LED lamps (and some fluorescent ones) may glow or flash when they're supposed to be off when used with electronic switching devices like solid state relays and dimmers. Here's why.
The main reason is usually the snubber network across a triac. This is usually a resistor and capacitor connected in series and appllied across the main terminals of the triac to attenuate sudden high speed glitches and transients that could result in the triac turning on when it wasn't supposed to. Triacs have a characteristic called DV/DT Where the D stands for delta, meaning "change in" so the characteristic relates to change in voltage / change in time. This relates to the triacs ability to turn off or remain off when a rapidly rising waveform is applied across it, like a pulse or transient. Typical values for a snubber network are 100 ohms and 100nF. Normally with a heavy load the capacitive coupling through the snubber network is not an issue as it gets shunted by the load. But with very low loads like LED lamps or small motors it may cause a situation where a lamp keeps glowing dimly or a small effects motor keeps running or shuddering slightly.
In some cases you can solve the problem by using another snubber network across the load as it then forms a divider with the one across the triac, and that can lower the leakage voltage to a level that the affected loads will not light or move.
A common approach to solving this issue in the theatre industry is to use a ghost load where a traditional lamp is used to load down a dimmer circuit controlling a small effect, and also help ensure the channel turns on properly, as triacs need a minimum holding current to remain latched.
If you enjoy this channel you can help support it with a dollar for coffee, cookies and random technical stuff at https://www.patreon.com/bigclive
The main reason is usually the snubber network across a triac. This is usually a resistor and capacitor connected in series and appllied across the main terminals of the triac to attenuate sudden high speed glitches and transients that could result in the triac turning on when it wasn't supposed to. Triacs have a characteristic called DV/DT Where the D stands for delta, meaning "change in" so the characteristic relates to change in voltage / change in time. This relates to the triacs ability to turn off or remain off when a rapidly rising waveform is applied across it, like a pulse or transient. Typical values for a snubber network are 100 ohms and 100nF. Normally with a heavy load the capacitive coupling through the snubber network is not an issue as it gets shunted by the load. But with very low loads like LED lamps or small motors it may cause a situation where a lamp keeps glowing dimly or a small effects motor keeps running or shuddering slightly.
In some cases you can solve the problem by using another snubber network across the load as it then forms a divider with the one across the triac, and that can lower the leakage voltage to a level that the affected loads will not light or move.
A common approach to solving this issue in the theatre industry is to use a ghost load where a traditional lamp is used to load down a dimmer circuit controlling a small effect, and also help ensure the channel turns on properly, as triacs need a minimum holding current to remain latched.
If you enjoy this channel you can help support it with a dollar for coffee, cookies and random technical stuff at https://www.patreon.com/bigclive
Ive gone back to halogen G9 in my polished chrome ceiling light fittings where Id tried LED bulbs that glow when off. A decent dimmer switch on the wall and they give off a much nicer light anyway. Not a single bulb blown in over 2 years. Im so tired of messing around with expensive LED lighting that just dosen't seem to give off a decent non defused light or as reliable .
I have a LED bulb that I clipped a resister out of, and it is glowing even when the switch at the wall is off. No dimmer, no relay. Just bog standard light switch. Is this an issue?
I bet this is even more fun in the case of 220v mains. 🙁 I'm using an incandescent lamp in the circuit as my solution.
Link to the bulbs that light up from the neutral when turned off???
There is always a leakage voltage on an SSR .It will allow low voltage low current devices to to stay illuminated .We will switch heater elements through and use a manual motor starter or contractor to disconnect the output going to heaters .Especially at 600V 3 phase heater banks used in commercial ovens .Croydom, Opto,or Carlo Gavazzi they all have the same issues
Thank you
Two way switching gives a similar effect here in UK, flickering/dim LED's.
I swapped 4 outdoor PIR Halogen floodlight bulbs for LED bulbs a few weeks ago and half of them are fine and completely dark when not triggered, but two of them light reasonably brightly when on, but not triggered, then go to full bright when the PIR triggers. i guess the good ones probabaly have normal relays in them? It's frustrating me!
love this stuff
How to prevent this ghosting by using zener in voltage line?
If they all leaking some current at what cost over a year. As my thinking all the usb socket chargers just a tiny bit. It like taking 2p out of every bank account in the UK.
Nice video!!! I bought a rope light that has the same issue, the thing is that I have the stuff around the whole yard and it never turns completely off…. What resistor would I add to an led strip (the rope light) that's about 150ft long? I'm estimating 800W and on although I use a dimmer to make it not as bright. since it's an LED strip can I just bridge the positive and negative terminals at the end of it? – t glows without the dimmer as well – Thanks so much!
Entre triac out triac
I ask, if the bulbs are switched off, will it use power? i have 20w led lamps and it still is on even switch are off
Or you could just wire your house properly and have the live wire going to your lamp, not the ground. Its just a thought 🙂
I ran into this problem recently after replacing all light switches in our house with the ones that have the gas-based light indicator(that turns on when you turn off the light). One of the lights in the house is an LED light fixture and when the switch is off, it blinks rather aggressively and frequently(like once every 2 seconds or so). I've been looking up solutions to the problem and I did get four different suggestions:
1. Connect a resistor and a capacitor in series with the light fixture
2. Connect just a resistor in series with the light fixture
3. Connect just a capacitor in series with the light fixture
4. Disconnect the light indicator(duh, but I bought the ones with the indicator on purpose and I'd rather have it work 😀 )
😀 I think I'm going to grab some resistors and some capacitors with different values(suggested resistor values were up to 1 W with resistance between 100k and 1M ohm and for the capacitor either 220nF/400V or 100nF 275VAC) and see if I can resolve the problem.
I have a weird LED bulb that continues to glow even when unplugged from the socket for hours. It's not always a steady glow, sometimes it will flicker, occasionally glowing bright enough to light up a room for a few moments.
Either there is a really big capacitor in it, or it's picking up electricity from some wireless source, like how a florescent bulb lights up near transmission power lines.
I tried putting a 47K 1/2 Watt resistor across the Live and Neutral wires, going to a 240V led bulb.
After a few minutes the resistor got to around 48 centigrade, and was too hot to touch.
The resistor did not breakdown, even when I extended the on time to 30 minutes.
The resistor stopped the led glowing when the relay was off.
I also tried connecting a wall wart type power supply across the Live and Neutral going to the 240V led bulb. That also took care of the led glow.
So, am I wasting energy, using these SSRS and curing the problem with 'heaters'?
Looks like it is more sensible to use mechanical relays for these problem 240V led applications.