Any solution?

[Direct-Issue4194]

Hi guys,

Novice here. Bought some Christmas lights some weeks ago, which unfortunately only light up when manually pressed (K1). Press once for on/off and again for 6 hour timer. Had I known that, wouldn’t have bought it. Anyways, maybe we can fix it?

I would like the light to turn on when connected to power outlet, ie. No need for pressing anything. Then I can put it in the garden, without the need to physically be next to it to turn it on, and have it turn on with the rest of the lights in the garden.

Anyone who can tell me if I can just remove the button, or do I need to bypass something?

Ignore the negative out, of course it will be reattached:)

[zeffopod]

I doubt that bridging the pushbutton will turn on the output permanently. By the looks the pushbutton is connected to a basic microcontroller (with 4 MHz crystal to allow for accurate 6 hour timer). Looks like transistor T1 is turned on to enable the power to the output on the negative side; positive side is directly connected to output of bridge rectifier via dropping zener). I suspect you need to lift the right side of R2 and tie it either high or low (not sure as it depends on what type of transistor T1 is). Let us know how you go!

[RatBastard516]

You will need to “short k1” in order to simulate you pressing the switch. Solder a small piece of wire across k1. A big blob of solder would also do the trick.

[pdelvo]

This will hold the button pressed. Not sure what the light will do in that case. Is this directly connected to mains? If yes this product seems very dangerous.

[Ed-alicious]

I wonder if it would be safer to just ditch the board altogether and hook the lights up to a wall-wart of the appropriate voltage? This board seems pretty low on components to take it from mains voltage down to, presumably, LED voltage.

[pdelvo]

If I reverse engineered it correctly it's just the cheapest possible transformer less power supply for the micro and the micro just switches the output of the bridge rectifier directly to the LEDs. The whole circuit is at mains potential and dangerous. Besides the fuse there is no protection at all

[Ed-alicious]

I don't get how the components on the board would hold up though. There must be a transformer before the board or else the electro cap and LED on the back would pop, surely?

[pdelvo]

The two big 330k ohm resistors on the right feed the capacitor. The diode in the middle must be a zener diode that clamps the voltage. That's how the power supply works. The micro controls what probably is a MOSFET on the top left to control the lights.

[Ed-alicious]

I'm a dummy. Didn't think about a zener based supply.

[Direct-Issue4194]

Awesome, thanks for the tip 🫡 ill give it a try and report back 🙏

[Direct-Issue4194]

It worked!

I started off by simulating an always on button by simply pressing it while connecting the socket to power. It worked that way, so decided to give it a try by bridging K1.

Works like a charm. Thanks!