LED Battern lighting is making my video flicker

[Automate007]

Hi I need brain stormers. I am building an office / studio / steaming channel for my wifes little cake business. The 2 rooms out of 4 built and now finished are super clean and bright and installed 8 to 10 of these https://www.sal.net.au/products/interior-led-lighting/led-linear-battens-and-profiles/BLADE-SL9709-TC in each room. The idea as we were working from home with studio lights everywhere and now we build this decided to blast heaps of light in the room eliminating studio lights so when she has a room full of students we don't have wires everywhere.

We powered up security camera's, logitech webcams for streaming and phone camera's. ALL produce flickering and unfortunately none of the devices have an option to set a frequency. Logitech can switch from 60hZ to 50hZ but it still flickers but not as bad.

The outlay for all the lights unfortunately has me in a position where budget won't allow to buy a pallet of other lights so now I'm thinking would it be an option to buy 1 more , open it up to get to the driver and modify it somehow to stop it from flickering on video.

I would have thought going from AC power to LED that there wouldn't be a frequency issue. I was convinced that Alternating current would get rectified to DC to power the LED's but clearly I was very very wrong, What am I missing here. Please any idea's or help would be greatly appreciated. Happy to disconnect the light driver and put in something else to power the fixed LED's inside this slimline batten to stop the frequency flicker all together 

[wasedadoc]

Yes the AC is rectified but if there is no smoothing capacitor there will be peaks and nulls.  Each at twice mains frequency if full wave rectifier.

[Automate007]

So in that case that gives me hope. I will buy another light to experiment with before I even think about modifying each one. So excuse my novice questions but integral electronic circuits is not my forte! Ok so where would the caps go roughly? Are they across the DC output to the lights or before that somewhere else on the circuit usually?

Once I get the spare batten I will try to draw out the circuit or provide pics of the board for further help

[jmelson]

I built my own ceiling lights for the kitchen and used commercial LED lighting power supplies.  I know they have big capacitors in them becuase the lights fade out for a second when turned off.  These lights have 20 LEDs in series and so drop about 70 V.  The power supplies are Thomas Research Products LED25W-72-C0350 from Digi-Key.
So, these ought to eliminate flicker, too.  These supplies will run strings at 350 mA from 36 - 72 V, so that is about 10 - 20 LEDs in series.

Jon

[Benta]

First, for a studio, a CRI of ~80 for your LED lights is lousy. Sorry, but it can get too cheap.
Second, for this kind of application, I'd never go for LEDs. For beautiful colour rendering, halogen rules.

Now for a solution. Can it be (it's about baking, after all) that you have three-phase service?
If so, patterning your lights onto all three phases might solve it. That's then just a rewiring issue.

[james_s]

This is common, LEDs have negligible phosphor persistance and no thermal mass like tungsten filament so if they receive pulsating current they will flicker. When the flicker of the lighting beats with the camera shutter frequency you get rolling bars and other artifacts. Your only solution is either replace the lights, or replace or modify the drivers to add some smoothing. It *might* work to simply add some capacitance across the output of the driver.

[Benta]

It *might* work to simply add some capacitance across the output of the driver.

More likely to let out the magic smoke, after I've seen how primitively those drivers are built. But give it a try. It can only burn the house down.

[james_s]

It *might* work to simply add some capacitance across the output of the driver.

More likely to let out the magic smoke, after I've seen how primitively those drivers are built. But give it a try. It can only burn the house down.

I don't think it'll burn the house down. Either it will reduce the flicker or it will let out the magic smoke on the bench. First thing I would do is reverse engineer the driver though, and then work out the best way to remove the flicker.

[Automate007]

Yeah hopefully to get another and pull it apart for smoothing cap on the bench. I'll have to hook up an osciliscope to play with different capacitance and minimise or eliminate the ripple.

The 3 phase idea above ..... hmmmm that one is interesting but not able to do that as 1 phase is going to a 3 gang switch powering the lights and no way to separate the 3 switches on different phases easily.

Thanks guys but I think cutting the ripple will ultimately fix the issue..... I think I would like to retain all the smoke in all the right places.... I'll update this post once I get more circuit info

[Automate007]

Yeah I thought the same as you with the CRI rating but they are at 5700K really bright and white. It's just flicker that is killing me.

Keep in mind for photography and product shots I've got that side professionally covered as I am a photographer but the standard ceiling (flickering) lighting is when we have students watching a large screen of the teacher doing detailed closeup work in real-time on the screen or for streaming classes on Facebook live (720p) .... Simple 3 x logitech webcam setup with OBS studio. CRI is not critical here and the colour of these SAL lights is really really good and even. No magenta, blue or yellow tint cast that is visible but they are super white light bouncing off bright vivid white walls..

[John B]

The integrated power supply will be very basic. More than likely it uses a low capacitance input switching supply (for good power factor), but that results in the output waveform with DC + a large amount of AC ripple, hence the flicker.

You'll probably need to invest in some high CRI panels without integrated power supplies, then use a good quality LED driver that uses active power correction and gives an output which is at least as clean as a regular DC adapter. I've always just gone to meanwell for supplies and never had an issue with them. You can also get ones with integrated dimming control.

[Automate007]

Ok had to quickly get this done as its late and I've got an interstate trip in the morning. Ok I have found its outputting around 115VDC to the LED'S. There appears to be a 160V 100uf capacitor which looks like on the output side. When I look at the ociliscope output I'm measuring a 11.4V ripple at 100hz. Is this just a question of when I get back to remove the 100uf cap and install a larger size uf instead? How can I calculate what size cap I need?

[Automate007]

These are some pics of the board

[Automate007]

Oscilloscope

[wasedadoc]

It looks to me that the +ve side of the 100uF 160 Volt electrolytic is on the +ve output of the 4 diode bridge rectifier on the incoming mains.

[Stray Electron]

     A friend of mine is a semi-professional photographer and the LED lighting in his photo studio was producing bars on the photos that he was taking.  The LED were run directly from the 60 HZ AC main so they were strobing at 120 Hz rate and the camera was capturing the strobing.  We looked at the specs for the LED bulbs and we found that they would also run from pure DC. The LED lighting was on a AC circuit with nothing else on it so we went into the circuit break box and added a bridge rectifier to the output of that particular circuit breaker and then added a large filter capacitor to the bridge output and then connected the lighting power circuit to that. So long story short, the circuit that powers the LED lighting is now pure DC.   It worked like a charm!  The lighting circuit actually doesn't draw much power and we checked the RC time constant of the cap that we used and there is almost no voltage drop during the zero-crossing of the AC input. 

   We stuffed the capacitor and the bridge rectifier inside of the circuit breaker box so we didn't need to make any changes to the wall or any of the existing wiring.  The building inspectors might not like the idea of the extra items inside of the CB panel or of the DC wiring, but it works!

[Automate007]

That's brilliant but I will need to research that a bit more cause here in Australia we are 240vac 50hz. But light input does say 220 - 240v 50hz

[Automate007]

It looks like yes the +v of the cap is connected to the +v output on the dc side of the bridge.... isn't that right? What I'm thinking it's got a smoothing cap but not big enough? Is it as simple as desoldering this 160v 100uf and trying around 1000uf ?

[james_s]

It looks like yes the +v of the cap is connected to the +v output on the dc side of the bridge.... isn't that right? What I'm thinking it's got a smoothing cap but not big enough? Is it as simple as desoldering this 160v 100uf and trying around 1000uf ?

That's exactly how I'd expect it to be arranged, that's clearly a SMPS.

Try increasing the capacitor value and see what happens. 1,000 may be a bit much, 470 is closer to what I'd expect. You have to be careful of inrush of a large low ESR capacitor popping the fuse or blowing the bridge.

[tunk]

No expert, but it could look like there's not much smoothing on the primary side
(what's the capacity of the two brown caps?). This could explain the 100Hz ripple.

[james_s]

Smoothing on the primary side is exactly what we're talking about. The bulk filter capacitor after the rectifier. There's only one of them.

[tunk]

To me it looks like the 100uf/160V cap is on the secondary (Australia uses 230Vac).
Note that PCS are rotated (the switch is on the left in the top photo and on the right in bottom photo).
 

[John B]

I tried to modify an LED driver with much the same layout as that, but even adding primary and secondary capacitance, it simply didn't clean up the output waveform enough.

I ended up ripping out the integrated drivers and running them as passive panels.

[Automate007]

Yes the pics are rotated note the switch position. Also the switch makes the led change temp. From warm to daylight 3000k to 5700k. The 160V 100uf is directly after the rectifier and on the +/- DC rail. I also would imagine that if it were on the primary side of the rectifier at 160V rating it wouldn't last very long if it were on the 240vac side..... yes?

Question can I desolder the caps off a couple of the other lights and add it to this circuit. By memory if I run the caps in parallel ... say 2 more added in parallel does that make it the same as a 160v 300uf?

[Automate007]

Ok I have scavenged a few caps from the other lights. This is what I have found
100uf = 11.4v ripple
200uf = 7.4v ripple
300uf = 5.2v ripple

Also this driver is outputting 120VDC and measuring 0.17amps on the input side

So I'm going to assume around a 1200uf will get me down to about 1v ripple?

Hmm it's physically too big and expensive for 20 lights to go this way. Any idea's?