Hi, so I’ve just received this little flashlight from Convoy, but noticed, that whenever I have it on Mid setting and I shine it close to some objects it whines.
What’s weird about this is that the whine is louder only when I keep the flashlight close to an object and only works on certain materials, plastic parts seem to work best. Do you know why is that?
I supposed it had something to do with the LED feeding a small amount of current back to the driver when it’s in intense light, but I can’t tell. Maybe something about static electricity?
It just doesn’t make any sense why it whines only when it’s close to the surface.
It could be inductor whine, if the Convoy uses a voltage regulator (which I’m not sure). Maybe the reason it reacts with certain objects is the magnetic field is interacting differently with different substances? Okay, that’s probably not realistic. Maybe it’s just the sound is being reflected off some surfaces, and you therefore hear it louder.
I was wondering that, but this effect happens on ex. red t-shirt, CD crystal case, but not on a ceramic plate or wooden door, then I move it over a black poster and it whines. It certainly has something to do with synthetic materials, but that doesn’t make any sense to me, as the light is almost completely shielded from all sides.
I would think it has something to do with varying load, since the LED can work like a little crude photovoltaic element, but it seems so inconsistent, maybe the effect only intensifies at certain light intensity, since on a white surface it’s quiet, and when moving it across a black poster with white lettering I can definitely hear volume modulation.
Maybe it has something to do with the black paint.
edit: yeah it surely works on black surfaces
The effect is present even from 30cm to the object, and when I block the hotspot with my hand,the light becomes quiet. So damn intriguing.
It’s just pwm which lets components oscillate, perhaps springs or wires. If you block the beam with your hand you also block the accustic waves on their way to the reflecting surface.
An electrical current going through a power-regulating component like a transformer or inductor is causing its electrical wiring to vibrate at a variable frequency. This happens in almost all electrical devices, usually at a frequency and volume that’s inaudible to humans, especially inside a metal or plastic case. My next step would be to disassemble for visual inspection, possibly some loose component.