# EL wire controller high pitch squealing ? is this normal ?

#### HonesTisThePathToLife

Joined Nov 25, 2018
27
Hello, I recently stumbled upon EL wire and thought it would be a great way to be seen when walking at night in the rainy season of Vancouver BC the rain capital of Canada.

But when the controller that uses 2 AA batteries is turned on the high pitched squealing is a little to loud to be ignored, is this normal and can this be fixed ?

Here is the EL wire I bought the Green is very bright but the squealing is sickening...

https://www.ebay.com/itm/Led-EL-Wir...var=630597294671&_trksid=p2057872.m2749.l2649

#### turboscrew

Joined Dec 7, 2018
16
I'm not sure, but I think the set is not supposed to be noisy.
My guess is that there are non-fit components used that the chopper makes to squeal.
Often it's inductors that squeal, but in some cases it can be capacitors that act like piezo devices.

#### cmartinez

Joined Jan 17, 2007
7,368
Hello, I recently stumbled upon EL wire and thought it would be a great way to be seen when walking at night in the rainy season of Vancouver BC the rain capital of Canada.

But when the controller that uses 2 AA batteries is turned on the high pitched squealing is a little to loud to be ignored, is this normal and can this be fixed ?

Here is the EL wire I bought the Green is very bright but the squealing is sickening...

https://www.ebay.com/itm/Led-EL-Wire-Tube-Rope-Flexible-Neon-Glow-Car-Party-Decor-Light-3V-12V-controller/361251750624?ssPageName=STRK:MEBIDX:IT&var=630597294671&_trksid=p2057872.m2749.l2649
The thing is most likely using PWM to control the amount of current reaching the wire, and the circuit is probably so badly designed that it doesn't have a basic EMI filter.

#### Alec_t

Joined Sep 17, 2013
12,149
The EL driver will be a boost converter. If that is operating at a frequency in the audio range then its transformer/inductor is probably the source of the noise.

#### wayneh

Joined Sep 9, 2010
17,153
Hello, I recently stumbled upon EL wire and thought it would be a great way to be seen when walking at night in the rainy season of Vancouver BC the rain capital of Canada.

But when the controller that uses 2 AA batteries is turned on the high pitched squealing is a little to loud to be ignored, is this normal and can this be fixed ?

Here is the EL wire I bought the Green is very bright but the squealing is sickening...

https://www.ebay.com/itm/Led-EL-Wire-Tube-Rope-Flexible-Neon-Glow-Car-Party-Decor-Light-3V-12V-controller/361251750624?ssPageName=STRK:MEBIDX:IT&var=630597294671&_trksid=p2057872.m2749.l2649
It's very common for EL supplies to squeal. They are designed to produce 100-200V at 200-3000Hz. So a typical device might be 120V at 2000Hz, smack dab in the range of human hearing. That oscillation in voltage needs to be converted to mechanical motion for you to be able to hear it, and that's where better designs achieve quiet operation.

#### wayneh

Joined Sep 9, 2010
17,153
The thing is most likely using PWM to control the amount of current reaching the wire, and the circuit is probably so badly designed that it doesn't have a basic EMI filter.
Not likely. The EL device resembles a capacitor with appreciable ESR. It generates light when being charged, meaning the power lost to the ESR is converted to light energy. Sort of. I don't think there is the same ESR during the discharge phase. But anyway, the ideal drive is a sine wave because it's the most gentle to the EL device. They have a lifespan and you want to treat them well. A square wave has high-frequency components and shortens the lifespan of the EL device. Changing the duty cycle of the square wave would have almost no effect on brightness. EL brightness is a function of voltage and frequency.

#### cmartinez

Joined Jan 17, 2007
7,368
Not likely. The EL device resembles a capacitor with appreciable ESR. It generates light when being charged, meaning the power lost to the ESR is converted to light energy. Sort of. I don't think there is the same ESR during the discharge phase. But anyway, the ideal drive is a sine wave because it's the most gentle to the EL device. They have a lifespan and you want to treat them well. A square wave has high-frequency components and shortens the lifespan of the EL device. Changing the duty cycle of the square wave would have almost no effect on brightness. EL brightness is a function of voltage and frequency.
Yeah, that downed on me when I read Alec's explanation. I misread EL with LED. The use of a boost converter makes perfect sense now.

#### HonesTisThePathToLife

Joined Nov 25, 2018
27

#### wayneh

Joined Sep 9, 2010
17,153
Hello Thank you all for the replies,

Here are some pictures of the board, its a foreign language I dont understand yet but I do own a nice soldering station and have the interest if it can be fixed ?

The controller is only noisy when the light string is attached when the light string is unplugged and controller on its no noise....

https://www.dropbox.com/s/2w6diwlpt3lvjuz/20181228_180547.jpg?dl=0

https://www.dropbox.com/s/5c4sder1xuqt1sz/20181228_181017.jpg?dl=0
That transformer is likely the noise maker. You could confirm this by using a plastic straw like a stethoscope to locate the source. But there’s not much you can do about it except to enclose the entire device in some foam or similar sound deadener.

#### ebp

Joined Feb 8, 2018
2,332
I agree with Wayne that it is likely the transformer. From the photo it looks like the core halves (two "E" pieces) are simply assembled with tape. This is not uncommon but isn't great. If the circuit operates in the audio frequency spectrum, the pieces can vibrate against each other and make a noxious racket. Vacuum impregnation of the whole thing with "transformer varnish" is often effective in quieting them, but of course you need a vacuum pump, a chamber and some varnish. Sometimes the wire in the windings can move enough to make noise and impregnation is the only way to fix this problem.

The following describes another method that might work. It is a bit time consuming, fiddly and there is a risk of wrecking the transformer in the process:

An alternative to impregnation is to try to "glue" the two halves of the core together. This pretty much requires removing the transformer from the board. The yellow tape around the core would be removed. The tricky part is then to glue the halves together without introducing an "air gap." It is possible that it is a flyback converter and already has a gap. In high volume production, only the centre leg is gapped. In low volume it is common to use spacers so all legs are gapped. If spacers are used, you're in trouble if you lose it or damage one since the spacing is quite critical. However, if the core is spaced already, a tiny bit of extra spacing due to glue won't be detrimental. If it isn't gapped, you really don't want to introduce any gap so the thinnest possible glueline is the objective. I would carefully clean the faces of the cores pieces with a solvent like isopropyl alcohol or acetone (both flammable), be sure they were free of any particulates and glue them with a low-viscosity cyanoacrylate adhesive ("super glue"). The pieces would need to be firmly held together during adhesive curing. This is a bit of a challenge because the ferrite is brittle and not very strong, so it is quite easily broken. The bobbin and pins get in the way of simple clamping methods, just to make things worse. Re-taping to hold the pieces together while the adhesive cured might work, but it becomes something of a 4-hands job that needs to be done quickly. Transformer tape isn't a common item but "Kapton" (polyimide) tape would probably be pretty good. It is slightly elastic which would help in getting it tight, whereas the standard stuff is polyester and not stretchy. Kapton tape isn't an everyday thing either but can be found from internet vendors.

Trying to keep drivers from squashing you is certainly a problem. I had some dolt do it today. He stopped short of the crosswalk, then when I was nearly in front of him started moving again while looking elsewhere. I said some very rude things to him. I also carry a whistle I bought at Mountain Equipment Co-op that will get the attention of dopey drivers who block crosswalks, but it is so damned loud it hurts to use it (MEC keeps them in the water sports section). I have some safety arm bands with Velcro to adjust size and 3M retroreflective material. I sometimes use one on each wrist or one on an ankle and one on a wrist. They seem to be pretty effective in getting drivers' attention. I have polyester mesh t-shirts with the reflective bands that I use when cycling in poor visibility conditions. Any place that sell hard hats or other safety gear will have them. I think even Walmart sells them.

#### HonesTisThePathToLife

Joined Nov 25, 2018
27
Thank you for that information I did not know about the glue vs tape vibrations.

Im going to probably just wrap the controller in bubble wrap and or high density foam and aluminum foil if that fails might try some sound proofing insulation they use for car audio.

#### Alec_t

Joined Sep 17, 2013
12,149
and aluminum foil
I wouldn't use that. If it works loose it could short-circuit something, with undesirable consequences.