x (RMS input voltage)) minus (2 x Vfwdof one diode). In other words, it's NOT going to be 120 VDC.

author: Red Squirrel
author_rank: Super Contributor
timestamp: November 26, 2016, 03:04:04 am
content: Quote from: alsetalokin4017 on November 26, 2016, 02:50:49 amInterestingly when I put my meter and set it to DC, I get 110vdc instead of 120vac when it's regular AC. Kinda interesting as I would have figured it would either be the same, or higher. If I throw in a capacitor it's 160vdc. I have not tried to plug the lights in with that though, it might be pushing it. I think it would probably work, but it might be exceeding the rating of the LEDs. I could use a dimmer to tune it but then that's getting more involved, and at that point I may as well go all the way and do a SMPS.As a side note it's kinda a pain inserting probes in a tamper proof receptacle. I guess that's the whole point.