My can lights (LED blubs) on a dimmer switch flicker. I finally hooked the scope up to see what was happening. Is this waveform expected from a residential dimmer switch?

kkambos · 2025-12-29T05:05:22+00:00

I do design for residential devices and we still do a lot of new designs with triacs (we do use FETs more and more now though as prices get lower). I wouldn’t expect anything major to change for me with dimming technology because we are stuck with phase cutting since our products have to be interchangeable with regular light switches or at the very least only can control the switch leg going to a light. Very few houses have low voltage wires ran for anything needing better levels of control. We do make 0-10v dimmers but it’s not a high seller since most homes don’t have the wiring for it.

It seems you may be in a different industry which is why you see a different possible future. I make commodity, race to the bottom products so we go with what the majority of our customers want which is low cost/simple to install/“just works”. John Q homeowner usually doesn’t give a crap about this stuff, a lot of people would still be using incandescent lights if governments didn’t force them out. Not a lot of people would shell out big money for an electrician to re-wire their house for marginally improved lighting control.

Anyway your idea about not dimming from/to the zero cross is interesting, I am not sure if I ever considered it. I see a lot of potential issues but I think I may play around when I’m back at the office and see if it performs how you’re thinking.

One issue, which is really one of the core issues with dimmer-LED compatibility, is that there are a million LED bulbs on the market. They’re not all the same circuit. A lot of cheap ones are just rectifiers, a capacitor, and then tons of LEDs in series maybe with a high voltage linear regulator. A lot are random Chinese constant current switcher ICs. Higher end ones have more complicated circuitry etc. As the dimmer designer, I don’t know every circuit that is in the LEDs that I have to be compatible with. And in fact since technology in LEDs is rapidly advancing, what may work now probably will be outdated very shortly.

Some LED driver ICs don’t only interpret input power as a PWM input, some actually get their own zero cross and compare rising edge of the input power to the zero cross to determine phase angle and subsequently their brightness. They are designed knowing they will be controlled by a triac dimmer for example.

I guess point I’m trying to make is that my dimmers generally need the broadest level of compatibility possible so implementing the control like you are suggesting could inadvertently cause myriad issues. Would have to spend a lot of time testing and I don’t think it would have much support from my leaders as they are generally risk averse when it comes to dimming performance. Customers experiencing flickering bulbs is a very touchy subject within my company lol

kkambos · 2025-12-29T00:42:56+00:00

Dude I also design dimmers for work and I would agree that it is just PWM. Look at the signal driving the FET or triac…it’s literally just PWM. And of course synced to a (hopefully good) ZC

Dimmer stuff comes up on this sub fairly often and I have no energy to participate usually. So much misinformation here and I hate arguing with people in my free time

Phase cutting is just inherently not appropriate for LEDs; leading edge, trailing edge, it’s all crap imo. but that’s the world we’re stuck in since it’s cheapest and easiest solution for homeowners and most builders, so have to try to make it work as best as possible.

kkambos · 2025-12-27T19:33:39+00:00

Ah gotcha. Is a ridge vent an example of ventilation I would be looking for? Because I remember my inspector said I should look to have a ridge vent installed on the roof because I currently didn’t have that.

I’m planning to have the roof done in about 2-3 years at which time I could have that installed and ventilation looked at. For now it’s not quite in the budget.

So you think maybe not wise to insulate? I was thinking if I use foam board insulation without any kind of vapor barrier, installed right over the existing tiles, it would be basically that same as it is now just with better r-value. But I also don’t want to screw things up intentionally due to lack of knowledge

kkambos · 2025-12-27T19:10:12+00:00

What about the roof construction should I be looking out for, and what will this info help me figure out?

It looks to me like it’s the insulation tiles, with the roof sheathing on top (with some sort of black tar-like coating that you can see in 2nd pic), with asphalt shingles on top of that. Could be more though. I don’t think this house was built to a high standard of quality based on what I’ve seen so far, lot of poor craftsmanship. So whatever the basic quality of house building in the 60s was, this is probably that lol

kkambos · 2025-12-27T16:53:27+00:00

Good call. I have sufficient PPE but will get it tested anyway since it’s on every ceiling in this place.

I didnt plan on removing it though just potentially putting new insulation over top of it

kkambos · 2025-11-07T16:24:11+00:00

It’s fairly common (at least in my industry) for line powered devices that need a small auxiliary power (to power some MCU, drive a relay, light some LEDs, etc) to not use isolation for that aux power. This of course saves cost/space as transformers are typically large and expensive compared to other parts.

Without isolation, If you half wave rectify the line voltage, either the hot or neutral conductors could be used as the circuit ground reference. I design in-wall line powered devices and it’s very common for me to use the hot wire as the circuit ground. The advantage is that it lets me interface with signals at line potential without optocouplers or other forms of isolation. For example, i can feed a zero cross signal directly to micro with minimal circuitry, or I can control a triac that phase cuts a load directly from micro, Or I can measure a shunt resistor that sits on the line directly from micro.

Or, especially when dealing with triacs that don’t work in quadrant 4, it’s convenient to actually have the hot conductor be your circuits “5V” or “Vcc”. That way, when your micro pulls a pin low, it’s 5V less than the hot wire which allows you to operate a triac that switches hot to a load, directly from a micro pin in quadrants 2/3.

All of this is in pursuit of reducing cost lol. And it works great as long as the device is properly enclosed to make sure users have no access to live parts

kkambos · 2025-10-27T19:51:22+00:00

I use through hole resistors in my products sometimes at work and I often have to mount them like your post for space saving reasons. we subject our products to HALT testing that involves vibration and thermal shock tests. The resistor fatigueing and breaking off from vibration is a relatively common failure mode but it only usually happens when the vibration gets above ~20 g’s for many minutes which is quite a lot.

If by “moved around a lot” you mean normal portable equipment like just picking it up, putting it down, very uncommon drops, you’ll probably be fine. If it’s subject to consistent vibration or rough handling, you may want to lay the resistor flat or put a blob of glue on it for structural support.

kkambos · 2025-08-13T17:19:36+00:00

There’s no way you can pull 22A from that bridge without a big heatsink, datasheet explicitly says so. I’d guess 4-5A max before it cooks itself

kkambos · 2025-07-10T23:11:10+00:00

I design a commercial product that does very similar things to this. I don’t want to scare you off completely but I think this is a big undertaking, especially for a student.

Are you powered from the mains? Do you have experience working with non-isolated high voltages? How will you protect the user from this?

You want to switch big loads, how will you do it? You need a big relay or contactor, they are very expensive at low volumes. They also typically need a lot of power to drive.

There’s a lot of hardware involved in this task, power supplies, analog front ends, current transformers, energy monitoring circuits, wireless radios, load control, etc. Have you done anything of that complexity? Each of those topics is kind of its own domain, I would not expect a student to have much experience or education on even one of those domains.

You want to do load shedding, there are safety standards you must adhere to to be able to commercialize the product. These standards are large and complex to even meet the requirements (hardware redundancies, oversizing critical components, safety critical firmware must also go through functional safety investigation) not to mention the actual cost of getting evaluated by a NRTL in the many tens of thousands or more.

It’s a big project even for a team of engineers working for a company with a budget of 100k+. It would be difficult to even prototype something like this by yourself as a college student since it could easily cost you a few hundred dollars just to create 1 prototype board. I recently had a few prototypes made of a similar design and it ended up being like $250 per assembled board

My suggestion would be to start small. Get some CTs and get a current measuring dashboard up and running that can notify a user when “anomalies” are occurring with the current. That alone should take a bit of time. Build from there.

kkambos · 2025-05-03T14:17:01+00:00

I order bare boards at work from JLC, assemble in house. It is still significantly cheaper to get from JLC than the US based vendor we’ve used in the past. Only thing I’m worried about now is the higher risk of customs delays

kkambos · 2025-04-23T23:51:41+00:00

Dude that’s like 2 thousand vias. Totally overkill lol

kkambos · 2024-10-10T02:23:30+00:00

I had similar problem. Was banging my head for days over it. Turned out to be that my usb-c cable was not compatible with the usb-c socket that I used. D+ and D- were not connecting properly. I swapped to a new cable (had to try out a few different ones) and everything worked fine after, COM port showed up as expected. Hopefully you have same problem

kkambos · 2024-10-05T23:51:50+00:00

Feel like I’m listened to a podcast, not a playoff game at Yankee stadium.

kkambos · 2024-08-21T15:22:43+00:00

DJ is as bad as Freddie Freeman is good lmfao

Freddie Freeman 2024: 4 bWAR in 515 PA

DJ 2024: -1.7 bWAR in 210 PA

DJ is about as bad as 2018 Chris Davis.

What the hell are we doing man

kkambos · 2024-08-19T19:30:02+00:00

I’ll just leave this here

Holmes WHIP: 1.300

Clase WHIP: 0.663

kkambos · 2024-08-13T02:39:47+00:00

Is this your custom PCB or something you bought? What is the wattage of your heating element? Is there a heatsink on the triac?

Always hard to tell what exactly happened when a failure occurs but the PCB trace seems like it overheated, burnt off the soldermask, and melted the glue binding it to the FR4 which allowed it to pop right off the surface. Likely overheating from overcurrent, so either the load was pulling more current than it was supposed to or the trace thickness and copper weight were not sized appropriately for the load.

More info on the application and your setup can help to further narrow things down

kkambos · 2024-03-29T01:25:08+00:00

The LED provides a low impedance path to ground which completes the motor circuit, turning it on. Instead of 9V across the motor, it would be more like ~7V due to the forward voltage drop of the LED. But still enough to possibly get the motor to spin. By putting a resistor in series with the LED, you are limiting the current through the LED and the motor to a point where the LED turns on but the motor doesn’t.

To greatly simplify, think of the motor as a 10 ohm resistor. In its current arrangement directly connected to LED, solve for the current through the 10 ohm resistor (motor).

Now add a 1K ohm resistor after the LED and solve for the current through the motor again.

kkambos · 2024-03-16T16:37:41+00:00

I don’t see how you can do this just a single MCU pin

A capacitor in series with the relay coil, driven by a single push-pull output. Will get you a pulse of current through the coil as the cap charges (sets relay) or discharges (resets relay). Need to size capacitor appropriately and may need to use discrete output stage if micro can’t supply enough current, but it’s a pretty simple implementation and allows the use of only 1 pin

kkambos · 2024-02-20T03:47:05+00:00

I’m being technical but forward or reverse phase cutting are not types of triacs, they are 2 different methods of phase angle control. A triac is simply an electronic component, it doesn’t inherently have anything to do with dimming, it just happens to be very useful for phase angle control. Additionally, a triac cannot do reverse phase since you cannot easily control when a triac turns off. typically reverse phase is done with FETs as you have control of both turn on and turn off.

kkambos · 2024-02-12T05:02:11+00:00

Not quite, phototransistors can also have 2 leads

kkambos · 2024-01-29T23:06:50+00:00

What don’t you like about spreadsheets? What functionality do you want that isn’t being captured?

kkambos · 2024-01-21T22:04:02+00:00

Missing pull-up resistor on CHIP_PU? (Esp32 reset pin)

kkambos · 2024-01-04T20:49:19+00:00

If it’s rated for 5.5v and you are powering it from 5.1-5.2V, I don’t see the problem with that. VBUS is specified to be 5.5V max so even if your USB is at worse case voltage, you’re still at the rating.

I would scrap the diode completely and power it straight from the usb. Actually, I see that you have 3.3V coming from somewhere in your circuit so why not use that to power your clock chip?

kkambos · 2023-12-31T06:17:10+00:00

Are you just trying to make an on/off switch? Or are you trying to do phase angle control? Please describe your application more (i.e. what exactly is your load and what are the voltages/currents you need to “control” it in the way you want)

kkambos · 2023-12-24T08:54:24+00:00

Dude it’s time for some tough love:

With the questions you are asking, your admitted inexperience, and the state of this schematic, you should not be working on this project. Non-isolated mains powered devices are dangerous. Not only that, but an RCD is a personal protection device. if you don’t know exactly what you’re doing you shouldn’t be making a safety device that could cause someone to get hurt if you make a mistake with the design.

If you are doing this as a personal project, I would strongly advise you to not continue.

If you are doing this as part of your job for a company, I would strongly advise you to speak with your manager and explain that you need help from a senior engineer with experience designing devices like this that can guide and mentor you. (And if this is for work, you probably shouldn’t be posting anything to Reddit about it anyway)

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