Another requested test. Putting a 10uF 400V capacitor across the LED array on the driverless 20W LED. This required a little silicone surgery to gain access to a concealed track.
The result was actually quite good, and got rid of the real harshness of the flicker.
If you try this then it's probably a good idea to use a couple of wires to jumper from the two connection points to a cooler area for the capacitor. I'd also suggest putting a 1 Megohm discharge resistor across the cap to avoid nasty surprises. I used a 10uF 400V electrolytic capacitor and added a 10 ohm resistor in series to limit the peak current as the capacitor charges at initial power-up.
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The result was actually quite good, and got rid of the real harshness of the flicker.
If you try this then it's probably a good idea to use a couple of wires to jumper from the two connection points to a cooler area for the capacitor. I'd also suggest putting a 1 Megohm discharge resistor across the cap to avoid nasty surprises. I used a 10uF 400V electrolytic capacitor and added a 10 ohm resistor in series to limit the peak current as the capacitor charges at initial power-up.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:-
http://www.bigclive.com/coffee.htm
Excellent three videos on these LEDs!
K Watt.
my brother has a 100w driver less slim version and after 5mins it starts smoking then after further 5mins the smokes gone and there's a shit load of flickering like in this video . i said to him i don't like the driver less ones lol . i have the 100w cw big heatsink version and there's 2 50w power supplies powering 2 sets of led arrays in one package . then a month down the line both power supplies gave up so what i did is buy a 1200w boost converter set it to 60v output then put the 2 arrays of 32v worth together in series to make it one array of 64v to the output of boost converter . then connected it to a 12v battery with solar and a pir sensor and its still working to this day drawing roughly 7 to 8A on 12v side when the pir sensor gets triggered but its not on 24/7 and dam its bright . its one of the newer ones that has loads of leds on one circuit board but split into 2 sets roughly 32v each and they never flicker like the direct mains versions which i dont like as the flickering bugs me . the leds are being driven at roughly 80 to 90w . and i also told him the driver less ones always gets grilled or overpowered so tend to fail quite quickly . so he said well if it does ill just buy another lol
great mod!
10UF is too low that is why you still see flicker, we have 120v mains in Canada & I normally use a 2500 to 3300 UF with a voltage rating about 10% higher than the working rectified voltage.
I have rewired many of the earlier LED bulbs with multiple series chip boards, I normally measure the rectified voltage with the cap across it than add up my LED voltage per chip to figure out how many I need in series or series parallel to slightly exceed the rectified supplied voltage as not to over drive the chips & thy have worked fine for years.
in this case of course that can not work as the number of LED's are embedded in the COB chip design, so that means the simplest way would be a simple full wave rectifier, cap & voltage regulator of some sort to feed the correct mains voltage into the module 120v or 240v rectified & smoothed DC into the module as once you drop the cap across the rectifier it will raise the voltage above that of the mains voltage & being so cheap I doubt they have built in voltage regulation before the LED's
in the simplest terms as they come with no smoothing cap in the design it is using all the power available, the LED's are digital so they respond very quickly & accurately to actual power so the flickering is the oscillation cycle of your AC hydro (50 / 60 HZ) & even though rectified to DC it is pulsed DC without the cap, the purpose of the cap is like adding a battery big enough to store enough power so when under normal load you can maintain a steady voltage & current throughout the sine-wave of the AC cycle thus it needs to store more reserve power than the device uses.
I can write clearly so I can translate
Hi I have found some of these led chips I like but they only have 220v ac. Would the light on 120v ac but dimmer / less wattage?
hmm… this was my idea as well where the capacitor should go. However, that 10ohm looks a bit big to me.
For bicycle, I used three capacitors with higher capacitance to smooth the flickering… just to find out that two Cree XP-G is totally fine without any resistor on a hub dynamo, and also will eat up the capacitors charge in an instant, so no light for me when I stop 😀
Is it not possible to use a large inductor in series to smooth the voltage?
Thank you for going across the LEDs! My first thought was the current limiting would result in lower average brightness (since it's "fixed-power" from the current limiting), but less flickering. Guess the voltage fluctuates enough to increase the consumed power and worsen the p.f. but still neat.
Thanks for your very educational videos! Can you tell me if your meter came equipped with USB port (at the top side, that we can't see)? I'm looking to purchase this, but I would like to have the USB port.
Can u may pls make measures with an oscilloscope? That would be awesome !
Love ur videos 🙂
Love watching your videos as am trying to build a grow light but I just keep getting to confused
Well I'm glad you take the flickering serious. Many people don't seem to care much about whether lights flicker or not. Which I never really understood, it annoys the hell out of me, some low frequency PWM brightness control too. It's so annoying when have this stop motion effect whenever you quickly look somewhere else.
I've always thought it's so ironic, that LEDs which don't have to flicker due to the way they work are so often powered in a way that makes them flicker. It makes them so much less pleasent.
I do think the idea of having the driver on the LED itself rather neat though and actually wanted to try soldering a capacitor across the LEDs on one of those driverless LEDs myself. I guess you beat me to it. 🙂
Hi, I have a similar COB module, 20W. I tried to place a capacitor plus resistor as suggested and the flickering improved slightly. I the used Viso Flicker tester (no affiliation) to use my phone as light meter. I noticed the following (I cannot load photos herein the comments): the module without modification gives no light until the LEDs begin to conduct (72 LEDs in my module), then the light output rises sharply and then stays constant, until the sharp fall and then no light until the next cycle.
With the capacitor and resistor added as you suggested, the rise of the light output is slightly slower (the capacitor steals current to the LEDs), but the decrease at the end of the cycle is much softer. However, the power at the plug is the same, because of the constant current driver is placed BEFORE the added capacitor and resistor (like in your case).
I would be interested in seeing the same measurement on your module before and after modificatio. The app is free anyway…
Thanks
take the resistor out up the uf
Another great video. Question: would multiple cobs, given a common 230v supply, flicker at a common frequency, or would the seperate drivers create multiple flickers and smooth the overall problem?
Clive, thanks for looking into this. Would a resistor along and after the capacitor placed between the bridge rectifier and before the LED's help to lower the light, the heat, and help keep the flickering reduced? It seems that the IC chips try to bring the heat down by turning the chips off and on creating some flicker to control the heat issue created by the capacitor. I would thing it would also help the LED's from being over driven when the (smoothing) capacitor is added to reduce the flickering. The makers have probably designed the led module calculating the resulting amount of LED's on time creating heat and figured the flicker would not bother anyone. When used as a street lamp, with reduced cost and complexity it would seem like a good idea.
Great results I would say. Considering the first test I recon this would be a fair bit better for indoor growing. It's quite interesting how the flickering effects growth on plants since it's literally limiting the amount of light the plants get. No flicker would be ideal but hell, the price of these things is a bargain compared to HPS, metal halide or even just fluorescent and incandescent. If however I had the cash I would still go with the outlook that, "diversity matters most" and build an array with every one of those lights.