Nightlight help - LED and timer content

Tunakid #4, and only Tunadaughter, wanted a night light. We dried a rose and some other flowers in dessicant powder for like a week and then added them and some fairy LED lights to a mason jar and filled it with resin over the next few days. It looks pretty good, but over time the cheap controller for the lights failed. I wanted to add a sleep timer and a button, so I found some stuff, added the button, but could not get the timer to work properly. Last week I decided just to try a different timer, and hooked it up to the battery, and realized something had gone wrong that caused the strand to stop working correctly. While this meant that the timer may not have been my issue, it also means that my strand doesn't work. It's confusing. I made a video. Help if you can.

Do you have a link to the lights?

Many LED lights like that get around the polarity issue by having a MOSFET/rectifier thing buried in the wires.  It more or less turns it into AC power on a pulsewidth modulation that is so fast you can't see the flicker.  In fact, old LEDs flickered so badly that newer ones are often advertised as "non-flickering."

Have you ever turned your eyes or your head past some LEDs and notice that your eye/brain sees a trail of dots?  Pulsewidth modulation.  Or have you watched one of those slo-mo stinger shots of an Audi R8 on Top Gear and the headlights are pulsing?  Yup.  Pulsewidth modulation.

My guess is your MOSFET died in the string which would explain the flash when you hook it up one way and nothing when you hook it up the other way.

These were the lights.

https://www.amazon.com/gp/product/B07V4Q6FK4/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Is there any way to fix them you think?

I'm curious about the string working with either polarity.  I suspect that there are actually two sets of LEDs wired at opposite polarities and that when you switch the battery around you're actually lighting different pairs.  This would allow the lights to run off a current limited AC supply without visible flicker since one set would be on when the other is off. 

Unfortunately I don't think it really matters when it comes to fixing your nightlight.  I'm pretty confident that you've got a poor connection internally somewhere that can't handle the current once they're fully turned on.

Actually, as I'm thinking about it.  It's possible that they'll work if you run them at a lower current.  All LEDs need some kind of current limiting.  In some cases that's in the string and in other cases it's in the controller.  When you connect a 9v battery directly to the string there might not be any current limiter.  Even if there's an internal resistor the original supply was 3 1.5v batteries so the string itself isn't designed for anything more than 4.5v.  What happens if you connect the string to a single cell battery like an AA?

Agreed.  Try wiring them up through the controller or adding an appropriate resistor

Very cool.  Remember those glass cutting things "As Seen on TV" in the 70s?  We cut a hole in the bottom of a 6 liter wine bottle and did the same thing.   Nice job Tuna.

914Driver said:

Very cool.  Remember those glass cutting things "As Seen on TV" in the 70s?  We cut a hole in the bottom of a 6 liter wine bottle and did the same thing.   Nice job Tuna.

Thanks!

I just wish that I could fix it for her. She's sad.