FULL BRIDGE Rectifying Christmas lights to overclock them to 120hz - Page 1
Forum section: electronics / general

author: Red Squirrel
author_rank: Super Contributor
timestamp: November 11, 2017, 03:24:56 am
content: Anyone else do this? I always find it annoying that LED Christmas lights have that awful flicker to them and that they arn't designed to run on smooth DC. So I usually plug them in a bridge rectifier to at least have the flicker be 120hz instead of 60hz and they seem a tad brighter due to increased duty cycle and the flicker is not as noticeable. Some sets require modifications as they may have multiple series strings wired with different polarity.I'm thinking of taking it a step further and adding a capacitor as well, but that will bring the voltage to 170vdc with 100% duty cycle, which they may not be designed for. But in reality, it's not like I'm really increasing the voltage, it's still 170v peak to peak. So would I actually be safe to simply do that, or am I going to greatly reduce their life span?Just curious if anyone else has done something like this to stop the flicker. I've only done the Christmas tree inside, but thinking of switching to LED outside (I still use the 7w C9s) so I'll have to build a weather proof bridge rectifier box for those.

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 11, 2017, 03:30:36 am
content: What about rectify to DC with a series capacitor/resistor on the AC side to keep the current the same as when running from AC?

author: Red Squirrel
author_rank: Super Contributor
timestamp: November 11, 2017, 03:41:23 am
content: Idealy this device would be fairly universal, so you can plug as many or little strings as you want. Not sure how that would work with any form of current limiting. Though I suppose you could just do it on a per string basis instead of relying on an external box.This is basically my current version: (indoor only)Anything I plug in it gets rectified AC. So I'm thinking of basically just adding a capacitor in parallel.As a side note, for the outdoor version I should probably have a GFCI outlet but would that work on DC, or would an upstream GFCI still work correctly if there is a fault on the DC side? I guess I can easily test that myself with this one by plugging it into a GFCI and contacting a load between positive and ground.

author: Cyberdragon
author_rank: Super Contributor
timestamp: November 11, 2017, 04:28:54 am
content: High end LED strings have rectifiers, problem is most of the ones now are cheap crap that don't. Even then they rarely have smoothing, usually just a box with an SMD bridge and a resistor. Oddly enough I find it annoying when in digital LED strings and even when people have setups that they use triacs for AC control of LEDs when they could use PWM DC and it would look allot smoother. Does AC have any effect on their lifespan though or is it just visually bad?

author: bjcuizon
author_rank: Frequent Contributor
timestamp: November 11, 2017, 07:25:32 am
content: Quote from: blueskull on November 11, 2017, 04:42:19 amhttps://youtu.be/sI5Ftm1-jik?t=1shttps://youtu.be/MCW5HUkrr-o?t=3m35sSorry I just had to put it. :-D

author: Halcyon
author_rank: Unknown
timestamp: November 11, 2017, 08:30:02 am
content: I'm not sure who annoys me more, ElectroBOOM or Linus Tech Tips.

author: Red Squirrel
author_rank: Super Contributor
timestamp: November 11, 2017, 11:47:18 am
content: The real question is, do you need a FULL BRIDGE RECTIFIER so you can connect to Tunnel Bear?

author: Gregg
author_rank: Super Contributor
timestamp: November 11, 2017, 08:13:17 pm
content: Perhaps under the BRIDGE RECTIFIER is FULL of TROLLS.

author: cdev
author_rank: Super Contributor
timestamp: November 11, 2017, 09:26:17 pm
content: I have the same problem with cheap Xmas lights.. and have thought about something like that..That said, maybe you should mark your DC rectified plug box to better indicate that its NOT a normal extension plug? Maybe they have plug covers for households with young children you could put on them or something? I would definitely label them with some warning.Quote from: Red Squirrel on November 11, 2017, 03:41:23 am

author: TheDane
author_rank: Regular Contributor
timestamp: November 12, 2017, 02:22:39 pm
content: Quote from: Red Squirrel on November 11, 2017, 03:24:56 amI don't use that many lights, but an LED is a diode - right?LED's can be vastly over driven, most IR remotes do this to perform better.- so adding a cap across the entire string should overdrive your LED's 100% of the time, and hence cut life time drastically as heat dissipation in the die goes way up. (If and Vf is not linear, in terms of Pdis)Lowering the input AC takes care of this, or adding more LED's in series. Happy choppingFYI - Caps with electrolyte can/will freeze at low enough temps, and the capacitance will drop drastically as the ion flow is inhibited. Your re-design should take this fact into account also, as the ripple voltage can increase to the point where the 'cap isn't there' - setting you back to square one.Debugging it inside, and there's no issues, only after 5+ hours outsideThen there is the varying Vforward/Iforward due to temperature.Perfect'ion

author: BBBbbb
author_rank: Unknown
timestamp: November 12, 2017, 02:33:57 pm
content: This is not going to end up cheaper than the quality Christmas LEDs :-)

author: Cyberdragon
author_rank: Super Contributor
timestamp: November 12, 2017, 08:45:11 pm
content: QuoteOnly at extremely low temperatures well below freezing. They can survive normal outdoor temps, otherwise every wizbang blinky holiday gizmo in your lawn would go haywire.EDIT: There's probably some places in the world where this would be a problem, but I guess no wizbang blinky gizmos for you.

author: Red Squirrel
author_rank: Super Contributor
timestamp: November 12, 2017, 10:52:17 pm
content: Quote from: BBBbbb on November 12, 2017, 02:33:57 pm99% of what's in the store is going to be cheap Chinese stuff that's built down to a price, they certainly won't be rectified, and even if there are some there is no way of really knowing until you get home with it. There's only so much to choose from. So it's more effective to just build a device that works universally on all strings. Some strings may still require some minor modifications so that all bulbs are on same polarity.And yeah I was actually kind of wondering about the capacitors in cold temps. I'd probably want some kind of heater, but maybe just the fact that it would be enclosed and weather tight would be enough as the rectifier will produce a small amount of heat.Think I might just skip the capacitor for now though, the move from 60hz to 120hz makes a half decent difference on it's own. I may later on get more fancy and do a SMPS and then I can get it to say 120 or 110vdc so that it's a safer voltage. Might try 170vdc as an experiment on a spare set of lights though. I have a whole bunch of LEDs that someone gave me a while back.

author: TheDane
author_rank: Regular Contributor
timestamp: November 13, 2017, 09:32:24 am
content: The freezing cap issue is more pronounced when the item is turned off for a long time, and the entire device reaches -40 degrees C, for example. (Or, whatever the cap is rated at)When running, the ripple current in the capacitor will cause self heating, and this will keep the system going. Perhaps not perfect, but some cases may be an emergency - and a service haul later on can be accepted.It's like starting a diesel engine at the poles and arctic regions. Not easy, if not impossible, without a VERY good battery. Putting a 60watt light bulb in the engine compartment keeps temps up, but I'm sure you know about the tricks, if you're located in such regions. Not sure how well LED lights would do - the best here is LEM (Light Emitting Metal) lamps, or incandedel-something_I_can't_spell_right_now as they're also called

author: BBBbbb
author_rank: Unknown
timestamp: November 13, 2017, 10:44:57 am
content: Quote from: Red Squirrel on November 12, 2017, 10:52:17 pmDon't get me wrong , I love topics where something starts simple and than people start to overengineer and go into really interesting (less talked about) details.If you plan on keeping the "adapter" outside, than temperatures are going to be a real problem, and I am interested in the result. So if you do a bridge rectifier w/ a cap and have a scope that would be cool share regarding cold start/hot start. Additionally you can play with LC choke filter to get a bet lower average DC value, but the further you go, you end up making full voltage regulator.

author: mavu
author_rank: Contributor
timestamp: November 13, 2017, 11:48:47 am
content: Quote from: Halcyon on November 11, 2017, 08:30:02 amOi!Don't talk bad about my favorite infotainment!

author: Red Squirrel
author_rank: Super Contributor
timestamp: November 14, 2017, 03:33:41 am
content: I kinda want to see both Electroboom and Linus together in one video now. "Today, we will be installing a rackmount tesla coil, what could go wrong? let's find out! " *tunnelbear advert*

author: mavu
author_rank: Contributor
timestamp: November 14, 2017, 12:36:11 pm
content: Quote from: Red Squirrel on November 14, 2017, 03:33:41 amAnd then Linus drops something and Electroboom gets shocked.Script basically finished, make it happen guys