Light switch ramp circuit to extend life - Page 1
Forum section: electronics / projects

author: edy
author_rank: Super Contributor
timestamp: March 14, 2016, 01:07:35 am
content: Hi folks,I met an older engineer who held some patents and we talked about some of his inventions which I thought were interesting. I'm not sure if they ever became commercially successful though, but I'm wondering what you thought about it and whether it was an issue of cost/benefit or something else that perhaps lead to it's lack of implementation.The patent and device is for a light switch that allows the circuit to complete only when the AC sinusoidal wave is at 0. That is, if there is any negative or positive voltage, there is a delay until it is at 0 volts and then allows it to complete. The idea is that this will prevent "shock" to the light bulb filament (or whatever device is on the switch) through getting an instantaneous maximum, and also perhaps save the contacts on the switch as well from sparking and prematurely wearing/burning. If the circuit actually always completes at 0 volts, there is a small "ramp" (in one direction or another) that is a fraction of a second nevertheless but still gradual sinusoidal change, rather than a square-wave "jump" which can happen otherwise randomly at any point in the curve depending on when you flip the switch.I don't remember how it was implemented exactly, but the circuit can't be that difficult and was cheap enough and small enough to implement in switches. Basically, keep open circuit when there is any voltage greater than 0 in either polarity direction on the AC line, and when it crosses the 0 threshold to turn it on so that it goes up.Is this something anyone has heard of? Any scientific proof that it will actually extend bulb life or other products by anything significant? I'd be interested in hearing your thoughts.

author: batteksystem
author_rank: Regular Contributor
timestamp: March 15, 2016, 03:57:49 am
content: Aren't this just zero crossing? pretty common nowadays.

author: edy
author_rank: Super Contributor
timestamp: March 15, 2016, 05:05:15 am
content: Quote from: batteksystem on March 15, 2016, 03:57:49 amYes I think that is what's going on. I didn't know the exact terminology and extent that it is used. I'm not sure how this engineer implemented and how sophisticated the circuit was, only that his intention was to ensure the device (whether it be a light bulb or other product) closed the circuit path at the zero point only. Presumably this was to time the system so that when you turn it on, you don't deliver an instantaneous voltage spike but actually catch it as it crosses zero and therefore take advantage of the sinusoidal ramp to the full voltage.So I assume there was some detecting circuit that would keep sensing zero crossing, and when you turn on the device switch it activates a second circuit which waits for the zero crossing signal to activate and when it sees it, only then physically allows the circuit to be completed to allow current the potential to begin flowing. Of course, at the zero point, for a brief moment there is no current as the voltage is zero. However, a short time later current begins to flow as voltage increases. However, once the device is "on", it ignores the zero-crossing detection anyways. So there has to be a latch that once the device is powered it doesn't depend on a zero-crossing to continue being powered.

author: Seekonk
author_rank: Super Contributor
timestamp: March 15, 2016, 07:19:13 am
content: Certainly a bigger issue is that a lamp draws 7 times more current when it is first turned on. Talk about a mechanical shock. The same issue with power supplies as they first charge up the caps. There are two lead devices that change resistance as they heat up to solve this. They even made disks that you dropped into a light socket to extend lamp life. Nobody got rich on that. Find a new problem to solve!

author: edy
author_rank: Super Contributor
timestamp: March 15, 2016, 12:52:41 pm
content: True, the resistance of a cold filament is lower than when it is white hot. I think you've all answered the original question I had which was why this old EE's patent (so he claimed) didn't really take off commercially.

author: SeanB
author_rank: Super Contributor
timestamp: March 15, 2016, 05:35:37 pm
content: Built some many years ago when I was in school, to tame the switch on surge of a light box used to expose printing plates, which used 20 40W golf ball lamps as a diffused light source for the photosensitive plates. It would trip the 20A breaker for the room around 1 switch on in 4, which could be an issue, as there was only a single breaker for the entire floor ( old building, and rented floor, and the landlord was not interested in spending money on "frivolous upgrades", and would not allow it to be done by the tenant). This used a triac and an unijunction transistor ( you could still buy them in the 1980's off the shelf, rarer than rocking horse droppings now) to slow start the lamp over a second, though you could not tell the difference in brightness, but it did not trip any more.Built another a few years later to drive a room light, where I wanted it to brighten up over a 5 minute period from dim to bright, so I could wake up in winter. Summer no problem, sun rise is at 5AM. Same circuit, just using a 2200uF 50V capacitor instead of the 1uF in the first one.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: March 15, 2016, 11:19:07 pm
content: Someone still has a crapping rocking horse.http://www.digikey.ca/product-detail/en/central-semiconductor-corp/CMPP6028%20TR/CMPP6028%20CT-ND/5324497

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 15, 2016, 11:51:56 pm
content: I think it would need to ramp up over more than a single cycle give optimal life improvement - if you're adding electronics to do it you might as well do it as best as possible.But LED lighting is now good enough that there's rarely a reason to use incandescent

author: han
author_rank: Frequent Contributor
timestamp: March 16, 2016, 12:16:53 am
content: Filament lighting tend to draw more current at start, so NTC will prevent current spiking

author: Salvatore Shiggerino
author_rank: Newbie
timestamp: March 16, 2016, 01:02:10 pm
content: What a coincidence, I just signed up specifically to discuss light bulb life extension, and here this thread is.My interest in the matter comes from being one of those old gits who refuse to get with the times and give up conventional light bulbs. I don't mind CFLs in hallways and storage rooms, and halogen in spotlights, but for reading lights I want the soft, diffuse light of a traditional matte incandescent bulb. So now that they are banned I need to make my hoard last as long as possible.For fixed lighting the simplest solution is to just put in an off-the-shelf dimmer switch, the ones I have do ramp up the light gradually. And for table- and floor lamps with the switch on the cord, there are off-the-shelf cord mounted dimmers to simply wire in. But for lamps with integrated switches that I don't feel like butchering I came up with the following device, to be placed between the electrical outlet and the lamp:A triac dimmer whose triggering circuit is controlled not by a potentiometer, but by a hall effect sensor sensing the current going to the lamp, forming a positive feedback loop. So it starts out dimmed all the way down, but as soon as the switch to the lamp is closed current begins to flow and it starts dimming the lamp up.I'm inexperienced about electronics, but how does that sound? Am I way off, or is it worth giving a try?Quote from: han on March 16, 2016, 12:16:53 amYou mean simply placing an NTC thermistor in series with the lamp? Sounds a lot simpler than my idea, perhaps it's worth trying, as long as it doesn't waste too much power.Quote from: mikeselectricstuff on March 15, 2016, 11:51:56 pmMakes sense. Right now I'm trying to find some studies on the longevity of light bulbs, to avoid going to a lot of trouble for very little gain.

author: Seekonk
author_rank: Super Contributor
timestamp: March 16, 2016, 01:10:20 pm
content: One should remember that a triac will always loose about 1.7V, so an active device will not likely be more efficient than a a thermal change resistor.

author: MK14
author_rank: Super Contributor
timestamp: March 16, 2016, 01:20:42 pm
content: Quote from: Salvatore Shiggerino on March 16, 2016, 01:02:10 pmMy understanding (from reading articles about it, here and there) is that because the modern filament bulbs, are coiled coilsIt (the filament), is relatively insensitive to on-off transitions, even if they are relatively sharp.FAQ:If the above is the case, then how come bulbs often seem to break/blow, when first switched on.What is happening is that the filament (usually over 1,000 or 2,000 hours), gradually evaporates away (that's why halogen bulbs last longer, because the extra gas (Halogen) pressure, significantly reduces the "gradual boil off", of the tungsten filament. (The fuller explanation, is considerably more complicated).So after its rated lifetime (approx 1,000 or 2,000 hours), the filament has gradually thinned itself out (through gradual boil off evaporation), so much that it is TOO THIN, to reliably work. So once it is TOO THIN, but on. It can actually remain like that for a while (many hours or more).BUT when you next turn it off, and let it fully cool. It will get a HUGE shock/tension/forces when you turn it on (because cold filaments have a considerably lower resistance (up to about 10x more current flows), because of tungsten's temperature coefficient).Hence it tends to break, when you switch it on.Turning it on gradually would only gain you a small bit of extra hours. E.g. 1% increased life, maybe.Report(s) that I have read (which seem reliable), basically say that the modern coiled coil, means that you essentially get the full life, WITHOUT needing to resort to assisted life extension methods (i.e. gentle on/off, etc).BUT (in theory) if you "*DIM*" it, you are going to potentially get a CONSIDERABLE life extension, because that (lower filament temperature) will give a (potentially) considerable life expectancy increase. But significantly worsen efficiency.So peoples results where softstart-dimmers give much longer lives, could be because the bulb is being run dimmer.Outside lamps, can have conventional looking bulbs (filament), which last 10,000 or even 20,000 hours (by running the filament cooler, i.e. as if its voltage rating was much higher than the real mains voltage). Not used much these days, because CFL or LEDs, are much better overall.

author: Salvatore Shiggerino
author_rank: Newbie
timestamp: March 16, 2016, 02:37:20 pm
content: Quote from: MK14 on March 16, 2016, 01:20:42 pmI was hoping to find an authoritative figure on that. Assuming a 20 year supply of light bulbs that would only give me a couple of months extra, hardly worth the trouble.Quote from: MK14 on March 16, 2016, 01:20:42 pmWhile doing research I found this study:http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=4504751It examines the use of a simple diode in series with the light bulb, and confirms that it extends life, but at certain other costs. I can also imagine it will cause noise and strain on the filament, like an old triac dimmer without an inductor choke. So I think the extension in life can simply be attributed to lower boil-off because it's essentially de-rating a higher-power bulb.So far it seems like the most sensible option is to install off-the-shelf dimmers on the cords and simply dim all the lamps to the lowest brightness and colour temperature that's still pleasing to the eye, and simply not worry about soft-starting them by not touching the integrated switches. Other better ideas is to not leave them on when leaving the room, or compromising with alternative bulbs as much as possible, which will probably get better over time. I'm thinking of trying out those E27 halogen bulbs in lamps that have the bulb covered by a piece of frosted glass anyway.

author: MK14
author_rank: Super Contributor
timestamp: March 16, 2016, 03:04:37 pm
content: Quote from: Salvatore Shiggerino on March 16, 2016, 02:37:20 pmDefinitely DON'T take my post (above) as definitive, for at least two reasons.(1)...It was primarily, low voltage (DC) bulbs, such as 6V ones, used in electronics projects, I was specifically researching (looking into). I was trying to find information, as to how much life expectancy DECREASE occurs, if your project flashes the bulb, at different frequencies.I.e. In theory the rapid flashing (heating/cooling), could over time, induce metal fatigue, in the filament.The article(s) and/or posts, seemed to say "NO", because of modern coiled coils, resistance to stresses and strains. Means that it has developed to the point of essentially NOT effecting the life expectancy.(2)...BUT the latest available bulbs, especially produced in the future (filament). May NOT be produced to the relatively high quality standards available, in recent years, when filament bulbs were popular and widely available in the West.E.g. Cheap Chinese ones, may or may NOT, last as long, and be as robust as ones we have got use to, over the last few decades.(I vaguely remember reading of poor quality Chinese made ones, sold on ebay).Hence they could be weak (poor quality), and susceptible to filament early failure, so actually need/benefit from soft-start etc. Even though quality ones may NOT need it.I suspect that you/we will be able to buy filament bulbs, for a long time, in the future. I.e. China (and maybe other countries) will probably still make them.I also suspect that modern alternatives, such as LED lighting, will get better and better. Making LED based, filament LIKE bulbs/lamps, readily available.As you mentioned above halogen bulbs (especially if diffused or something), are partly similar as well.It is possible that if the bulbs are partly poorly made (I will refrain from mentioning a country that begins with C...), they might still benefit from soft-start and such, because of weaker/poorly constructed filaments (WILD SPECULATION).In theory, LEDs are so technically powerful nowadays, I would have thought a pretty good, filament bulb simulation/emulation could be constructed and/or a decent "daylight" type bulb (LED).

author: Seekonk
author_rank: Super Contributor
timestamp: March 16, 2016, 04:01:19 pm
content: Brings back memories. Worked on a project that inspected those filaments, large glass disk and a camera. A jet of air would kick out anu kinked ones. The amazing thing was an entire months supply for production of lamps would (and did) fit in a peanut butter jar. And a vibratory feeder would unsnarl the mess!

author: Kilrah
author_rank: Unknown
timestamp: March 16, 2016, 04:35:19 pm
content: Quote from: Salvatore Shiggerino on March 16, 2016, 01:02:10 pmI always hated CFLs too and always had something for good old incandescent so was saying the same. But now matte warm white LED globe lights are a perfect replacement, no point in incandescents at all anymore. Replaced everything with them and not looking back.

author: SeanB
author_rank: Super Contributor
timestamp: March 16, 2016, 06:09:10 pm
content: Still have a nice collection of genuine antique incandescent lamps, with many made pre 1939. More than a lifetime's worth there. Strangely I also use LED lighting these days, the lower power bills are worth it in many cases.

author: suicidaleggroll
author_rank: Super Contributor
timestamp: March 16, 2016, 07:27:45 pm
content: Quote from: Kilrah on March 16, 2016, 04:35:19 pmAgreed.CFLs are the worst, but there are plenty of LEDs out now that match the warmth of incandescent. There's no need for incandescent bulbs anymore, they have literally zero advantages, other than as a space heater in the winter.

author: SL4P
author_rank: Super Contributor
timestamp: March 16, 2016, 07:39:07 pm
content: Topic keywords...IncandescentSoft-startThermal shockVibrationOver-temperature

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: March 18, 2016, 11:46:28 pm
content: http://moodle1315.up.pt/pluginfile.php/167981/mod_resource/content/1/Incandescent_Light_Physics.pdfSuper interesting.Also I recall a PTC thingy you put at the base of the bulb and it acted as a surge suppressor to reduce the inrush current.Oh and yeah, I've put LEDs in a lot of places in my humble abode, as the old bulbs go I replace them with LEDs.

author: batteksystem
author_rank: Regular Contributor
timestamp: March 21, 2016, 06:51:36 am
content: Quote from: Alex Eisenhut on March 18, 2016, 11:46:28 pmPTC only work if you let it cool down, otherwise if you turn it on and off quickly, it will not protect the device.